Evolution Characteristics Of Drought Research Articles

Anthropogenic and atmospheric variability intensifies flash drought episodes in South Asia

Flash droughts are abrupt and rapid intensification of droughts that affect agriculture, water, and ecosystems and are commonplace in South Asia. Despite their potential impact, flash drought evolution characteristics and underlying mechanisms in South Asia remain underexplored. We use a multivariate approach to analyze the onset speed, frequency, severity, duration, and return period of flash droughts, and the role of atmospheric circulation and human-induced climate change. We find that flash droughts are more common and intense in the crop season, especially in central India, western Pakistan, and eastern Afghanistan. They are caused by persistent atmospheric patterns that block moisture transport to South Asia. Additionally, anthropogenic climate change has intensified flash droughts in the spring-summer season, with a median fraction of attributable risk of 60%, 80%, and 90% for Afghanistan, Pakistan, and India, respectively. Our results suggest that flash droughts will expand and worsen in the future, requiring adaptation measures for the water, agriculture, and energy sectors.

Spatial and temporal characteristics of drought in the Mu Us Sandy Land based on the Standardized Precipitation Index

The environment of the Mu Us Sandy Land, northern Shaanxi, is fragile, so the temporal and spatial evolution of drought can provide a reference for ecological construction and agricultural production. Based on the daily precipitation data of five meteorological stations from 1967 to 2020, the spatial and temporal evolution characteristics of drought in the Mu Us Sandy Land of northern Shaanxi were analyzed using the methods Standardized Precipitation Index (SPI) and run-length theory. The results show that 1) the smaller the time scale, the higher the sensitivity of the SPI to primary precipitation. 2) The annual, summer, autumn, and winter SPI showed an upward and a wetting trend, and the fastest wetting speed is observed in summer, while spring showed an increasing trend of drought. 3) In the past 54 years, the duration, degree, and intensity of drought events at SPI-3 and SPI-12 scales in the Mu Us Sandy Land of northern Shaanxi showed an insignificant decreasing trend, but the decreasing rate at the SPI-12 scale was faster than that at the SPI-3 scale. The serious periods of drought are November 2018 to May 2019 and April 1999 to July 2021. 4) The duration of drought events at two timescales in each region showed a decreasing trend. The longest durations of drought were in Yulin and Jingbian; Shenmu and Dingbian are the regions with the fastest reduction rate of drought degree at the two scales. Hengshan shows rapid reduction of drought intensity at the two scales and also the region with large average drought intensity. These results are helpful in understanding and describing drought events for drought risk management under the condition of global warming.

Analysis of Agricultural Drought Evolution Characteristics and Driving Factors in Inner Mongolia Inland River Basin Based on Three-Dimensional Recognition

Agricultural drought events have become more frequent in the Inner Mongolia inland river basin in recent years, and the spatio-temporal evolution characteristics and development rules can be accurately and comprehensively understood using the three-dimensional identification method. In this paper, standardized soil moisture index (SSMI) was used to characterize agricultural drought, and modified Mann–Kendall trend test (MMK) and 3D recognition of drought events were used to analyze the spatio-temporal evolution characteristics of agricultural drought events in this basin and reveal the drought development law. The relationships between drought and temperature (T), precipitation (P), evapotranspiration (E), and humidity (H) were analyzed using a cross-wavelet method. The results are as follows: (1) When the time scale of agricultural drought was short (monthly scale), the alternations of dry and wet were frequent, but the SSMI index of all scales showed a downward trend; (2) The spatial distribution characteristics of drought change trend in four seasons were similar, but the area with a significant downward trend of drought in spring was the largest, and the area of high frequency region was also the largest, and the drought trend was the most obvious; (3) The most serious agricultural drought event occurred from October 2000 to May 2002, and reached its maximum value in September 2001 (drought area and drought severity of 2.26 × 105 km2 and 3.61 × 105 months·km2, respectively), which mainly experienced five processes—drought onset–intensification–decay–re-intensification–termination—and the migration path of the drought center showed the characteristics of southwest–northeast transmission; (4) All the four meteorological factors were correlated with SSMI, and P had a greater impact on SSMI. This article aims to reveal the spatio-temporal evolution of agricultural drought events in the Inner Mongolia inland river basin, and provide a new way to accurately evaluate the spatio-temporal evolution of drought.

Ecological drought evolution characteristics under different climatic regions in the Yangtze River basin

The increase in the frequency and intensity of drought has caused serious changes and threats to the ecosystem. There is an urgent need to improve the characterization performance of the ecological drought index to better monitor the ecological drought. Thus, this study constructed a new ecological drought index, the standardized ecological water shortage index (SEWSI). The definition of SEWSI was based on the difference between ecological water requirement and consumption. Utilizing vegetation water requirement models to comprehensively consider environmental conditions, such as climate, soil, and vegetation. And, the twi-difference algorithm method was used to divide the crop planting system. The spatio-temporal evolution characteristics of drought, including drought frequency, drought intensity, drought duration, and affected area in three climatic regions (plateau mountain climate region, north subtropical humid region central subtropical humid region) in the Yangtze River Basin (YRB), were analyzed by the run theory method. Besides, the EOF model was used to determine the spatio-temporal distribution of ecological drought. The results showed that the ecological drought in the YRB presents a catabatic trend. An average of 31 ecological drought events occurred, and the average duration of the drought was about 3.18 months from 1980 to 2020. The frequency of light drought was more than 15 %, accounting for 55.82 % of climate region I. About 26.11 % and 26.91 % of climate region II and climate region III, where the frequency of severe drought was more than 5 %. The average duration of ecological drought in climate region I was the longest and the average drought intensity was the largest. The first four modes of EOF can explain 73.20 % of the temporal and spatial changes of ecological drought. Although various climatic regions generally exhibit a trend of humidification, there is also a trend of drought in some regions, such as drylands in Climate II, and Sichuan and Chongqing regions in Climate III.

Estimation of water budget components and its driving factors analysis in arid grassland

Clarifying the dependence of the grassland water budget change and its components on environmental factors is significant for the sustainable development of dryland ecosystems. Here, the Hydrus-1D model was used to simulate the water budget of natural grassland for 42 years (1980–2021). The standardized precipitation evapotranspiration index (SPEI) and soil moisture deficit index (SMDI) were used to analyze the soil drought evolution characteristics and the water use dynamic of the grassland in dry and wet years. Here, the calibrated Hydrus-1D model accurately identified the dynamic of grassland soil moisture in 2020 and 2021. The simulated data showed that evaporation (E) and transpiration (Tc) were the main pathways of soil water consumption, accounting for 96.5 % and 86.1 % of rainfall in dry and wet years, respectively. The soil water storage did not present a difference in precipitation proportion in dry (2.4 %) and wet (1.2 %) years, and the deep percolation accounted for a maximum of 12.8 % in wet years. Rainfall from 380 to 400 mm was the threshold, as it not only corresponds to the maximum water use efficiency (Tc/ET = 0.52, ET = E + Tc) but also serves as an important turning point for drought and deep percolation (below 150 cm) within the soil. The structural equation model further indicated that the dependence of E and Tc on meteorological factors was the main reason for the change of their proportions in dry and wet years. Tc was more sensitive to meteorological factors (R2 = 0.63), while E was not (R2 = 0.27). The SMDI had a greater impact on determining the threshold for water budget components than the SPEI. These results deepen the understanding of the hydrological process of grasslands in sandy areas, including the interaction between water budget components and environmental factors in wet and dry scenarios.

A novel comprehensive agricultural drought index accounting for precipitation, evapotranspiration, and soil moisture

Univariate drought indices do not reflect the integrated process through which droughts develop and occur. Therefore, developing a multivariate drought index that accounts for precipitation, evapotranspiration, and soil moisture is crucial for comprehensive drought prediction and evaluation. In this study, a comprehensive agricultural drought index (CADI) was developed using a combination of five commonly used binary copulas by considering evapotranspiration factors based on the Multivariate Standardized Drought Index (MSDI), which is based on both precipitation and soil moisture, and the drought monitoring capability of CADI was evaluated. The relationship between the CADI and the yield anomalies of winter wheat and summer maize in the rainfed and irrigated croplands of the North China Plain (NCP) was analyzed, and the drought evolution characteristics and trends in rainfed and irrigated croplands were examined. The results indicated that compared with the Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Soil Moisture Index (SSI), and MSDI, the proposed CADI accurately reflected the integrated process of meteorological and agricultural drought occurrence and evolution. In addition, the strength of the correlation between the CADI and the yield anomalies of winter wheat and summer maize in the rainfed and irrigated croplands of the NCP surpassed that of the SPEI, SSI, and MSDI, thereby confirming the validity and reliability of the proposed CADI for drought monitoring. Over the past four decades, droughts in the rainfed and irrigated croplands of the NCP have demonstrated a decreasing trend, and severe droughts have been concentrated in winter. Overall, the results of this study can be used in agrometeorological drought early warning and agricultural impact assessment and can provide theoretical guidance for drought monitoring in other regions.

Copula-based comprehensive drought identification and evaluation over the Xijiang River Basin in South China

The reasonable and appropriate drought indicator is a crucial instrument for drought investigation and assessment, which can objectively compare the severity, duration, and frequency of drought events, so as to achieve the purpose of accurately monitoring and evaluating drought. However, a univariate drought index is often difficult to precisely describe the complex drought situation, and it is urgent to establish a multivariate comprehensive drought index to identify and reveal the drought characteristics. Based on Copula models, combined with meteorological factors precipitation and hydrological factors runoff, this paper constructed a Multivariate Standardized Drought Index (MSDI), which can characterize meteorological drought and hydrological drought simultaneously and evaluate the spatial–temporal evolution characteristics of drought over the Xijiang River Basin (XJB) in South China. The results indicated that: (1) the proposed MSDI can capture the occurrence of drought as sensitively as the Standardized Precipitation Index (SPI), and can represent the termination of drought as effectively as the Standardized Runoff Index (SRI), which can comprehensively depict the drought situation in the XJB, China; (2) since the 1980 s, there was a tendency of aridity with a mutation point of 1983 in the downstream of Xijiang River (DXJB), and the worst comprehensive drought occurred in 1989; (3) among the tributaries, the comprehensive drought severity was the heaviest in the DXJB, with an average MSDI value of –0.75; (4) based on the run theory and Copula model, the most serious drought event occurred from September 1988 to October 1990, with a drought severity of 33.36, a drought duration of 27 months, and a drought return period exceeding 50 years; and (5) the drought evolution was significantly influenced by abnormal atmospheric circulation factors, while ENSO had the largest influence on the drought variation in the XJB, followed by sunspot.

Spatiotemporal Features and Time-Lagged Effects of Drought on Terrestrial Ecosystem in Southwest China

With global warming, the increase in the frequency and intensity of droughts have severely affected the balance of terrestrial ecosystems. Although the immediate effects of drought on vegetation growth have been widely studied, the time-lagged effects have been neglected, particularly in ecologically fragile karst areas. We examined the vegetation growth trends and abrupt changes in southwest China from 1990 to 2018 by reconstructing the normalized difference vegetation index (NDVI); we then used the standardized precipitation and evapotranspiration index (SPEI) to explore the drought evolution characteristics and the time-lagged effect of drought on vegetation growth. The results showed that 97% of the study area exhibited a greening trend, which accelerated after 1995. Spring drought increased noticeably. We demonstrated that drought had a time-lagged effect on vegetation growth; 27.28% of the vegetation lands had a lag time of less than 3 months, and the mean lagged time in karst areas was shorter than that in non-karst areas. Compared to other vegetation types, the cultivated vegetation had weaker drought resistance, while the mixed-forest had stronger tolerance to drought. This study contributes to a further understanding of the drought–vegetation relationship and has important implications for optimizing vegetation conservation strategies in southwest China while coping with climate change.

Higher atmospheric evapotranspiration demand intensified drought in semi‐arid sandy lands, northern China

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

A New Drought Fluorescence Monitoring Index Established for Detecting Drought Evolution Characteristics in the Middle and Lower Reaches of the Yangtze River, China During 2001–2020

A New Drought Fluorescence Monitoring Index Established for Detecting Drought Evolution Characteristics in the Middle and Lower Reaches of the Yangtze River, China During 2001–2020

Spatiotemporal evolution analysis and prediction of drought in Henan Province based on standardized precipitation evapotranspiration index

Abstract Drought is one of the major natural disasters in the world, and it is important to understand and grasp the spatiotemporal evolution characteristics of drought for drought monitoring and prevention. In this study, the standardized precipitation evapotranspiration index (SPEI) was calculated based on monthly precipitation and average temperature data from 15 meteorological stations in Henan Province, China during the period 1987–2020. The spatiotemporal evolution characteristics of droughts in Henan Province were analyzed using run theory and Moran's I, and drought prediction was carried out using grey disaster theory. The results show that: (1) During the period 1987–2020, the overall drought in Henan Province shows a slow intensification trend, and SPEI-12 has a certain adaptability in the drought characterization of Henan Province; (2) The frequency of droughts in the northern and eastern regions of Henan Province is high, the southern region is prone to continuous drought, the drought ephemeris and intensity show a strong positive correlation, and the spatial spillover effect of autumn drought is the most obvious; (3) The grey disaster prediction model has excellent accuracy and predicts that the next possible drought in Henan Province will be in the east of Henan Province in the spring of 2023.

The regional characteristics of meteorological drought event and its multidimensional factors measurement by daily SPEI in Guangxi, China

The frequent occurrence of extreme drought events in Guangxi has caused huge losses to human beings and economy in the region for many years. For fine identification of drought evolution characteristics, this study adopted the objective identification method of regional extreme events (OITREE) to carry out the comprehensive feature identification involving multidimensional elements such as intensity, duration and area of meteorological drought events based on the daily standardized precipitation evapotranspiration index (SPEI) data of Guangxi from 1979 to 2018a. By comparing the evolution characteristics of drought elements identified by grid SPEI statistical analysis and OITREE, a comprehensive analysis framework for drought characteristics of multidimensional factor’s measurement is formed in this study. Specifically, the grid analysis is more convenient to identify single point drought characteristics, and the OITREE method is better at describing the overall spatiotemporal evolution of drought events. The study found that flash droughts and seasonal droughts occurred alternately and were superimposed concurrently in Guangxi, and the multidimensional spatial and temporal characteristics of these two types of droughts were significantly different. In concrete terms, the average annual frequency of flash drought events in Guangxi was 2.0–3.8, the average annual duration varied from 20 to 60 d, and the concentration point of drought events had a region-wide dispersion; while the average annual frequency of seasonal drought events in Guangxi was 0.82–1.65, the average annual duration varied from 40 to 105 d, and the concentration point of drought events had a local concentration. Furthermore, for the flash drought, seasonal drought and total drought in Guangxi, the three-dimension clustering method was introduced to realize the comprehensive intensity spatial heterogeneity clustering partition and temporal heterogeneity clustering mapping of meteorological drought in Guangxi. The research results can provide important scientific support for promoting the operational risk assessment and regulation of regional drought disasters and forecasting and warning.

Analysis of Spatio-Temporal Evolution Characteristics of Drought and Its Driving Factors in Yangtze River Basin Based on SPEI

Using a dataset of 114 meteorological stations in the Yangtze River Basin from 1980–2019, the standardized precipitation evapotranspiration index (SPEI) was calculated based on the Penman-Monteith evapotranspiration model for multiple time scales, and the spatial and temporal evolution characteristics and driving factors of drought in the Yangtze River Basin were analyzed by combining spatial and temporal analysis methods as well as geodetector. The main results obtained are as follows: (1) The climate of the Yangtze River Basin is an overall wet trend, and the trend of summer drought is more similar to the annual scale trend. (2) Most areas in the Yangtze River Basin showed mild drought or no drought, and there is little difference in drought condition among the Yangtze River Basin regions. The areas with drought conditions are mainly distributed in the southwest and east of the Yangtze River Basin. (3) There are significant seasonal differences in drought conditions in all regions, and the drought condition is more different in autumn compared to spring, summer and winter. (4) The average annual precipitation and elevation factors are the dominant driving factors of drought in the Yangtze River Basin, and the double-factor interaction has a greater influence on the drought variation in the Yangtze River Basin than the single-factor effect, indicating that the difference of drought condition in the Yangtze River Basin is the result of the combination of multiple factors.

Spatial and temporal evolution characteristics of meteorological drought in the Northwest of Yellow River Basin and its response to large-scale climatic factors

Abstract The Northwest of Yellow River Basin (YRB) is an arid and semi-arid region. This study employs wavelet analysis, dry area coverage, drought frequency, and Mann–Kendall test trend to investigates the evolution characteristics of drought in the Northwest of YRB and the impact of macro climatic conditions on drought. The scale of season and year Standardized Precipitation Evapotranspiration Index (SPEI) was mostly represented as alternating dry and wet weather in this region. SPEI decreased significantly in each season, indicating increased drought. The drought situation changed abruptly in 1968, and the change was more obvious around 2000. Drought trend in autumn is more noticeable than in the other three seasons. The average annual dry area covers 34%. The drought frequency in each station at the annual scale was between 30.78% and 46.15%, its high values are mainly concentrated in the western region. The main cycles of annual SPEI changes are 37 and 5 years; spring is 45 and 10 years; summer is 20 and 5 years; autumn is 36, 10, and 5 years; winter is 45, 22, and 5 years. Furthermore, drought occurrence and changes are closely related to large-scale climatic factors, with El Niño-Southern Oscillation having the greatest impact on drought.

Construction and application of Optimized Comprehensive Drought Index based on lag time: A case study in the middle reaches of Yellow River Basin, China

Drought is a complex and dynamic natural phenomenon. A single drought index can hardly reflect the multi-type characteristics of drought, and comprehensive drought indices that incorporate data from multiple sources have been proposed recently. In this study, an Optimized Comprehensive Drought Index (OCDI) was constructed by taking into account the lag time of meteorological drought, agricultural drought and hydrological drought. The Standardized Precipitation Evapotranspiration Index (SPEI), Vegetation Condition Index (VCI), and Water Storage Deficit Index (WSDI) represented the three types of droughts, respectively. Specifically, we used the Solar-induced Chlorophyll Fluorescence (SIF) to characterize the vegetation condition instead of the Normalized Difference Vegetation Index (NDVI). The application results of the proposed drought index in the middle reaches of Yellow River basin (MRYRB) showed that the lag time of different types of drought indices had seasonal differences, with a shorter lag time in summer (0–4 months) and a longer lag time in winter and spring (> 4 months). For typical drought events, the drought intensity and duration identified by OCDI were compatible with the drought evolution characteristics and consistent with the historical records, therefore, OCDI is more suitable for drought monitoring in the study area. Based on the monitoring results of the OCDI, the average number of droughts in the MRYRB was 16 times, with a duration of 2.8 months and an average drought intensity of 0.28 (at moderate drought grade). Drought times and intensity were higher in the northwestern part of the study area, and spring was a high-frequency period for drought occurrences.

An analysis of drought evolution characteristics based on standardized precipitation index: a case study in Southwest Guizhou Autonomous Prefecture, China

Drought is a worldwide concerned issue which causes huge losses in agriculture, economic and damages in natural ecosystems. The precise assessment of drought evolution characteristics is essential for agricultural water management and drought resistance, while such work is rarely reported. Thus, eight meteorological stations located within the Southwest Guizhou Autonomous Prefecture (SGAP) were selected, and the Standardized Precipitation Index (SPI) was used to assess the drought evolution characteristics. The results revealed that the drought occurrences number in Pu'an station was the largest (23 droughts), and the average drought duration in Xingren station was the longest (48.75 months). Moreover, the drought characteristics of the eight stations have account for the largest proportion under normal conditions, was more than 60%, the frequency of drought disaster occurring in Xingren is the highest (30.05%), followed by Wangmo (23.73%). The results of this study will provide theoretical guidance for drought resistance and agricultural production in Southwest Guizhou Autonomous Prefecture of China.

Evolution characteristics and relationship of meteorological and hydrological droughts from 1961 to 2018 in Hanjiang River Basin, China

Abstract In the context of global warming and increasing human activities, the acceleration of the water cycle will increase the risk of basin drought. In this study, to analyze the spatial and temporal evolution characteristics of hydrological and meteorological droughts over the Hanjiang River Basin (HRB), the Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI) were selected and applied for the period 1961–2018. In addition, the cross-wavelet method was used to discuss the relationship between hydrological drought and meteorological droughts. The results and analysis indicated that: (1) the meteorological drought in the HRB showed a complex cyclical change trend of flood-drought-flood from 1961 to 2018. The basin drought began to intensify from the 1990s and eased in the 2010s. The characteristics of drought evolution in various regions are different based on scale. (2) During the past 58 years, the hydrological drought in the HRB has shown a significant trend of intensification, particularly in autumn. Also, the hydrological droughts had occurred frequently since the 1990s, and there were also regional differences in the evolution characteristics of drought in various regions. (3) Reservoir operation reduces the frequency of extreme hydrological drought events. The effect of reducing the duration and intensity of hydrological drought events by releasing water from the reservoir is most obvious at Huangjiagang Station, which is the nearest to Danjiangkou Reservoir. (4) The hydrological drought and meteorological drought in the HRB have the strongest correlation on the yearly scale. After 1990, severe human activities and climate change have not only reduced the correlation between hydrological drought and meteorological drought in the middle and lower reaches of the basin, but also reduced the lag time between them. Among them, the hydrological drought in the upper reaches of the basin lags behind the meteorological drought by 1 month, and the hydrological drought in the middle and lower reaches of the basin has changed from 2 months before 1990 to 1 month lagging after 1990.

Analysis of Characteristics of Hydrological and Meteorological Drought Evolution in Southwest China

Based on the data of 82 meteorological stations and six representative hydrological stations in four provinces in Southwest China (Guizhou, Sichuan, Yunnan, Chongqing), this paper uses standardized precipitation evapotranspiration index (SPEI) and standardized runoff index (SRI) to analyze the spatial and temporal evolution characteristics of drought in the study area from 1968 to 2018. Combined with the Southwest monsoon index and historical drought data, the correlation of drought and the applicability of different drought indices were verified. The results show that: (1) SPEI-12 in Southwest China shows a downward trend from 1968 to 2018, with a linear trend rate of −0.074/10a, and SPEI-3 has a downward trend in four seasons, the maximum linear trend rate being −0.106/10a in autumn;(2) The change in SRI-12 and SRI-24 value directly reflected the decrease in SRI value, indicating that drought events are increasing in recent times, especially in the 21st century (3). Severe drought occurred in the south of Southwest China, as indicated by the increase of drought frequency in this area. The main reason for the variations in the frequency distribution of drought in Southwest China is the combined effect of the change of precipitation and evapotranspiration. (4) The correlation between hydrological drought index and disaster areas is stronger than the correlation between meteorological drought and disaster areas.

Evolution characteristics research on summer-autumn consistent drought of Poyang Lake based on the copula in the changing environment

The precipitation series is the main data to calculate the parameters and the frequency of drought, aim to the less considering with the inconsistency of precipitation series in study of drought research under the changing environment, and the less reasearch on the drought evolution characteristics within the basin before and after the hydrological alteration, the hydrological alteration diagnosis system was used to diagnose the summer and fall precipitation series of Yichun, Nanchang etc. and 9 meteorological station in total within the basin of Poyang lake. Based on the hydrological alteration results and considering the Copula function, the percentage of precipitation anomaly (Pa) was taken as the drought index to calculate the percentage of summer-fall consistent drought of meteorological stations. The results show that, the alteration of precipitation series in summer was obvious at Poyang lake, comparing with the period before the alteraion, the percentage of summer-fall consistent drought of Poyang Lake is decreasing, that means the recurrence period of summer-fall consistent drought becomes longer, the main reason that induce the much more serious drought in the Poyang Lake is the factor of water expenditure.

A Multi-Index Evaluation of Drought Characteristics in the Yarlung Zangbo River Basin of Tibetan Plateau, Southwest China

The Yarlung Zangbo River (YZR) basin occupies a crucial position in the formation and development of atmospheric circulation and climate change in the Tibetan Plateau, where is the potential trigger and amplifier in global climate fluctuations. Previous studies mainly focused on meteorological drought induced by variations of precipitation and temperature. In this study, a multi-index evaluation of drought characteristics from the perspective of meteorology and agriculture was implemented. GLDAS (Global Land Data Assimilation System) precipitation, surface air temperature and soil moisture data from 1982 to 2015 were used to calculate the meteorological drought index (Standardized Precipitation Evapotranspiration Index) and agricultural drought index (Soil Water Deficit Index), respectively. Meanwhile, the scPDSI (self-calibrating Palmer Drought Severity Index) dataset provided by CRU (Climate Research Unit) was also utilized to represent the meteorological drought, with the aim of comprehensively investigating the spatiotemporal evolution characteristics of drought in the YZR basin. Results indicated that although there was a slightly wetting tendency of the whole basin from 1982 to 2015, drought condition from the perspective of meteorology and agriculture at both annual and growing seasonal scales showed a transition from alleviation to aggravation during 1982–2015, with an abrupt change from wetting to drying occurring at the year of 2000 detected by multiple statistical tests including Mann-Kendall test, Moving t-test and Yamamoto test. Specifically, since the 21st century, the meteorological drought in the YZR basin has changed from moderate wet to moderate dry, while the agricultural drought relieved to moderate dry from severe dry with a much more complicated fluctuation. From the perspective of spatial pattern, the annual and growing season variation trends of all three drought indices were identically consistent during 1982–2015. Areas with extremely significant decreasing trend (2.24%~21.09%) were mostly distributed in the west upstream and southwest downstream dominating the overall wetting trend of the YZR basin during the period of 1982–2015, while the transition from wet to dry after 2000 was attributed to the aggravating drought of the western upstream and southeastern downstream. Results of this study have important implications for drought monitoring and eco-environmental sustainability in alpine regions.