Drought In China Research Articles

Agricultural Vulnerability to Drought in China’s Agro-pastoral Ecotone: A Case Study of Yulin City, Shaanxi Province

Agricultural Vulnerability to Drought in China’s Agro-pastoral Ecotone: A Case Study of Yulin City, Shaanxi Province

Triple-Dip La Niña Contributes to Pakistan Flooding and Southern China Drought in Summer 2022

Abstract In the summer of 2022, a long-lasting La Niña entered its third year. In Asia, southern China was in the grip of a historic drought while heavy rainfall ravaged Pakistan. Using a climate model forced by observed sea surface temperatures (SST) over the equatorial Pacific, we show that the back-to-back La Niña events from 2020 to 2022 are a key contributor to the global SST pattern in 2022, including the negative-phase Pacific decadal oscillation and exceptionally strong negative Indian Ocean dipole. The model reproduces the observed precipitation pattern over South and East Asia, including enhanced rainfall over Pakistan–northwest India and reduced rainfall over southern China. Additional model simulations indicate that the negative Indian Ocean dipole combined with La Niña reduces southern China rainfall by causing anomalous subsidence and anticyclonic flows. These results highlight the dominant role of long-lasting La Niña in modulating rainfall over heavily populated monsoon Asia.

Effects of extreme drought events on vegetation activity from the perspectives of meteorological and soil droughts in southwestern China

Under climate warming, extreme drought events (EDEs) in southwestern China have become more frequent and severe and have had significant impacts on vegetation growth. Clarifying the influence of soil and meteorological droughts on the vegetation photosynthetic rate (PHR) and respiration rate (RER) can help policymakers to anticipate the impacts of drought on vegetation and take measures to reduce losses. In this study, the frequency and features of EDEs from 1990 to 2021 were analyzed using the standardized precipitation evapotranspiration index, and the longest-lasting and most severe EDE was chosen to assess the effects of drought on vegetation activity. Then, a land surface model was used to simulate the vegetation PHR and RER. Finally, the effects of the EDE on the vegetation PHR and RER were analyzed from the perspectives of soil and meteorological droughts. The results revealed that from 1990 to 2021, a total of 11 EDEs were observed in southwestern China, and the longest-lasting and most severe EDE occurred in 2009–2010 (EDE2009/2010). EDE2009/2010 significantly reduced the monthly mean PHR and RER by 9.82 g C m−2 month−1 and 0.80 g C m−2 month−1, respectively, causing a cumulative reduction of approximately 5.61 × 1013 g C. Soil and meteorological droughts had a driving force of 39 % on the PHR changes and an explanatory force of 42 % on the RER reduction. In particular, the soil drought had an average explanatory force of 25 % on the PHR and made a contribution of 24 % to the RER. The drought affected different types of vegetation differently, and crops were more susceptible than grassland and forests on the monthly time scale. The vegetation exhibited resilience to drought, returning to normal PHR and RER levels 2 months after the end of EDE2009/2010. This research contributes to understanding and predicting the impact of EDEs on vegetation growth in southwestern China.

Wind resource droughts in China

With the rising share of wind energy in power generation, the occurrence of low-wind-power events (termed ‘wind resource droughts’) are becoming critical in understanding the national electricity supply and the security of power systems. We use hourly wind speed data (2428 meteorological stations; in the years 2010–2020) to analyze the occurrence of wind resource droughts in seven onshore wind energy planning regions over China. We find that wind resource droughts tend to occur in warm season (summer and autumn) in most regions (i.e., Northeast China, East China, Central China, South China and Tibetan Plateau). In these regions, the number of moderate wind resource drought events (wind capacity factor below 10%) in the warm season (summer and autumn) was about 3–13 times higher than in the cold season (spring and winter). By contrast, for North China and Northwest China, the wind resource droughts mainly occurred in the autumn and winter. Averaged over 11 years, Northeast China experienced the most moderate wind resource droughts with 30 d yr−1, while Northwest China had only 1 d yr−1. Some of these wind resource drought events occurred consecutively, in which Northeast China experienced nine wind resource drought events that lasted for at least five days (where the longest reached 9 d) across the 11 years from 2010 to 2020; North China and South China exhibited one five-day wind resource drought events; while Northwest China, East China, Central China and Tibetan Plateau had none. Moreover, we found that increasing the aggregated area of wind resource can reduce the volatilities of wind energy. Therefore, improving the cross-regional transmission capacity can substantially help reduce the number of wind resource drought events. These findings should assist decision-makers to establish the counterplan to mitigate the energy shortages and instability in power supply caused by the uncertainty of wind resource droughts.

Adaptation to seasonal drought in irrigation districts of south China: A copula-based fuzzy-flexible stochastic multi-objective approach for precise irrigation planning

The occurrence of seasonal drought has led to periodic water shortages in irrigation districts of south China, posing significant agricultural challenges on water and food security. Consequently, there is a pressing need for high-efficient water resources management from a sustainability perspective. To address this issue, a copula-based fuzzy-flexible stochastic multi-objective programming (CFSMP) model was proposed to facilitate irrigation planning under the combined influence of seasonal dry and wet conditions. The model was aimed to simultaneously achieve maximum economic benefit, water productivity and green water use efficiency, considering the economic, social, and environmental spheres of the irrigation district. The CFSMP model represented an innovative solution that was capable of (1) precisely describing the response of crop yield to water supply at ten-day time scale, which can be matched with practical irrigation demand; (2) characterizing joint distributions of seasonal dry and wet conditions of precipitation during different crop growth periods based on the copula function; (3) reconciling conflicts on objectives among economic, social, and environmental spheres of the irrigation district in complex and uncertain environments. The proposed model was applied to the Dongfeng Reservoir Irrigation District in south China. The downscaled ten-day Jensen water production functions of main grain and cash crops were fitted to recognize precise distributions of crop water demand and water sensitivity index. The Frank copula, with the smallest value of squared Euclidean distribution, was selected to describe the joint distribution of seasonal precipitation and gain insights into actual seasonal water availability and water scarcity. The results showed that the proposed model produced more water-saving and yield-promoting irrigation planning policies than the current quota. The average water allocation of rice, wheat, maize, rape, and citrus decreased by 352.6 mm, 10.6 mm, 67.7 mm, 7.44 mm, and 54.6 mm, respectively. Except for a yield reduction of 8.8% for rape, crop yields of rice, wheat, maize, and citrus were improved by 33.3%, 45.4%, 29.9%, and 12.3%, respectively. The coordination degree of the model reached 0.827, demonstrating excellent performance on generating coordinated and robust solutions. Therefore, the CSFMP model has the potential to alleviate seasonal drought in south China and can be applied in similar regions with comparable resources crisis.

Compensatory response of ecosystem carbon-water cycling following severe drought in Southwestern China

Climate change has increased the frequency and length of droughts, but many uncertainties remain regarding the impacts of this aridification on terrestrial ecosystem function. Vegetation water use efficiency and carbon sequestration capacity are crucial determinants that both respond to and mediate the effects of drought. However, it is important to note that the consequences of drought on these processes can persist for years. A deeper exploration of these “drought legacy effects” will help improve our understanding of how climate change alter ecosystem carbon-water cycling. Here, we investigate the spatial patterns of drought legacy effects on remotely-sensed vegetation greenness (NDVI), net primary productivity (NPP) and water use efficiency (WUE) in southwestern China, a biodiversity hotspot that was impacted by an extreme drought in 2009–2010, with a particular focus on the tradeoff between WUE and NPP. Despite widespread negative drought legacy effects in NDVI (impacting 61.26 % of the study region), there was a general increase in NPP (58.68 %) and a decrease in WUE (67.53 %) in the year following drought (2011). This drought legacy effect was most evident in forests, while drought legacies in grasslands were less common. Drought legacies were also most apparent in relatively warm and humid areas. During the study period (2002 to 2018), we found that drought impacts on WUE also lagged behind changes in NPP by 1–2 years in forests, which highlights how drought legacies may manifest differently across ecosystem processes. Our study demonstrated that severe drought conditions may significantly affect the carbon sequestration capacity and water use efficiency of vegetation in southwestern China, and that forests may compensate for the detrimental effects of water stress by increasing water use and biomass growth after drought episodes.

Spatiotemporal characteristics and forecasting of short-term meteorological drought in China

Intense short-term meteorological drought may lead to rapid declines in soil moisture, triggering flash drought that can cause major agricultural or socioeconomic damage. Machine learning methods have proven effective in forecasting hydrometeorology, but short-term drought forecasting is still inadequate. We developed a pentad-time-scale (5-day) standardized precipitation evapotranspiration index (SPEI-5d) to quantify short-term meteorological drought and analyzed its spatiotemporal distribution characteristics in China during the period 1962–2018. We used historical SPEI-5d as input and employed five machine learning methods for drought hindcasting: an autoregressive integrated moving average (ARIMA), random forest (RF), recurrent neural network (RNN), long short-term memory (LSTM), and convolutional long short-term memory (ConvLSTM). The results show the following: (1) During the period 1962–2018, 61.9% of the study region showed decreasing trends in drought severity, while 69.6% of the region showed increasing trends in drought intensity. (2) Drought duration, severity, and intensity have distinct seasonal characteristics, and different forecasting models perform differently in each season, with generally lower forecasting accuracy in summer and higher forecasting accuracy in winter. (3) The ConvLSTM model can capture spatiotemporal information well compared to traditional time-series forecasting models; it has the best performance (root mean square error = 0.29, and Nash-Sutcliffe efficiency = 0.92) in the test set and has high forecasting accuracy (R2 > 0.8) for lead times of 1–5 days (with accuracy decreasing as lead time increases). Our findings highlight the spatiotemporal variability of short-term meteorological drought and provide valuable scientific insights for short-term meteorological drought forecasting at 1–5 days of lead time.

Historical Trends and Characteristics of Meteorological Drought Based on Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index over the Past 70 Years in China (1951–2020)

Against the backdrop of global climate change, the frequency of drought events is increasing, leading to significant impacts on human society and development. Therefore, it is crucial to study the propagation patterns and trends of drought characteristics over a long timescale. The main objective of this study is to delineate the dynamics of drought characteristics by examining their propagation patterns in China from 1951 to 2020. In this study, precipitation data from meteorological stations across mainland China were used. A comprehensive dataset consisting of 700 stations over the past 70 years was collected and analyzed. To ensure data accuracy, the GPCC (the Global Precipitation Climatology Center) database was employed for data correction and gap-filling. Long-term drought evolution was assessed using both the SPI-12 (standardized precipitation index) and SPEI-12 (standardized precipitation evapotranspiration index) to detect drought characteristics. Two Moran indices were applied to identify propagation patterns, and the MK (the Mann–Kendall) analysis method, along with the Theil–Sen slope estimator, was utilized to track historical trends of these indices. The findings of this study reveal the following key results: (i) Based on the SPI-12, the main areas of China that are prone to drought are mostly concentrated around the Hu Huanyong Line, indicating a tendency towards drying based on the decadal change analysis. (ii) The distribution of drought-prone areas in China, as indicated by the SPEI-12, is extensive and widely distributed, with a correlation to urbanization and population density. These drought-prone areas are gradually expanding. (iii) Between 2010 and 2011, China experienced the most severe drought event in nearly 70 years, affecting nearly 50% of the country’s area with a high degree of severity. This event may be attributed to atmospheric circulation variability, exacerbated by the impact of urbanization on precipitation and drought. (iv) The frequency of drought occurrence in China gradually decreases from south to north, with the northeast and northern regions being less affected. However, areas with less frequent droughts experience longer and more severe drought durations. In conclusion, this study provides valuable insights into the characteristics and propagation patterns of drought in China, offering essential information for the development of effective strategies to mitigate the impacts of drought events.

Stemming droughts in China’s Yellow River

Stemming droughts in China’s Yellow River

Anthropogenic influence on the extreme drought in eastern China in 2022 and its future risk

In July–August 2022, eastern China was hit by an extreme drought event characterized by extraordinarily long persistence. The authors selected the minimum accumulated precipitation during a consecutive seven-week period during July–August (Rx49day) as the criterion to capture persistent drought extremes. Quantified by Rx49day, the 2022 drought extreme was 57.5% dryer than the climatology, and estimated as a 1-in-73-year event based on a statistical analysis. Utilizing the DAMIP (Detection and Attribution Model Intercomparison Project) runs, the study shows that anthropogenic forcing increases the occurrence probability of a 2022Drought-like event by 56%. This change is probably associated with the change in mean state over eastern China, including decreased moisture and weakened upward motion. Further, three GHG emission scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) were employed to investigate how the risk of a 2022Drought-like event will change under global warming. The projected results show that such an event is 92% less likely to occur under the low-emissions scenario, which is related to the increased background moisture and enhanced upward motion. In sharp contrast, the high-emissions scenario simulations projected an increased occurrence probability that is 79% higher than the present-day climate, probably caused by the strengthened background descending motion. The results indicate a nonlinear change in 2022Drought-like events in response to a warmer world. It is hoped that this work will provide useful information for policymakers in developing strategies that prevent eastern China from experiencing similar natural disasters.摘要2022年夏季中国东部地区遭遇了一次持续性极端高温干旱事件. 本文利用CMIP6检测归因比较计划 (DAMIP) 数据, 量化了人为强迫对类2022年极端干旱事件发生概率的影响, 并基于未来不同增暖情景试验给出了此类极端干旱事件的未来变化预估. 通过分析不同外强迫因子作用下此类极端干旱事件的发生概率变化, 发现人为强迫使此类极端干旱事件的发生概率提高约56%, 这主要与人为强迫下中国东部平均水汽减少和平均上升运动减弱有关. 进一步通过分析此类极端干旱事件对不同温室气体排放情景 (SSP1-2.6, SSP2-4.5, SSP5-8.5) 的响应, 发现在低排放情景下类2022年极端干旱事件的发生概率较当今气候显著下降, 这主要与中国东部平均水汽的增加和平均环流的变化有关, 而在高排放情景 (SSP5-8.5) 下, 此类极端干旱事件的发生概率较当今气候增加约79%, 这主要与高排放情景下平均下沉运动增强有关. 该研究表明, 人为强迫通过调制气候平均背景场从而引起极端事件发生频次的变化是人类活动影响极端气候事件的重要途径之一, 极端干旱事件对温室气体排放量的响应可能是非线性的.

Recovery of ecosystem carbon and water fluxes after drought in China

Drought recovery time is a crucial indicator of ecosystem resilience. However, existing drought recovery quantification methods have some limitations in terms of drought identification and selection of recovery factors. In addition, drought recovery time in China and related impacts on different landcover types are largely unknown. Therefore, the present study sought to develop a new drought recovery quantification system that considers recovery of ecosystem carbon- and water-related variables in China across seasons (wet and dry) and landcover types. The results showed that drought conditions worsened, especially in northern and western China, from 1982 to 2016. Drought had a strong effect on soil water storage (SWS), with runoff and SWS decreasing in more than 65% of the study area after drought. Drought led to decreases in gross primary productivity (GPP) and water use efficiency (WUE) over 58.7% and 45.2% of the total area, respectively. The mean drought recovery time of SWS (10.4 months) was much longer than that of GPP (3.2 months), WUE (3.7 months), and runoff (2.5 months), especially in northern China. Drought-reduced carbon and water needed more time to recover from drought in grasslands than in other landcover types due to the lower water availability and high evaporative demand. The mean recovery time after dry season drought was longer than that after wet season drought. In a comparison of recent (2001–2016) and past (1982–2000) periods, increased recovery times for runoff and SWS were observed for all landcover types except for SWS (-0.4 month) in grasslands. However, recent recovery times for GPP and WUE were shorter than that in the past. Highly decreased recovery times for GPP (-2.2 months) and WUE (-2.4 months) were found in grasslands. Runoff recovery time increased by 4.9 months in forest and SWS recovery time increased by 1.4 months in cropland. These results improved our understanding of regional drought recovery mechanisms and future trends in different landcover types.

Attribution of Extreme Drought Events and Associated Physical Drivers across Southwest China Using the Budyko Framework

Drought is a meteorological phenomenon that negatively impacts agricultural production. In recent years, southwest China has frequently experienced agricultural droughts; these have significantly impacted the economy and the ecological environment. Although several studies have been conducted on agricultural droughts, few have examined the factors driving agricultural droughts from the perspective of water and energy balance. This study aimed to address this gap by utilizing the Standardized Soil Moisture Index (SSMI) and the Budyko model to investigate agricultural drought in southwest China. The study identified four areas in Southwest China with a high incidence of agricultural drought from 2000 to 2020. Yunnan and the Sichuan-Chongqing border regions experienced drought in 10% of the months during the study period, while Guangxi and Guizhou had around 8% of months with drought. The droughts in these regions exhibited distinct seasonal characteristics, with Yunnan experiencing significantly higher drought frequency than other periods from January to June, while Guizhou and other areas were prone to severe droughts in summer and autumn. The Budyko model is widely used as the mainstream international framework for studying regional water and energy balance. In this research, the Budyko model was applied to analyze the water and energy balance characteristics in several arid regions of southwest China using drought monitoring data. Results indicate that the water and energy balances in Yunnan and Sichuan-Chongqing are more moisture-constrained, whereas those in Guizhou and Guangxi are relatively stable, suggesting lower susceptibility to extreme droughts. Furthermore, during severe drought periods, evapotranspiration becomes a dominant component of the water cycle, while available water resources such as soil moisture decrease. After comparing the causes of drought and non-drought years, it was found that the average rainfall in southwest China is approximately 30% below normal during drought years, and the temperature is 1–2% higher than normal. These phenomena are most noticeable during the spring and winter months. Additionally, vegetation transpiration is about 10% greater than normal during dry years in Southwest China, and soil evaporation increases by about 5% during the summer and autumn months compared to normal conditions.

Irrigation strategy optimization in irrigation districts with seasonal agricultural drought in southwest China: A copula-based stochastic multiobjective approach

Irrigation strategy optimization in irrigation districts with seasonal agricultural drought in southwest China: A copula-based stochastic multiobjective approach

Analysis of the Variability Characteristics and Applicability of SPEI in Mainland China from 1985 to 2018

Drought is one of the most destructive natural disasters in China and can cause serious environmental and socio-economic impacts. Based on monthly precipitation and temperature data from 571 meteorological stations, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated on a 12-month scale (SPEI-12) from 1985 to 2018 in mainland China, and it was compared with the records of the Bulletin of Flood and Drought Disasters in China to verify its drought monitoring accuracy. Then, run theory was used to explore in depth the spatiotemporal distribution of drought characteristics and trends in various climatic sub-regions. The results showed that: (1) the comparison with the Bulletin of Flood and Drought Disasters in China indicated that the results of SPEI-12 monitoring drought had high accuracy and could identify drought events in mainland China. (2) About 70% of the regions in mainland China experienced droughts more than 50 times, and about 43% of the regions had drought durations of between 100 and 110 months. Nearly 11% of the regions had drought severities of more than 130, which were mainly located in the Northwest Desert (NWC), the southern part of Northeast China (NEC), and the western part of North China (NC). (3) In the past 34 years, the droughts in the Northwest Desert (NWC), the western part of Inner Mongolia (IM), and the Qinghai-Tibet Plateau (TP) showed an aridity trend, while the droughts in South China (SC) and eastern Central and South China (CSC) presented a mitigation tendency. (4) Specifically, the droughts in South China (SC) were more influenced by precipitation, while those in the Northwest Desert (NWC) and Northeast China (NEC) were influenced by temperature and potential evapotranspiration, and the evolution of drought in North China (NC) and the Qinghai-Tibet Plateau (TP) was mainly influenced by soil moisture. The study could provide scientific guidance and a reference for drought response and sustainable development in China.

Changes in drought characteristics over China during 1961–2019

Drought is extremely complex and can be influenced by various factors. This study uses Penman-Monteith (PM) method to calculate the potential evapotranspiration and get the monthly drought metric of Standardized Precipitation-Evapotranspiration Index (SPEI) across China during the period of 1961–2019. Results show that the regions of the west of Northwest China (WNWC), Northeast China (NEC), and South China (SC) are reported to experience a wetting trend, while the droughts in the regions of the east of Northwest China (ENWC), North China (NC), and Southwest China (SWC) deteriorated over the past decades. Seasonally, the significant wetting trends mainly occurred in summer, autumn, and winter for WNWC, while mainly in winter for the region of NEC. Additionally, the droughts in China show an obvious interdecadal variability, with more severe droughts for the periods of 1961–1979 and 2000–2019, but with relatively fewer events in the period of 1980–1999. During the 1960 s and 1970 s, droughts in China are observed to mainly happen in summer and winter, while the droughts mainly occurred in autumn and winter during the 1980 s and 1990 s. Since the early 21st century, both the frequency and intensity of spring droughts have increased obviously and played a dominant role in seasonal droughts. Further studies indicate that the drought changes in southern China are mainly affected by the precipitation anomalies, while that in northern China are mainly influenced by the temperature and wind speed anomalies. Hence, our analyses provide theoretical basis for further understanding the drought changes and the prevention control of drought disasters in China.

State of China's climate in 2022

China experienced a warm and dry climate in 2022. The average annual surface air temperature (SAT) was 10.51°C, which was the second highest since 1961. The annual average rainfall was 606.1 mm, which was the lowest since 2012. The seasonal SAT broke the record in spring, summer, and autumn, while the SAT in winter was slightly cooler. More rainfall was observed in winter and spring, but less in summer and autumn. During the flood season from May to September, rainfall was 11.9% less than normal, which was the third lowest since 1961. The spatial distribution of rainfall anomalies exhibited a wet/dry pattern in the north/south of central and eastern China. The onset of the rainy season was generally earlier but with significant differences in rainfall. More rainfall was observed in the pre-flood season in South China and the rainy season in North China and Northeast China. In contrast, less rainfall occurred in the Mei-yu season in the middle and lower reaches of the Yangtze and Huaihe River valleys, the southwestern rainy season, and the autumn rainy season in West China. In 2022, China's drought and flood disasters were stark, and heat waves were strong. Severe droughts occurred along the Yangtze River valley during summer and autumn, while heavy rainfall and flooding struck South China in the pre-flood season and Northeast China in June–July. A historically strongest summer heat wave occurred in central and eastern China, while drastic cooling prevailed in most of China at the end of November. Landfalling typhoons were extremely less frequent.摘要2022 年我国气候暖干特征明显, 年平均气温偏高 0.62℃, 位居1961年以来历史第二高; 年降水量偏少5%, 为2012 年以来最少, 冬春季降水偏多, 夏秋季降水偏少. 汛期(5–9 月)降水量偏少11.9%, 位居1961年以来第3少, 中东部降水距平呈“北多南少”分布. 雨季进程偏早, 雨量空间差异大, 华南前汛期, 华北雨季, 东北雨季降水量偏多, 而长江中下游和江淮梅雨降水偏少. 华南, 东北洪涝灾害重, 南方夏秋连旱严重, 中东部遭遇最强高温过程, 登录台风异常偏少.

Seasonal variations of soil bacterial and fungal communities in a subtropical Eucalyptus plantation and their responses to throughfall reduction.

Climatic change causes obvious seasonal meteorological drought in southern China, yet there is a lack of comprehensive in situ studies on the effects of drought in Eucalyptus plantations. Here, a 50% throughfall reduction (TR) experiment was conducted to investigate the seasonal variations of soil bacterial and fungal communities and functions in a subtropical Eucalyptus plantation and their responses to TR treatment. Soil samples were collected from control (CK) and TR plots in the dry and rainy seasons and were subjected to high-throughput sequencing analysis. Results showed that TR treatment significantly reduced soil water content (SWC) in the rainy season. In CK and TR treatments, fungal alpha-diversity decreased in the rainy season while bacterial alpha-diversity did not change significantly between dry and rainy seasons. Moreover, bacterial networks were more affected by seasonal variations compared with fungal networks. Redundancy analysis showed that alkali hydrolyzed nitrogen and SWC contributed the most to the bacterial and fungal communities, respectively. Functional prediction indicated that the expression of soil bacterial metabolic functions and symbiotic fungi decreased in the rainy season. In conclusion, seasonal variations have a stronger effect on soil microbial community composition, diversity, and function compared with TR treatment. These findings could be used to develop management practices for subtropical Eucalyptus plantations and help maintain soil microbial diversity to sustain long-term ecosystem function and services in response to future changes in precipitation patterns.

Drought Disasters in China from 1991 to 2018: Analysis of Spatiotemporal Trends and Characteristics

Droughts have emerged as a global problem in contemporary societies. China suffers from different degrees of drought almost every year, with increasing drought severity each year. Droughts in China are seasonal and can severely impact crops. This study used spatiotemporal trend and characteristics analysis of drought disaster data from 1991 to 2018 in Chinese provinces, in addition to the Mann–Kendall test and wavelet analysis. The drought disaster data included the crop damage area, drought-affected area of the crops, and crop failure area. The outputs of the crops decreased by 10%, 30%, and 80%, respectively. The population with reduced drinking water caused by drought, and the domestic animals with reduced drinking water caused by drought, were numbered in the tens of thousands. The results of the study show that the crop damage areas owing to drought disasters, drought-affected areas of crops, and crop failure areas in China were mainly distributed in the northern, eastern, northeaster, and southwestern regions. The number of people and domestic animals with reduced drinking water owing to drought in China were mainly concentrated in the northern and southwestern regions. These indicators showed a general increasing trend. Tibet, Fujian, Shandong, Jiangsu, Anhui, and Henan provinces and autonomous regions also showed a slightly increasing trend. In particular, the number of domestic animals with reduced drinking water caused by drought in the Inner Mongolia Autonomous Region showed a clear increasing trend with a significant Z-value of 2.2629. The results of this research can be used to provide scientific evidence for predicting future trends in drought and for practising the best management of drought prevention and resistance.

Substantial increase in abrupt shifts between drought and flood events in China based on observations and model simulations

Drought-flood abrupt alternation (DFAA) refers to the rapid transformation between droughts and floods, posing serious threats to ecological security, food production, and human safety. Previous studies have insufficiently investigated DFAA events at large regional scales using high-resolution observations and model simulations. In this study, the standardized precipitation evapotranspiration index was used to construct the DFAA magnitude index, which considers the asymmetric effects of drought and flood alternations. Four types of DFAA events were then investigated using high-resolution station observations and NEX-GDDP-CMIP6 model simulations. The results showed that hotspot areas of drought-flood and flood-drought alternation events were mainly in the northern and eastern parts of China, while the hotspot areas of drought-flood-drought and flood-drought-flood alternation events were obviously smaller than those of drought-flood and flood-drought alternation events. Drought-flood, flood-drought, and drought-flood-drought alternation events showed significant upward trends at rates of 0.075, 0.057, and 0.051 events/decade, respectively, and these increases were attributed to significant increases in moderate, severe, and extreme events across China during 1981–2020. Generally, the total number of DFAA events above moderate grade in the northern, central, and some areas in the southern parts of China increased obviously (>50 %) during 2001–2020 compared to 1981–2000. NEX-GDDP-CMIP6 can reasonably represent the multi-year averages and long-term trends of precipitation, temperature, and DFAA events in China. Except for the flood-drought-flood alternation events, the other three types of DFAA events showed significant increasing trends in the future, with higher rates under the SSP585 scenario than under the SSP245 scenario (e.g., drought-flood alternation events at rates of 0.033 and 0.046 events/decade under SSP245 and SSP585, respectively, during 1981–2100). DFAA events above the moderate grade were predicted to increase significantly in both 2032–2065 and 2066–2099 compared to 1981–2014, especially in northern China for the 2066–2099 under the SSP585 scenario.

Enhanced Linkage of Summer Drought in Southern China to the North Pacific Oscillation Since 2000

AbstractBased on the standardized precipitation evaporation index and reanalysis data, this article reveals that the relationship between the North Pacific Oscillation (NPO) and the drought over southern China in summer shifts from an insignificant correlation to a significant negative correlation after 2000. During the significant period (2001–2018), the positive NPO phase corresponds to an anomalous anticyclonic circulation dominating the mid‐low latitude North Pacific, which suppresses the moisture transport into southern China. Meanwhile, the easterly anomalies south of the anomalous anticyclonic circulation prevailing in the equatorial Pacific are coupled with a cooling of sea surface temperature in the central tropical Pacific, which enhances the Walker circulation and further induces an anomalous meridional circulation with the descending anomalies over southern China. Such moisture and dynamical conditions favor the occurrence of drought in southern China. During the former period (1983–2000), however, the NPO‐related atmospheric circulations over the North Pacific shift northward. In this case, the NPO shows insignificant relations with the moisture and dynamical conditions over southern China, thereby diluting the linkage of the NPO to the drought in southern China. The interdecadal strengthening in the relationship between the NPO and above atmospheric conditions is attributed to the westward (southward) extension of the NPO northern (southern) center. The larger interannual variability of spring sea ice in the Bering Sea and the southward movement of summer storm track over the North Pacific are hypothesized to account for the expansion of the NPO structure.