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ABSTRACT Heavy rain events or rainstorms of various scales often occur in Hong Kong from April to September. In extremes cases, they lead to serious landslides and flash floods resulting in loss of life, and damage to property and infrastructure. With climate change, extreme rain events are projected to be more frequent and more intense in this region. A system to gauge and label the severity of rainstorms would be useful for identifying and communicating extreme conditions in warning and disaster prevention operations. In parallel, a better understanding of the characteristics of rainstorms would also be important for impact assessments and engineering design purposes. This paper formulates a practical framework to index the magnitude and severity of rainstorms in Hong Kong. An index termed as the Severity Index combining the magnitude of different rainstorm attributes is devised for quantifying the overall severity of rainstorms. This index is flexible to allow tuning for specific applications. [ABSTRACT FROM AUTHOR]

ABSTRACT The arid region in northwestern China covers 2·02 million square kilometres and is one of the most arid regions in the world. Positioned at the central part of the Eurasian Continent, this region experiences little influence from the Eastern and Southern Asian Monsoons and precipitation is formed mostly from westerly vapour. With a hyper arid climate, the annual precipitation in this region ranges from less than 20 mm at the oasis area to around 600 mm in the mountain regions, whereas potential evaporation can amount to 2000-3000 mm per annum. It is reported that strong evapotranspiration characterizes and dominates the water cycle in the arid basins. Nearly all the water resources of the oasis, where the human society exists, come from the mountain areas as river discharge from glacier/snow melting water, rainfall and subsurface flow from bedrock cracks. As a result, the hydrographs of the arid basins are affected by climate change via changes in precipitation partitioning (the ratio of rainfall and snowfall) and changes to seasonal distributions of precipitation and air temperature. These changes in turn directly affect the water yield and the vegetation response. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Changes in precipitation can be expected to have a major influence on the frequency and severity of flooding in the Taihu Basin. As part of an integrated assessment of flood risk in the Taihu Basin, this paper addresses the hydrological conditions and the potential impacts of climate change on Taihu Lake water levels. The hydrological system is simulated by using the distributed hydrological model VIC ( Variable Infiltration Capacity), with future climate scenarios generated by the regional climate model PRECIS (Providing Regional Climates for Impacts Studies). The results indicate that maximum and mean flood water levels under the A2 and B2 scenarios for 2021-2050 will be higher than the levels during the baseline period (1961-1990), with larger increases under the B2 scenario than for the A2 scenario. The storm return periods leading to extreme water levels in the Taihu Lake in the future is projected to decrease significantly in comparison to the baseline period, implying the potential for the more frequent occurrence of major floods. These results indicate the importance of planning for future flood control in the Taihu Basin. [ABSTRACT FROM AUTHOR]

Influences of climatic change on the components of global hydrological cycle, including runoff and evapotranspiration are significant in the mid- and high-latitude basins. In this paper, the effect of climatic change on annual runoff is evaluated in a large basin-Songhua River basin which is located in the northeast of China. A method based on Budyko-type equation is applied to separate the contributions of climatic factors to changes in annual runoff from 1960 to 2008, which are computed by multiplying their partial derivatives by the slopes of trends in climate factors. Furthermore, annual runoff changes are predicted under IPCC SRES A2 and B2 scenarios with projections from five GCMs. The results showed that contribution of annual precipitation to annual runoff change was more significant than that of annual potential evapotranspiration in the Songhua River basin; and the factors contributing to annual potential evapotranspiration change were ranked as temperature, wind speed, vapour pressure, and sunshine duration. In the 2020s, 2050s, and 2080s, changes in annual runoff estimated with the GCM projections exhibited noticeable difference and ranged from − 8·4 to − 16·8 mm a−1 (−5·77 to − 11·53% of mean annual runoff). Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The magnitude and frequency of regional extreme precipitation events may have variability under climate change. This study investigates the time-space variability and statistical probability characteristics of extreme precipitation under climate change in the Haihe River Basin. Hydrological alteration diagnosis methods are implemented to detect the occurrence time, style and degree of alteration such as trend and jump in the extreme precipitation series, and stationarity and serial independence are tested prior to frequency analysis. Then, the historical extreme precipitation frequency and spatio-temporal variations analyses are conducted via generalized extreme value and generalized Pareto distributions. Furthermore, the occurrence frequency of extreme precipitation events in future is analysed on the basis of the Fourth Assessment Report of the Intergovermental Panel on Climate Change multi-mode climate models under different greenhouse gases emission scenarios (SRES-A2, A1B and B1). Results indicate that (1) in the past, alteration of extreme precipitation mainly occurred in the area north of 38°N. Decreasing trends of extreme precipitation are detected at most stations, whereas jump alteration is not obvious at most stations. (2) Spatial variation of estimated extreme precipitation under different return periods shows similarity. Bounded by the Taihang Mountain-Yan Mountain, extreme rainfall in the Haihe River Basin gradually reduces from the southeast to the northwest, which is consistent with the geographical features of the Haihe River Basin. (3) In the future, extreme precipitation with return period 5-20 years accounts for a significant portion of the total occurrence times. The frequency of extreme precipitation events has an increase trend under A1B and A2 scenarios. The total occurrence times of extreme precipitation under A1B senario are not more than that under B1 senario until the 2030s. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

It is important to understand the hydroclimate history of water‐deficient regions, such as the Alxa desert of northwest China. However, there are few high‐resolution proxy records for the hydroclimate changes over the past centuries in the Alxa desert. Fortunately, there are many tree‐ring hydroclimate reconstructions from the nearby mountains. However, the hydroclimate correlations between the Alxa desert and adjacent mountains are unclear. Here, we collected high‐quality data from 43 meteorological stations in northwest China (1960–2017). We found increasing mean temperatures in the study area, both on seasonal and annual timescales. We also found that while relative humidity had mostly decreased in the Mt. Qilian and Alxa desert, precipitation and the standardized precipitation evapotranspiration index (SPEI) increased mostly. In the Mt. Helan and Hasi ranges, relative humidity, precipitation, and SPEI all showed decreasing trends. Empirical orthogonal function analysis indicated that precipitation, relative humidity, and SPEI in the Mt. Qilian were similar to the corresponding conditions in the central and western Alxa desert. Hydroclimate conditions in the Mt. Helan and Hasi ranges were correlated with data from the eastern desert. Tree‐ring records of precipitation and SPEI from the mountains were used to validate the hydroclimate correlations during the instrumental period. We found strong similarities between hydroclimatic changes in the Mt. Qilian and those in the central and western Alxa desert, on both annual and decadal timescales, from 1877 to 2006. Tree‐ring width chronologies from mountainous areas were shown to faithfully represent the hydroclimatic history of the desert area. Plain Language Summary: Northwestern China has faced serious ecological challenges over the past five decades, including intensified desertification and declining lake levels. Understanding the regional hydroclimate history is necessary to manage water resources in this water‐deficient region. However, there are few climate proxies for these desert areas. In contrast, high‐resolution tree‐ring climate proxies have been studied intensively in the nearby mountains. This study attempts to find reliable correlations between mountain and desert hydroclimate. We found increasing mean temperatures over the entire study area. We also found that precipitation, relative humidity, and drought index data from the western and central desert were strongly correlated with data from Mt. Qilian, while data from the eastern desert were correlated with those from the Helan and Hasi mountain ranges. When relative humidity decreased mostly in the Mt. Qilian, precipitation and SPEI mostly increased; in the Mt. Helan and Hasi areas, relative humidity, precipitation and SPEI mostly decreased. Tree‐ring records from the mountains were compared to validate these correlations. Significant correlations were found between the precipitation reconstructions from the central desert and Mt. Qilian from 1877 to 2006. We also used tree‐ring width chronologies to show that they could represent the hydroclimatic history of the Alxa desert. Key Points: Precipitation and SPEI indicate wetter trends in Mt. Qilian but drier trends in Mt. Helan and Hasi ranges from 1960 to 2017Precipitation, relative humidity, and SPEI in western and central (eastern) Alxa desert resemble conditions in Mt. Qilian (Helan and Hasi)Tree‐ring proxies from nearby mountains can faithfully represent the hydroclimate history of the Alxa desert [ABSTRACT FROM AUTHOR]

This study compares the impacts of global warming and intense urban anthropogenic heat (AH) on extreme hourly precipitation over the Pearl River Delta (PRD) megacity, located in coastal South China. Using the cloud‐resolving Weather Research and Forecasting (WRF) model coupled with the single‐layer urban canopy model (SLUCM), three downscaling experiments were carried out: the first (second) having zero (300 W/m2) as diurnal maximum AH values prescribed over PRD urban grids, under the current climate conditions. The third experiment with diurnal maximum AH of 300 W/m2 under future projected climate representative concentration pathway (RCP) 8.5. Boundary conditions were derived from PRD extreme rainfall episodes, identified from the Geophysical Fluid Dynamics Laboratory Earth System Model (GFDL‐ESM2M) historical and RCP8.5 runs. Global warming forcing leads to ∼20% to more than 100% increase in the probability of hourly precipitation with the magnitude of 20–100 mm/hr over urban locations. The enhancements from intense AH forcing were similar. However, two forcings have distinct signatures in modulating the thermodynamic environment. Warming due to AH is limited to the lowest 1 km above ground, while global warming warms up the whole troposphere. Intense AH results in enhanced convective available potential energy (CAPE) and reduced convective inhibition (CIN) within the megacity, allowing convection to be triggered more easily and with more vigor. On the other hand, global warming enhances CAPE and CIN, over both urban and rural areas. Our results highlight the different mechanisms of AH and global warming in exacerbating extreme urban rainfall, despite the similar impacts on the rainfall intensity. Plain Language Summary: Human activities can generate extra heat in cities, called anthropogenic heat. This heat can exacerbate the heavy rainfall in the urban area over the Pearl River Delta urban area, where located at the south China coast. We used computational models to simulate and compare the situation of the presence and absence of anthropogenic heat during a list of extreme rainfall events under a current and global warming environment. Results show that anthropogenic heat enhances the heavy rainfall in the urban area, while global warming enhances heavy rainfall over both urban and nonurban area in the Pearl River Delta. Both enhancements are comparable to each other. Anthropogenic heat causes a localized urban temperature increment, while global warming causes a global temperature increment. The different temperature response creates the differences of rainfall response. Key Points: Anthropogenic heat creates higher convective available potential energy (CAPE) and lower convective inhibition (CIN) in urban locations within the Pearl River Delta and intensifies urban extreme rainfallGlobal warming results in higher CAPE, which exacerbates extreme rainfall in both urban and surrounding rural areasImpacts due to intense anthropogenic heat and global warming on extreme rainfall can be comparable over highly urbanized coastal locales [ABSTRACT FROM AUTHOR]

Climate elasticity of runoff is an important indicator for evaluating the effects of climate change on runoff. Consequently, this paper proposes an analytical derivation of climate elasticity. Based on the mean annual water-energy balance equation, two dimensionless numbers (the elasticities of runoff to precipitation and potential evaporation) were derived. Combining the first-order differential of the Penman equation, the elasticities of runoff to precipitation, net radiation, air temperature, wind speed, and relative humidity were derived to separate the contributions of different climatic variables. The case study was carried out in the Futuo River catchment in the Hai River basin, as well as in 89 catchments of the Hai River and the Yellow River basins of China. Based on the mean annual of climatic variables, the climate elasticity in the Futuo River basin was estimated as follows: precipitation elasticity ϵP} = 2.4$, net radiation elasticity ϵRn = - 0.8, air temperature elasticity ϵT} = -0.05°C-1 wind speed elasticity ϵU} = -0.3, and relative humidity elasticity ϵRH0.8. In this catchment, precipitation decrease was mainly responsible for runoff decline, and wind speed decline had the second greatest effect on runoff. In the 89 catchments of the Hai River and the Yellow River basins of China, climate elasticity was estimated as follows: ϵPranging from 1.6 to 3.9, ϵRn ranging from -1.9 to -0.3, ϵET ranging from -0.11 to -0.02°C-1, ϵU ranging from -0.8 to -0.1, and ϵRH ranging from 0.2 to 1.9. Additional analysis shows that climate elasticity was sensitive to catchment characteristics. [ABSTRACT FROM AUTHOR]

The selection of general circulation models (GCMs) with high capability to represent the past and likely future climate for a specific geographical location is a crucial step to assess impacts of climate change on different sectors. This study included pool of 105 and 78 GCMs for representative concentration pathways (RCPs) 4.5 and 8.5, respectively, from Coupled Model Intercomparison Project—Phase 5, applied an advanced envelope‐based selection approach to select representative GCMs for the Koshi river basin in China and Nepal at short‐term (2016–2045), mid‐century (2036–2065) and end‐of‐century (2071–2100) periods, and developed range of possible future precipitation and temperature scenarios with high resolution downscaled data (10 × 10 km2), which is the novelty contribution of the study. Considering RCP4.5, average annual precipitation is expected to increase by 0–16%, 4–23% and 4–24% in the short‐term, mid‐century and end‐of‐century periods, respectively. Using RCP8.5, equivalent predictions are 6–20%, 6–36% and 13–49% in the short‐term, mid‐century and end‐of‐century periods, respectively. Average annual temperature is expected to increase, but with higher increases during winter than in the monsoon period. Considering RCP4.5, average annual temperature is expected to increase by 1–1.4°C, 1.3–1.9°C and 1.6–2.8°C in the short‐term, mid‐century and end‐of‐century periods, respectively. Similarly, using RCP8.5, equivalent predictions are 1–1.6°C, 1.8–2.9°C and 3.1–5.6°C in the short‐term, mid‐century and end‐of‐century periods, respectively. The ensemble mean of absolute change in average precipitation and temperature projects that High Himalaya and Tibet regions are more sensitive to climate change considering precipitation and temperature, respectively. The results also suggest that GCMs selection for a catchment varies with climate scenarios and specific future time periods. [ABSTRACT FROM AUTHOR]

Precipitation is projected to change intensity and seasonal regime under current global projections. However, little is known about how seasonal precipitation changes will affect soil respiration, especially in seasonally dry tropical forests. In a seasonally dry tropical forest in South China, we conducted a precipitation manipulation experiment to simulate a delayed wet season (DW) and a wetter wet season (WW) over a three‐year period. In DW, we reduced 60% throughfall in April and May to delay the onset of the wet season and irrigated the same amount water into the plots in October and November to extend the end of the wet season. In WW, we irrigated 25% annual precipitation into plots in July and August. A control treatment (CT) receiving ambient precipitation was also established. Compared with CT, DW significantly increased soil moisture by 54% during October to November, and by 30% during December to April. The treatment of WW did not significantly affect monthly measured soil moisture. In 2015, DW significantly increased leaf area index and soil microbial biomass but decreased fine root biomass. In contrast, WW significantly decreased fine root biomass and forest floor litter stocks. Soil respiration was not affected by DW, which could be attributed to the increased microbial biomass offsetting the decrease in fine root biomass. In contrast, WW significantly increased soil respiration from 3.40 to 3.90 μmol m−2 s−1 in the third year, mainly due to the increased litter decomposition and soil pH (from 4.48 to 4.68). The present study suggests that both a delayed wet season and a wetter wet season will have significant impacts on soil respiration‐associated ecosystem components. However, the ecosystem components can respond in different directions to the same change in precipitation, which ultimately affected soil respiration. [ABSTRACT FROM AUTHOR]

Plant community may provide products and services to humans. However, patterns and drivers of community stability along a precipitation gradient remain unclear. A regional‐scale transect survey was conducted over a 3‐year period from 2013 to 2015, along a precipitation gradient from 275 to 555 mm and spanning 440 km in length from west to east in a temperate semiarid grassland of northern China, a central part of the Eurasian steppe. Our study provided regional‐scale evidence that the community stability increased with increasing precipitation in the semiarid ecosystem. The patterns of community stability along a precipitation gradient were ascribed to community composition and community dynamics, such as species richness and species asynchrony, rather than the abiotic effect of precipitation. Species richness regulated the temporal mean (μ) of aboveground net primary productivity (ANPP), while species asynchrony regulated the temporal standard deviation (σ) of ANPP, which in turn contributed to community stability. Our findings highlight the crucial role of community composition and community dynamics in regulating community stability under climate change. [ABSTRACT FROM AUTHOR]

Climate change and urbanization collectively influence precipitation changes. However, their separate potential contributions to precipitation changes are not well understood due to their complex interactions. Hence, a "trajectory"‐based method was used to separate their potential contributions across national, regional and local scales in China. Precipitation changes in non‐urban regions can be regarded as representing the influence of climate change and can serve as a reference for isolating precipitation changes due to urbanization in urban areas. Our results revealed that climate change was the dominant factor for precipitation trends, while urbanization exhibited a relatively weak influence, especially for extreme precipitation at the national scale. At the regional scale, the impacts of urbanization on precipitation became more significant. About 20.2 and −30.6% of positive and negative trends in total precipitation originated from urbanization. At the local scale, the potential contribution of urbanization was strongly correlated with local environmental characteristics. Although there were differences in the potential contributions of climate change and urbanization at national, regional and local scales, climate change was the dominant factor for precipitation trends and urbanization acted as a regulator to drying or wetting due to precipitation under climate change. In general, urbanization causes a greater impact on total precipitation than on precipitation extremes. Due to this, attribution approach is static and broad‐based and does not render the level of confidence that is needed for scale‐aware attribution, future studies are needed to understand the physical mechanisms of impacts of local environment changes on precipitation trends at different geographical locations over China. [ABSTRACT FROM AUTHOR]

Risk analysis of urban flood and drought can provide useful guidance for urban rainwater management. Based on an analysis of urban climate characteristics in 2,264 Chinese cities from 1958 to 2017, this study evaluated urban flood and drought risks. The results demonstrated that the annual average values of precipitation, aridity index, frequency and intensity of extreme precipitation and extreme drought events differed significantly in these cities. The values of the above six climatic indicators in the cities ranged from 9.29–2639.30 mm, 0.47–54.73, 1.08–8.79 time, 7.82–107.25 mm, 0.76–2.99 time, and 10.30–131.19 days, respectively. The geographical patterns of urban precipitation, aridity index, intensity and frequency of extreme precipitation and drought events in China fit well to the Hu‐Huanyong Line that was created in 1940s to identify the pattern of population distribution. Extreme precipitation in most cities has upward trends, except for those around the Hu‐Huanyong Line. The extreme drought events had upward trends in the cities east of the Hu‐Huanyong Line, but there were downward trends in the cities west of the line. The risk assessment indicated that 3.80% cities were facing serious flood and 6.01% cities were facing serious drought risks, which are located in the coast of southern China and northwestern China, respectively, and other 90.19% cities were facing different types of drought and flood risks in terms of their intensity and frequency. [ABSTRACT FROM AUTHOR]

Glacial retreat and the thawing of permafrost due to climate warming have altered the hydrological cycle in cryospheric‐dominated watersheds. In this study, we analysed the impacts of climate change on the water budget for the upstream of the Shule River Basin on the northeast Tibetan Plateau. The results showed that temperature and precipitation increased significantly during 1957–2010 in the study area. The hydrological cycle in the study area has intensified and accelerated under recent climate change. The average increasing rate of discharge in the upstream of the Shule River Basin was 7.9 × 106 m3/year during 1957–2010. As the mean annual glacier mass balance lost −62.4 mm/year, the impact of glacier discharge on river flow has increased, especially after the 2000s. The contribution of glacier melt to discharge was approximately 187.99 × 108 m3 or 33.4% of the total discharge over the study period. The results suggested that the impact of warming overcome the effect of precipitation increase on run‐off increase during the study period. The evapotranspiration (ET) increased during 1957–2010 with a rate of 13.4 mm/10 years. On the basis of water balance and the Gravity Recovery and Climate Experiment and the Global Land Data Assimilation System data, the total water storage change showed a decreasing trend, whereas groundwater increased dramatically after 2006. As permafrost has degraded under climate warming, surface water can infiltrate deep into the ground, thus changing both the watershed storage and the mechanisms of discharge generation. Both the change in terrestrial water storage and changes in groundwater have had a strong control on surface discharge in the upstream of the Shule River Basin. Future trends in run‐off are forecasted based on climate scenarios. It is suggested that the impact of warming will overcome the effect of precipitation increase on run‐off in the study area. Further studies such as this will improve understanding of water balance in cold high‐elevation regions. [ABSTRACT FROM AUTHOR]

This study examines potential benefits of performance‐based multi‐model ensembles (MMEs) in projecting the impacts of climate change on extreme precipitation indices over East Asia (EA) using the data from 19 GCMs in the coupled model intercomparison project 5 (CMIP5). The Taylor skill score is adopted as the measure of the model skills in simulating the spatial and interannual variability of the selected extreme precipitation indices over four EA regions. The overall rank based on the total skill score (TSC) is used to construct two skill‐based MMEs, MME of high‐skill, MMH (MME of low‐skill, MML) that include the top (bottom) seven models, in addition to the simple ensemble of all 19 GCMs (ENS). Inter‐GCM consistency is measured using the signal‐to‐noise ratio (SNR). In the present‐day period, MMH yields higher skill scores than MML and ENS for almost all extreme precipitation indices as well as regions. Regional variations in biases, inter‐model consistency, and TSC are large. The inter‐model consistency is highest for Northern China and Manchuria and is lowest for Southern China. The most notable differences in the key properties of climate change signals from the three MMEs among the three ensembles are that the climate change signals from MMH and ENS exceed the 90% significance level in much larger areas than those from MML. However, the differences in the climate change signals between MMH and MML are generally below the 90% significance level. The SNR of the projected climate change signals shows that MMH yields more consistent climate change signals than ENS/MML. Both the SNR differences and the area in which statistical significance exceed the 90% level suggest that constructing climate change signals from a group of higher‐skill models may yield more reliable projections than constructing MMEs from the entire models or a group of lower‐skilled models. The domains used in the study (SOUTH: 110°–140°E, 20°–30°N, MIDDLE: 110°–140°E, 30°–40°N), NORTH: 110°–140°E, 40°–50°N, EA: 110°–140°E, 20°–50°N) [ABSTRACT FROM AUTHOR]

Understanding the changes in aridity is crucial because of the substantial impacts it can have on human society. However, realistic aridity changes and their underlying climatic mechanisms demonstrate large uncertainties in China. Here we adopted the aridity index (AI) to assess the aridity changes in China, and we quantified the relative contributions of various climatic drivers (the precipitation, net radiation, wind speed, relative humidity, and air temperature) to AI changes based on the station data during 1961–2016. Our results showed that the arid/semi‐arid northwest China and Tibet Plateau experienced wetting trends, while western sub‐humid north and northeast China and western humid south China exhibited drying trends during 1961–2016. The dominant climatic drivers involved in the changing AI trends changed from arid to humid regions. In arid northwest China, increasing precipitation and decreasing wind speeds contributed the most to the wetting trends (0.024 and 0.017 in 56 years, respectively). In the semi‐arid Tibet Plateau, increasing precipitation dominated the wetting trends (0.045 in 56 years). However, in sub‐humid/humid north and northeast China and south China, decreasing wind speed and net radiation dominated the annual AI changes (0.061 and 0.092 in 56 years, respectively). In addition, AI of northwest China and the Tibet Plateau exhibited a significant abrupt change in 1987 and exhibited wetter states afterwards, which could be caused by the abrupt increase in precipitation in 1987. This study could improve current understanding of the aridity changes in China and help adapt its potential impacts. This study investigated the aridity changes and their underlying climatic mechanisms in China using station data during 1961–2016. Results showed that the "arid regions getting drier; humid regions getting wetter" is not applicable to China. The dominant climatic driver for aridity changes varies from arid to humid regions. Precipitation dominates the wetting trends in arid/semi‐arid northwest China and the Tibet Plateau, whereas wind speed and net radiation dominate aridity changes in sub‐humid/humid north and northeast China and south China. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) play vital roles in plant growth and development. Yet how climate regimes and soil fertility influence plant N and P stoichiometry is not well understood, especially in the belowground plant parts. Here we investigated plant aboveground and belowground N and P concentrations ([N] and [P]) and their stoichiometry in three dominant genera along a 2200 km long climatic gradient in northern China. Results showed that temperature explained more variation of [N] and [P] in C4 plants, whereas precipitation exerted a stronger influence on [N] and [P] in C3 plants. Both plant aboveground and belowground [N] and [P] increased with decreasing precipitation, and increasing temperatures yet were negatively correlated with soil [N] and [P]. Plant N:P ratios were unrelated with all climate and soil variables. Plant aboveground and belowground [N] followed an allometric scaling relationship, but the allocation of [P] was isometric. These results imply that internal processes stabilize plant N:P ratios and hence tissue N:P ratios may not be an effective parameter for predicting plant nutrient limitation. Our results also imply that past positive relationships between plant and nutrient stocks may be challenged under changing climatic conditions. While any modeling would need to be able to replicate currently observed relationships, it is conceivable that some relationships, such as those between temperature or rainfall and carbon:nutrient ratios, should be different under changing climatic conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Daily precipitation data from 34 weather stations in Northeast China from 1960 to 2008 are used to examine trends in the occurrence of dry days and prolonged dry episodes. Trends in the mean length and frequency of prolonged dry episodes, as well as the number of dry days within prolonged dry episodes ( DDPDE), are computed regionally and for individual stations at the threshold levels of 1 and 2 mm day−1. Regionally, the number of dry days is increasing in the summer half-year and decreasing in the winter half-year. DDPDE is significantly increasing in the summer half-year; the increased frequency of dry spells has the greatest effect. The mean length of prolonged dry episodes in the winter half-year has decreased significantly. Our results indicate that neither the frequency nor the mean length of prolonged dry episodes, alone, can adequately describe the short-term dry conditions of an area. Multiple characteristics of dry spells, including frequency, length, and the number of DDPDE should be considered. DDPDE is a function of both the frequency and length of dry episodes, but may be more influenced by one or the other characteristics of dry spells, depending on the season or region. [ABSTRACT FROM AUTHOR]

Aim The long-term cyclical patterns of China's geopolitical shifts are of great interest to scholars and the public, but to date there has been no satisfactory explanation for the alternating occupancy patterns of the country's pastoral and agrarian polities. We fill this gap by differentiating the agroecological settings of these polities over time and quantitatively analysing the relationships between climate change and historical geopolitical variations. Location China. Methods Our dataset comprised 38 palaeohydroclimate reconstructions, the historical boundaries of China's empire and the changes in its size, and 1028 wars and 2737 battle locations over the past 2300 years. China-wide precipitation during the period was reconstructed using the 'weighted composite plus scale' method. Time-series analyses were performed to identify the strength of the associations between climate change and the geopolitical variables. Granger causality analysis and wavelet analysis were performed to verify the hypothesized causal links. Wavelet analysis was also used to identify the possible interactions (i.e. frequencies, significance, consistency and synchrony) between the signal components of the climatic and geopolitical variables at different temporal scales. Results China's mean precipitation fell into three multicentennial cycles. The geopolitical variables corresponded to those cycles in the imperial era. The spatial-temporal frequencies of the boundaries and size of the agriculturalist empires and its frontiers with pastoralist empires were regulated by the long-term (low-frequency) precipitation fluctuations at the multicentennial scale. Wars of aggression were an important explanatory factor driving the land-occupancy patterns of the two ecoempires under climate change, and caused most of the territorial shifts. Short-term (high-frequency) geopolitical changes were not associated with climate change. Main conclusions Precipitation-induced ecological change was an important factor governing the macrogeopolitical cycles in imperial China. Long-term territorial expansion favoured the polity (agriculturalist or pastoralist) that was better adapted to the changing ecological conditions in the country's heartland. [ABSTRACT FROM AUTHOR]

ABSTRACT Impacts of land use and climate change on runoff were investigated by studying the runoff in the Yarlung Zangbo River basin, China. Trends in precipitation, mean air temperature, and runoff were analysed by non-parametric Mann-Kendall tests. Land-use changes were examined with land-use transition matrix and geographic information system tools. Land-use and climate changes showed several characteristics, including increased reforestation, decreased grassland, retreat of glaciers and increased desertification. Human activity caused great impact, especially within densely populated regions and cities. Reforestation and degradation of grasslands were more frequent than deforestation and cultivation of grasslands. Annual mean air temperature, precipitation and runoff showed increasing trends between 1974 and 2000. The impacts of land use and climate change on runoff had different effects depending on region and season. In the season of freezing, climate change clearly affected runoff within regions that experienced precipitation. Altered evapotranspiration accounted for about 80 per cent of runoff changes, whereas land-use changes appear to have had greatest impact on runoff changes within regions that have inconsistent relationships between runoff and climate change. It was demonstrated that afforestation leads to increased runoff in dry seasons. It was estimated that glacier snow melt has caused annual runoff to increase at least 6·0 mm/10yr, 2·1 mm/10yr and 1·7 mm/10yr in Regions 1, 3 and 4, respectively, whereas evapotranspiration caused annual runoff to decrease at least 7·4 mm/10yr in Region 2. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hydrological processes change from the impacts of climate variability and human activities. Runoff in the upper reaches of the Hun-Taizi River basin, which is mainly covered by forests in northeast China, decreased from 1960 to 2006. The data used in this study were based on runoff records from six hydrological stations in the upper reaches of the Hun-Taizi River basin. Nonparametric Mann-Kendall statistic was used to identify change trends and abrupt change points and consequently analyze the change characteristics in hydrological processes. The abrupt change in the annual runoff in most subcatchments appeared after 1975. Finally, the effects of climate change and land cover change on water resources were identified using regression analysis and a hydrology model. Results of the regression analysis suggest that the correlation coefficients between precipitation and runoff prior to the abrupt change were higher compared with those after the abrupt change. Moreover, using hydrology model analysis, the water yield was found to increase because of the decrease in forest land. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Daily weather records from a historical private diary provide important data for studying historical climate change. We compiled daily weather records from the Weng Tong-He Diary and counted the number of monthly precipitation days during 1860-1897 AD for Beijing; then, using the number of monthly precipitation days, we reconstructed the seasonal precipitation using regression models relating the precipitation and precipitation days. The findings show that the monthly mean number of precipitation days for 1860-1897 was greater than that for 1951-2009 by about 1 d month−1 and that the summer (June to August, JJA) precipitation for 1860-1897 was 471.8 mm greater than that for 1951-2009 by about 15.5%. The JJA precipitation of 1860-1897 had not only inter-annual variations but also inter-decadal variations that were characterized by less precipitation before 1886 (about 421.9 mm) and more precipitation thereafter (about 550.7 mm). As a consequence, the JJA precipitation of 1860-1897 showed an evident positive trend with a rate of about 57.9 mm per decade. These precipitation variations were confirmed by other datasets. However, it is worth noting that our reconstruction underestimates the historical precipitation values (by about 22.5%) because of rainfall/snowfall events missed in Weng's diary and the poor ability of the regression models to capture extreme years. In the future, new methods of reconstructing precipitation with the consideration of missed rainfall/snowfall events are needed. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

We present a 620-year long ring width record from the middle Qilian Mountains, where it is presently controlled by the Westerlies. The chronology was developed from Qilian juniper ( Sabina przewalskii) growing at sites near the western distribution limit of the species in the northern Qilian Mountains, Gansu Province, China. A linear regression model between ring width and annual (July to June) precipitation accounts for 34.9% of the observed instrumental precipitation variance during the period 1952 to 2007. Spatial correlation analyses between the reconstruction and gridded precipitation data shows that the annual precipitation reconstruction captures regional climatic variations over the Qilian Mountains and the nearby Hexi Corridor. We also show the scaled standard chronology adjusted to the mean and variance of the instrumental data. Relatively wet periods are identified for AD 1390-1413, 1425-1450, 1530-1649, 1792-1920, 1937-1949 and 1980-1985. Dry conditions prevailed during AD 1414-1424, 1451-1529, 1650-1791, 1921-1936, 1950-1979 and 1986-2007. In comparison with the regression-based reconstruction, the scaled reconstruction indicates considerably wetter conditions during 1390-1413, 1425-1450, 1570-1630 and 1790-1920. The interval AD 1451-1529 was the most intense and longest drought epoch in the Hexi Corridor over the past six centuries. This drought was not only recorded in the Qilian Mountains but also occurred in northern and eastern China. It might be caused by a substantial weakening of the Asian summer monsoon induced by the joint effects of solar and volcanic activities at that time. Our results also suggest that the Hexi Corridor was under the control of the Asian monsoon circulation on inter-decadal to centennial timescales in the past centuries. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

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Three methods were used to distinguish the characteristics of changes in climate variability and normalized difference vegetation index (NDVI) during the period from 1982 to 2000 in China. Great changes in climate variability and an increased trend in NDVI were observed. The changes in precipitation variability were greater than the changes in temperature variability in each month, which is attributed to changes in the monsoon system in East Asia. The abrupt changes in climate and NDVI were more significant in 1983 than in the other years due to the impacts of El Niño/Southern Oscillation (ENSO). Using these results, the influences of changes in climate variability on vegetation were studied in the whole nation, and eight regions were defined according to the vegetation division map of China. The results show that abrupt climate changes at a small scale cannot cause abrupt NDVI changes directly. At a nationwide level, over a longer time scale the persistence of above/below average temperature determines the changes in NDVI; at a shorter time scale, changes in the magnitude of precipitation influence NDVI significantly. Such regional climate variability affects vegetation in different ways owing to the diversity of vegetation types, climatic conditions and topography of the land. [ABSTRACT FROM AUTHOR]

The article presents a study on the long-term monotonic trend and abrupt changes for major climate variables at 23 meteorological stations in the headwater catchment of the Yellow River basin in China from 1960 to 2001 on the basis of mean air temperature, precipitation, sunshine duration and pan evaporation. It states that the abrupt changes have been examined in terms of a five-year moving averaged annual series using the moving t-test (MTT) method, Yamamoto method and Mann-Kendall method. The results indicated that the annual air temperature has increased by 0.80 degrees Celsius in the headwater catchment of the Yellow River basin during the past 42 years.

The article analyzes the periodic properties of the annual runoff series for the last 40 years in Tarim River Basin in Xinjiang, China which were collected at hydrological gauging stations in its three main branches. It notes that analysis of variance and extrapolation method were employed to identify the annual runoff periods and predicted the future changes in the watershed using simulation methods. It also mentions that the Global Climate Model (GCM) has predicted the basin's long term trend of runoff because of the global increase in air temperature and precipitation in 1990.

The article reports on the study of the historical climate variations and climate change in the Brahmaputra basin such as Tibetan plateau (TP), Himalayan belt and the floodplains (FP). The study analyses the historical trends in temperature and precipitation of the TP, FP, and Himalayan belt through a global 100 year monthly high resolution dataset. It shows that precipitation in the basin is determined by the strength by the monsoons. It expresses that El Niño Southern Oscillation teleconnection does not have an important role in the changes in monsoon precipitation. The study also demonstrates the relationship among air temperature, FP, TP, and the strength of the monsoon.

This article discusses spatial temporal climatic changes which could lead to the drying up phenomenon of the Yellow River in China. The authors used data from satellites and meteorological stations to measure the temperature, precipitation changes, and vegetation condition in the past few decades. They concluded that the temperature increased and precipitation decreased in most parts of the Yellow River basin. The evaporative demand of the atmosphere increases only in the lower reaches of the river. The vegetation condition in the irrigation districts apparently has been improved by human activities.

The hydrological response to climate change in the Tarim River Basin was investigated by analysing the hydrological, temperature and precipitation data of the past 50 years. The long-term trend of the hydrological time-series, including air temperature, precipitation, and streamflow, was examined by using both parametric and non-parametric techniques and the plausible association between streamflow and climate change by the method of grey correlation analysis. The results show that the study area became warmer in the last few decades. The air temperature experienced a significant monotonic increase by 5%; the precipitation showed a significant decrease in the 1970s and then a major increase in the 1980s and 1990s, with average annual precipitation up by 6-8 mm per decade. A step change occurred in both temperature and precipitation around 1986, with mean temperature and precipitation increasing from 67°C and 146 mm before 1986 to 7.3°C and 180 mm respectively after 1986. The temperature has risen by nearly 1 °C over the past 50 years, possibly resulting from the impact of global climate change. Streamflows in the Aksu River and the Yarkant River have shown a significant (P < 0.05) tendency of increase. This is particularly the case for the Aksu River. The coefficients of streamflow increase in the Aksu and Yarkant Rivers are 0.41 and 0.13 respectively. The results of grey correlation analysis show that in the Aksu River, which is located in the northwest of the basin, the impact of precipitation on streamflow is much greater than that of temperature. However, in the Hotan River, which is located in the southwest of the basin, the impact of temperature on streamflow is much greater than that of precipitation. This is likely to be related to the geographic distribution of the headstreams of the rivers. [ABSTRACT FROM AUTHOR]

This study investigates the interdecadal changes in the relationship between the Eurasian snow cover extent (SCE) and spring precipitation over southern China. The results show that the spring precipitation over southern China has experienced an obvious change from an active to a quiet period since the late 1980s. The entire data set is divided into two subperiods, that is, 1972–1987 (P1) and 1988–2009 (P2). The interannual variation of the spring precipitation of southern China is found to be significantly related to Eurasian SCE anomalies around northwest of Lake Baikal. Less‐than‐normal SCE northwest of Lake Baikal corresponds to more‐than‐normal spring precipitation over southern China. The result of a numerical experiment performed using a baroclinic atmospheric model indicates that the Eurasian snow anomalies around northwest of Lake Baikal can impact the variation of spring precipitation over southern China by modulating the atmospheric circulations over eastern Asia and the western North Pacific region. Further examination shows that the SCE anomalies around Lake Baikal contribute differently to the variation of spring precipitation over southern China before and after the late 1980s. During P1, the SCE anomalies around Lake Baikal contribute to the variation of spring precipitation over China in the form of a mono‐sign pattern, which is similar to the first empirical orthogonal function mode of spring precipitation, while in P2, the SCE anomalies around Lake Baikal favor a north‐south dipole mode of the spring precipitation variation, which bears considerable similarity to the second empirical orthogonal function mode of spring precipitation over China. Key Points: The spring precipitation over southern China shows a pronounced climate change at 1987The spring precipitation over southern China is significantly correlated with spring SCE anomalies northwest of Lake BaikalThe SCE anomalies around Lake Baikal contributed to the spring precipitation in the form of EOF1 and EOF2 mode before and after 1987 [ABSTRACT FROM AUTHOR]