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This paper analyzed the drought situation in southwestern China with the standardized precipitation index (SPI) and the standardized precipitation–evapotranspiration index (SPEI) on multiple time scales. The spatial distribution, seasonal variation and features of drought in southwestern China were examined separately by drought frequency, probability of non-exceedance and runs theory. The results showed that the precipitation sequence will change suddenly near 2073 and an obvious, long-term drought will occur after 2073 due to the decline in precipitation. The spatial distribution of drought frequency indicated that the drought frequency will grow obviously in 2071–2100, and the growth rate will increase from the peripheral to the center of the region. The probability of non-exceedance for SPEI-1 less than − 1.0 will be 14.6% in the spring of 2011–2040, grow in 2041–2070 and reach 25.9% in 2071–2100, while that of SPEI in winter will gradually increase in all periods. When the SPEI-12 is smaller than − 1.0, the non-exceedance probability of the index in all seasons of 1981–2100 was and will be growing gradually, indicating that climate change has and will cause severe droughts in spring and winter from 1981 through 2100, especially the medium- and long-term drought. Through the analysis of the SPI and SPEI time sequences by runs theory, it is observed that the drought severity predicted by SPI-12 was and will be increasing over time, and the long-term drought will become more serious. On all time scales, if the SPEI is smaller than − 1.0, the drought duration will gradually increase from 1981–2010 to 2071–2100, indicating the drought in the study region will worsen due to climate change. [ABSTRACT FROM AUTHOR]

The present paper examined the teleconnections between two huge Asian summer monsoon components (South and East Asia) during three time slices in future: near-(2010–2039), mid-(2040–2069) and far-(2070–2100) futures under the RCP4.5 and RCP8.5 scenarios. For this purpose, a high-resolution atmospheric general circulation model is used and integrated at 40 km horizontal resolution. To get more insight into the relationships between the two Asian monsoon components, we have studied the spatial displaying correlation coefficients (CCs) pattern of precipitation over the entire Asian monsoon region with that of South Asia and three regions of East Asia (North China, Korea–Japan and Southern China) separately during the same three time slices. The possible factors responsible for these teleconnections are explored by using mean sea level pressure (MSLP) and wind fields at 850 hPa. The CC pattern of precipitation over South Asia shows an in-phase relationship with North China and an out-of-phase relationship with Korea–Japan, while precipitation variations over Korea–Japan and Southern China exhibit an out-of-phase relationship with South Asia. The CCs analysis between the two Asian blocks during different time slices shows the strongest CCs during the near and far future with the RCP8.5 scenario. The CC pattern of precipitation over Korea–Japan and Southern China with the wind (at 850 hPa) and MSLP fields indicate that the major parts of the moisture over Korea–Japan gets transported from the west Pacific along the western limb of NPSH, while the moisture over Southern China comes from the Bay of Bengal and South China Seas for good monsoon activity. [ABSTRACT FROM AUTHOR]

Based on hydrological and climatic data covering the period from 1961 to 2008, this paper studies the hydrological responses to climate change and to human activities in the Ebinur Lake Catchment. The results show that the annual runoff of three rivers in Ebinur Lake Catchment exhibited different change trends. Specifically, in Jinghe River and Kuytun River exhibited a slightly increasing trend, but an adverse trend in Bortala River, and the variation trend has been the most dramatic since the mid-1990s. The observed variation in the runoff was resulted from the elevated alpine precipitation, rather than rising temperature, and that precipitation is a major factor for runoff generation. The runoff CAR model proposed by this paper can be used to predict the annual runoff in three rivers, and demonstrated annual runoff in Bortala River and Jinghe River will display an increased trend, while a less decreasing trend in Kuytun River under the climate change scenarios of warm-humid variation. In addition, the exploitation of the area of cultivated land led to more water resources consumption, primarily for agriculture irrigation, is the cause of the persistently ecoenvironment degradation, which have reached in a critical state thus, a more pressing concern is the development a scientifically reasonable and administratively practical water resource management scheme. [ABSTRACT FROM AUTHOR]

In this paper, the data envelopment analysis (DEA) method is introduced to analyze the input-output efficiency of energy consumption and economic indicators in Beijing city under the influence of short-term climatic factors. Total energy consumption, fixed asset investment, average temperature, precipitation, sunshine hours, average wind velocity and the average pressure being employed as the input variables, gross domestic product (GDP) and per capita disposable income being employed as the output variables, effective technology and the validity of the scale of DEA of 31 decision-making units ( DMUs) under the influence of the short-term climatic factors are analyzed, and the inefficient DMUs are improved. Empirical analysis shows that both energy consumption and economic growth are sensitive to short-term climate condition, and the reasonable employing of extreme climatic conditions is a question worthy of consideration. This study provides effective basis for the scientific and reasonable arrangement of Beijing city's short-term climatic resources and energy-economic development. [ABSTRACT FROM AUTHOR]

The parameterization of physical processes is one of the critical elements to properly simulate the regional climate over eastern China. It is essential to conduct detailed analyses on the effect of physical parameterization schemes on regional climate simulation, to provide more reliable regional climate change information. In this paper, we evaluate the 25-year (1983-2007) summer monsoon climate characteristics of precipitation and surface air temperature by using the regional spectral model (RSM) with different physical schemes. The ensemble results using the reliability ensemble averaging (REA) method are also assessed. The result shows that the RSM model has the capacity to reproduce the spatial patterns, the variations, and the temporal tendency of surface air temperature and precipitation over eastern China. And it tends to predict better climatology characteristics over the Yangtze River basin and the South China. The impact of different physical schemes on RSM simulations is also investigated. Generally, the CLD3 cloud water prediction scheme tends to produce larger precipitation because of its overestimation of the low-level moisture. The systematic biases derived from the KF2 cumulus scheme are larger than those from the RAS scheme. The scale-selective bias correction (SSBC) method improves the simulation of the temporal and spatial characteristics of surface air temperature and precipitation and advances the circulation simulation capacity. The REA ensemble results show significant improvement in simulating temperature and precipitation distribution, which have much higher correlation coefficient and lower root mean square error. The REA result of selected experiments is better than that of nonselected experiments, indicating the necessity of choosing better ensemble samples for ensemble. [ABSTRACT FROM AUTHOR]

Lakes under natural conditions are potential indicators of climate change, but limited evidence has been proposed to explicitly explain the mechanisms of large-scale lake changes associated with climate. In this paper, satellite imageries from the 1970s to 2010 were compared to track the dynamic change patterns of plateau lakes. It aims to identify the forcing of climate change on the lakes in plateau regions of China. Results revealed that: (1) widespread expanding trends in the area and abundance of lakes on wetter plateau regions, by increasing precipitation and snow presented a positive effect on lake levels, as well as warming resulted glacier melting and permafrost degrading contributed to expansion of lakes in the regions covered by glaciers on the Tibetan Plateau by 58-62 % and of 13-20 % on the western Inner Mongolia and Xinjiang Plateau; (2) shrinkage lakes in the main portion of the arid regions were mainly caused by the decreasing wind speed resulted water balance change, irrigation and other human utilization of water resources. Although precipitation decreased, wind speed also has the most dominant impact on decreasing evaporation, followed by solar radiation, both of which offset the effect of increasing temperature, especially in eastern Inner Mongolia and Xinjiang Plateau; (3) thawing permafrost led to shrinkage of lakes in an area of seasonal permafrost, the shrinking and splitting of lakes in a discontinuous permafrost zone, and the rising of lake levels in an area of continuous permafrost; (4) the future of the plateau lakes under climate change must be in question, because the glacier and snow melting water is not sustainable for wetter regions, and the increasing water consumption caused by the farmland expansion for arid regions. [ABSTRACT FROM AUTHOR]

This paper presents a 457-year reconstruction of precipitation in the southeastern Qinghai-Tibet Plateau using tree-ring records. Tree-ring samples were collected from the Hengduan Mountains in the southeastern part of the Qinghai-Tibet Plateau, China. A nearly 500-year chronology was developed using tree-ring width records. Correlation analysis shows moisture is the main factor limiting tree growth in this region. Ring-widths were significantly positively correlated with the Palmer Drought Severity Index (PDSI) and precipitation in many months. The highest correlation coefficient was found between the annual growth of trees and precipitation from the previous September to the current June (0.738). Based on this relationship, we reconstructed the precipitation history from 1509 to 2006. The reconstruction explains 54.4% ( R=53.5%, N=49, F=56.12) of the actual precipitation variation during the calibration period (1958-2006). During the reliable period of the reconstruction (1549-2006), some low-frequency climate signals are included, indicating this region has been getting wetter in the last 20 years. The reconstruction documents six apparently dry and five pluvial periods and the 17th century dry period lasted longer than any other. When compared with other recent studies, this study and these earlier reconstructions show a similar trend in the variation of drought and pluvial. Further spatial correlation analysis confirms that the reconstructed precipitation adequately represents the rainfall history of the entire Hengduan Mountain area. The Multi-taper method, a type of spectral analysis, reveals that precipitation in this area had significant ( P<0.01) spectral peaks at 3-5 a, 60 a and 79-85 a. [ABSTRACT FROM AUTHOR]

Hydrological processes depend directly on climate conditions [e.g., precipitation, potential evapotranspiration ( PE)] based on the water balance. This paper examines streamflow datasets at four hydrological stations and meteorological observations at 79 weather stations to reveal the streamflow changes and underlying drivers in four typical watersheds (Meigang, Saitang, Gaosha, and Xiashan) within Poyang Lake Basin from 1961 to 2000. Most of the less than 90th percentile of daily streamflow in each watershed increases significantly at different rates. As an important indicator of the seasonal changes in the streamflow, CT (the timing of the mass center of the streamflow) in each watershed shows a negligible change. The annual streamflow in each watershed increases at different rates, with a statistically significant trend (at the 5 % level) of 9.87 and 7.72 mm year, respectively, in Meigang and Gaosha watersheds. Given the existence of interactions between precipitation and PE, the original climate elasticity of streamflow can not reflect the relationship of streamflow with precipitation and PE effectively. We modify this method and find the modified climate elasticity to be more accurate and reasonable using the correlation analysis. The analyses from the modified climate elasticity in the four watersheds show that a 10 % increase (decrease) in precipitation will increase (decrease) the annual streamflow by 14.1-16.3 %, while a 10 % increase (decrease) in PE will decrease (increase) the annual streamflow by −10.2 to −2.1 %. In addition, the modified climate elasticity is applied to estimate the contribution of annual precipitation and PE to the increasing annual streamflow in each watershed over the past 40 years. Our result suggests that the percentage attribution of the increasing precipitation is more than 59 % and the decreasing in PE is less than 41 %, indicating that the increasing precipitation is the major driving factor for the annual streamflow increase for each watershed. [ABSTRACT FROM AUTHOR]

Reliable projections of extremes at finer spatial scales are important in assessing the potential impacts of climate change on societal and natural systems, particularly for elevated and cold regions in the Tibetan Plateau. This paper presents future projections of extremes of daily precipitation and temperature, under different future scenarios in the headwater catchment of Yellow River basin over the 21st century, using the statistical downscaling model (SDSM). The results indicate that: (1) although the mean temperature was simulated perfectly, followed by monthly pan evaporation, the skill scores in simulating extreme indices of precipitation are inadequate; (2) The inter-annual variabilities for most extreme indices were underestimated, although the model could reproduce the extreme temperatures well. In fact, the simulation of extreme indices for precipitation and evaporation were not satisfactory in many cases. (3) In future period from 2011 to 2100, increases in the temperature and evaporation indices are projected under a range of climate scenarios, although decreasing mean and maximum precipitation are found in summer during 2020s. The findings of this work will contribute toward a better understanding of future climate changes for this unique region. [ABSTRACT FROM AUTHOR]

Extreme weather exerts a huge impact on human beings and it is of vital importance to study the regular pattern of meteorological and hydrological factors. In this paper, a selection of seven extreme indices is used to analyze the trend of precipitation extremes of 18 meteorological stations located in Zhejiang Province, east China using the Mann-Kendall test. Then the precipitation trends in the plum season (from May to July) and typhoon season (from August to October) are studied separately. The results show that the precipitation trend varies from east to west. There is a positive trend in the east and a negative one in the west. The largest part of Zhejiang Province shows a positive trend in heavy precipitation and the most significant upward trend is detected in Dinghai with 3.4 mm/year for precipitation on very wet days. Although the upward trend of extreme precipitation is not prevailing, the range of increase in specific areas is apparent, like Dinghai with 1.3 mm/year. Precipitation intensity exhibits an upward trend in most areas and a typical upward trend can be found in Dachendao, Tianmushan, and Yuhuan with 0.04, 0.02, and 0.05 mm/year respectively. Precipitation intensity in both plum and typhoon seasons has increased too, especially for the coastal stations. [ABSTRACT FROM AUTHOR]

This paper describes 2007/2008 inter-annual changes in runoff from the Zhadang Glacier located on the northern slope of Nyainqêntanglha Range, Tibet, and analyzes their causes. Precipitation increased by 17.9% in summer months of 2008 compared with the same period in 2007, drainage basin runoff decreased by 33.3%, and glacial meltwater decreased by 53.8%. Change in positive accumulated air temperature explained approximately half of the inter-annual difference in glacial meltwater using a degree-day model. This suggests that the glacier is extremely sensitive to changes in air temperature. Energy balance analysis showed that change in glacier surface albedo, considered to be caused by difference in precipitation form, resulted in the large inter-annual difference in glacial meltwater. It was shown statistically that precipitation form in the summer months of 2007 was mainly rainfall which comprised 71.5% of total precipitation, while during the same period in 2008 rainfall accounted for 30.7%, with the majority of precipitation falling as snow. Precipitation form should be considered an independent factor when analyzing glacier sensitivity to climate change or forecasting the runoff from certain glaciers. [ABSTRACT FROM AUTHOR]

Snow is an important component of a climate system, and very sensitive to climate change, and it can be an indicator of checking and monitoring global change. This paper is concerned with identifying changes in the time series of snowfall in Qinghai, located in western China. We used the Mann-Kendall test to evaluate the annual and monthly trends in snowfall in Qinghai during the periods 1957/58–2006/07 based on data obtained from 25 stations. Significant positive and negative trends at the 90, 95, and 99 percent confidence levels were detected for numerous stations. In order to understand the regional pattern of snowfall in Qinghai, the detected trends are spatially interpolated using the inverse distance weighted interpolation method in a GIS environment. The results indicate that in January snowfall in the most area of Qinghai shows a significant upward trend, especially in the Delingha and Nomhon area in northern Qaidam Basin, as well as southeastern Qinghai, however, there is no significant downward trend area. The trend analysis indicates that annual snowfall has a significant upward trend in Delingha and Nomhon area in northern Qaidam Basin, and the downward trends occurred in the Qilian mountain area and Gonghe Basin. This is especially the case for highlighting the spatial structure of snowfall trends. The research results help in further understanding the regional pattern of snowfall in Qinghai and its response to global climatic warming. [ABSTRACT FROM AUTHOR]

Monthly precipitation data of 42 rain stations over the Pearl River basin for 1960–2005 were analyzed to classify anomalously wet and dry conditions by using the standardized precipitation index (SPI) and aridity index ( I) for the rainy season (April–September) and winter (December–February). Trends of the number of wet and dry months decided by SPI were detected with Mann-Kendall technique. Furthermore, we also investigated possible causes behind wet and dry variations by analyzing NCAR/NCEP reanalysis dataset. The results indicate that: (1) the Pearl River basin tends to be dryer in the rainy season and comes to be wetter in winter. However, different wetting and drying properties can be identified across the basin: west parts of the basin tend to be dryer; and southeast parts tend to be wetter; (2) the Pearl River basin is dominated by dry tendency in the rainy season and is further substantiated by aridity index ( I) variations; and (3) water vapor flux, moisture content changes in the rainy season and winter indicate different influences of moisture changes on wet and dry conditions across the Pearl River basin. Increasing moisture content gives rise to an increasing number of wet months in winter. However, no fixed relationships can be observed between moisture content changes and number of wet months in the rainy season, indicating that more than one factor can influence the dry or wet conditions of the study region. The results of this paper will be helpful for basin-scale water resource management under the changing climate. [ABSTRACT FROM AUTHOR]

Estimates of forest vegetation carbon storage in China varied due to different methods used in the assessments. In this paper, we estimated the forest vegetation carbon storage from the Fourth Forest Inventory Data (FFID) in China using a modified volume-derived method. Results showed that total carbon storage and mean carbon density of forest vegetation in China were 3.8 Pg C (about 1.1% of the global vegetation carbon stock) and 41.32 Mg/ha, respectively. In addition, based on linear multiple regression equation and factor analysis method, we analyzed contributions of biotic and abiotic factors (including mean forest age, mean annual temperature, annual precipitation, and altitude) to forest carbon storage. Our results indicated that forest vegetation carbon storage was more sensitive to changes of mean annual temperature than other factors, suggesting that global warming would seriously affect the forest carbon storage. [ABSTRACT FROM AUTHOR]

This paper measures the economic impacts of climate change on China's agriculture based on the Ricardian model. By using county-level cross-sectional data on agricultural net revenue, climate, and other economic and geographical data for 1275 agriculture dominated counties, we find that under most climate change scenarios both higher temperature and more precipitation would have an overall positive impact on China's agriculture. However, the impacts vary seasonally and regionally. Autumn effect is the most positive, but spring effect is the most negative. Applying the model to five climate scenarios in the year 2050 shows that the East, the Central part, the South, the northern part of the Northeast, and the Plateau would benefit from climate change, but the Southwest, the Northwest and the southern part of the Northeast may be negatively affected. In the North, most scenarios show that they may benefit from climate change. In summary, all of China would benefit from climate change in most scenarios. [ABSTRACT FROM AUTHOR]

Spatio-temporal variations in precipitation are affecting agricultural production in China in the context of climate change. Based on daily precipitation data from 63 national meteorological stations on the Huang-Huai-Hai Plain from 1963 to 2012, this paper analysed the spatio-temporal variations in precipitation in terms of precipitation days and intensity, using spatial interpolation, linear trend estimation and wavelet analysis. The results indicated that: (i) from 1963 to 2012, the number of annual precipitation days and intensity decreased gradually from the southeast to the northwest. Additionally, the distribution of the extreme precipitation index was similar to that of the annual precipitation index; (ii) the number of annual precipitation days and heavy precipitation days gradually decreased, while precipitation intensity and extreme precipitation days and extreme rainfall intensity remained relatively stable or decreased. The spatial patterns of annual variation trends were considerably different. The annual precipitation days and intensity trends are consistent with the overall trend, while that of the extreme rainfall index in some regions differs from the overall trend; (iii) the precipitation index displayed different periodic oscillations during the period, and the precipitation index values differed at different time scales. However, all the precipitation index values exhibited a 28-yr oscillation. [ABSTRACT FROM AUTHOR]

A persistent concern about the social consequences of climate change is that large, vulnerable populations will be involuntarily displaced. Existing evidence suggests that changes in precipitation and temperature can increase migration in particular contexts, but the potential for this relationship to evolve over time alongside processes of adaptation and development has not been widely explored. To address this issue, we link longitudinal data from 20 thousand Chinese adults from 1989 to 2011 to external data on climate anomalies and use this linked dataset to explore how climatic effects on internal migration have changed over time while controlling for potential spatial and temporal confounders. We find that temperature anomalies initially displaced permanent migrants at the beginning of our study period, but that this effect had reversed by the end of the study period. A parallel analysis of income shares suggests that the explanation might lie in climate vulnerability shifting from agricultural to non-agricultural livelihood activities. Taken together with evidence from previous case studies, our results open the door to a potential future in which development and in situ adaptation allow climate-induced migration to decline over time, even as climate change unfolds. [ABSTRACT FROM AUTHOR]

Purpose: Fungi play an essential role in regulating the functioning of terrestrial ecosystems and are sensitive to climate change factors. Climate change incidents, such as N deposition and altered precipitation, create abiotic stress regarding the water use efficiency of soil and nutrient limitation impacting the activity of soil fungi. This study aimed to examine the combined effects of N fertilization and altered precipitation on soil fungal diversity and composition in the desert steppe. Materials and methods: In the present study, we carried out a field experiment to assess the soil fungal diversity and composition of the desert steppe in response to N fertilizer (0 or 35 kg N ha−1 year−1) and precipitation changes (control, − 50% precipitation, or + 50% precipitation) in the desert steppe. The study was initiated in 2012, and plant and soil samples were collected after 5 years (August, 2017) of field treatments. High-throughput sequencing was applied to estimate the fungal diversity and composition. Results and discussion: The soil fungal communities were dominated by Ascomycota (87.85% ± 1.26%), which primarily drove the fungal community composition. Decreased precipitation promoted strong shifts in fungal community composition under both N fertilizer levels. Increased precipitation significantly reduced Shannon-Wiener indices by 9.96%. The increasing relative abundances of fungal functional groups (lichenized saprotroph, animaland plant pathogens) resulted in a marked shift in fungal community composition from decreased precipitation to increased precipitation, which is attributed to the important role of the Ascomycota phylum in fungal communities. Structural equation modeling (SEM) indicated that C4 biomass was the predominant factor determining the Shannon-Wiener index for these fungi. Direct altered precipitation, indirect soil pH, and C4 biomass together controlled soil fungal community composition, with altered precipitation as the main driver. Conclusions: The interactive effects of N fertilizer and altered precipitation on grassland plant density, biomass, and soil properties may play an essential role in determining fungal diversity and community composition. Precipitation is a primary limiting factor that influences fungal community composition. Effects of N fertilizer on soil fungal community composition are highly dependent on changes in precipitation. [ABSTRACT FROM AUTHOR]

Self-organizing map (SOM) is used to simulate summer daily precipitation over the Yangtze–Huaihe river basin in Eastern China, including future projections. SOM shows good behaviors in terms of probability distribution of daily rainfall and spatial distribution of rainfall indices, as well as consistency of multi-model simulations. Under RCP4.5 Scenario, daily rainfall at most sites (63%) is projected to shift towards larger values. For the early 21st century (2016–2035), precipitation in the central basin increases, yet decreases occur over the middle reaches of the Yangtze River as well as a part of its southeast area. For the late 21st century (2081–2100), the mean precipitation and extreme indices experience an overall increase except for a few southeast stations. The total precipitation in the lower reaches of the Yangtze River and in its south area is projected to increase from 7% at 1.5 °C global warming to 11% at 2 °C, while the intensity enhancement is more significant in southern and western sites of the domain. A clustering allows to regroup all SOM nodes into four distinct regimes. Such regional synoptic regimes show remarkable stability for future climate. The overall intensification of precipitation in future climate is linked to the occurrence-frequency rise of a wet regime which brings longitudinally closer the South Asia High (eastward extended) and the Western Pacific Subtropical High (westward extended), as well as the reduction of a dry pattern which makes the two atmospheric centers of action move away from each other. [ABSTRACT FROM AUTHOR]

Gridded climatic datasets with fine spatial resolution can potentially be used to depict the climatic characteristics across the complex topography of China. In this study, we collected records of monthly temperature at 1153 stations and precipitation at 1202 stations in China and neighboring countries to construct a monthly climate dataset in China with a 0.025° resolution (~ 2.5 km). The dataset, named LZU0025, was designed by Lanzhou University and used a partial thin plate smoothing method embedded in the ANUSPLIN software. The accuracy of LZU0025 was evaluated based on three aspects: (1) Diagnostic statistics from the surface fitting model during 1951–2011. The results indicate a low mean square root of generalized cross validation (RTGCV) for the monthly air temperature surface (1.06 °C) and monthly precipitation surface (1.97 mm1/2). The method used variable square root transformation for the spline surface fitting to reduce positive skewness in the measured precipitation values and no variable transformation in air temperature case. This indicates that the surface fitting models are accurate. (2) Error statistics of comparisons between interpolated monthly LZU0025 with the withholding of climatic data from 265 stations during 1951–2011. The results show that the predicted values closely tracked the real true values with values of mean absolute error (MAE) of 0.59 °C and 70.5 mm and standard deviation of the mean error (STD) of 1.27 °C and 122.6 mm. In addition, the monthly STDs exhibited a consistent pattern of variation with RTGCV. (3) Comparison with other datasets. This was done in two ways. The first was via comparison of standard deviation, mean, and time trend derived from all datasets to a reference dataset released by the China Meteorological Administration (CMA), using Taylor diagrams. The second was to compare LZU0025 with the station dataset in the Tibetan Plateau. Taylor diagrams show that the standard deviation derived from LZU had a higher correlation with that produced by the CMA (R = 0.76 for air temperature, and R = 0.96 for precipitation) compared to those from other datasets. The standard deviation for the index derived from LZU was more close to that induced from CMA, and the centered normalized root-mean-square difference for this index derived from LZU and CMA was lower. A similar superior performance of LZU was found in the comparison of mean and time trend derived from LZU and those from other datasets. LZU0025 had high correlation with the Coordinated Energy and Water Cycle Observation Project (CEOP)—Asian Monsoon Project (CAMP) Tibet surface meteorology station dataset for air temperature, despite a non-significant correlation for precipitation at a few stations. Based on this comprehensive analysis, we conclude that LZU0025 is a reliable dataset. LZU0025, which has a fine resolution, can be used to identify a greater number of climate types, such as tundra and subpolar continental, along the Himalayan Mountain. We anticipate that LZU0025 can be used for the monitoring of regional climate change and precision agriculture modulation under global climate change. [ABSTRACT FROM AUTHOR]

The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover, most of the published studies focus mainly on the evolution of moisture conditions, and there have been few attempts to address changes in seasonality. In this study, records of δ13Corg, TOC, TN, C/N and grain size were obtained from lacustrine sediments at Yili Basin, Xinjiang, NW China. Our aim was to reconstruct the trend in seasonality of precipitation from the last glaciation to the Holocene. The organic matter content of the sediments is derived predominantly from terrestrial plants. The δ13Corg values vary from -19.4% to -24.8%, indicating that the vegetation was dominated by C3 plants. Winter-spring precipitation is identified as the factor determining the relative proportions of C3 and C4 plants in the region. A negative trend in δ13Corg corresponding to an increase in the relative abundance of C3 plants indicate a trend of increasing winter-spring precipitation from the last glaciation to the Holocene. The increased incidence of wintertime storms in the interior of Asia is suggested to result in the increase of winterspring precipitation in the Holocene. [ABSTRACT FROM AUTHOR]

In this study, we use four statistical downscaling methods to statistically downscale seven Coupled Model Intercomparison Project (CMIP5) Global Climate Models (GCMs) and project the changes in precipitation and temperature over China under RCP4.5 and RCP8.5 emission scenarios. The four statistical downscaling methods are bias-correction and spatial downscaling (BCSD), bias-correction and climate imprint (BCCI), bias correction constructed analogues with quantile mapping reordering (BCCAQ), and cumulative distribution function transform (CDF-t). Though large inter-model variability exists in the distribution and magnitude of changes in projected precipitation, particularly for wet spell length (CWD), all downscaling methods generally project a consistent enhancement of precipitation in both summer and winter over most parts of China. For the arid and semiarid Northwest China, the shortened dry spell length (CDD) is accompanied by the pronouncedly intensified very wet days (R95p), as well as the increase in maximum 5-day precipitation amount (Rx5day). In contrast, southeastern regions may experience more consecutive dry days and more severe wet precipitation extremes. The projected changes from different downscaling techniques are fairly similar for temperature, apart from the diurnal temperature range for BCSD. Warming is projected across the whole domain with larger magnitude over the north and in winter under RCP8.5. More summer days and fewer frost days would appear in the future. The bias correction components of downscaling methods cause a higher degree of agreement among models, and the downscaled results generally retain the main climate change signal of the driving models. [ABSTRACT FROM AUTHOR]

The Wetness Index was calculated using gridded monthly precipitation and potential evapotranspiration in China during 1924-2013. Variations of dry and wet periods in different areas and the impact of meteorological factors were analyzed. The results show the following: (1) Drought areas (W ≤ 0.5) and wet areas (W > 0.65) in China constituted 33-56% and 35-55%, respectively, of the total land area and there were no secular trends during 1924-2013. During this period, the areas of drought and wet were inversely proportional, but had different changes among seven regions. (2) Since 1954, the overall trend in China has changed from wet to dry. Drought areas increased significantly (p < 0.05) during 1954-1983. Drought areas increased (not significantly) during 1984-2013, but the rate of drought/wetness clearly decreased (tendency rates were between − 0.05 and 0.05/30 year, and accounted for 54.79% of China). (3) Dry/wet variation in North, Northeast, Central, and Southwest China played major roles. (4) Except in the North region, drought/wet conditions were affected by surface warming. [ABSTRACT FROM AUTHOR]

Due to spatial and temporal heterogeneity in moisture conditions, the responses of arid/humid climate regions (AHCR) to climate change are complex. In this study, we delineated the AHCR of China using information about the balance of the atmospheric water supply and demand collected from 581 meteorological stations over the past 50 years. We also analyzed inter-decadal shifts and linear trends in the AHCR and examined the influence of precipitation and reference evapotranspiration. The results indicate that the semi-arid region expanded significantly over the last five decades, mainly in northwest China, northern China, and the Tibetan Plateau and, by the 2000s, had increased by 33.53% relative to its extent in the 1960s; in contrast, the arid region shrank by 20.75%. The semi-arid region grew mainly because of transfers from the arid region in western China and the sub-humid region in eastern China. The decreased reference evapotranspiration and significantly increased precipitation together contributed to the expansion of the semi-arid region in northwest China and the Tibetan Plateau over the last 50 years. In contrast, the expansion of the semi-arid region in Inner Mongolia and northern China reflects the counteractive influence of decreased reference evapotranspiration and decreased precipitation. [ABSTRACT FROM AUTHOR]

The effect of spring Arctic Stratospheric Ozone (ASO) changes on spring precipitation in China is analyzed using observations, reanalysis data, and the Whole Atmosphere Community Climate Model version 4 (WACCM4). We find that February-March mean ASO changes have a significant impact on April-May mean precipitation over Loess Plateau and middle-lower reaches of the Yangtze River—two important grain-producing regions with large populations. Changes in the polar vortex link the ASO to precipitation in China. Stratospheric circulation anomalies caused by ASO changes can propagate to the North Pacific. An increase in ASO leads to enhanced westerlies in the high and low latitudes of the North Pacific but weakened westerly in the mid-latitudes of the North Pacific. The circulation anomalies over the North Pacific, forced by the increase of ASO, can extend westwards to East Asia, leading to an abnormal anticyclone in the East Asian upper and middle troposphere, and an abnormal cyclone in the lower troposphere. This enhances the warm and humid airstream from Western Pacific to Chinese mainland and strengthens upwelling over Loess Plateau and middle-lower reaches of the Yangtze River. These conditions enhance precipitation in central China during positive ASO anomaly events and reduce precipitation during negative events. The WACCM4 simulations support the results from statistical analysis of observations and reanalysis data. Our results suggest that ASO variation can serve as a predictor of spring precipitation variation over Loess Plateau and middle-lower reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]

A slight variation in the magnitude of stream flow can have a substantial influence on the development of water resources. The Songhua River Basin (SRB) serves as a major grain commodity basin and is located in the northeastern region of China. Recent studies have identified a gradual decrease in stream flows, which presents a serious risk to water resources of the region. It is therefore necessary to assess the variation in stream flow and to predict the future of stream flows and droughts to make a comprehensive plan for agricultural irrigation. The simulation of monthly stream flows and the investigation of the influence of climate on the stream flow in the SRB were performed by utilizing the Integrated Water Evaluation and Planning (WEAP) tool coupled with observed precipitation data, as well as the Asian Precipitation-Highly-Resolved Observational Data Integration towards Evaluation of Water Resources (APHRODITE’s Water Resources) precipitation product. The Nash-Sutcliffe coefficient (NSC) was used to assess the WEAP efficiency. During the time of calibration, NSC was obtained as 0.90 and 0.67 using observed and APHRODITE precipitation data, respectively. The results indicate that WEAP can be used effectively in the SRB. The application of the model suggested a maximum decline in stream flow, reaching 24% until the end of 21st century under future climate change scenarios. The drought indices (standardized drought index and percent of normal index) demonstrated that chances of severe to extreme drought events are highest in 2059, 2060 and 2085, while in the remaining time period mild to moderate drought events may occur in the entire study area. The drought duration, severity and intensity for the period of 2011-2099 under all scenarios, [(A1B: 12, − 1.55, − 0.12), (A2: 12, − 1.41, − 0.09), (max. wetting and warming conditions: 12, − 1.37, − 0.11) and (min. wetting and warming conditions: 12, − 1.69, − 0.19)], respectively. [ABSTRACT FROM AUTHOR]

The community of climate change impact assessments and adaptations research needs regional high-resolution (spatial) meteorological data. This study produced two downscaled precipitation datasets with spatial resolutions of as high as 3 km by 3 km for the Heihe River Basin (HRB) from 2011 to 2014 using the Weather Research and Forecast (WRF) model nested with Final Analysis (FNL) from the National Center for Environmental Prediction (NCEP) and ERA-Interim from the European Centre for Medium-Range Weather Forecasts (ECMWF) (hereafter referred to as FNLexp and ERAexp, respectively). Both of the downscaling simulations generally reproduced the observed spatial patterns of precipitation. However, users should keep in mind that the two downscaled datasets are not exactly the same in terms of observations. In comparison to the remote sensing-based estimation, the FNLexp produced a bias of heavy precipitation centers. In comparison to the ground gauge-based measurements, for the warm season (May to September), the ERAexp produced more precipitation (root-mean-square error (RMSE) = 295.4 mm, across the 43 sites) and more heavy rainfall days, while the FNLexp produced less precipitation (RMSE = 115.6 mm) and less heavy rainfall days. Both the ERAexp and FNLexp produced considerably more precipitation for the cold season (October to April) with RMSE values of 119.5 and 32.2 mm, respectively, and more heavy precipitation days. Along with simulating a higher number of heavy precipitation days, both the FNLexp and ERAexp also simulated stronger extreme precipitation. Sensitivity experiments show that the bias of these simulations is much more sensitive to micro-physical parameterizations than to the spatial resolution of topography data. For the HRB, application of the WSM3 scheme may improve the performance of the WRF model. [ABSTRACT FROM AUTHOR]

Traditionally, the evaluation of pollen-based quantitative paleoclimate reconstructions focuses on the ability of calibration sets to infer present climatic conditions and/or the similarity between fossil and modern assemblages. Objective criteria for choosing the most appropriate climate parameter(s) to be reconstructed at a specific site are thus lacking. Using a novel approach for testing the statistical significance of a quantitative reconstruction using random environmental data, in combination with the advantageous large environmental gradients, abundant vegetation types and comprehensive modern pollen databases in China, we describe a new procedure for pollen-based quantitative paleoclimatic reconstructions. First, the most significant environmental variable controlling the fossil pollen assemblage changes is identified. Second, a calibration set to infer changes in this targeted variable is built up, by limiting the modern ranges of other environmental variables. Finally, the pollen-based quantitative reconstruction is obtained and its statistical significance assessed. This novel procedure was used to reconstruct the mean annual precipitation ( P ) from Gonghai Lake in the Lvliang Mountains, and Tianchi Lake in the Liupan Mountains, on the eastern and western fringe of the Chinese Loess Plateau, respectively. Both P reconstructions are statistically significant ( p<0.001), and a sound and stable correlation relationship exists in their common period, showing a rapid precipitation decrease since 3300 cal yr BP. Thus, we propose that this procedure has great potential for reducing the uncertainties associated with pollen-based quantitative paleoclimatic reconstructions in China. [ABSTRACT FROM AUTHOR]

In order to understand the changes in precipitation variability associated with the climate shift around mid-1970s, the precipitation regime changes have been analyzed over both China and the USA. Specifically, a new variable is designed based on Benford's Law (BL) to detect precipitation regime shift by using only the first digit information of the datasets. This new variable describes the decadal precipitation regime shift more directly and clearly than the traditional variables, such mean or trend of yearly precipitation amount. It is found that there is an obvious out-phased relation for precipitation regime shift over China and the USA, i.e., a significant shift from the lower to the higher BL's goodness of fit (weaker to stronger precipitation intensity) in the Southern China occurred in 1979, and a significant shift from the higher to the lower BL's goodness of fit (stronger to weaker precipitation intensity) in the USA occurred around 1978. [ABSTRACT FROM AUTHOR]

The persistent temperature and precipitation extremes may bring damage to the economy and human due to their intensity, duration and areal coverage. Understanding the quality of reanalysis datasets in descripting these extreme events is important for detection, attribution and model evaluation. In this study, the performances of two reanalysis datasets [the twentieth century reanalysis (20CR) and Interim ECMWF reanalysis (ERA-Interim)] in reproducing the persistent temperature and precipitation extremes in China are evaluated. For the persistent temperature extremes, the two datasets can better capture the intensity indices than the frequency indices. The increasing/decreasing trend of persistent warm/cold extremes has been reasonably detected by the two datasets, particularly in the northern part of China. The ERA-Interim better reproduces the climatology and tendency of persistent warm extremes, while the 20CR has better skill to depict the persistent cold extremes. For the persistent precipitation extremes, the two datasets have the ability to reproduce the maximum consecutive 5-day precipitation. The two datasets largely underestimate the maximum consecutive dry days over the northern part of China, while overestimate the maximum consecutive wet days over the southern part of China. For the response of the precipitation extremes against the temperature variations, the ERA-Interim has good ability to depict the relationship among persistent precipitation extremes, local persistent temperature extremes, and global temperature variations over specific regions. [ABSTRACT FROM AUTHOR]

This study reveals the impacts of climatic variable trends on drought severity in Xinjiang, China. Four drought indices, including the self-calibrating Palmer drought severity index (sc-PDSI), Erinç's index ( I ), Sahin's index ( I ), and UNEP aridity index (AI), were used to compare drought severity. The ensemble empirical mode decomposition and the modified Mann-Kendall trend test were applied to analyze the nonlinear components and trends of the climatic variable and drought indices. Four and six climatic scenarios were generated in sc-PDSI, I , I , and AI with different combinations of the observed and detrended climatic variables, respectively. In Xinjiang, generally increasing trends in minimal, average, and maximal air temperature ( T , T , T ) and precipitation ( P) were found, whereas a decreasing trend in wind speed at 2 m height ( U ) was observed. There were significantly increasing trends in all of the four studied drought indices. Drought relief was more obvious in northern Xinjiang than in southern Xinjiang. The strong influences of increased P on drought relief and the weak influences of increased T , T , and T on drought aggravation were shown by comparing four drought indices under different climate scenarios. Decreased U had a weak influence on drought, as shown by the AI in different climate scenarios. The weak influences of T and U were considered to be masked by the strong influences of P on droughts. Droughts were expected to be more severe if P did not increase, but were likely milder without an increase in air temperature and with a decrease in U . [ABSTRACT FROM AUTHOR]

Exploring possible relationships between climate-induced maize yield and rainy-season precipitation under climate change is fundamental to science-based decision for food security in Inner Mongolia Autonomous Region (IMAR). To determine the relationship of maize yield with precipitation variables across IMAR during 1960-2012, we selected 11 precipitation indices of rainy season and divided IMAR into four sub-regions-west, middle, east, and northeast using principal component analysis and K-means clustering methods. Results show that climate-induced maize yield is more sensitive to precipitation variability in the west and middle IMAR. The most important precipitation factor that limits maize yield is moderate precipitation days in these two sub-regions. Moreover, west and middle Inner Mongolia was dominated by decreasing precipitation during the rainy season. Furthermore, the El Niño/La Niña-Southern Oscillation cycle has the significant influence on the rainy-season precipitation in the west and middle IMAR. [ABSTRACT FROM AUTHOR]

Projections of changes in climate are important in assessing the potential impacts of climate change on natural and social systems. However, current knowledge on assembling different GCMs to estimate future climate change over the Pear River basin is still limited so far. This study examined the capability of BMA and arithmetic mean (AM) method in assembling precipitation and temperature from CMIP5 under RCP2.6, RCP4.5 and RCP8.5 scenarios over the Pearl River basin. Results show that the BMA outperforms the traditional AM method. Precipitation tends to increase over the basin under RCP2.6 and RCP4.5 scenarios, whereas decrease under RCP8.5. The most remarkable increase of precipitation is found in the northern region under RCP2.6 scenario. The linear trend of the monthly mean near-surface air temperature increases with the growing CO concentration. The warming trends in four seasons are distinct. The warming rate is prominent in summer and spring than that in other season, meanwhile it is larger in western region than in other parts of the basin. The findings can provide beneficial reference to water resources and agriculture management strategies, as well as the adaptation and mitigation strategies for floods and droughts under the context of global climate change. [ABSTRACT FROM AUTHOR]

Under the exacerbation of climate change, climate extreme events, especially for drought, happened frequently and intensively across the globe with greater spatial differences. We used the Standardized Precipitation-Evapotranspiration Index computed from the routine meteorological observations at 269 sites in Southwest China (SWC) to study the drought characteristics (e.g., extent, duration and intensity) and their decadal variations during 1971-2012. It was revealed that the drought, in responses to the coupling between decadal precipitation and potential evapotranspiration (PET) anomalies, differed among regions and periods. For the entire SWC, droughts in 1970s and 2000s+ was generally stronger than in 1980s and 1990s with respect to their spatial extent, duration and intensity, especially in 2000s+. It was well-known that drought was closely related with a lack of precipitation; however, the impact of atmospheric demand of evaporation (reflected by PET here) on drought (e.g., duration and intensity) was rarely paid enough attentions. To that end, a spatial multi-linear regression approach was proposed in this study for quantifying the contributions of decadal PET and precipitation variations to drought duration and intensity. We have found that the contributions of decadal PET anomalies to drought duration and intensity could exceed those of precipitation, e.g., during 1980s and 1990s in SWC. Additionally, despite the strongest droughts in 2000s+, it was suggested that PET could exert comparable impacts on drought anomalies as precipitation. All these findings implied that PET plays a critical role in drought event, which acts to amplify drought duration and intensity. To sum up, this study stressed the need for enough attentions for PET processes in drought studies. [ABSTRACT FROM AUTHOR]

A dynamic recycling model (DRM) with an analytical moisture trajectory tracking method, together with Japan Meteorological Agency 25-year reanalysis data, is used to study the regional precipitation recycling process across China, by calculating the regional recycling ratio ( ρ ) at the daily time scale during 1979-2010. The distribution of ρ shows that, in western China, especially the Tibetan Plateau and its surrounding areas, precipitation is strongly dependent on the recycling process associated with regional evaporation. In Southeast China, however, the contribution from the recycling processes is much smaller due to the influence of the summer monsoon. A precipitation threshold value of about 4 mm/day is obtained from detailed analysis of both extreme and all-range ρ years. According to this threshold, China is classified into three types of sub-regions: low-precipitation sub-regions (mainly in the northwest), high-precipitation sub-regions (mainly in the south), and medium-precipitation sub-regions (mainly in the northeast). It is found that ρ correlates positively with precipitation, as well as convective precipitation ( P ) and large-scale precipitation ( P ) in the low-precipitation sub-regions. However, negative ρ ∼ P correlations are found in the high-precipitation sub-regions and nonsignificant correlations exist in the medium-precipitation sub-regions. As P is mainly locally generated due to mid-latitude mesoscale systems and the cumulus parameterization used in producing the reanalysis, the recycling ratio positively correlates to the ratio P / P in almost all sub-regions, particularly in the Tibetan Plateau and its surrounding areas. The correlation between radiation flux and ρ suggests more net radiation supports more evaporation and higher ρ , especially in the high-precipitation sub-regions. The influence of clouds on shortwave radiation is crucial, since evaporation is suppressed when the amount of cloudiness increases, especially in the high-precipitation sub-regions. Together with the consideration of soil moisture, it can be inferred that limited soil moisture inhibits evaporation in the low-precipitation sub-regions, while the energy or radiation is the dominant factor controlling evaporation in the high-precipitation sub-regions. [ABSTRACT FROM AUTHOR]

Drought over Southwest China occurs frequently and has an obvious seasonal characteristic. Proper management of regional droughts requires knowledge of the expected frequency or probability of specific climate information. This study utilized k-means classification and copulas to demonstrate the regional drought occurrence probability and return period based on trivariate drought properties, i.e., drought duration, severity, and peak. A drought event in this study was defined when 3-month Standardized Precipitation Evapotranspiration Index (SPEI) was less than −0.99 according to the regional climate characteristic. Then, the next step was to classify the region into six clusters by k-means method based on annual and seasonal precipitation and temperature and to establish marginal probabilistic distributions for each drought property in each sub-region. Several copula types were selected to test the best fit distribution, and Student t copula was recognized as the best one to integrate drought duration, severity, and peak. The results indicated that a proper classification was important for a regional drought frequency analysis, and copulas were useful tools in exploring the associations of the correlated drought variables and analyzing drought frequency. Student t copula was a robust and proper function for drought joint probability and return period analysis, which is important for analyzing and predicting the regional drought risks. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is particularly sensitive to the influences of climate change. As indicators of climate change, lakes on the TP play a key role in the Earth's climatic system. Lake Yazi (LY), Lake Tuohepingco (LT) and Lake Changtiao (LC) in the Tuohepingco Basin are three inland lakes on the plateau. The extents of LY, LT and LC were obtained using object-based image analysis for remote sensing and 22 images from Landsat satellites (from September to December between 1972 and 2015). Inter-annual changes in the extent of LY, LT and LC were then analyzed. The results show that the total area of the three lakes underwent a change from shrinkage to expansion between 1972 and 2015. In general, there was a trend toward shrinkage during 1972-1999, distinct expansion during 2000-2007 and slight expansion during 2008-2015. Moreover, we found that 14 other lakes have also expanded dramatically since 2000. Lakes at 30°N and 35°N (LY, LT and LC are also located in this region) exhibited the same dramatic period of expansion between 2000 and 2005. In other words, 2000 appears to be a critical transition point for changes in lake size on the TP. Lakes at the same latitudes in the Tibetan Plateau interior may have a similar period of dramatic expansion after 2000. The warming-triggered deglaciation or permafrost degradation, increased precipitation and decreased evapotranspiration may be the influencing factors of lake expansion in the Tuohepingco Basin. Temperature showed relatively higher correlation with lake extent, while precipitation and evaporation were slightly correlated with lake area. Given the importance of wetlands to human society, these are no trivial issues, and we now need accelerated research based on long-term and continuous remote sensing. [ABSTRACT FROM AUTHOR]

Urbanization and its resultant urban heat island provide a means for evaluating the impact of climate warming on vegetation phenology. To predict the possible response of vegetation phenology to rise of temperature, it is necessary to investigate factors influencing vegetation phenology in different climate zones. The start of growing season (SOS) in seven cities located in the middle temperate humid, semi-humid, semi-arid, and arid climate zones in China was extracted based on satellite-derived normalized difference vegetation index (NDVI) data. The dynamics of urban SOS from 2000 to 2009 and the correlations between urban SOS and land surface temperatures (LST), precipitation, and sunshine duration, respectively, were analyzed. The results showed that there were no obvious change trends for urban SOS, and the heat island induced by urbanization can make SOS earlier in urban areas than that in adjacent rural areas. And the impact of altitude on SOS was also not negligible in regions with obvious altitude difference between urban and adjacent rural areas. Precipitation and temperature were two main natural factors influencing urban SOS in the middle temperate zone, but their impacts varied with climate zones. Only in Harbin city with lower sunshine duration in spring, sunshine duration had more significant impact than temperature and precipitation. Interference of human activities on urban vegetation was non-negligible, which can lower the dependence of urban SOS on natural climatic factors. [ABSTRACT FROM AUTHOR]

Given the severe impacts of hot summers on human and natural systems, we attempt to quantify future changes in extreme hot summer frequency in China using the Coupled Model Intercomparison Project Phase 5 (CMIP5) projections. Unlike previous studies focusing on fixed future time slices, we investigate the changes as a function of global mean temperature (GMT) rise. Analyses show that extreme hot summers (June-July-August mean temperature higher than 90 % quantile of 1971-2000 climatology) are projected to occur at least 80 % of the time across China with a GMT rise of 2 °C. The fraction of land area with extreme hot summers becoming the norm (median of future summer temperatures exceed the extreme) will increase from ~15 % with 0.5 °C of GMT rise to ~97 % with 2.5 °C GMT rise, which is much greater than for the global land surface as a whole. A distinct spatial pattern of the GMT rise threshold over which the local extreme hot summer first becomes the norm is revealed. When averaged over the country, the GMT rise threshold is 0.96 °C. Earth system models exhibit comparable results to climate system models, but with a relatively larger spread. Further analysis shows that the concurrence of hot and dry summers will increase significantly with the spatial structure of responses depending on the definition of drying. The increase of concurrent hot and dry conditions will induce potential droughts which would be more severe than those induced by only precipitation deficits. [ABSTRACT FROM AUTHOR]

We developed a new reconstruction of annual precipitation (August-July) for the Helan Mountains near the southern edge of the Gobi Desert, using a regional tree-ring width chronology. The reconstruction explained 52.1 % of the observed precipitation variance during the period 1953-2008. In addition to the new precipitation reconstruction for the Helan Mountains, two previously published annual precipitation reconstructions from the same region were also used to infer the large-scale precipitation signal of the southern edge of the Gobi Desert. Spatial correlation analyses with gridded precipitation data showed that the tree-ring records were indeed able to capture much of the regional interannual precipitation variability. Using principal component analyses on the precipitation reconstructions and documentary records, 29 large-scale dry events were found during the period AD 1760-2006. Many of these dry events have had profound impacts on the people of the study area over the past several centuries. A notably good agreement with a temperature reconstruction for Zhangye suggests that the precipitation of the Gobi Desert has the characteristics of monsoon rainfall variability (wet-warm and cold-dry). Our precipitation reconstruction exhibited a downward trend during the last two decades, a trend also found in northern and eastern China. It might be caused by a weakening of the Asian summer monsoon induced by global warming (especially increased sea surface temperature). [ABSTRACT FROM AUTHOR]

Drought hazard is the main restrictive factor in the field of food production in China, and climate change may aggravate it over the long run. The present study aims to assess the potential drought hazard at present, as well as determine future different climate change scenarios based on the data of monthly precipitation and temperature. Drought is defined using the Standardized Precipitation-Evapotranspiration Index. The probability density function of SPEI was used to create the drought hazard index (DH), which provides a comprehensive overview of the frequency and intensity of drought events. The statistical downscale method was used to convert the regional climate model output grid data into meteorological station data for the near future (2020-2050) under three Representative Concentration Pathways (RCPs). The results showed that in the baseline (1981-2010), DH is much serious in Jilin compared with Henan. In the near future (2020-2050), DH increases in the case of RCP8.5, and the increased scale is larger in Henan. In the case of RCP4.5, the DH will be flat with baseline in Jilin and slightly increase in Henan. DH may relieve in case of RCP2.6. The results can help to optimize agriculture allocation and policy making with regard to climate change adaptation. [ABSTRACT FROM AUTHOR]

Global warming brings a huge challenge to society and human being. Understanding historic and future potential climate change will be beneficial to regional crop, forest, and water management. This study aims to analyze the precipitation and temperature changes in the historic period and future period 2021-2050 in the Xiangjiang River Basin, China. The Mann-Kendall rank test for trend and change point analysis was used to analyze the changes in trend and magnitude based on historic precipitation and temperature time series. Four global climate models (GCMs) and a statistical downscaling approach, LARS-WG, were used to estimate future precipitation and temperature under RCP4.5. The results show that annual precipitation in the basin is increasing, although not significant, and will probably continue to increase in the future on the basis of ensemble projections of four GCMs. Temperature is increasing in a significant way and all GCMs projected continuous temperature increase in the future. There will be more extreme events in the future, including both extreme precipitation and temperature. [ABSTRACT FROM AUTHOR]

We developed a tree-ring width chronology from pine trees ( Pinus tabulaeformis and Pinus armandii) stand near the peaks of Huashan, Shaanxi, north-central China. Growth-climate response analyses showed that the radial growth of pine trees is mainly influenced by April-June precipitation. A model to reconstruct precipitation based on tree widths was constructed, accounting for 55 % of the instrumental variance during the period 1953-2012. Spatial correlation analyses between the reconstruction and observed gridded precipitation data shows that the seasonal precipitation reconstruction captures regional climatic variations over north China. Compared with the historical archives and other tree-ring records in north China, many large-scale drought events, linked to the El Niño-Southern Oscillation (ENSO), were found. Many of these events have had profound impacts on the people of north China over the past several centuries. Composite maps of sea surface temperatures and 500 hPa geopotential heights for selected extremely dry and wet years in Huashan show characteristics similar to those related to the ENSO patterns, particularly with regard to ocean and atmospheric conditions in the equatorial and north Pacific. Our 531-year precipitation reconstruction for Huashan provides a long-term perspective on current and 20th century wet and dry events in north China, and is useful to guide expectations of future variability, and helps us to address climate change. [ABSTRACT FROM AUTHOR]

Much attention has recently been focused on the effects that precipitation and potential evapotranspiration (PET) have had on runoff change; however, the influence of temperature on runoff needs to be further studied. We attempted to employ the improved elasticity method to evaluate the effects of climate factors (CF, especially temperature) on runoff change for Aksu River in the arid region of northwest China. Data from Aksu River in the arid region of northwest China were analyzed to investigate changes in annual runoff and CF during the period of 1960-2010. The key findings of this study indicated that the annual runoff had a significant ( P < 0.01) increasing trend with a rate of 3.78 × 10 m/decade, and the temperature and precipitation also exhibited significant rising trends, at a rate of 0.28 °C/decade ( P < 0.01) and 15.11 mm/decade ( P < 0.05), respectively, while PET showed a decreasing trend (22.66 mm/decade, P < 0.01). Step change point in runoff occurred in the year 1993. Thus, we employed the mean runoff and climate factors during the period 1960-1993 as the benchmark value to measure the change. In 1994-2010, mean runoff increased by 22 %. Results also revealed that temperature rising was the most important factor that increased runoff with contribution of 45 %, while precipitation and PET were responsible for 22 and 27 % of the runoff change, respectively, indicating that the runoff of increasing percentage only accounted for 6 % owing to human activities and other factors, and showed that climate variability was the main reason for the runoff change in Aksu River. [ABSTRACT FROM AUTHOR]

Water resources are very important for grain production in China. In this study, we investigate the changes in streamflow and grain production in China from 1956 to 2008. Since the 1980s, the increase of total grain production was mainly contributed by northern China where significantly decreasing precipitation and available water resources were observed. From 1985 to 2008, northern China accounted for 92.9 % of the national total grain production growth. Consequently, the main grain production area has shifted from the south to the north. However, the shift was mismatching the spatial distributions and temporal changes in precipitation and available water resources in China. During 1956 through 2008, precipitation decreased in the main grain production areas of the northern China by 1.23-1.27 mm per year. During the same period, observed streamflows in the five major rivers in northern China decreased by 13.4-92.4 %. Current grain production in northern China is dependent on overexploitation of groundwater. From 1987 to 2000, the average groundwater table declined 10.8 m with a maximum decrease of 34.8 m in North China Plain. Furthermore, the impacts of climate change and projected industrial development exacerbate the uncertainty of grain supply by northern China in the future. This study also indicated the potential of southern China for a more important role in ensuring sustainable food security of China, with increasing precipitation and streamflows observed in the Yangtze River and Pearl River basins. [ABSTRACT FROM AUTHOR]

Six global climate models (GCMs) from Coupled Model Intercomparison Project Phase 5 under three Respectively Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5) were used to assess the impact of climate change on streamflow for the Huangnizhuang catchment (HNZ) in China. Change factor method was used for bias correction between GCM outputs and observations and the SWAT model was used to simulate the hydrological processes. The results indicated that the SWAT model performed well in the study catchment with a monthly Nash-Sutcliffe efficiency (NS) of 0.93 and 0.91 and daily NS of 0.63 and 0.68 for calibration and validation periods respectively. Their corresponding relative errors were −2.2 and 8.9, and −2.6 and 8.5 % respectively. The ensemble of multi-GCMs projected an increase of precipitation in the middle and end of twenty-first century over the HNZ, ranging from −2.4 to 9 %. However, streamflow is likely to decline in the future, ranging −6.9 to 0.8 %, mainly due to an increase of evapotranspiration in a warming world, as air temperature shows steadily increases for all the GCMs and RCPs. Average monthly streamflow from six GCMs are likely to increase in August and September but decline from October to June. The associated uncertainties of the reported results were also discussed. It includes, but is not limit to, different GCMs, emissions scenarios, downscaling techniques as well as hydrological simulations. The results of this study can inform planning of long-term basin water management strategies taking into account global change scenarios. [ABSTRACT FROM AUTHOR]

Water resources are contingent on the combined effects of climate change and watershed characteristics. An analytical model devised from the Budyko framework was used to investigate the partitioning of precipitation ( P) into actual evapotranspiration ( E) and streamflow ( Q) parameters for the Yellow River Basin (YRB), a water-limited basin, to estimate the response of E and Q to P and potential evapotranspiration ( E). Although a steady state was assumed, the analytical model, incorporating an adjustable parameter characteristic of catchment conditions ( ω), can be run to analyze the sensitivity of catchment characteristics on water resources. The theory predicts that Q and E are more sensitive to P than to E. For example, a 10 % increase in P will result in a 22.8 % increase in Q, while a 10 % increase in E will decrease Q by 13.2 %. The model shows that, to some extent, water balance is governed by changing catchment characteristics (such as changes in vegetation on annual scales). These findings indicate that additional elucidative data can be drawn from the Budyko framework when taking into account catchment characteristics. Furthermore, the model can analyze the response of water resources to climate change on different temporal and spatial scales. [ABSTRACT FROM AUTHOR]

This study examines persistent and short-lived heavy precipitation events (PHPEs and SHPEs, respectively) in South China during summer (July-September) 1975-2009 in association with large-scale circulation and moisture processes at different timescales. Compared to SHPEs, PHPEs are characterized by long-lasting enhanced convection and cyclonic moisture circulation as well as strengthened moisture convergence over South China. Examination of environmental variables at different timescales suggests that intraseasonal and synoptic components play a deterministic role in regulating the overall changes in convection and moisture convergence, while the low-frequency background state plays only a marginal role. Further analysis of the moisture divergence terms also reveals that the overall changes in moisture divergence during PHPEs and SHPEs stem primarily from variations in the intraseasonal and synoptic wind fields rather than in the humidity fields. Overall, it is found that the location and strength of the intraseasonal oscillation (ISO) and the synoptic disturbances play a decisive role in controlling the severity and duration of rainfall events over South China. The synchronization and persistence of the enhanced convection and moisture circulation of the ISO and synoptic disturbances jointly contribute to prolonged heavy precipitation over South China, while the weakening and asynchrony of the associated convection and moisture circulation at different timescales result in rainfall events of weaker intensity and shorter duration. [ABSTRACT FROM AUTHOR]

Individual impacts of climate change, land use/coverage change, the regulation of water reservoir and water use to intra-annual distribution of streamflow of the Dongjiang River basin, South China, are quantitatively separated. Data on precipitation, streamflow, regulation of water reservoirs, and water use are used in the analysis. Changes in the concentration degree and non-uniformity coefficient of intra-annual distribution of streamflow over time scales from daily to monthly are evaluated. Trend and change point analyses are applied to determine characteristics of intra-annual distribution of streamflow. By comparison with the difference among region precipitation, naturalized streamflow and observed streamflow, the contribution of main impact factors to the intra-annual distribution of streamflow are quantified. Results demonstrate the non-uniformity coefficient decreases with a negative logarithmic linear function of the time scale. Change points of the concentration degree and non-uniformity coefficient occurred in 1973 exhibited a significant downward trend. In the period posterior to the change point the former and the latter decrease approximately by 15-34 % and by 29-40 %, respectively. The decrease in concentration degree and non-uniformity coefficient is due to the regulation of water reservoirs and land use/cover change; while the increase is the result of water use and climate change. The individual contributions to the impact on the intra-annual distribution of streamflow from regulation of water reservoirs, land use/cover change, water use, and climate change are approximately −33.5, −9.0, 4.5 and 1.0 %. It is observed that the impacts of the regulations of the Xinfengjiang, Fengshuba, and Baipenzhu reservoirs account for −21, −10, and −2 %, respectively. There is an increasing tendency in the impacts of land use/cover change and water use in the past 30 years. [ABSTRACT FROM AUTHOR]

As one of the most important climatic variables, annual evapotranspiration ( E) reflects the complex interactions between atmosphere, vegetation, soil and hydrological process at global and regional scales. It is largely determined by potential evapotranspiration ( E) and precipitation ( P). Aridity index ( E/ P) which can be defined as the ratio of annual potential evapotranspiration to annual precipitation, can be used to represent annual evapotranspiration. As result it has become an important indicator to assess water-related climate change. This study utilizes the aridity index to reveal the recent climate change patterns in the Lancang River Basin, China. A new non parametric estimator of climate elasticity has also been developed. Using the daily meteorological records (1961-2005) of precipitation, air temperature, wind speed, relative humidity and sunshine hours from 35 stations, changes in spatial and temporal characteristics of P, E , E, and E/ P are analyzed. The results reveal some important new findings, which can be summarized as: (a) new findings show that the spatial distribution of, and the correlation coefficients between P, E, E, and E/ P possess strong latitude zonality; (b) high consistency in the temporal variation of P and E has been detected. The main periodicity of the E and E/ P series varies greatly for the three sub basins, and an anti-phase relationship between them has also been found; (c) our newly developed nonparametric estimator of climate elasticity can be successfully used in assessing the sensitivity of climate system. Climate elasticity of E in relation to E and P increases for most of the regions in the study area, suggesting that E becomes more sensitive to changes in the corresponding climatic variable during the study period. The study demonstrates the importance of the aridity index in the water-related climate change studies which has been neglected for a long time by most hydrologists and managers. [ABSTRACT FROM AUTHOR]