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A significantly negative interannual relationship is identified between the ground surface temperature (GTS) over the Tibetan Plateau (TP) and the rainfall over northwestern China and western Mongolia (NWC-WM) through analyzing the Chinese weather station data, GPCP precipitation, and ERA-Interim reanalysis in July during 1980-2012. This relationship is verified by the model sensitivity experiments carried out by using RegCM4.1 during 1982-2011. The positive/negative GTS forcing of three different magnitudes is added in two key regions over the TP in RegCM4.1. One of the key regions covers the central and eastern TP (denoted as TPC). The other covers the northern and north slope of the TP (denoted as TPN). The model results suggest that when the GTS anomalies in either of the two key regions are negative (positive), the rainfall anomalies over NWC-WM are positive (negative), which is consistent with observations. Furthermore, rainfall anomalies over NWC-WM are more sensitive to the GTS anomalies over the TPN region than those over the southern TP. The model results also reveal that the negative (positive) GTS anomalies over region TPN mainly cause the decrease (increase) of the latent heat release related to rainfall (surface sensible heat) and descent (ascent) over the TPN region but ascent (descent) to the north of the TP between 40° and 50° N. In addition, the specific humidity between 40° and 50° N is increased (decreased). Therefore, the increase (decrease) in specific humidity and the ascent (descent) between 40° and 50° N cause the increase (decrease) in the rainfall over NWC-WM. [ABSTRACT FROM AUTHOR]

Xinjiang is an important maize cultivation area in Northwest China. Investigating the relationship between meteorological drought and climate-driven maize yield can help to mitigate the negative impacts of drought on agricultural production in Xinjiang. In this study, multi-source data, including meteorological, agricultural, and socio-economic data, are collected to analyze the spatiotemporal patterns of drought and assess drought disaster risk. The standardized precipitation evapotranspiration index is calculated to classify different drought grades in the study area. The main results are as follows: (1) the relationship between drought and climate-driven maize yield is determined using a stepwise regression analysis, which indicates that drought conditions occurring from May to July are crucial for the yield in Xinjiang; (2) the modified Mann-Kendall test detects that the frequency-intensity-coverage of drought from May to July shows a decreasing tendency as a whole in the study area; (3) the correlation analysis shows that the multivariate ENSO index may be the dominant force in regional drought evolution; and (4) a drought disaster risk assessment system is constructed based on principles of natural disaster management. The drought disaster risk is higher in southwestern and northwestern Xinjiang, areas that should deserve more attention. [ABSTRACT FROM AUTHOR]

In order to define the spatial temporal distribution of drought characteristics and its response to climate change in the Beijing-Tianjin- Hebei region at different time scales, daily climatic data of 24 meteorological stations from 1961 to 2016 were selected in this study. The standardized precipitation evapotranspiration index ( SPEI) was established by using precipitation and reference crop evapotranspiration (ET0) data at different time scales, in which ET0 was calculated by FAO Penman Monteith equation. In order to find out the drought characteristics, Mann Kendall test, drought indices, climate tendency rate and rotated empirical orthogonal function (REOF) analysis were carried out on the SPEI. The results show that from the inter annual changes, there is a humid trend in Beijing-Tianjin-Hebei region; from the seasonal perspective, it is getting wet in spring, autumn (P<0. 05) and winter, and there is a drought trend in summer. The drought coverage appears as the features of the domain drought at the annual scale and the intensity of drought is light and moderate mainly. Viewing form spatial distribution, the western region has a humid trend, while it is dry in the eastern part of Beijing-Tianjin-Hebei region. According to spatial abnormal distribution of loading vectors in the Beijing Tianjin Hebei region, it can be divided into 4 sub regions: central area in the north region (sub-regionⅠ), east area in the north region (sub-region II), west area in the north region (sub-region III) and southern region (subregion IV). Drought in Ⅲ and Ⅳ sub regions gradually alleviates, while Ⅰ and Ⅱ sub regions shows a trend of getting dry. [ABSTRACT FROM AUTHOR]

Drought is occurring with increased frequency under climate warming. To understand the behavior of drought and its variation in the future, current and future drought in the twenty-first century over China is discussed. The drought frequency and trend of drought intensity are assessed using the Palmer Drought Severity Index (PDSI), which is calculated based on historical meteorological observations and outputs of the fifth Coupled Model Intercomparison Project (CMIP5) under three representative concentration pathway (RCP) scenarios. The simulation results of drought period, defined by PDSI class, could capture more than 90% of historical drought events. Projection results indicate that drought frequency will increase over China in the twenty-first century under the RCP4.5 and RCP8.5 scenarios. In the mid-twenty-first century (2021-2050), similar patterns of drought frequency are found under the three emission scenarios, and annual drought duration would last 3.5-4 months. At the end of the twenty-first century (2071-2100), annual drought duration could exceed 5 months in northwestern China as well as coastal areas of eastern and southern China under the RCP8.5 scenario. Drought is slightly reduced over the entire twenty-first century under the RCP2.6 scenario, whereas drought hazards will be more serious in most regions of China under the RCP8.5 scenario. [ABSTRACT FROM AUTHOR]

Droughts are natural disasters that pose significant threats to agricultural production as well as living conditions, and a spatial-temporal difference analysis of agricultural drought risk can help determine the spatial distribution and temporal variation of the drought risk within a region. Moreover, this type of analysis can provide a theoretical basis for the identification, prevention, and mitigation of drought disasters. In this study, the overall dispersion and local aggregation of projection points were based on research by Friedman and Tukey (IEEE Trans on Computer 23:881-890, 1974). In this work, high-dimensional samples were clustered by cluster analysis. The clustering results were represented by the clustering matrix, which determined the local density in the projection index. This method avoids the problem of determining a cutoff radius. An improved projection pursuit model is proposed that combines cluster analysis and the projection pursuit model, which offer advantages for classification and assessment, respectively. The improved model was applied to analyze the agricultural drought risk of 13 cities in Heilongjiang Province over 6 years (2004, 2006, 2008, 2010, 2012, and 2014). The risk of an agricultural drought disaster was characterized by 14 indicators and the following four aspects: hazard, exposure, sensitivity, and resistance capacity. The spatial distribution and temporal variation characteristics of the agricultural drought risk in Heilongjiang Province were analyzed. The spatial distribution results indicated that Suihua, Qigihar, Daqing, Harbin, and Jiamusi are located in high-risk areas, Daxing’anling and Yichun are located in low-risk areas, and the differences among the regions were primarily caused by the aspects exposure and resistance capacity. The temporal variation results indicated that the risk of agricultural drought in most areas presented an initially increasing and then decreasing trend. A higher value for the exposure aspect increased the risk of drought, whereas a higher value for the resistance capacity aspect reduced the risk of drought. Over the long term, the exposure level of the region presented limited increases, whereas the resistance capacity presented considerable increases. Therefore, the risk of agricultural drought in Heilongjiang Province will continue to exhibit a decreasing trend. [ABSTRACT FROM AUTHOR]

Guizhou Province, China, experienced several severe drought events over the period from 1960 to 2013, causing great economic loss and intractable conflicts over water. In this study, the spatial and temporal characteristics of droughts are analyzed with the standard precipitation index (SPI), comprehensive meteorological drought index (CI), and reconnaissance drought index (RDI). Meanwhile, historical drought records are used to test the performance of each index at identifying droughts. All three indices show decreasing annual and autumn trends, with the latter particularly prominent. 29, 30, and 32 drought events were identified during 1960–2013 by the SPI, CI, and RDI, respectively. Continuous drought is more frequent in winter–spring and summer–autumn. There is a significant increasing trend in drought event frequency, peak, and strength since the start of the 21st century. Drought duration indicated by CI shows longer durations in the higher-elevation region of central and western Guizhou. The corresponding drought severity is high in these regions. SPI and RDI indicate longer drought durations in the lower elevation central and eastern regions of Guizhou Province, where the corresponding drought severity is also very strong. SPI shows an increasing trend in drought duration and drought severity across most of the regions of Guizhou. In general, SPI and RDI show an increasing trend in the western Guizhou Province and a decreasing trend in central and eastern Guizhou. Comparing these three drought indices with historical records, the RDI is found to be more objective and reliable than the SPI and CI when identifying the periods of drought in Guizhou. [ABSTRACT FROM AUTHOR]

One of the effects of global climate change is increase in the frequency and severity of drought, which strongly affects the Chinese agricultural production. In order to cope these changes more effectively, it is important to document and analyze the agricultural losses caused by drought. We collected and analyzed conventional meteorological data and agricultural statistics data, in order to outline trends in drought occurrence and decline in agricultural yield. Data were assembled for the period 1960-2010. The study pays particular attention to regional differences between northern and southern China. Our results show the drought-caused agricultural loss rates (DCALR) in China have increased by approximately 0.5% per decade in the past 50 years. The study area in this paper is for the whole of the People's Republic of China, minus the Qinghai-Tibetan Plateau; when we analyzed regional differences, we found that losses increased by approximately 0.6% per decade in northern China, close to twice the increase in southern China. Moreover, drought risks and agricultural losses are rising faster in northern China. Our results also indicate that the agriculture in northern China is more sensitive to changes in precipitation, whereas the agriculture in southern China is more sensitive to temperature changes. [ABSTRACT FROM AUTHOR]

Drought is one of the most devastating climate disasters. Hence, drought forecasting plays an important role in mitigating some of the adverse effects of drought. Data-driven models are widely used for drought forecasting such as ARIMA model, artificial neural network (ANN) model, wavelet neural network (WANN) model, support vector regression model, grey model and so on. Three data-driven models (ARIMA model; ANN model; WANN model) are used in this study for drought forecasting based on standard precipitation index of two time scales (SPI; SPI-6 and SPI-12). The optimal data-driven model and time scale of SPI are then selected for effective drought forecasting in the North of Haihe River Basin. The effectiveness of the three data-models is compared by Kolmogorov-Smirnov (K-S) test, Kendall rank correlation, and the correlation coefficients (R). The forecast results shows that the WANN model is more suitable and effective for forecasting SPI-6 and SPI-12 values in the north of Haihe River Basin. [ABSTRACT FROM AUTHOR]

The monthly accumulated precipitation and monthly average temperature of 117 meteorological stations in Song-Liao River Basin (SLRB) were used to calculate the Standardized Precipitation Evapotranspiration Indices (SPEI) to analyze the drought characteristics, including long-term trends, drought affected area, climate abrupt change, intensive drought occurrence regions, and drought durations during 1964–2013 with the support of GIS. The Area Drought Severity (ADS), a comprehensive index, is proposed to assess both the variations of drought degree and the extent of the drought affected area. The results revealed that (1) the drought happening probability and degree are rising and the affected areas of all degrees of drought have an increasing trend during the last 50 years; (2) there is a climate abrupt change which occurred in around 1994, and the area with declining SPEI is larger than that with declining SPI, which could be due to the rising temperature after the climate abrupt change; (3) all degrees of drought occurrence probability increased, and the intensive drought occurrence regions altered from the northern SLRB to the southwestern SLRB after the climate abrupt change; (4) the drought duration increased from 1994, and the increased drought durations occurred in most parts of SLRB. [ABSTRACT FROM AUTHOR]

Drought is a complex and recurrent climate phenomenon, and understanding the development of the drought event is of great significance in preventing the damage. Current studies have analyzed the drought duration and severity based on run theory and Coupla function but few focuses on the drought recurrent interval and its relationship with agricultural drought disaster. In this study, the drought recurrence interval was investigated based on the drought duration and severity using run theory and Coupla function and the results were applied to agricultural drought disaster analysis in order to verify the reliability of the method for agricultural application. The study area was Northern Shannxi and the precipitation data from 1960 to 2015 were collected for drought grade classification based on standardized precipitation index (SPI). The drought duration and severity of drought event was calculated based on SPI values using run theory. Each drought characteristic index was evaluated for its distribution by comparing 7 different distributions. Then, the joint distribution of the 2 indices was established based on their correlation. Then the recurrence interval of each index was calculated for determination of their joint recurrence interval. The agricultural disaster area data were obtained from Statistic Yellow Book. The results showed that the drought occurred 94-103 times in 1960-2015 in the Northern Shannxi. The main drought area with high frequency was the area such as Yunlin, Yanan et al and that with low frequency was in the area such as Baoji, Xian, Xianyang et al. The distribution of drought duration and severity belonged to Weibull and Gamma distribution, respectively. The joint function of the 2 indices could be well fitted by the Frank-copula function with smaller squared euclidean distance and akaike information criterions. With the increase of drought duration and severity, the joint probability and recurrence interval gradually increased. The joint recurrence interval variation of different meteorological stations had different changing trend. The actual droughtaffected area of the crops in the Northen Shannxi was closely related to the drought duration and severity. The drought events joint recurrence interval was coincide with the actual drought disaster situation in the region. In the period of 1995-2005, the actual and theoretical drought duration was consistent mostly and the absolute errors between the actual and theoretical drought recurrence interval were only 0.1-0.3 a. The results indicated that the method proposed here was reliable in analyzing drought characteristics and could be used for agricultural drought disaster assessment. [ABSTRACT FROM AUTHOR]

Drought is a recurrent disaster that occurs in virtually all climatic zones of the world. However, drought characteristics vary substantially among different climatic regions. In this study, multifractal and wavelet analyses are used to characterize drought based on monthly precipitation. The rainfall data of 28 precipitation stations from 1958 to 2011 in Jilin province were collected to calculate the standardized precipitation index (SPI), and the negative monthly SPI time-series is used in a multiscaling approach to determine drought characteristics in Jilin province. Simple scaling and multiscaling analyses show significant variations in monthly droughts in the region. Morlet wavelet analysis also shows that significant cycles and multiple time-scales of drought exist in all stations. Cross wavelet analysis shows that drought occurrence in the region is mainly influenced by different climatic factor scales. However, different factors have different degrees of influence at different regions. The enduring influence of medium and long-term climatic patterns (such as El Niño events) may lead to the simple scaling behavior of drought for some regions. [ABSTRACT FROM AUTHOR]

Remote sensing can provide real-time and dynamic information for terrestrial ecosystems, facilitating effective drought monitoring. A recently proposed remotely sensed Drought Severity Index (DSI), integrating both vegetation condition and evapotranspiration information, shows considerable potential for drought monitoring at the global scale. However, there has been little research on regional DSI applications, especially concerning agricultural drought. As the most important winter wheat producing region in China, North China has suffered from frequent droughts in recent years, demonstrating high demand for efficient agricultural drought monitoring and drought impact analyses. In this paper, the capability of the MODIS DSI for agricultural drought monitoring was evaluated and the drought impacts on winter wheat yield were assessed for 5 provinces in North China. First, the MODIS DSI was compared with precipitation and soil moisture at the province level to examine its capability for characterizing moisture status. Then specifically for agricultural drought monitoring, the MODIS DSI was evaluated against agricultural drought severity at the province level. The impacts of agricultural drought on winter wheat yield during the main growing season were also explored using 8-day MODIS DSI data. Overall, the MODIS DSI is generally effective for characterizing moisture conditions at the province level, with varying ability during the main winter wheat growing season and the best relationship observed in April during the jointing and booting stages. The MODIS DSI agrees well with agricultural drought severity at the province level, with better performance in rainfed-dominated than irrigation-dominated regions. Drought shows varying impacts on winter wheat yield at different stages of the main growing season, with the most significant impacts found during the heading and grain-filling stages, which could be used as the key alert period for effective agricultural drought monitoring. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the relationships among the tree-ring chronology, meteorological drought (precipitation), agricultural drought (Palmer Drought Severity Index PDSI), hydrological drought (runoff), and agricultural data in the Shanxi province of North China. Correlation analyses indicate that the tree-ring chronology is significantly correlated with all of the drought indices during the main growing season from March to July. Sign test analyses further indicate that the tree-ring chronology shows variation similar to that of the drought indices in both high and low frequencies. Comparisons of the years with narrow tree rings to the severe droughts reflected in all three indices from 1957 to 2008 reveal that the radial growth of the trees in the study region can accurately record the severe drought for which all three indices were in agreement (1972, 1999, 2000, and 2001). Comparisons with the dryness/wetness index indicate that tree-ring growth can properly record the severe droughts in the history. Correlation analyses among agricultural data, tree-ring chronology, and drought indices indicate that the per-unit yield of summer crops is relatively well correlated with the agricultural drought, as indicated by the PDSI. The PDSI is the climatic factor that significantly influences both tree growth and per-unit yield of summer crops in the study region. These results indicate that the PDSI and tree-ring chronology have the potential to be used to monitor and predict the yield of summer crops. Tree-ring chronology is an important tool for drought research and for wider applications in agricultural and hydrological research. [ABSTRACT FROM AUTHOR]

Based on data of agricultural drought situation and sown area of main crops in each county or district of the Sichuan Basin, the spatial distribution and probability of agricultural drought risk at different risk levels were studied using normal information diffusion method, and the risk zoning was carried out. The results showed that normal information diifusion method could fit the distribution of agricultural drought risk in the Sichuan Basin. By comparison with the end of the 20th century, agricultural drought risk in Meishan, Chongqing City and so on increased at the beginning of the 21st century when xi⩾10% or xi⩾40%. Agricultural drought risk was low in the west of the Sichuan Basin, which was related to rich precipitation here, but it was high in Bazhong, Zhongjiang, Luxian and so forth. The risk zoning results can provide scientific references for disaster prevention and emergency management of government. [ABSTRACT FROM AUTHOR]

Water resources are an essential part of the ecosystem in the extremely arid northwestern part of China. Previous studies revealed a dry-to-wet climate change since the late 1980s in this region, which suggested a relief from the drought condition. However, the analysis in this study using the updated data shows that the arid situation has continued and even intensified in the past decade. This is reflected by the fact that the low-level air relative humidity and deep soil relative humidity have decreased in the past decade. Examination of the standardized precipitation evapotranspiration index (SPEI) and self-calibrating Palmer drought severity index (sc-PDSI) indicates that the severity and spatial extent of aridity and drought have increased substantially in northwestern China in the most recent decade. It is shown that the drought intensification in northwestern China is mainly caused by the increase of evaporation that results from the continuous rise in temperature, which will pose a continuous threat to the ecosystem and economic development in this region, especially under the background of global warming. [ABSTRACT FROM AUTHOR]

Probabilistic characteristics of hydrological droughts in a basin are closely related to the variability and availability of water resources of the basin. The East River basin in China is the main source for water supply for mega cities in the Pearl River Delta and cities in the vicinity of the Delta, such as Hong Kong. The water supply is subject to the vagaries of weather and water resources in the basin exhibit probabilistic characteristics. Using daily streamflow data for a period of 1975-2009 from 4 hydrological stations in the East River basin, this study attempts to determine probabilistic characteristics of hydrological droughts using copula functions. The bivariate quantile curves of the secondary return periods for hydrological drought of all the hydrological stations have been built and the results a higher risk of hydrological droughts in the upper East River basin. Furthermore, water resources should be managed by considering the entire East River basin in order to sustain the regional socio-economic development, and the extreme value copula has been used to describe the extreme drought events in the East River basin. [ABSTRACT FROM AUTHOR]

Historical annual dry-wet index for 1470-2003 combined with instrumental precipitation since 1951 were used to identify extremely dry years and events near the northern fringe of the East Asian summer monsoon in China-the Great Bend of the Yellow River (GBYR) region. In total, 49 drought years, of which 26 were severe, were identified. Composites of the dry-wet index under the drought years show an opposite wet pattern over the Southeast China. The longest drought event lasted for 6 years (1528-1533), the second longest one 4 years (1637-1640). The most severe 2-year-long drought occurred in 1928-1929, and the two driest single years were 1900 and 1965. These persistent and extreme drought events caused severe famines and huge losses of human lives. Wavelet transform applied to the dry-wet index indicates that the severe drought years are nested in several significant dry-wet variations across multiple timescales, i.e., the 65-85 year timescale during 1600- 1800, 40-55 year timescale before 1640 and 20-35 year timescale mainly from 1550 to 1640. These timescales of dry-wet variations are discussed in relation to those forcing such as cycles of solar radiation, oscillation in the thermohaline circulation and the Pacific Decadal Oscillation (PDO). Comparing 850 hPa winds in Asia in extremely dry and wet years, it was concluded that dry-wet variability in the GBYR region strongly depends upon whether the southerly monsoon flow can reach northern China. [ABSTRACT FROM AUTHOR]

Numerous dams and reservoirs in the Yangtze River basin have been constructed. Thus understanding the variability of hydroclimatological time series is important for the development of an optimal reservoir management strategy. This is crucial for life in the densely populated basin known to be highly susceptible to floods and droughts. Time series of annual precipitation totals and precipitation totals from May to September (the rainy season) for the period from 1961 to 2002 were averaged within the subbasins of the Yangtze River. The resulting time series were analyzed for similarities and differences and continuous wavelet transforms were produced to identify inherent quasi-periodicity. The western subbasins have shown a diverse pattern of periods with high and low precipitation variance. We have detected prominent periods of high precipitation variance for the central and eastern subbasins in the 1980s and 1990s, respectively. [ABSTRACT FROM AUTHOR]

Drought is the most critical environmental factor limiting the productivity of agricultural crops worldwide. Increased frequency and severity of drought are expected to accompany climate change and will negatively impact global food security. Wide yield variability from field to field, and consequently reduced average yield on a regional scale often occur under drought conditions. The reasons for the yield variability are still poorly understood. In this study, we explored sources of soybean yield variability among fields in a rural village of Northeast China associated with a severe drought growing season in 2007. Soil parameter measurements were made on fields following three transects with different distances from homestead. Management data were assembled from household interviews. The relative importance of soil parameters and management practices resulting in yield variability among fields was analyzed with general linear model (GLM) and classification and regression trees (CARTs) models. Our analysis showed that variability in management options, as opposed to variability in soil parameters, caused the majority of yield variability from field to field. The amount of P applied was the most important variable determining yield variability and explained roughly 61% of the variability. Whether or not manure was added into fields was of secondary importance. The classification tree analysis indicated that yield differences among transects was attributed to the content of K nutrient. This might result from variations of long-term management options with distance from homestead. CART models are robust technique for predicting yield variability responses to variations of soil properties and management practices due to its low prediction error. Our study highlights the pressing need to adjust management strategies for narrowing yield variability and increasing crop production in drought years. We recommend that in addition to testing soil, government programs in China should also pay close attention to management practices of farmers. [Copyright &y& Elsevier]