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Drought is an important meteorological event in China and can cause severe damage to both livelihoods and socio‐ecological systems, but current seasonal prediction skill for drought is far from successful. This study used convolutional neural network (CNN) to build an effective seasonal forecast model for the summer consecutive dry days (CDD) over China. The principal components (PC) of the six leading empirical orthogonal function modes of CDD anomaly were predicted by CNN, using the previous winter precipitation, 2‐m temperature and 500 hPa geopotential height as predictors. These predicted PCs were then projected onto the observed spatial patterns to obtain the final predicted summer CDD anomaly over China. In the independent hindcast period of 2007–2018, the interannual variabilities of first six PCs were significantly predicted by CNN. The spatial patterns of CDD were then skillfully predicted with anomaly correlation coefficient skills generally higher than 0.2. The interannual variability of summer CDD over the middle and lower Yangtze River valley, northwestern China and northern China were significant predicted by our CNN model three months in advance. CNN identified that the previous winter precipitation was the important predictor for PC1–PC3, whereas the previous winter 2‐m temperature and 500 hPa geopotential height were important for the prediction of PC4–PC6. This research provides a new and effective method for the seasonal prediction of summer drought. Plain Language Summary: Drought can cause serious agricultural and ecosystem disasters, so its forecast is valuable for preventing and mitigating related natural disasters and regional socioeconomic sustainability. However, current prediction skill for drought is far from successful since its extreme feature. The gradually emerging deep learning methods offer new possibilities, but how to effectively apply deep learning models in climate prediction with a small sample size remains an open question. In this paper, we build seasonal prediction convolutional neural network model for summer consecutive dry days over China using previous winter predictors. This model achieves significant prediction skill three months in advance. The empirical orthogonal function decomposition is used to reduce the dimensionality of consecutive dry days data in our model. Our research provides a new perspective for drought prediction, and it is expected that such method will be also useful for other seasonal climate prediction problems. Key Points: Convolutional neural network (CNN) skillfully predicts summer consecutive dry days (CDD) over China three months in advanceThe principal components of CDD are predicted by CNN and then projected on the observed spatial patternsPrevious winter 2‐m temperature, geopotential height at 500 hPa and precipitation are the essential predictors in CNN [ABSTRACT FROM AUTHOR]

Drought seriously endangers the development of agro‐pastoral ecotone in arid and semi‐arid regions. However, drought evolution characteristics of semi‐arid sandy grassland and its drivers are not well understood in the complex climate change context. Thus, in this paper, the revised standardized precipitation evaporation indices on one‐month (SPEI‐1) and growing‐season (SPEI‐6) scale, flash drought and dry spells (DS) were calculated as drought indicators, and the temporal variabilities and meteorological drivers of drought in Horqin Sandy Land during the growing period (April–September) from 2007 to 2021 were studied. The results showed that SPEI‐1 and SPEI‐6 exhibited negative trends and periodic change. This drought aggravation was manifested in increased grades and numbers of drought months. Flash droughts can occur every month during the growing season. And its occurrence was not only positively correlated with all drought events in frequency but also synchronized in time. The increased number of DS showed an asymmetrical shift towards 7‐day‐and‐longer DS. SPEI sensitivity to precipitation (P) was noticeably higher than to atmospheric evapotranspiration demand (AED) at both monthly and growing season scales. SPEI sensitivity to AED was modulated by P amounts, which was higher during low P period. Apart from the amounts of P and AED, their temporal variability also strongly determined how they affect the drought severity. P was also the main driver for flash drought and long DS, but AED with larger amount and higher variability is the reason for their aggravation. Our results demonstrate the complexity of drought intensification in semi‐arid sandy grasslands and highlight the important role of AED anomalies in it. [ABSTRACT FROM AUTHOR]

Arid and semiarid areas generally face problems of natural resource degradation. In this paper, two indicators are proposed to characterize the utilization of rainwater: rainwater resource utilization quantity (RRU, mm) and rainwater resource utilization rate (RRUR, dimensionless ratio). A spatiotemporal assessment model (rainwater utilization assessment [RUA] model) for the RRUR and its influencing factors is constructed. The RUA model is based on Soil and Water Assessment Tool and Geographically Temporal Weighted Regression. The Zuli River Basin, located on the Loess Plateau in China, was selected as the study basin. The results show that the annual averages of the RRU and RRUR are 164 mm and 0.44, respectively, in the study basin. The RRU ranged from 71.4 to 243.2 mm, and the RRUR ranged from 0.32 to 0.53 during the evaluation period. Eight explanatory variables were selected, of which the leaf area index (LAI) and rainfall had a significant positive effect on RRUR, but there was spatial and temporal variability in the effects. The forest rehabilitation and crop rotations that can increase the LAI can effectively increase the RRUR, which increased by 0.10 and 0.11, respectively, and the increase in RRU was at least 36.42 mm, with a water volume of 3.85 × 108 m3. The impact of grassland rehabilitation and parallel terracing on the RRUR was small. We found that there is an interval effect and a threshold effect on rainfall utilization in the basin. The interval effect causes the RRUR to fluctuate within a certain range for rainfall intervals of 300–400 or 400–500 mm (Zuli River Basin). Threshold effects can guide the determination of the potential for rainwater utilization in different areas to ensure that the RRUR can be effectively enhanced with management measures. Recommendations for Resource ManagersWe have constructed an assessment model of rainwater resource utilization (RRU) and influencing factors.We have proposed two evaluation indices based on water balance, namely, the RRU quantity and rainwater resource utilization rate (RRUR).The leaf area index of vegetation is the most important influence on rainwater utilization, and the more severe the drought is, the more effective the regulation of water cycle processes by vegetation.The interval effect causes uncertainty in the RRUR for a certain interval of rainfall, with the RRUR fluctuating within a defined range.The threshold effect can guide us in determining the potential for rainwater utilization, and areas where the current RRUR is below the threshold can take management measures to ensure that the RRUR can be effectively increased. [ABSTRACT FROM AUTHOR]

China has lots of funds, materials, and human resources in cloud seeding operations to help with water shortage problems across the country. But there is little guide about when and where the operations would obtain better benefits. To fill this gap, the modified Water Utilization Level (WUL) map of China mainland was plotted with the acquirable water utilization data on sub‐watershed scales in this study. Then the agricultural drought levels map of different counties were integrated with the modified WUL Map under preset rules to generate an integrated water scarcity map. Lastly, the cloud seeding demand maps of different seasons were drawn by integrating the agricultural drought seasons map of different counties with the integrated water scarcity map and the modified WUL map. Results showed that the middle north of China should have the highest priorities for cloud seeding operations during spring and summer, and some regions at the south during winter and spring, a few scattered regions at the northwest during spring and summer and a few regions at the middle of southeast China during summer and autumn should also have high priorities of cloud seeding operations. This research can help rain enhancement operations to obtain better effects on easing water scarcity problems and deepen the cooperation of water resources department and weather modification department in China. The designed intersecting rules of different maps in this paper also might inspire other relevant researches. Key Points: The results gave a clear demand from water resources field to weather modification department in China mainlandThe middle north areas of China have the severest water scarcity problems, especially during spring and summerSome less developed regions at the south, the northwest and the southeast have high water scarcity levels in different seasons [ABSTRACT FROM AUTHOR]

Drought occurs more frequently in the context of climate change and threatens water security worldwide. An appropriate fitting distribution is crucial for accurately identifying drought using drought indices. Here, seven two‐parameter distributions (Gamma, Gumbel, Logistic, Log–Logistic, Log‐normal, Normal, and Weibull) and four distributions (general logistic, generalized extreme value, Normal, and Pearson Type III) are applied to calculate the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI), respectively, to choose the most appropriate fit for the 541 stations in China. The results show that, in most cases, Gamma and general logistic were the best distributions for SPI and SPEI, respectively. Nevertheless, we noted that Pearson Type III and generalized extreme value also fit the SPEI series well, indicating the importance of distribution fitting assessment for various regions. The annual and seasonal drought evolutions across China were clarified, with drought decreasing significantly in western Northwest China (annually and each season), northern North China (spring and winter), the Tibetan Plateau (spring), and the lower reaches of the Yangtze River (winter) and increasing mainly in South China (spring) and western South China (summer and autumn). The intensity, duration and severity of light, moderate, and severe drought were also detected; the results suggest that drought in China is mainly concentrated around the changes in light and moderate drought. Additionally, we assessed the sensitivity of drought evolution to various meteorological variables. The most sensitive variable in South China, North China and the Tibetan Plateau is precipitation, followed by wind speed, temperature, relative humidity, and sunshine duration; in Northwest China, the order is wind speed, precipitation, temperature, relative humidity, and sunshine duration. Furthermore, the correlation results also indicate that the drought evolution is affected by the multivariate ENSO index, while the influencing characteristics are different in various seasons and regions. The results in this paper contribute to drought mitigation and the effective utilization of water resources in China. [ABSTRACT FROM AUTHOR]

Drought is a common natural disaster in arid Central Asia, and the severity and frequency of drought and other hydroclimatic events are critical to the region's ecology and its residents' livelihoods. In particular, water resource management requires reliable knowledge of climatic variability and annual and centennial drought patterns. In this paper, we establish a 587-year tree ring chronology using 215 Schrenk spruce ( Picea schrenkiana Fisch. et Mey) samples and reconstruct a spring Palmer Drought Severity Index ( PDSI) for the inner Tianshan Mountains spanning the 1645-2008 period. The reconstruction explains 40.3% of the variance during the sub-period for which we also have reliable observational data (1938-2005). Cross-validation during this common period also supports our reconstruction model. Spatial correlation analyses with gridded PDSI data show that our PDSI reconstruction reveals a strong regional drought signal for the central and western Tianshan Mountains. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, an objective identification technique for regional extreme events (OITREE) is used to identify regional drought events (RDEs) in southern China based on the daily precipitation dataset of 342 stations from 1961 to 2012. Generally RDEs in southern China occur over an entire year, with high frequencies from January to April and peak frequencies in February and March. The spatial distributions of frequency and intensity of RDEs are consistent, with high frequencies of more than 60 and the annual average number of drought days being more than 30 in most regions of southern China east of 105 ° E. The trend distributions of the frequency and intensity of RDEs in southern China are similar, with increasing trends in most western regions and decreasing trends in most eastern regions. The decreasing trends of RDEs in most eastern regions were mainly affected by the weakening of East Asia summer moonsoon (EASM) from the 1960s to the 1990s, which resulted in the summer main rain belts in eastern China moving from North China to southern China and caused the precipitation increasing in eastern regions of southern China from the 1960s to the 1990s. While the increasing trends of RDEs in most western regions were not only affected by the EASM, but also associated with the weakening of the India-Burma Trough (IBT) that caused less wet air transport to Southwest China and the decrease of precipitation in western regions of southern China. [ABSTRACT FROM AUTHOR]

Meteorological drought, especially when influenced by human activities, significantly impacts agriculture. We assessed the Yangtze River Basin (YRB)'s crop ecosystem resilience during the 2022 southern China drought. Using the elasticity framework, we quantified crop Leaf Area Index (LAI) changes with meteorological factors and human activities (irrigation) in the YRB. Our study covered maize, wheat, early and late‐season rice, evaluating model accuracy with and without irrigation. Results indicate high accuracy (R2 > 0.8, p < 0.05) in simulating LAI changes, notably improved with irrigation. Irrigation emerged as the primary driver of LAI changes in the past two decades, except for solar radiation's impact on maize. In 2022, irrigation crucially influenced LAI changes, particularly in rice varieties. Early‐season rice and late‐season rice saw over 40% contribution from irrigation, while maize and wheat responded mainly to precipitation and radiation. Overall, 2022 yields remained stable, with late‐season rice showing an apparent increase. Drought timing correlated with maize, wheat, and early‐season rice yields, consistent with natural patterns. Conversely, late‐season rice exhibited the opposite pattern due to artificial irrigation, impacting 58% of the growing areas in 2022. The study offers insights into investigating farmland ecosystems responding to extreme droughts. Plain Language Summary: Drought, a natural disaster that has long impacted agriculture, has become more frequent and severe due to global warming. In China, droughts have traditionally affected the northern regions, but recent years have seen an increase in occurrence in the southern regions as well. The Southern Drought of 2022 was considered the worst drought in the Yangtze River Basin (YRB) since 1961. This study investigates the resilience of agricultural systems in the YRB during the severe drought of 2022. It examines the factors influencing crop Leaf Area Index variations and the impact of climate and human activities, such as irrigation. Findings deepen our understanding of drought effects on agriculture and highlight the crucial role of human irrigation interventions. Despite the severe drought, crop yields did not substantially decline, largely due to human interventions increasing late‐season rice yields. These findings have significant implications for sustainable agriculture. Key Points: Climate and irrigation both significantly impact crop Leaf Area Index (LAI) variations in the Yangtze River Basin (YRB), with irrigation being a major contributorIrrigation dominants and enhances agricultural resilience in the 2022 extreme drought in YRBOver 50% LAI change of rice driven primarily by irrigation, while maize and wheat are by precipitation and radiation respectively in 2022 [ABSTRACT FROM AUTHOR]

Many agricultural regions in China are likely to become appreciably wetter or drier as the global climate warming increases. However, the impact of these climate change patterns on the intensity of soil greenhouse gas (GHG) emissions (GHGI, GHG emissions per unit of crop yield) has not yet been rigorously assessed. By integrating an improved agricultural ecosystem model and a meta‐analysis of multiple field studies, we found that climate change is expected to cause a 20.0% crop yield loss, while stimulating soil GHG emissions by 12.2% between 2061 and 2090 in China's agricultural regions. A wetter‐warmer (WW) climate would adversely impact crop yield on an equal basis and lead to a 1.8‐fold‐ increase in GHG emissions relative to those in a drier‐warmer (DW) climate. Without water limitation/excess, extreme heat (an increase of more than 1.5°C in average temperature) during the growing season would amplify 15.7% more yield while simultaneously elevating GHG emissions by 42.5% compared to an increase of below 1.5°C. However, when coupled with extreme drought, it would aggravate crop yield loss by 61.8% without reducing the corresponding GHG emissions. Furthermore, the emission intensity in an extreme WW climate would increase by 22.6% compared to an extreme DW climate. Under this intense WW climate, the use of nitrogen fertilizer would lead to a 37.9% increase in soil GHG emissions without necessarily gaining a corresponding yield advantage compared to a DW climate. These findings suggest that the threat of a wetter‐warmer world to efforts to reduce GHG emissions intensity may be as great as or even greater than that of a drier‐warmer world. Plain Language Summary: Both climate observations and projections suggest that warmer temperatures will intensify convective precipitation, resulting in drier regions becoming drier and wetter regions becoming wetter. By integrating an improved agricultural ecosystem model and a meta‐analysis of multiple field studies, this study has investigated the effects of drier‐warmer (DW) and wetter‐warmer (WW) climates on crop yield and soil greenhouse gas emissions in China. Our findings indicate that the cost of greenhouse gas emissions in a wetter‐warmer world for crop production could be as high as or even higher than in a drier‐warmer world. Moreover, this study suggests that effective climate mitigation practices need to account for the combined effects of extreme climate changes and nitrogen addition on greenhouse gas emissions and crop production. Therefore, China would need to exert considerably more effort in a future with warmer and wetter conditions to achieve its greenhouse gas emission reduction targets. Key Points: Climate change would cause a 20% crop yield loss and an increase of 12.2% in soil greenhouse gas (GHG) emissions between 2061 and 2090A Wetter‐Warmer climate would cause a more significant crop yield loss and about double the GHG emissions of a Drier‐Warmer climateNitrogen fertilizer‐induced GHG emissions in a Wetter‐Warmer climate would increase 37.9% compared to those in a Drier‐Warmer climate [ABSTRACT FROM AUTHOR]

Background: Under the background of global warming, the intensity and frequency of extreme meteorological events in the maize growing season in northeast China are increasing. In order to clarify the occurrence characteristics of extreme meteorological events in northeast China, this study focused on three extreme agrometeorological events, i.e., high temperatures, drought, and the compound events of high‐temperature and drought during the maize growing season (May–September), impacting maize production. Results: Based on historical (1981–2017) and future (2021–2060) climate data, we analyzed the spatial‐temporal patterns of these three events with different intensities in northeast China. The results indicated that slight high‐temperatures and moderate and severe droughts occurred more frequently in the study area during the historical period. The frequency of the different grades of the compound events of high‐temperature and drought will exhibit an increasing trend in the future, as will the frequency of the compound events of high‐temperature and drought. This is particularly evident in the northwest of the study area. Conclusion: The compound events of high‐temperature and drought mainly occurred in late July and early August, encompassing the flowering stage of maize varieties. It is important to identify the area and time of major extreme weather events to implement the necessary preventive measures. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The three principal fates of axillary meristem in flowering plants are growth (G), reproduction (R), and inactivity (I). The allocation relationships between each meristem and plant size in annual herbaceous plants tend to change with altered precipitation (P) patterns in arid and semiarid grasslands. Here, we examined the allometry and plasticity of meristem allocation in three dominant annual herbaceous plants: Setaria viridis, Corispermum macrocarpum, and Bassia dasyphylla in a semiarid sandy grassland in northern China. We determined the range of plant sizes for each of the three species in the following treatments: ambient environment (Amb), P increased by 30% (P[+]) and by 60% (P[++]), P decreased by 30% (P[−]) and by 60% (P[− −]), drought for 46 days from May 1st to June 15th (D1) and from July 1st to August 15th (D2). We found that meristem allocation to branching intensity increased while allocation to apical dominance decreased with increasing plant size under decreased precipitation and seasonal drought. Decreased precipitation and seasonal drought caused the slope of allometry of meristem allocation in the three species to be significantly different from 1. Plasticity of meristem allocation to G, R, and I in S. viridis tended to be significantly greater in August under P(+) and P(++) while in C. macrocarpum tended to be greater in July under P(−), P(− −), D1, and D2. Our findings are important components of an adaptive strategy in annual herbaceous plants throughout the development stage, which will contribute to predict their developmental dynamics in the semiarid sandy grassland under future climate change. [ABSTRACT FROM AUTHOR]

Asexual reproduction plays a fundamental role in the structure, dynamics and persistence of perennial grasslands. Thus, assessing how asexual reproductive traits of plant communities respond to drought may be key for understanding grassland resistance to drought and recovery following drought.Here, we quantified three asexual reproductive traits (i.e. above‐ground tiller abundance, below‐ground bud abundance and the ratio of tillers to buds) during a 4‐year severe drought and a 2‐year drought recovery period in four grasslands that spanned an aridity gradient in northern China. We also assessed the relationship between these traits and the resistance and recovery of above‐ground net primary productivity (ANPP).We found that drought had limited and largely inconsistent effects on asexual reproduction among drought and recovery years and grasslands overall. Drought increased tiller abundance in the first treatment year and reduced bud banks by the fourth treatment year across grasslands. However, neither of the three asexual reproductive traits were correlated with drought resistance of ANPP. Drought legacies differed among the four grasslands with positive, negative and no legacies evident for the three asexual reproductive traits, and no clear relationship with aridity. Bud banks and tiller to bud ratio decreased and increased, respectively, in the first recovery year, but not in the second recovery year. In contrast to drought resistance, community bud abundance was strongly related to recovery, such that communities with higher bud abundance had greater ANPP recovery following drought.Synthesis. These results suggest that asexual reproductive traits may be important drivers of ecosystem recovery after drought, but that variable responses of these asexual reproduction traits during drought complicates predictions of overall grassland responses. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the patterns of drought and flood alternation in adjacent months is essential for enabling climate adaptation and mitigation strategies. However, there is a paucity of knowledge regarding short‐cycle drought–flood abrupt alteration (s‐DFAA) and its responses to multiple environmental factors at various timescales. This is because of the inadequate formula construction of the existing short‐cycle drought–flood abrupt alteration index (SDFAI), such as the inability to introduce drought standards. To accurately capture the s‐DFAA's characteristics in the Qinling‐Daba Mountains (Qinba Mountains), we proposed a revised SDFAI (R‐SDFAI), which incorporates the standardized precipitation index (SPI) and allows for the customization of drought standards. Next, we used wavelet transform coherence and multiple wavelet coherence to investigate the timescale relationships between s‐DFAA events and their influence factors such as relative humidity, sunshine duration, temperature, evaporation, Arctic Oscillation (AO), Niño3.4 SSTA Index (Niño3.4), Total Sunspot Number Index (TSNI) and Pacific Decadal Oscillation Index (PDO). Our results showed that the R‐SDFAI outperformed traditional SDFAI in capturing s‐DFAA events and characterizing their severity. Furthermore, s‐DFAA events identified by R‐SDFAI at different levels (i.e., mild, moderate, severe, extreme and total) displayed insignificant downward trends. Spatially, there were more s‐DFAA events in the east than the west. Wavelet analysis indicated that meteorological factors and teleconnections significantly impact s‐DFAA events at large timescales, though their driving mechanisms differed substantially. Among meteorological factors, single relative humidity and its related combinations exhibited relatively high percent area of significant coherence (PASC, ranging from 17.47 to 29.46). Each teleconnection and its combinations are irreplaceable, with PASC values always increasing with the number of variables. The PASC ranges from 8.3 to 10.29 for one factor, 12.38 to 18.65 for two factors, 24.02 to 30.58 for three factors and 40.88 for four factors, respectively. [ABSTRACT FROM AUTHOR]

The stable oxygen isotope composition of precipitation (δ18Op) in southern China is considered as a valuable proxy of climatic conditions. However, their interpretations have been controversial. In this study, based on the observed and simulated data (isoGSM2) on oxygen isotope composition of precipitation, the linkage between summer precipitation (P) and δ18Op in the Dongting Lake basin and their possible influencing factors were investigated. The results indicate that the interannual variation of summer δ18Op is consistent with that of annual δ18Op. They both show a significantly negative correlation with the summer P, suggesting that the stable isotope composition in precipitation may be considered as a proxy of summer precipitation in the Dongting Lake basin. Statistically, the amount effect and circulation effect are significant in the isotope composition of precipitation in the basin. Based on either the observed data in Changsha or the simulated data for the basin, the local amount effect appears more important than large‐scale circulation for δ18Op during extreme summers. These results can potentially improve the reconstruction of paleoclimate in the East Asian monsoon region. Further study is needed to determine the contribution of local and large‐scale factors to the oxygen isotope composition of precipitation and to quantify the integral rainout along the moisture transporting paths. [ABSTRACT FROM AUTHOR]

Restoration of natural secondary forests and afforestation of introduced tree species are major effective measures for revegetation. The semiarid Loess Plateau region, characterised by fragile ecosystems and severe soil erosion, is a key area for ecological restoration and protection in China. To illustrate water use characteristics and adaptation to drought in the main forests in this area, we monitored the xylem sap flow of two typical adjacent forest communities with similar climatic characters, a secondary natural forest dominated by oak (Quercus liaotungensis) and a pure plantation of black locust (Robinia pseudoacacia), during 2011–2019 using Granier‐type thermal dissipation probes. Solar radiation (RS), air temperature, relative humidity (RH), precipitation and soil water content (SWC) were measured simultaneously. Throughout the whole study period, the mean diameter at breast height (DBH) and total sapwood area increased by 4.5 cm and 1.10 m2 ha−1, respectively in the oak forest and by 1.0 cm and 0.22 m2 ha−1, respectively in the black locust plantation. The monthly stand transpiration was jointly determined by phenological and meteorological factors. At the annual timescale, transpiration of the oak stand was significantly correlated with potential reference evapotranspiration (ET0) and rainfall in the previous year, whereas a significant positive relationship was detected between stand transpiration and SWC in the black locust stand. The analyses of differences between dry and wet years showed that the oak forest exhibited significantly different parameters in the regression analysis of stand transpiration to vapour pressure deficit (VPD), whereas only one parameter was clearly distinct in the black locust plantation, suggesting that its transpiration status did not fully recover even in wet years. The management of black locust plantations with weakened growth conditions should be adjusted under prolonged drought conditions. In contrast, oak forest can maintain the water balance and stable growth by efficiently controlling stomatal behaviour. [ABSTRACT FROM AUTHOR]

Grasslands are expected to experience droughts of unprecedented frequency and magnitude in the future. Characterizing grassland responses and recovery from drought is therefore critical to predict the vulnerability of grassland ecosystems to climate change. Most previous studies have focused on ecosystem responses during drought while investigations of post‐drought recovery are rare. Few studies have used functional traits, and in particular bud or clonal traits, to explore the mechanisms underlying grassland responses to and recovery from drought.To address this issue, we experimentally imposed a four‐year drought in a C3‐dominated grassland in northeastern China and monitored recovery for 3 years post‐drought. We investigated the immediate and legacy effects of drought on total above‐ground net primary productivity (ANPP), ANPP of functional groups (rhizomatous grasses, bunch grasses and forbs), and how the legacy effects were driven by plant species diversity, clonal traits and vegetative traits.We found that drought progressively reduced total ANPP over the 4‐year period. The reductions in total ANPP in the first and third drought years were caused by the decrease in ANPP of bunch grasses only, while that of the second year was caused by declines in ANPP of bunch grasses and forbs, and the fourth year decline was linked to all three functional groups. The post‐drought recovery of ANPP, which occurred despite the continued loss of plant species diversity, was mainly driven by rapid recovery of rhizomatous and bunch grasses, which compensated for the slow response by forbs. The rapid post‐drought recovery of these grasses can be attributed to their relatively large, intact bud and shoot densities post‐drought, as well as the recovery of plant height and specific leaf area. The rapid recovery of grasses possibly restricted the growth and distribution of forbs, resulting in reduced forb ANPP and, consequently, lower species diversity during the recovery period.Synthesis. These results highlight the potential for positive legacy effects of drought on ANPP as well as the important and complementary roles of plant reproductive and vegetative traits in mediating ecosystem recovery from drought in a C3‐dominated grassland. [ABSTRACT FROM AUTHOR]

Questions: Interannual precipitation changes, both in amount and frequency, are expected to increase due to climate change, and these changes could dramatically affect the structure and function of ecosystems. However, how plant life‐forms and dominant species regulate the plant community structure after precipitation changes remains unclear. Location: Gaolan Experiment Station for Ecology and Agriculture Research of the Northwest Eco‐Environment and Resources Research Institute of the Chinese Academy of Sciences, located in the desert grassland of the western Loess Plateau, China. Methods: To investigate the effect of precipitation changes on the growth of communities, life‐forms, and species, we used rain shelters and irrigation to create a variety of precipitation gradients (i.e., −40%, −20%, 0% [= CK, i.e., control treatment], +20%, +40% of ambient precipitation) in desert grasslands from 2014 to 2015. Results: The plant community density, coverage, and height were significantly decreased in the −40% treatment compared to CK. In contrast, species richness, Shannon–Wiener index, and Pielous' evenness did not respond significantly to the precipitation treatment. In addition, at the level of life‐forms, the density of perennial herbaceous plants was significantly increased by the +40% treatment in 2015, while the richness and density of annual herb were significantly inhibited by extreme drought. The effect on the shrub growth index of increasing and decreasing precipitation compared to the CK was insignificant. Furthermore, at the level of species, the growth of dominant species was obviously suppressed by the −40% and +40% treatment in 2015. However, the positive effect of the +40% treatment on the growth of rare species reached significant levels in 2015. Also, the change in precipitation did not have a significant effect on the growth of companion species. Dominant species primarily drove the response of community‐level plant growth to precipitation changes over the three‐year study period. Conclusion: The response of plant community composition to changes in precipitation in desert grassland is largely regulated by changes in the composition of the dominant species. This finding could also provide a better prediction of the effects of extreme drought on desert grassland plant communities in the scenarios of future global climate change. [ABSTRACT FROM AUTHOR]

The simultaneous occurrence of droughts and floods in neighboring regions amplifies the threats posed by droughts and floods individually. Nonetheless, few studies have been conducted to investigate the simultaneous occurrence of drought and flood events. Here we explore the spatiotemporal characteristics and the shift pattern of droughts and pluvials over Eastern China from a three‐dimensional perspective, using the self‐calibrated Palmer Drought Severity Index and the Climate Research Unit data set as well as four regional climate model simulations. We find that Eastern China experienced droughts and pluvials simultaneously in different locations during boreal summer, and it is projected to simultaneously experience more frequent and more intense droughts and pluvials under a warming climate. Specifically, we investigate the pattern of more pluvials in Southeast China and more droughts in Northeast China for the historical period of 1975–2004. This pattern dynamically evolves under climate warming: the pluvial‐dominated regime shifts from Southeast to Northeast China, while the drought‐dominated regime shifts from Northeast to Southeast China. The weakening strength of the western Pacific subtropical high and a northward displacement of the monsoon rain belt may both contribute to the pattern of more pluvials in Northeast China and more droughts in Southeast China. These findings provide insights into the development of adaptation strategies and emergency response plans for enhancing society's resilience to the spatial co‐occurrence of dry and wet extremes. Plain Language Summary: The spatial co‐occurrence of drought and flood events has been receiving widespread attention in recent years since the superimposed condition of drought and flood has brought unprecedented challenges to disaster prevention, mitigation, and relief work. Eastern China is prone to droughts and floods, but their spatial interconnections are not yet well understood. Thus, we explore the historical evolution and the future change of simultaneous occurrence of droughts and floods over Eastern China under a warming climate. The spatial co‐occurrence of droughts and floods is projected to affect more land areas and become more frequent as climate warms. Eastern China experienced a pattern of more floods in Southeast China and more droughts in Northeast China during 1975–2004. We find that droughts tend to become more intense in Southeast China and the severity of floods is expected to increase in the northern region of East China, resulting in a shift pattern of more droughts in Southeast China and more floods in Northeast China. The shift pattern may be attributed to the weakening of western Pacific subtropical high strength and a northward displacement of the monsoon rain band in a changing climate. Key Points: Eastern China is projected to experience more frequent and more intense droughts and pluvials simultaneouslyThe spatial pattern of more pluvials in Southeast China and more droughts in Northeast China is expected to become an opposite pattern under a warming climateThe weakening strength of the western Pacific subtropical high and a northward displacement of the monsoon rain belt may contribute to the pattern of more pluvials in Northeast China and more droughts in Southeast China [ABSTRACT FROM AUTHOR]

Drought is one of the most serious natural disasters exacerbated by climate change. Changes in precipitation and temperature in the future increase the likelihood of drought in China. In this study, a stepwise cluster ensemble downscaling (SCED) model was developed to bias‐correct projections of temperature and precipitation from multiple RCM outputs, and further characterized the drought hazards. The developed SCED model was used to aggregate and correct the results of multiple regional climate models, and its performance was proved to be reliable by comparing with the observed results. The proposed SCED method has been applied for drought projections over the Fujian province, China. The results showed that the changes of precipitation and temperature in Fujian would have obvious spatial heterogeneous characteristics. The temperature in the southeast coastal areas will increase by up to 4°C and the precipitation will decrease by 3.1% in the late 21st century, while the temperature rises and precipitation increases in the southwest. Temperature in inland areas will be lower and precipitation will be less. The drought hazards were also characterized by both SPI and SPEI based on biased‐corrected projections from SCED model. According to the SPI and SPEI indices, although the number of dry months in Fujian province will not change significantly in future, the spatial and temporal heterogeneity may become more explicit. Moreover, the moderate drought (from SPI) may increase while the general drought may decrease (from both SPI and SPEI). For extreme droughts, there would not be visible changes detected by SPI, but an increasing trend characterized since the impact of temperature was included in SPEI. In addition, there would be an increasing trend on drought when increasing temperature and precipitation occurred simultaneously. [ABSTRACT FROM AUTHOR]

Climate warming is steadily increasing drought risk in many regions of the world. However, the contribution of warming over the past few decades to drought evolution in China remains unclear. This study used the self‐calibrating Palmer drought severity index (sc‐PDSI) and a detrending experiment to quantify the contribution of warming to severe drought (sc‐PDSI < −3.0) characteristics (intensity, frequency, and duration) over China from 1980 to 2019. Differences in drought characteristics calculated from original and detrended temperature data were attributed to warming effects. The results showed that 93.8% of areas in China have experienced a significant (p <.05) warming trend from 1980 to 2019. Warming remarkably intensified severe drought characteristics across China. Without warming, the extent, frequency, and duration of severe droughts in China would reduce by 2.04%, 2.0%, and 0.82 months. In addition, there are apparent regional differences in the response of severe drought characteristics to warming. Severe drought characteristics in high elevations and high latitudes are more sensitive to warming than in other regions. [ABSTRACT FROM AUTHOR]

The Tarim River, the largest inland river in China, sits in the Tarim River Basin (TRB), which is an arid area with the ecosystem primarily sustained by water from melting snow and glaciers in the headstream area. To evaluate the pressures of natural disasters in this climate‐change‐sensitive basin, this study projected flash droughts in the headstream area of the TRB. We used the variable infiltration capacity (VIC) model to describe the hydrological processes of the study area, Markov chain Monte Carlo to quantify the parameter uncertainty of the VIC model. Ten downscaled general circulation models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) were used to drive the VIC model, and the standardized evaporative stress ratio was applied to identify flash droughts. The results demonstrated that the VIC model after Bayesian parameters uncertainty analysis can efficiently describe the hydrological processes of the study area. In the future (2021–2100), compared with the plain region, the alpine region has higher flash drought frequency and intensity. Compared with the historical period (1961–2014), the frequency, duration, and intensity of flash droughts tend to increase throughout the study area, especially for the alpine area. Moreover, based on variance decomposition, CMIP6 model is the most important uncertainty source for flash drought projection, followed by the shared socioeconomic pathway of climate change scenario and VIC model parameters. Plain Language Summary: The Tarim River is the largest inland river in China, which is an arid area with the ecosystem primarily sustained by water from melting snow and glaciers in the headstream area. Compared with long‐duration drought, flash drought is more difficult to forecast and identify. We used the variable infiltration capacity model to build a hydrological model of the headstream area of the Tarim River Basin, and the model output (ET data) was used to identify flash droughts. Based on 10 representative Coupled Model Intercomparison Project Phase 6 (CMIP6) models, this study projected the future flash droughts in the study area under climate change. The findings indicated that the alpine region is likely to experience a greater frequency and intensity of flash droughts in the future (2021–2100) compared to the plain region. Compared with the historical period (1961–2014), the frequency, duration, and intensity of flash droughts tend to increase throughout the study area, especially for the alpine area. In addition, the result of uncertainty decomposition revealed that the CMIP6 model is the most important uncertainty source for flash drought projection. Key Points: The hydrological processes of study area are well described by the variable infiltration capacity model and Bayesian uncertainty analysisCompared with the plain region, the alpine region has higher flash drought frequency and intensity in the futureThe Coupled Model Intercomparison Project Phase 6 model is the most important uncertainty source for flash drought projection [ABSTRACT FROM AUTHOR]

Understanding and exploring hydrological (H) or soil moisture (SM) drought due to meteorological (M) drought under changing climate is crucial for drought early warning. Previously, different methods were used to calculate drought propagation from one state (M to another [H or SM]). However, each method has its pros and cons and thus cannot describe appropriate propagation attributes. In this study, a time series analysis is carried out to explore the propagation process in the Yellow River Basin (YRB) and Hai River Basin (HRB) of China. Standardized Streamflow Index (SSI), Standardized SM Index (SSMI), and Standardized Precipitation Index (SPI) 1‐month time series were calculated using streamflow, satellite‐based SM, and precipitation from 1979 to 2016. The time series framework identifies the average drought propagation as 3.4–8.3 months (M–H) and 2.3–5 months (M–SM) in YRB, while 2.8–7.7 months (M–H) and 2.3–8.5 months (M–SM) in HRB. Cross‐wavelet analysis indicated that periodic characteristics of M drought are responsible for these droughts. Overall, the findings of this study may help to minimize the drought hazards posed by M droughts. [ABSTRACT FROM AUTHOR]

Based on the standardized precipitation evaporation index and reanalysis data, this article reveals that the relationship between the North Pacific Oscillation (NPO) and the drought over southern China in summer shifts from an insignificant correlation to a significant negative correlation after 2000. During the significant period (2001–2018), the positive NPO phase corresponds to an anomalous anticyclonic circulation dominating the mid‐low latitude North Pacific, which suppresses the moisture transport into southern China. Meanwhile, the easterly anomalies south of the anomalous anticyclonic circulation prevailing in the equatorial Pacific are coupled with a cooling of sea surface temperature in the central tropical Pacific, which enhances the Walker circulation and further induces an anomalous meridional circulation with the descending anomalies over southern China. Such moisture and dynamical conditions favor the occurrence of drought in southern China. During the former period (1983–2000), however, the NPO‐related atmospheric circulations over the North Pacific shift northward. In this case, the NPO shows insignificant relations with the moisture and dynamical conditions over southern China, thereby diluting the linkage of the NPO to the drought in southern China. The interdecadal strengthening in the relationship between the NPO and above atmospheric conditions is attributed to the westward (southward) extension of the NPO northern (southern) center. The larger interannual variability of spring sea ice in the Bering Sea and the southward movement of summer storm track over the North Pacific are hypothesized to account for the expansion of the NPO structure. Plain Language Summary: Southern China is an economically developed region with a large population. In recent decades, droughts frequently occurred in this region and severely affected agriculture production, forest‐fire prevention, and human lives. Therefore, it is very necessary to understand the physical mechanisms underlying the variability of droughts in southern China. In this study, we addressed the relationship of summer drought in southern China with the North Pacific Oscillation (NPO), which is characterized by the north–south seesaw pattern in sea level pressure over the North Pacific. We revealed that their relationship exhibits an interdecadal change around 2000, from an insignificant correlation to a significant negative correlation. Such an interdecadal strengthening is due to the expansion of the NPO structure, which may result from the changes of the spring sea ice in the Bering Sea and the summer storm track over the North Pacific. These findings are expected to deepen our understanding for the variation of drought in southern China and are also important for disaster prevention and mitigation. Key Points: Relationship between the summer drought in southern China and the North Pacific Oscillation (NPO) has strengthened after 2000Such a strengthening is attributed to the westward (southward) extension of the NPO northern (southern) centerThe expansion of the NPO structure is related to changes of spring sea ice in the Bering Sea and summer storm track over the North Pacific [ABSTRACT FROM AUTHOR]

Pressure on river water resources may increase continuously under global climate change and the increasing intensity of human activity, and the identification of river water sources is needed to maintain water resource sustainability. In this study, river water sources were studied using hydrochemical tracers (i.e. the major ions) and end‐member mixing analysis (EMMA) during two hydrological years, in the subtropical monsoon basin of the Xiangjiang River in the south‐central China. Various water types including precipitation, river water, and mountain creek water, were collected in the basin at a high frequency. The results of EMMA showed that the average contributions from the direct input of precipitation, near‐surface runoff (represented by mountain creek water), and groundwater (represented by river water sampled during the base flow period) were 28 ± 24%, 49 ± 24% and 23 ± 16%, respectively. The contributions from these water sources to the river water varied greatly within the year, which may indicate a shift in the major flow pathways from direct precipitation input and near‐surface flow pathways in the spring rainy months (e.g. from March to May), to a deeper flow pathway in the dry or rainless months (e.g. January, February, July and December). The shift of the major flow pathways may be due to the factors such as the seasonality of precipitation, evapotranspiration and soil wetness conditions. Groundwater and near‐subsurface runoff dominated the river water and the direct input of precipitation was negligible during the dry or rainless months, and consequently, the river water chemistry was less diluted and more influenced by water‐soil/rock interactions and anthropogenic pollution during these months. The creek water contribution to the river water was relatively high in summer, especially in June and July 2021, which may indicate the substantial inter‐seasonal carryover of precipitation that contributed to the river water. With the projected increased frequency of extreme weather events such as seasonal drought, streamflow in the subtropical monsoon regions may experience greater recharge by deeper flow pathways, with the enhanced role of base flow in regulating streamflow, and there may be an increased risk to the water resource security under the condition of the decreased river dilution capacity and increased anthropogenic pollution. [ABSTRACT FROM AUTHOR]

Crop production security is an essential guarantee for the prosperity of country and the well‐being of people. In the context of frequent occurrence of extreme weather events, how to comprehensively evaluate the risk of multiple hazards and quantitatively describe spatial differences will be one of the significant topics in agricultural disaster mitigation. In this study, based on the gridded meteorological data and other datasets (crop, socioeconomic, disaster loss, and actual planting location) from 2000 to 2020, multihazard risk model for different growth period was built to assess the comprehensive risk of winter wheat in the upper Huaihe River basin (UHRB), China. The conclusions were as follows: (a) The spatial distribution of continuous rain risk increased gradually from north to south; the area of the highest lodging risk was located in the east; the spatial trend of drought risk was the highest in the south and the lowest in the northeast. (b) The weights of continuous rain, lodging, and drought disasters were 41, 31, and 28%, respectively, which indicated that winter wheat in UHRB was most affected by continuous rain during the harvest period. (c) The spatial distribution of comprehensive disaster risk assessment showed that the higher risk areas were located in the central and southern parts (Huaibin, Linquan, Luoshan). After verification by historical disasters information, the results are credible, providing a concrete scientific basis for implementing regional agricultural disaster response measures. [ABSTRACT FROM AUTHOR]

Dry/wet conditions are one of the key constituents of climate change. The understanding of dry/wet variability is vital for production and water resources management. In this research, the temporal variations of 12‐month timescale standardized precipitation evapotranspiration (SPEI) over 2021–2100 under the SSP1‐2.6, SSP2‐4.5, SSP3‐7.0 and SSP5‐8.5 scenarios in seven subregions and China's mainland were investigated over the baseline period of 1961–2000. The run theory was used to project the variations of dry/wet frequency, duration and severity at different levels during 1961–2000, 2021–2060 and 2061–2100 based on the estimated SPEI. The results showed that dry tendency would occur in northwest China. The linear trend for SSP1‐2.6, SSP2‐4.5, SSP3‐7.0 and SSP5‐8.5 were −0.056, −0.031, 0.009 and −0.072 per decade, respectively. While wet tendency would occur in the other regions over 2021–2100. The mild, moderate and severe dry/wet duration and severity over 2021–2060 and 2061–2100 would gradually decrease. Except for northwest China and Qinghai‐Tibetan Plateau, the extreme drought duration and severity would increase in the other subregions, while the extreme wet duration and severity would increase in most regions of China. The drought frequency in north China would range from 0 to 14 times and be smaller than the other regions over 2021–2060 and 2060–2100. However, the wet frequency in south China would be larger than that in the other regions. The dry/wet frequency duration and severity for the SSP5‐8.5 scenario would be the largest among the four scenarios. The projected dry/wet conditions can provide useful information for future water resources management. [ABSTRACT FROM AUTHOR]

Compound dry and hot events or extremes (CDHEs) may cause more severe impacts on natural and human systems than individual extremes and have received increasing attention in recent years. Previous studies on variations of CDHEs in China mainly focused on individual characteristics based on single drought indicators, which falls short in characterizing the variability of CDHEs. This study assesses changes in multiple characteristics of CDHEs (i.e., frequency, duration, severity, magnitude, and timing) in China during summer from 1960 to 2017 based on different drought indicators, including Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), and Standardized Precipitation Evapotranspiration Index (SPEI). Results show that CDHEs become more frequent, longer, severer, stronger, and earlier in most parts of mainland China. Specifically, the frequency, duration, and severity of CDHEs show significant increases in the area from northeastern to southwestern China, whereas certain decreases are found in eastern China, central China, and parts of northwestern China. Changes in characteristics of CDHEs with various drought indicators differ to some extent, especially in arid regions. Furthermore, the spatiotemporal changes in precipitation, temperature, wind speed, relative humidity, and sunshine duration are employed to explain changes in CDHEs. Our findings could be useful for assessing the changes in CDHEs to cope with climate extremes under global warming. [ABSTRACT FROM AUTHOR]

Drought can develop rapidly over a short period, the so‐called "flash drought". The widely used standardized precipitation evapotranspiration index (SPEI), with traditional time scales longer than 1 month, cannot easily capture flash drought signals. Here, the SPEI with a 5‐day (pentad) time scale was proposed to investigate flash droughts in China from 1980 to 2017. New criteria for flash droughts based on the high‐resolution index were also developed. Flash droughts were stronger and longer in western and northern China. The intensity and duration of mild, moderate, and severe flash droughts increased during the study period, while severe flash droughts showed the largest increase. The high‐resolution SPEI permits us to examine the process of a drought event, that is, how a mild flash drought develops into a severe flash drought. The contribution of precipitation deficit to the duration of mild flash droughts was 50%. As the intensity of flash droughts increased, the contribution of high temperature and increased net radiation to flash drought duration increased from 50% (mild flash droughts) to 74% (severe flash droughts). When flash droughts occurred, Northwestern China and Southwestern China were dominated by unusually weak water vapor transport, while Northeastern China, Northern China, Southern China ,and Middle‐Lower Yangtze were mainly dominated by abnormal downward motion. The downward motion was generally accompanied by clear sky conditions with fewer clouds, higher air temperature, and higher surface solar radiation, which accelerated and amplified flash droughts triggered by initial precipitation deficits. Plain Language Summary: In recent years, a rapidly developing drought has attracted widespread attention, and it is known as the "flash drought". However, existing drought indices do not capture the signals of flash drought event life cycles. In this study, the existing drought index (SPEI) was upgraded to a higher temporal resolution to explore the spatial distribution and temporal changes in flash droughts in China. The results showed that the flash drought was intense and long‐lasting in western and northern China. In the past 38 yr, flash droughts have become more intense and more difficult to recover from, especially severe flash droughts. As the intensity of flash droughts increased, the impact of precipitation decreased, while temperature and net radiation gradually played leading roles. Flash droughts in Northwestern China and Southwestern China were mainly related to weak water vapor transport, while they were affected by strong downward motion in Northeastern China, Northern China, Southern China, and Middle‐Lower Yangtze. The downward motion was generally accompanied by clear sky conditions with fewer clouds, higher air temperature, and higher surface solar radiation, which accelerated and amplified flash droughts triggered by initial precipitation deficits. Key Points: A high temporal resolution drought index and new criteria were developed to identify flash droughts over ChinaThe intensity and duration of the flash drought increased significantly from 1980 to 2017 over China, especially the severe flash droughtThe precipitation deficit initiated a mild flash drought, and interactions with air temperature and net radiation amplified the drought intensity [ABSTRACT FROM AUTHOR]

Global climate change is projected to increase the probability of occurrence and severity of droughts. Increased CO2 concentration drives partial closure of plant stomata and reduces evapotranspiration. However, the impact of reduced evapotranspiration due to CO2 on future droughts characteristics in China is unclear. In this study, we have used the Coupled Model Intercomparison Project Phase 6 (CMIP6) global climate model simulations (GCMs) under historical period, and four shared socioeconomic pathway scenarios (SSP1‐2.6, SSP2‐4.5, SSP3‐7.0, and SSP5‐8.5) to estimate drought. We used a widely applicable drought index (i.e., the self‐calibrating Palmer Drought Severity Index [scPDSI]) to evaluate the historical and future drought conditions, using the Penman–Monteith formula with and without the CO2 concentrations. The results show that the increasing trend of scPDSI slows down when the CO2 effect is considered in all scenarios, especially in Heilongjiang, northern Xinjiang, and the Qinghai–Tibet Plateau. The divergence in the slowdown trend among the different scenarios becomes greater after 2030, with higher emission scenarios implying a greater slowdown in the increasing trend of scPDSI. After considering CO2, drought characteristics such as the drought frequency, intensity, and drought area decrease. Increased CO2 concentration on vegetation physiological processes could mitigate future drought. Therefore, the effects of CO2 on plant physiology should be considered in studies of future drought trends to develop more realistic response and adaptation policies to future drought changes. [ABSTRACT FROM AUTHOR]

Accurate prediction of spring drought in China is helpful toward reducing associated agricultural losses. In this study, spring drought is defined as the three‐month Standardized Precipitation Evapotranspiration Index (SPEI) ending in May. Based on the year‐to‐year increment and downscaling method, three single‐predictor prediction models (P1 model, P2 model, and P3 model) and two multi‐predictor models for spring drought at 677 stations in China are developed for the period 1983–2020. As physical processes affecting spring drought in the China region, the tropical Pacific–Indian Ocean sea surface temperature (SST) in winter, the Davis Strait–Barents sea‐ice concentration (SIC) in winter, and the 500‐hPa spring vertical velocity, predicted by the Climate Forecast System, version 2 (CFSv2), are considered in the prediction models. The prediction skill of the downscaling models for the spring SPEI is measured by cross‐validation for the period 1983–2020. The CFSv2 model only shows convincing prediction skill for the spring SPEI at 35 of 677 stations. However, among the 677 stations, the temporal correlation coefficient between the observed and predicted spring SPEI at 621 stations for P1 model, 598 stations for P2 model, 545 stations for P3 model, 674 stations for the statistical downscaling model (SD model), and 675 stations for the hybrid downscaling dynamical–statistical prediction model (HD model) exceeds the 95% confidence level. Therefore, compared to the CFSv2 model, the prediction skill for spring drought is improved by the single‐predictor and multi‐predictor models. The prediction skill of HD model for spring drought, which combines preceding observational predictors and the simultaneous predictor of the CFSv2 model, is higher than that of SD model. In addition, the severe drought that occurred in Northeast and North China in spring 2017 can be successfully predicted by HD model. [ABSTRACT FROM AUTHOR]

Questions: Drought timing during the growing season can profoundly influence plant diversity and cover, with subsequent impacts on ecosystem functions and services in terrestrial environments. However, the different responses of plant communities to drought in different periods of the growing season remain uncertain. Location: The research was conducted in a semi‐arid grassland at the Duolun Restoration Ecology Research and Demonstration Station, in Inner Mongolia, China. Methods: The responses of plant species richness and cover to early‐ and late‐season drought with a four‐year field experiment were examined in a semi‐arid grassland in northern China. Soil moisture at different depths was measured to explore the underlying mechanisms of the drought effects on plant richness and cover. Results: Over the four years, late‐ rather than early‐season drought suppressed plant richness. Decreased species richness (−1.65 species) under late‐season drought was mainly due to suppressed perennial forb richness (−1.88 species). Late‐season drought also exerted greater negative effects on plant cover than early‐season drought. Effects of late‐season drought on plant cover depended on annual precipitation. Reduced plant cover (−7.5%) under early‐season drought stemmed from declines in shrubs and semi‐shrubs, particularly Artemisia frigida cover (−4.9%), which is sensitive to water deficits because of its shallow root depth (14.01 cm). Declined plant cover (−39.0%) under late‐season drought was mainly caused by suppressed perennial forb (−21.5%) and shrub and semi‐shrubs cover (−17.4%). The combined effects of early‐ and late‐season drought on plant cover were greater than the treatment alone, likely due to aggravating water deficits under growing‐season drought. Conclusions: Our results suggest late‐season drought is more critical for shifting plant communities. than early‐season drought. Our findings highlight the regulatory role of drought timing on plant community composition and development in arid and semi‐arid regions. [ABSTRACT FROM AUTHOR]

Flash drought occurs in a short timescale and has more adverse impacts on society and ecosystems than regular drought. Considering flash drought as a special type of regular drought and identifying it by the rate of the first intensification period might ignore posterior intensification periods. To this end, we introduced the combinatorial decomposable flash drought identification framework (CDFDI) to identify flash drought from the perspective of regarding it as the subphase of drought and explore the characteristics and vegetation response of flash drought in the Loess Plateau (LP), China, where is prone to drought and its ecological environment is very fragile. The neffectiveness of the framework is evaluated through the comparison analysis with a preexisting identification method proposed by Li et al. (2020, https://doi.org/10.5194/essd-12-1217-2020). Results indicate that: (a) the CDFDI framework can better capture flash drought events than the Liu's method in terms of time series and spatial patterns, its rationality was further demonstrated by the obvious latitudinal pattern of correlation between flash drought and normalized difference vegetation index (NDVI); (b) the correlation shows an southeast (positive) and northwest (negative) contrasting pattern in the LP; (c) such contrasting pattern was also found in the response time of GPP, which suggests a more rapid impact on vegetation of flash drought in the arid northwestern LP; and (d) flash drought shows an exacerbating trend across the LP under the background of climate warming and mainly concentrated in the southern part. In general, this study provides new insights on flash drought connotations in a changing environment. Plain Language Summary: Flash drought is an extreme disaster in which drought condition develops rapidly. Identification method considering flash drought as a special type of regular drought and regarding it as an entire drought event has potential limitations. In this study, we develop a new flash drought identification framework that considers it as the subphase of regular drought to fill this gap, and use it to explore the flash drought characteristics and vegetation response in the Loess Plateau (LP). The framework showed a better performance in capturing flash drought compared with the method proposed by Li et al. (2020, https://doi.org/10.5194/essd-12-1217-2020). It can be found that the southern LP is the hotspot of flash drought and large areas of the LP are dominated by summer. Larger exacerbating trend was also observed in the southeastern part which could be related to the warming climate. The correlation between flash drought and normalized difference vegetation index (NDVI) is positive in the southeastern LP and negative in the northwestern LP, and such contrasting pattern was also found in the response time of GPP, where the value is much shorter in the arid northwestern LP. It suggests a more rapid impact on vegetation of flash drought in the area that needs to be alerted. Key Points: An improved framework to identify flash drought considering it as the subphase of drought is proposed and verified in the Loess PlateauThe contrasting pattern was observed in the response of normalized difference vegetation index and gross primary production to flash drought across the Loess PlateauThe southern Loess Plateau is the hotspot of frequent and severe flash drought with an increasing trend [ABSTRACT FROM AUTHOR]

Meteorological and soil drought is disastrous to natural and social systems. It is expected that the occurrence of meteorological and soil drought compound events will become more frequent and extreme in the future. The propagation process of meteorological drought to soil drought plays an essential role in the occurrence of drought. However, the drought propagation process is not clear, especially the quantification of drought characteristic propagation process is rarely realized. This study constructs drought intensity propagation index (DIP) and drought duration propagation index (DDP), and then puts forward drought propagation partition in China. Furthermore, this study preliminarily discussed the driving factors of drought propagation and the relationship between land‐atmosphere interaction and main drought propagation partition (arid type drought propagation area, peer‐to‐peer type drought propagation area, and humid type drought propagation area). The results show that DDP and DIP are significantly negatively correlated in China from 1981 to 2020. From southeast to northwest, the propagation of drought intensity from meteorological drought to soil drought gradually increased and the propagation of drought duration gradually decreased. We further concluded that 68% of regions with similar intensity and duration of meteorological drought and soil drought (peer‐to‐peer type drought propagation area) are concentrated in semiarid and dry subhumid, which is exactly the area with strong land‐atmosphere interaction. In all land use types, grasslands are most prone to peer‐to‐peer propagation of drought. This study further reveals the law and mechanism of drought propagation and provides a new idea and attempt to clarify the drought propagation process. Key Points: Drought intensity propagation index and drought duration propagation index for quantifying drought propagation characteristics are proposedDividing drought propagation partitionDiscovery of drought propagation close peer‐to‐peer in areas with strongest land‐atmosphere coupling [ABSTRACT FROM AUTHOR]

Droughts and heatwaves are the most detrimental climatic threats to global wheat production, their spatiotemporal coexistence (compound drought and heatwave events [CDHEs]) can cause synergistic and amplified impacts on wheat yield, which call for an improved understating of their characteristics and variations that related to wheat growth. Past decade has witnessed a surge in the study of CDHEs in terms of their causative mechanisms, variabilities and impacts; however, changes in CDHEs occurring within crops' growing seasons are barely discussed, especially on global scale. In this study, we proposed a novel approach to identify and summarize CDHEs by taking "crop growing season" as accumulated period, and investigated the spatiotemporal changes of CDHEs occurring within wheat growing seasons over global wheat‐producing areas during 1981–2020, including their spatial extent, frequency and duration. Results show that the spatial extent of CDHEs experienced rapid expansion during wheat growing seasons of 1981–2020, meanwhile, droughts and heatwaves increasingly tended to occur simultaneously. More than 92% of wheat‐producing areas experienced at least one CDHE in each wheat growing season, the frequency of CDHEs increased significantly in 28.2% of wheat‐producing areas, and the total duration of CDHEs increased significantly in 33.2% of wheat‐producing areas. Europe, eastern China, western US and northern Argentina are the hotspot regions with the biggest contradiction between fast‐increasing CDHEs and wheat production, pointing to the urgency of marking spatially targeted adaptation measures for disaster reduction and risk management. [ABSTRACT FROM AUTHOR]

The evolution of hydroclimate in East Asia during the Pliocene—a potential analog of the future greenhouse climate—remains highly uncertain. Here we reconstruct changes in the hydroclimate of Northern China during this epoch. Our results reveal previously undocumented severe drought conditions that persisted through the early Pliocene with a significantly greater magnitude than suggested by other records. Using a broad hierarchy of climate simulations, we find that reduction in the Pacific meridional sea surface temperature (SST) gradient has particularly strong impacts on precipitation over Northern China, which suggests its key role in maintaining drought conditions during the early Pliocene. The weaker Pacific meridional SST gradient causes the weakening of the East Asian summer monsoon precipitation over this region via a reduction of atmospheric northward moisture transport from the ocean, which enhances aridity inland. Our results highlight the fundamental control of the tropical ocean on the extra‐tropical hydrological cycle. Plain Language Summary: Understanding East Asian rainfall changes with global warming is an important issue of climate sciences. The Pliocene epoch provides a potential analog to the future greenhouse climate. Here, for the first time we reconstruct high‐resolution aridity changes over the Chinese Loess Plateau (CLP) in northern East Asia during the Pliocene. Our results indicate persistent drought conditions over CLP during the early Pliocene. Analyzing a broad range of climate model simulations, we find that the reduced meridional sea surface temperature gradient is a critical factor in the weakening of the East Asian summer monsoon over Northern China and in maintaining drought conditions during the early Pliocene relative to the late Pliocene. Our results expand the Asian inland paleoclimate records during the Pliocene, providing new information on past Asian monsoon precipitation variations during the warm Pliocene with potential implications for future hydroclimate changes under greenhouse warming in East Asia. Key Points: Severe drought conditions persisted throughout the early Pliocene epoch over Northern ChinaWe link these conditions to the reduced meridional temperature gradient in the Pacific OceanThe reduced Pacific meridional temperature gradient acts to weaken the summer East Asian monsoon precipitation over Northern China [ABSTRACT FROM AUTHOR]

Drought is showing an increasing trend as a result of the significant variation in precipitation and temperature in China. This study investigated the impacts of drought on ecosystem water use efficiency (WUE) in southwest China. The spatiotemporal distribution of drought and ecosystem WUE were analysed through integrated approaches based on observed climate and satellite remote sensing datasets to understand the response of ecosystem WUE to drought. Also, the impacts of climatic variables on gross primary productivity (GPP), evapotranspiration (ET) and WUE have been discussed. More than 30% of the total area can be categorized as suffering moderate drought. Six drought events (autumn 2006, autumn 2009, winter 2010, summer 2011, autumn 2011 and winter 2013) were identified during the period of 2001–2016. The average monthly WUE was 2.37 gC/kgH2O, showing a decreasing trend under the combined effects of drought and other environmental factors. Autumn 2006 exhibited the highest significant positive effect of drought on WUE on more than 80% of the total area that concentrated in the forest, shrubland, savanna and agriculture ecosystems. The results of this study have implications for ecosystem management and climate policy making that could allow implementing feasible water use strategies under a warming climate. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is an important component in water budgets in forest ecosystems, and the associated latent heat flux has important implications for regional climate. However, biophysical control mechanisms on variations in ecosystem ET on intra‐annual scales may have year‐to‐year variations in different years with contrasting precipitation and soil water contents. Related research is lacking in natural oak forests in Central China. Based on eddy‐covariance technique, we investigated variations of ET and controlling factors in a natural oak forest in central China over three years (2017–2019) with contrasting soil water contents (SWCs) and precipitation. The ET of the oak forest was mainly affected by surface conductance (gs) in growing seasons, and the restriction from stoma on ET was aggravated in dry year. High vapour pressure deficit (VPD) promoted gs and ET in wet year but decreased gs and ET in dry year. There was a positive relationship between shallow soil water contents and gs in dry year but no relationship between the two variables in wet year. The ET were 738.1, 750.6 and 513.1 mm, respectively, for 2017–2019, with a coefficient of variation (CV) of 20%, while the corresponding precipitation (P) were 1239.4, 855.8 and 645.6 mm, with a CV of 33%. Annual ET was the lowest in the year with the lowest P, SWC and gs. Short‐term droughts (periods with relative extractable water content less than 0.1 for less than 15 days) only constrained gs and ET in short timescales (e.g., hours). Long‐term droughts (periods with relative extractable water content less than 0.1 for more than 15 days) evidently decreased the gs, thus reducing the ET and affecting energy partitioning in the corresponding period. ET/P were 0.6, 0.88 and 0.79 in 2017–2019, respectively, indicating that ET consumed most of the rain. The ratios of latent heat flux (LE) to net radiation (Rn) were 0.86, 0.88 and 0.6 during growing seasons in 2017–2019, respectively. Our study suggested that the natural oak forest has high ET rate and soil moisture affects the variations of ET. [ABSTRACT FROM AUTHOR]

Concurrent hot extremes and droughts undoubtedly aggravate the impacts of droughts on agriculture, natural environment, and human society. Recent studies mainly focus on the trends and changes in frequency and severity of compound drought and hot extreme events. However, relatively little attention has been paid to the changes in mean temperature during drought conditions. In this study, we investigated the mean temperature changes during droughts in observed and projected periods across China on a century time‐scale and explored the possible contributions of land surface‐atmosphere interactions or atmospheric moisture conditions to these changes. China experienced reduced rather than amplified warming under droughts both in observations and future projections. A drier condition or a higher emission scenario was projected to result in a larger range of mean temperature changes under droughts in the future. We attributed the reduced mean temperatures under droughts to increasing winter droughts and higher atmospheric moisture conditions. This study provides a reference for water resource management, drought risk reduction, as well as mitigation of agricultural crop loss and public health damage. Plain Language Summary: Previous climate studies generally focus on the trend analysis of concurrent droughts and hot extremes, especially in summer. There are gaps in our knowledge on how does the mean temperature under droughts change under climate warming, and what are the underlying driving factors? We investigated the changes in mean temperature during droughts across China using monthly observed data and projected data. China experienced reduced rather than amplified warming under droughts both in observations and future projections. A drier condition or a higher emission scenario could result in a larger range of mean temperature changes under droughts in the future. Increasing winter droughts and higher atmospheric moisture conditions resulted in the reduced mean temperatures under droughts. Our study provides references for policymakers to inform water resource management, drought risk reduction, and mitigation of agricultural crop loss. Key Points: China experienced reduced rather than amplified warming under drought conditions both in observations and future projectionsA drier condition or a higher emission scenario resulted in a larger range of mean temperature changes under future droughtsWe attributed the reduced mean temperatures under droughts to increasing winter droughts and higher atmospheric moisture conditions [ABSTRACT FROM AUTHOR]

Previous studies show that volcanic eruptions can intensify and extend drought events triggered by internal variability over Eastern China. However, it has remained unclear whether volcanic eruptions occurring in different drought phases have different impacts. Here, based on multiple reconstructions, simulations, as well as volcanic sensitivity experiments with volcanic forcing imposed in the early and late phases of droughts, we propose a nonlinear effect of volcanic eruptions on drought events. Late‐phase volcanic eruptions exert greater impact on drought persistence and intensity while early‐phase volcanic eruptions induce modest and weaker impacts. The evolutions of drought differ substantially from the typical volcanic‐only influence or the linear combination of the drought triggered by internal variability and volcanic‐only influences, which are hypothesized to be associated with positive feedbacks of soil moisture to precipitation, as well as its interaction with the evolution of the East Asia Summer monsoon. Plain Language Summary: The effects of volcanic eruptions on precipitation changes are usually considered only on short timescales, however, recent studies have found that volcanic eruptions can influence decadal mega‐drought when superposed on drought events triggered by internal variability in the climate system (Ning et al., 2019; F. Chen et al., 2020). Our modeling and observational studies further show that the response of droughts to volcanic eruptions also depends significantly on the timing of the eruption. A volcanic eruption occurs in the late‐phase of a drought intensify the drought and extends the drought the most, and this impact decreases when the followed eruptions occur toward the early‐phase. These nonlinear responses may be explained by the nonlinear feedbacks of local soil moisture to precipitation and nonlinear changes of East Asia Summer Monsoon after volcanic eruptions. Key Points: Droughts over eastern China responds nonlinearly to volcanic eruptions at different phases of droughts induced by internal variabilityThis nonlinear response can be attributed to the nonlinear influences of volcanic eruptions on EASMThe positive feedbacks between local soil moisture and precipitation can also contribute to this nonlinear response [ABSTRACT FROM AUTHOR]

Bias‐corrected monthly precipitation and surface temperature datasets are constructed for the monsoon transitional zone (MTZ) in China during 1965–2100 based on 21 coupled climate models from phase 6 of the Coupled Model Intercomparison Project (CMIP6) using the equi‐ratio and equidistant cumulative distribution function quantile‐based mapping methods (equi‐ratio cumulative distribution function [ERCDF] and equidistant cumulative distribution function [EDCDF]), respectively. The efficiencies of the two methods are verified via cross‐validation by the jack‐knife method, and the biases are remarkably reduced compared to those of the raw model outputs. Then, the bias‐corrected model outputs are applied to future projections of precipitation, surface temperatures and drought events under the medium (SSP2‐4.5) and high (SSP5‐8.5) shared socioeconomic pathway scenarios. The obtained results present pronounced increases in both the projected annual mean precipitation and temperature fields for the model ensemble mean. In accompany, the MTZ is predicted to become drier in the three future periods; this result was attributed to the dramatic increases in semiarid events and to the decreases in humid events. The drought tension showed more rapid development under SSP585 than under the other scenario, with comparable occurrence frequencies of relatively wet and dry events in the long‐term period, posing a serious threat to regional sustainable development. [ABSTRACT FROM AUTHOR]

Antecedent or concurrent drought conditions are recognized as important factors for triggering or intensifying heatwaves through local land‐atmosphere interaction, but recent studies show nonlocal effects for a few mega‐heatwaves. To quantify the impacts of upwind droughts on all related heatwaves, a Lagrangian heat tracing model driven by reanalysis data is employed over North China, a region influenced by monsoon and westerly significantly. Through analyzing 17 major heatwaves over North China during 1979–2019, we find eight of them are significantly enhanced by upwind droughts. The advected sensible heat that results from circulation anomalies and upwind soil moisture droughts contributes to 71% of the heat for heatwaves. For eight drought‐related heatwave events, the upwind soil droughts from southern and western source regions contribute to 67.9% of the heat anomalies, with 3/5 of them coming from the south. This study suggests that upwind droughts are important for early warning and adaptation for heatwaves. Plain Language Summary: Droughts and heatwaves usually occur simultaneously, which are referred to as compound extreme events. These compound events have become more frequent in recent years and are projected to be more extreme in the future. Through land‐atmosphere interaction, local droughts can intensify heat conditions, and result in heatwaves. In addition to the local effects, the upwind drought can also have a significant effect on heatwaves through the advected heat, which is usually ignored in the heatwave mechanism diagnosis. This study presents a synthetic analysis for all historical heatwave events that occurred over North China during 1979–2019 by using a heat‐tracking model and shows that the contributions of advected sensible heat from nearby regions are greater than the local effect. The upwind droughts, especially in the southern source region, significantly enhance half of the heatwaves over North China through the advected heat. This study suggests an urgent need to understand upwind droughts for unraveling the heatwave mechanisms and developing early warning and adaptation facilities, especially over the regions influenced by monsoon significantly. Key Points: Advected sensible heat contributed to 71% of the heat for 17 major heatwaves over North China during 1979–2019Half of the heatwaves over North China were enhanced by upwind droughts from southern and western source regionsThe upwind droughts contributed to 67.9% of the heat anomalies for the related heatwaves [ABSTRACT FROM AUTHOR]

Concurrent meteorological droughts and consecutive cold events can significantly impact local ecosystems, socio‐economies, and human health. The respective characteristics of droughts and cold extremes have been extensively studied, however, their concurrent extremes have received very little attention. In this study, we used the Huai River Basin as a case to build a magnitude index of concurrent meteorological droughts and consecutive cold events (CDCMI) based on daily minimum temperature data and a 1‐month standardized precipitation evapotranspiration index (SPEI) from 1961 to 2018. Results show that the magnitude of meteorological droughts increased over the observation period, while consecutive cold events significantly decreased. CDCMI showed a significant downward trend at a rate of −0.14 per decade. Large differences were observed between 1990–2018 and 1961–1989—especially in the southern parts of the basin (around −50%). The frequency of mild and moderate concurrent meteorological droughts and consecutive cold events showed no significant upward or downward trends, but severe and extreme concurrent events showed pronounced decreasing trends at rates of −0.03 events/decade and − 0.036 events/decade, respectively. Under the same return period, high CDCMI values are present in the southeastern part of the basin, indicating that the concurrent events in this region are more serious. When CDCMI = 1.79 (extreme grade), the return period in the southeastern part of the basin (5–10 years) is much lower than that in the northwestern part of the basin (>100 years), indicating that this part is harmed to a greater extent by the concurrent extremes than elsewhere in the basin. The spatial pattern of maximum CDCMI again indicates that the southeastern part of the basin is at a high risk for concurrent events. The proposed magnitude index may be a useful tool for analysing concurrent (compound) droughts and cold events as well as their potential impacts. [ABSTRACT FROM AUTHOR]

Monitoring and prediction of agricultural drought are paramount to food security at the global and regional scales, particularly under the influence of climate change and anthropogenic activities. Soil moisture is an effective indicator for monitoring and characterizing agricultural drought. Soil moisture (agricultural drought) is mainly affected by precipitation (meteorological drought) and temperature (hot conditions). Owing to the flexibility of vine copulas in handling multidimensional variables by decomposing them into pair copula constructions (PCCs), we propose a novel drought prediction method using three predictors, namely antecedent meteorological drought, previous hot conditions, and persistent agricultural drought, based on the conditional distributions of C‐vine copulas in a four‐dimensional scenario. The proposed model was applied to agricultural drought (characterized by the standardized soil moisture index (SSI)) prediction with 1–2‐months lead time for the summer season (i.e., August at a 6‐months timescale) in China. Taking two severe agricultural drought events that occurred in many regions across China in August of 2006 and 2014 as validation cases, the SSI predictions with 1–2‐months lead time using the conditional C‐vine copulas model were found to be generally consistent with the corresponding historical SSI observations in most parts of China. Performance evaluation using the Nash‐Sutcliffe efficiency (NSE), coefficient of determination (R2), and F1 score (F1S) for different climate regions also indicated that this model provided a reliable prediction of agricultural drought for most areas of China. The outcome of this study can serve as a guidance for drought prediction, early warning, and drought mitigation. Key Points: A novel drought prediction model is proposed via conditional vine copulas for ChinaWe develop a detailed approach for agricultural drought prediction based on the vine‐copulaGood prediction performance is presented for different climate regions of China [ABSTRACT FROM AUTHOR]

The climate history of the Alxa desert of northwestern China must be sought both in recent instrumental records (dating from 1960) and in high‐resolution proxy data. Climate proxies are scarce in desert areas; however, long‐lived desert shrubs can offer one such proxy. We have used shrub‐ring data from Zygophyllum xanthoxylum, collected in the central Alxa desert, to reconstruct the Self‐calibrating Palmer Drought Severity Index (scPDSI) for the period 1880–2015. The data covers the May–July growth season. When we compared the history constructed from the shrub‐ring data with the instrumental data collected 1960–2015, we found that the reconstructed history explained 41% of the variance in scPDSI data (40% after adjusting for loss of degrees of freedom). The reconstructed history shows that this region has experienced six persistent droughts and four seasons wetter than usual during the period under study. Of note is a severe drought event in 1920s that affected much of northern China (as noted in contemporary documents). The droughts and wet seasons identified in our reconstruction are consistent with reports from other researchers who have studied the climate history or the region. Our study suggests that it is feasible to reconstruct climate history using shrub‐ring data from long‐lived desert shrubs. [ABSTRACT FROM AUTHOR]

Frequent drought events under climate change are endangering food security and sustainable agricultural development. Quantitative assessment of crop yield anomalies under drought conditions is essential for effective water resources management and adaptative drought risk mitigation strategies. In this study, a copula‐based bivariate probabilistic framework model is developed to assess the impacts of drought events on crop yield, where the correlation of crop yield anomalies and standardized precipitation evapotranspiration index (SPEI) at multi‐month lags are quantified. This model has advantages in quantifying the impacts of drought scales on crop yield through the joint probability of the corresponding series. Then, the model is applied to Xinjiang Province in Northwestern China, an arid region with extensive agricultural activities. SPEI and yield anomalies of wheat, maize and cotton during 1984–2015 are firstly identified, and then copula‐based framework is constructed to quantify probabilistic crop yield losses caused by drought events. Finally, crop water amounts and irrigation requirements under different drought severity conditions are compared and analysed. Our findings are: (a) wheat and maize yield anomalies are vulnerable to long drought time‐scales, with exceedance probabilities of required yield anomalies returning to normal are 19.3% for wheat and 21.1% for maize, while cotton is susceptible to short drought time‐scales, with exceedance probability of 42.3% for drought recovery; (b) response of wheat crop yield anomalies to the SPEI at 1‐, 3‐, 6‐ and 12‐month scales is the most sensitive, followed by maize, and cotton is the least; (c) under extreme drought conditions, the probability of cotton yield reduction is lower than that of wheat and maize. Results may enhance our understanding of the impacts of drought scales on crops during the growing season, thus providing general guidance for rational irrigation management of crops and incentives for irrigation to mitigate drought risk, ultimately promoting sustainable agricultural development. [ABSTRACT FROM AUTHOR]

Volcanic eruptions are an important driver for climate changes. However, the response of climate to volcanic eruptions sometimes varies from region to region. Although some studies reported that volcanic eruptions induced drought in Eastern China, the others argued that there is a possibility of wetter condition after volcanic eruptions in Eastern China. Until now, the response of dryness/wetness changes in this region to volcanic eruptions is controversial. Based on the dryness/wetness indexes from 100 sites in Central and Eastern China (CEC) over the past 500 years (1470–1999), the effects of volcanic eruptions occurred in the northern mid‐high latitudes (17 events) and the tropics (19 events) on dryness/wetness changes in CEC were analysed. Our results show that the significant response of dryness/wetness changes in CEC to volcanic eruptions occurred in the third or fourth year after the eruptions. Moreover, there is a significant north–south heterogeneity of the response of dryness/wetness changes in CEC to volcanic eruptions. Specifically, the response of dryness/wetness changes in northern CEC to volcanic eruptions is generally more sensitive than that in southern CEC. A persistent drying during the first to the fourth years post the volcanic events occurred in the northern mid‐high latitudes was found in north CEC, but not in south CEC. After the tropical volcanic events, there is a generally wetting in CEC, but it is stronger in north CEC than in south CEC. These results imply that, to some extent, volcanic eruptions occurred in the northern mid‐high latitudes may amplify dryness in north CEC, but may mitigate wetness in south CEC, while tropical volcanic eruptions may mitigate dryness in north CEC and amplify wetness in south CEC. [ABSTRACT FROM AUTHOR]

Drought largely affects terrestrial gross primary productivity (GPP) by its duration (i.e., drought time‐scales). However, the large‐scale impact of drought time‐scales on GPP is still not well understood, partly due to limited understanding of ecological processes and difficulties in quantifying drought time‐scales. Here, we examined the responses of GPP to drought in China during the last four decades, using state‐of‐the‐art GPP data estimates and a multiscalar drought metric. Most of the GPP data suggested that the time‐scales at which drought has the largest influence on annual GPP (dominant drought time‐scales) were well related to climate region and vegetation type. The GPP responded to drought more rapidly in arid regions than that in semiarid and subhumid regions, with a mean dominant drought time‐scale of 15 and 20 months, respectively; as plants in arid regions can rapidly adapt to water shortage through physiological strategies, while, in semiarid and subhumid regions plants usually can withstand a degree of water deficits. In a humid region, GPP did not rapidly respond to drought, probably because the high soil water availability buffered the effect of drought. In addition, most of the GPP estimates suggested that grasslands and croplands tended to respond to drought at shorter time‐scales than that of forests, shrublands, and sparse vegetation. The study highlights the importance of improving the effects of water availability on vegetation activity and further consideration of vegetation adaptability to drought in both remote sensing GPP algorithms and parameterizations of current terrestrial ecosystem models. Plain Language Summary: Gross primary productivity (GPP) is the entire photosynthetic production of organic compounds in an ecosystem. It plays an important role in carbon cycles, and is the basis for food, fiber, and wood production. Drought widespreadly and negatively affects GPP by its duration (i.e., drought time‐scales). Thus, it is critical to understand the dominant time‐scale at which drought has the largest influence on GPP. We investigated dominant time‐scales of GPP response to drought in China using six GPP estimates and a multiscalar drought metric. We found that the dominant time‐scales were well related to climate region and vegetation type. The GPP responded to drought more quickly in arid regions than that in semiarid and subhumid regions. This might be due to plants in arid regions can rapidly adapt them to water shortage, while, in semiarid and subhumid regions, plants can withstand a degree of water deficits. In a humid region, GPP did not rapidly respond to drought, probably because the high soil water availability buffered the effect of drought. The grasslands and croplands responded to drought at shorter time‐scales than forests, shrublands, and sparse vegetation. The study could benefit the management and mitigation of drought effects on GPP. Key Points: The magnitudes of gross primary productivity (GPP) response to drought highly vary among different GPP estimates and across time‐scalesGPP responds to drought at shorter time‐scales in arid regions than that in other climate regionsGPP of forests responds to drought at longer time‐scales than that of shrublands, grasslands, and croplands [ABSTRACT FROM AUTHOR]

Biodiversity can stabilise productivity through different mechanisms, such as asynchronous species responses to environmental variability and species stability. Global changes, like intensified drought, could negatively affect species richness, species asynchrony and species stability, but it is unclear how changes in these mechanisms will affect the stability of above‐ground primary productivity (ANPP) across ecosystems.We studied the effects of a 4‐year extreme drought on ANPP stability and the underlying mechanisms (species richness, species asynchrony and species stability) across six grasslands in Northern China. We also assessed the relative importance of these mechanisms in determining ANPP stability under extreme drought.We found that extreme drought decreased ANPP stability, species richness, species asynchrony and species stability across the six grasslands. However, structural equation modelling revealed that species asynchrony, not species richness or species stability, was the most important mechanism promoting stability of ANPP, regardless of drought across the six grasslands.Synthesis. Our results suggest that species asynchrony, not species richness and species stability, consistently buffers ecosystem stability against extreme drought across and within grasslands spanning a broad precipitation gradient. Thus, species asynchrony may be a more general mechanism for promoting stability of ANPP in grasslands in the face of intensified drought. [ABSTRACT FROM AUTHOR]

The prolonged droughts that frequently occur in northern China are related to persistent anomalies of circulation and the low‐frequency waves. To explore the formation of the low‐frequency waves and the related internal variability and external forcing, the intra‐seasonal kinetic energy (KE) and the corresponding energy transfer terms are investigated algorithmically with multiscale energy and vorticity analysis. The results show two major energy sources located over the central North Atlantic (NA) and Europe, with increasing baroclinicity and energy conversion. The major energy conversion is from basic flow to intra‐seasonal KE, which corresponds to a southeastern extension of NA jet stream (JS) exit and the northward shift in the entrance of Afro Asian JS. JS shifts are helpful to the conjunction of both JS, and thereby enhance JS waveguide and wave energy dispersion. In addition, with increasing surface temperature and diabatic heating over Europe and the Mediterranean Sea, there are increase baroclinicity that facilitates the buoyancy energy conversion, ascending KE flux and positive pressure flux in the lower troposphere, those result in higher mid‐upper‐troposphere KE. The divergent energy contributes to the development and enhancement of the low‐frequency waves, favouring the extratropical eddy, wave structure, and quasi‐stationary waves amplitude, which is thereby conducive to magnified wave amplitude and extreme droughts in northern China. The results emphasize the internal dynamics and local forcing and provide prediction reference for extratropical extremes. [ABSTRACT FROM AUTHOR]

Extreme droughts, of increased frequency due to climate change, are threatening the sustainability of dryland plantations worldwide by exacerbating water scarcity. Here we aim to disentangle the impacts of combinations of terracing and mulching on water use strategy and their response to extreme droughts in a rainfed jujube (Ziziphus jujuba Mill.) plantation on the semiarid Loess Plateau of China, using 3‐year in situ field observations. Pruned jujube branches and maize straw were mulched on half‐moon terraces to form two combined treatments, referred to as JBT and MST, respectively. The efficacy of these two combinations on the water use strategy of jujube trees was compared with terracing alone (SHT) and control (no terrace). We found that under extreme drought there was clearly reduced soil water storage (SWS) for different treatments. However, the combined treatments showed significantly (p <.05) higher SWS than the SHT and control. Furthermore, the combined treatments enhanced soil water use in deep layers during both normal and drought years, thus helping jujube trees to resist droughts. Moreover, under extreme drought there was greatly reduced transpiration whereas for moderate drought increased transpiration at both seasonal and annual scales. Nonetheless, the combined treatments were associated with enhanced transpiration compared to the SHT and control during drought periods. Finally, jujube trees exhibited isohydric behavior which also helped them to cope with prolonged droughts. Overall, the findings here may provide insights into land management of dryland plantations worldwide under climate change. [ABSTRACT FROM AUTHOR]