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Changes in precipitation as a result of climate change are becoming a widespread issue all around the world. A lack of rainfall causes a meteorological drought. The short-term Standardized Precipitation Index (SPI-6) index was used to estimate meteorological drought conditions in Saudi Arabia's Asir region from 1970 to 2017. Innovative trend analysis (ITA), the Modified Mann–Kendall test (MMK), the Sequential Mann–Kendall test, and Morlet wavelet transformation were used to detect trend and periodicity in meteorological drought conditions in the Asir region. In addition, the meteorological drought conditions were forecasted by integrating Particle Swarm Optimization (PSO) ensemble machine learning algorithm and an artificial neural network (ANN). Droughts of varying severity have become more frequent in Asir, according to the findings. In most stations, ITA and MMK tests have revealed a significant increase in drought. In all stations, the SQMK test revealed a big sudden year-over-year drought trend. With the exception of one station, all stations experienced extreme drought frequency discovered using Morlet Wavelet Transformation over a long period of time (10 years or more) (station 34). The PSO-ANN hybrid learning algorithm predicted SPI-6 values that had a strong correlation with actual SPI-6 values and also had lower error values, indicating that this model performed well. The PSO-ANN model predicts that the Asir region of Saudi Arabia will experience major moderate to extreme drought events in the coming years (2018–2025). The findings of this analysis will assist planners and policymakers in planning for the acquisition of sustainable agriculture in the study area.

Eastern Thailand and Rayong province face perennial drought and water scarcity due to natural characteristics of climate and geology. Therefore, increasing water surface by man-made reservoirs is one of the priorities in the regional development plan to provide water adequately for industrial purposes, domestic consumption, and agriculture. The large reservoir constructions may induce land use, land cover changes (LULCC), yet it also is expected to alleviate the drought harshness in the region. By delineating Landsat satellite images and spatial analysis, this study revealed the LULCC in Rayong from 1990 to 2020. The most prominent LULCC was surface water expansion, about 10.9% per year, yet the increase was the most substantial in the first decade rather than the last two decades. Vegetation expansion was observed, contributing to an increase in forests/plantations and intensified agriculture by 39.19% and 25.54%, respectively. The LULCC corresponded to a 3.64% increase in ecosystem service values (ESV), implying positive benefits from the LULCC. Vegetation drought conditions monitored by the vegetation health index (VHI) exhibited an improvement trend, especially in the eastern basins. The development of artificial reservoirs was proven to stimulate the expansion of intensive agriculture and vegetation drought mitigation with spatial heterogeneity, spreading mainly across areas of the basins rather than remote areas. The research findings inform the efficiency of the reservoirs and irrigation systems regarding the beneficial effects on drought mitigation and water scarcity for agricultural cultivation. They also provide spatial information on areas still hindered by water problems that should be addressed in future strategies.

Concurrent hot extremes and droughts undoubtedly aggravate the impacts of droughts on agriculture, natural environment, and human society. Recent studies mainly focus on the trends and changes in frequency and severity of compound drought and hot extreme events. However, relatively little attention has been paid to the changes in mean temperature during drought conditions. In this study, we investigated the mean temperature changes during droughts in observed and projected periods across China on a century time‐scale and explored the possible contributions of land surface‐atmosphere interactions or atmospheric moisture conditions to these changes. China experienced reduced rather than amplified warming under droughts both in observations and future projections. A drier condition or a higher emission scenario was projected to result in a larger range of mean temperature changes under droughts in the future. We attributed the reduced mean temperatures under droughts to increasing winter droughts and higher atmospheric moisture conditions. This study provides a reference for water resource management, drought risk reduction, as well as mitigation of agricultural crop loss and public health damage. Plain Language Summary Previous climate studies generally focus on the trend analysis of concurrent droughts and hot extremes, especially in summer. There are gaps in our knowledge on how does the mean temperature under droughts change under climate warming, and what are the underlying driving factors? We investigated the changes in mean temperature during droughts across China using monthly observed data and projected data. China experienced reduced rather than amplified warming under droughts both in observations and future projections. A drier condition or a higher emission scenario could result in a larger range of mean temperature changes under droughts in the future. Increasing winter droughts and higher atmospheric moisture conditions resulted in the reduced mean temperatures under droughts. Our study provides references for policymakers to inform water resource management, drought risk reduction, and mitigation of agricultural crop loss. Key Points China experienced reduced rather than amplified warming under drought conditions both in observations and future projections A drier condition or a higher emission scenario resulted in a larger range of mean temperature changes under future droughts We attributed the reduced mean temperatures under droughts to increasing winter droughts and higher atmospheric moisture conditions

The 2022 Compound Drought and Heatwave (CDHW) caused widespread crop damage, water shortages, and wildfires across Europe. Our study analyzed this event’s severity and return period (RP) and compared it with past mega CDHWs in Europe. The hardest‐hit areas were Iberian Peninsula, France, and Italy, where temperatures exceeded 2.5°C above normal, and severe droughts persisted from May to August. Using a Bayesian approach, we estimated the RP for the 2022 CDHW event, which was unprecedented in Northern Italy, Iberian Peninsula, and western parts of France, with RPs of 354, 420, and 280 years, respectively. The reduced soil moisture due to precipitation deficits and high temperatures contributed to the persistence and severity of drought, creating a positive feedback loop where dry soils led to even drier conditions. In light of our findings, it is evident that global warming poses increased risks of severe CDHW events, which are likely to increase. Plain Language Summary We studied how severe was 2022 Compound Drought and Heatwave (CDHW) event over Europe, identified hotspots, and compared them with past mega‐events. The most impacted regions include the Iberian Peninsula, France, and Italy, experiencing higher‐than‐normal temperatures and severe drought conditions from May to August. Our study estimated the return period of this event, which indicates how often an event of this magnitude is expected to occur, and found that it was unprecedented in large parts of Northern Italy, Iberian Peninsula, and France. The hot and dry weather that continued from the Spring season caused the soil to lose moisture, worsening the drought. This, in turn, made the soil even drier, intensifying the drought and heatwaves further, aggravating the risks of wildfires across France and the Mediterranean region. Key Points Spatiotemporal patterns of 2022 compound drought and heatwave events were compared with past 2003, 2015, and 2018 extreme events Iberian Peninsula, France, and Italy experienced higher‐than‐normal temperatures and severe drought conditions from May to August 2022 compound event was unprecedented in most part of Europe, such as Iberian Peninsula, Italy, and western parts of France

The Yangtze River Basin experienced one of the worst flash droughts on record during 2022 summer, but the relative contributions of precipitation deficit and high temperature to drought onset speed and intensity are difficult to separate due to the compounding feature of hot and dry extremes caused by persistent high‐pressure anomalies. Based on high‐resolution land surface model ensemble simulations with specified meteorological conditions that reproduce precipitation deficit and/or high temperature anomalies during 2022, we find the precipitation deficit is the dominant factor for triggering the flash drought. Meanwhile, high temperature further accelerates the decrease of soil moisture and intensifies drought condition by increasing evapotranspiration, which contributes 37% ± 14% (31% ± 15%) and 36% ± 11% (30% ± 15%) of the drought onset speed and intensity over upper reach (middle and lower reaches). Our study reveals the nontrivial role of high temperature in intensifying the 2022 Yangtze flash drought, which might be more significant in the warmer future. Plain Language Summary As the extremely high temperature sweeping the Northern Hemisphere in the summer of 2022, an unprecedented flash drought broke out over the Yangtze River Basin (YRB), which caused a serious impact on the ecological environment, agricultural production, and even livelihood. It was ranked as one of the top 10 weather and climate extreme events of 2022 in China. In this study, we focused on the physical mechanism of the onset process of 2022 flash drought and quantified the contribution of precipitation deficit and high temperature through a set of high‐resolution land surface model simulations with specified climate anomalies. The results show that the unprecedented flash drought has a rapid onset speed and strong intensity, which is the result of the combined impact of precipitation deficit, high temperature, and strong radiation. The precipitation deficit played a dominant role in triggering the flash drought. In addition, the high temperature and strong radiation aggravated the drought conditions by increasing evapotranspiration and further accelerating the onset speed and enhancing the drought intensity. With the hot extremes being increasing in the future, flash droughts could be a great threat to food, energy and water security even in humid regions including the YRB. Key Points The 2022 Yangtze flash drought broke out over upstream in July and downstream areas in August, with rapid onset speed and strong intensity Precipitation deficit far exceeded the evapotranspiration excess for increasing the onset speed and intensity during drought onset High temperature aggravated drought onset speed and intensity, with contributions of 37 (31)% and 36 (30)% for upstream (downstream) areas

In the past several decades, field studies have shown that woody plants can access substantial volumes of water from the pores and fractures of bedrock 1 – 3 . If, like soil moisture, bedrock water storage serves as an important source of plant-available water, then conceptual paradigms regarding water and carbon cycling may need to be revised to incorporate bedrock properties and processes 4 – 6 . Here we present a lower-bound estimate of the contribution of bedrock water storage to transpiration across the continental United States using distributed, publicly available datasets. Temporal and spatial patterns of bedrock water use across the continental United States indicate that woody plants extensively access bedrock water for transpiration. Plants across diverse climates and biomes access bedrock water routinely and not just during extreme drought conditions. On an annual basis in California, the volumes of bedrock water transpiration exceed the volumes of water stored in human-made reservoirs, and woody vegetation that accesses bedrock water accounts for over 50% of the aboveground carbon stocks in the state. Our findings indicate that plants commonly access rock moisture, as opposed to groundwater, from bedrock and that, like soil moisture, rock moisture is a critical component of terrestrial water and carbon cycling. Woody plants across the continental United States make extensive use of water stored in bedrock across diverse climates and biomes.

While climate change will alter the distribution of water in time and space, quantifications of drought risk under global warming remain uncertain. Here, we show that in Europe, drought damages could strongly increase with global warming and cause a regional imbalance in future drought impacts. In the absence of climate action (4 °C in 2100 and no adaptation), annual drought losses in the European Union and United Kingdom combined are projected to rise to more than €65 billion per year compared with €9 billion per year currently, or two times larger when expressed relative to the size of the economy. Drought losses show the strongest rise in southern and western parts of Europe, where drought conditions at 4 °C could reduce regional agriculture economic output by 10%. With high warming, drought impacts will become a fraction of current impacts in northern and northeastern regions. Keeping global warming well below 2 °C would avoid most impacts in affected regions.Climate change impacts precipitation patterns, and thus the risk for drought. Damages from drought in Europe will increase with losses more than €65 billion per year in a scenario without climate mitigation; keeping warming below 2 °C avoids most impacts.

Under climate change, drought assessment, which can address nonstationarity in drought indicators and anthropogenic implications, is required to mitigate drought impacts. However, the development of drought indices for a reliable drought assessment is a challenging task in the warming climate. Thus, this study discusses factors that should be considered in developing drought indices in changing climate. Inconsistent drought assessment can be obtained, depending on the baseline period defined in developing drought indices. Therefore, the baseline period should represent the contemporary climate but should also correspond to long enough observations for stable parameter estimation. The importance of accurate potential evapotranspiration ( PET ) for drought indices becomes higher under a warming climate. Although the Penman–Monteith method yields accurate PET values, depending on the climate and vegetation cover, other suitable PET formulas, such as the Hargreaves method, with fewer hydrometeorological data can be used. Since a single drought index is not enough to properly monitor drought evolution, a method that can objectively combine multiple drought indices is required. Besides, quantifying anthropogenic impacts, which can add more uncertainty, on drought assessment is also important to adapt to the changing drought conditions and minimize human-induced drought. Drought is expected to occur more frequently with more severe, longer, and larger areal extent under global warming, since a more arid background, which climate change will provide, intensifies land–atmosphere feedback, leading to the desiccation of land and drying atmosphere. Thus, an accurate drought assessment, based on robust drought indices, is required.

The monthly standardized precipitation evapotranspiration index (SPEI) can be used to monitor and assess drought characteristics with 1-month or longer drought duration. Based on data from 1961 to 2018 at 427 meteorological stations across mainland China, we developed a daily SPEI dataset to overcome the shortcoming of the coarse temporal scale of monthly SPEI. Our dataset not only can be used to identify the start and end dates of drought events, but also can be used to investigate the meteorological, agricultural, hydrological, and socioeconomic droughts with a different timescales. In the present study, the SPEI data with 3-month (about 90 d) timescale were taken as a demonstration example to analyze spatial distribution and temporal changes in drought conditions for mainland China. The SPEI data with a 3-month (about 90 d) timescale showed no obvious intensifying trends in terms of severity, duration, and frequency of drought events from 1961 to 2018. Our drought dataset serves as a unique resource with daily resolution to a variety of research communities including meteorology, geography, and natural hazard studies. The daily SPEI dataset developed is free, open, and publicly available from this study. The dataset with daily SPEI is publicly available via the figshare portal (Wang et al., 2020c), with https://doi.org/10.6084/m9.figshare.12568280.Highlights. A multi-scale daily SPEI dataset was developed across mainland China from 1961 to 2018. The daily SPEI dataset can be used to identify the start and end days of the drought event. The developed daily SPEI dataset in this study is free, open, and publicly available.