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The study of regional drought characteristics is vital for identifying drought patterns and offering scientifically informed guidance for drought warnings. This research focuses on the Sichuan Basin, where the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated across various time scales using meteorological data from 1963 to 2022. Wavelet analysis was applied to examine the periodic fluctuations of the SPEI across different time scales. Drought events were identified using run-length theory and spatially visualized with ArcGIS 10.7 interpolation techniques to elucidate the temporal and spatial dynamics of drought occurrences. The findings are as follows: (1) Over nearly 60 years, the SPEI in the Sichuan Basin fluctuated between −1.5 and 1, with an insignificant annual downward trend but a significant downward trend in autumn (p < 0.05). (2) The SPEI displayed a primary cycle of 6 years in spring, autumn, and winter, while the summer cycle matched the annual SPEI cycle of 8 years. (3) Drought events were more frequent in the eastern part of the basin compared to the west. The area with high drought frequency shifted counterclockwise from east to north, northwest, west, and south with the changing seasons. (4) Drought duration was longer in the western and northern regions of the basin than in the east. Severe drought events were mainly concentrated in the Chengdu Plain and the Central Sichuan Hilly Region, although the drought intensity index was lowest in the Chengdu Plain and Chongqing in eastern Sichuan. The peak values of drought showed an insignificant decreasing trend, indicating a potential expansion in the extreme impacts of drought disasters in the study area. [ABSTRACT FROM AUTHOR]

As warmer and drier conditions associated with global warming are projected to increase in southern Europe, the Mediterranean countries are currently the most prone to wildfire danger. In the present study, we investigated the statistical relationship between drought and fire weather risks in the context of climate change using drought index and fire weather-related indicators. We focused on the vulnerable and long-suffering area of the Attica region using high-resolution gridded climate datasets. Concerning fire weather components and fire hazard days, the majority of Attica consistently produced values that were moderately to highly anti-correlated (−0.5 to −0.9). This suggests that drier circumstances raise the risk of fires. Additionally, it was shown that the spatial dependence of each variable on the 6-months scale Standardized Precipitation Evapotranspiration Index (SPEI6), varied based on the period and climate scenario. Under both scenarios, an increasing rate of change between the drought index and fire indicators was calculated over future periods versus the historical period. In the case of mean and 95th percentiles of FWI with SPEI6, abrupt changes in linear regression slope values were observed, shifting from lower in the past to higher values in the future periods. Finally, the fire indicators' future projections demonstrated a tendency towards an increasing fire weather risk for the region's non-urban (forested and agricultural) areas. This increase was evident from the probability distributions shifting to higher mean and even more extreme values in future periods and scenarios. The study demonstrated the region's growing vulnerability to future fire incidents in the context of climate change. [ABSTRACT FROM AUTHOR]

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Gansu Province is located in an ecologically fragile area, with complex climate conditions, high probability and wide range of drought. In order to better study the temporal and spatial variation characteristics of drought in Gansu Province, it was divided into four cli- mate zones according to the climate type and geographical characteristics and the standardized precipitation evapotranspiration indices (SPEI- 3 and SPEI-12) at quarterly and annual scales for the next 76 years (2024-2099) were calculated. Under the four scenarios of SSP126, SSP245, SSP370 and SSP585, Mann Kendall mutation test, spatial interpolation and other methods were used to estimate the temperature, precipitation, and drought evolution status of Gansu Province in the future 80 in the CMIP6 climate model. The main conclusion is as follows: In the CMIP6 model, the temperature and precipitation in different regions of Gansu Province in the future from 2024 to 2099 show an upward trend over time under different scenarios and the climate tendency rate of temperature and precipitation under different scenarios is from small to large as SSP126, SSP245, SSP370 and SSP585. Under the SSP126, SSP245, SSP370 and SSP585 scenarios in the CMIP6 model, Gansu Province will show the development trend of drought in spring, summer and autumn in the coming 2024 to 2099. The mutation years from humid to arid are concentrated between 2040 and 2060. In winter, there is a trend of wetting, with a sudden change from drought to humidification in the SSP121 scenario occurring in 2033, and other scenarios occurring between 2040 and 2060. The frequency of different types of drought is different between different scenarios. Light drought and extreme drought have the highest frequency under the SSP370 scenario, moderate drought has the highest frequency under the SSP245 scenario, and severe drought has the highest frequency under the SSP585 scenario. The frequency of different levels of drought in different climatic regions of Gansu Province under different climatic scenarios is from large to small of light drought, moderate drought, severe drought and extreme drought. [ABSTRACT FROM AUTHOR]

In the context of global warming, escalating water cycles have led to a surge in drought frequency and severity. Yet, multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately understood. This study examined the multide-cadal changes in drought characteristics (frequency, duration, and severity) and their geographical focal points within China's north-south transitional zone, the Qinling-Daba Mountains (QDM), from 1960 to 2017 using the Standardized Precipitation Evapotranspiration Index (SPEI). In addition, a suite of eight scenarios, correlation analysis, and wavelet coherence were used to identify the meteorological and circulation factors that influenced drought characteristics. The results indicate the following: (1) From 1960 to 2017, the QDM experienced significant interdecadal variations in drought frequency, duration, and severity, the climate was relatively humid before the 1990s, but drought intensified thereafter. Specifically, the 1990s marked the period of the longest drought duration and greatest severity, while the years spanning 2010 to 2017 experienced the highest frequency of drought events. (2) Spatially, the Qinling Mountains, particularly the western Qinling Mountain, exhibited higher drought frequency, duration, and severity than the Daba Mountains. This disparity can be attributed to higher rates of temperature increase and precipitation decrease in the western Qinling Mountain. (3) Interdecadal variations in droughts in the QDM were directly influenced by the synergistic effects of interdecadal fluctuations in air temperature and precipitation. Circulation factors modulate temperature and precipitation through phase transitions, thereby affecting drought dynamics in the QDM. The Atlantic Multidecadal Oscillation emerges as the primary circulation factors influencing temperature changes, with a mid-1990s shift to a positive phase favoring warming. The East Asian Summer Monsoon and El Niño-Southern Oscillation are the main circulation factors affecting precipitation changes, with positive phase transitions associated with reduced precipitation, and vice versa for increased precipitation. [ABSTRACT FROM AUTHOR]

As warmer and drier conditions associated with global warming are projected to increase in southern Europe, the Mediterranean countries are currently the most prone to wildfire danger. In the present study, we investigated the statistical relationship between drought and fire weather risks in the context of climate change using drought index and fire weather-related indicators. We focused on the vulnerable and long-suffering area of the Attica region using high-resolution gridded climate datasets. Concerning fire weather components and fire hazard days, the majority of Attica consistently produced values that were moderately to highly anti-correlated (−0.5 to −0.9). This suggests that drier circumstances raise the risk of fires. Additionally, it was shown that the spatial dependence of each variable on the 6-months scale Standardized Precipitation Evapotranspiration Index (SPEI6), varied based on the period and climate scenario. Under both scenarios, an increasing rate of change between the drought index and fire indicators was calculated over future periods versus the historical period. In the case of mean and 95th percentiles of FWI with SPEI6, abrupt changes in linear regression slope values were observed, shifting from lower in the past to higher values in the future periods. Finally, the fire indicators’ future projections demonstrated a tendency towards an increasing fire weather risk for the region’s non-urban (forested and agricultural) areas. This increase was evident from the probability distributions shifting to higher mean and even more extreme values in future periods and scenarios. The study demonstrated the region’s growing vulnerability to future fire incidents in the context of climate change.

Quantifying variation in precipitation and drought in the context of a changing climate is important to assess climate-induced changes and propose feasible mitigation strategies, particularly in agrarian economies. This study investigates the main characteristics and historical drought trend for the period 1980–2016 using the Standard Precipitation Index (SPI), Standard Precipitation Evaporation Index (SPEI), Run Theory and Mann–Kendall Trend Test at seven stations across the Upper Draa Basin. The results indicate that rainfall has the largest magnitude over the M'semrir and Agouim (>218 mm/pa) and the lowest in the Agouilal, Mansour Eddahbi Dam, and Assaka subregions (104 mm–134 mm/pa). The annual rainfall exhibited high variability with a coefficient of variation between 35−57% and was positively related to altitude with a correlation coefficient of 0.86. However, no significant annual rainfall trend was detected for all stations. The drought analysis results showed severe drought in 1981–1984, 2000–2001, and 2013–2014, with 2001 being the driest year during the study period and over 75% of both SPEI and SPI values returned drought. Conversely, wet years were experienced in 1988–1990 and 2007–2010, with 1989 being the wettest year. The drought frequency was low (<19%) across all the timescales considered for both SPI and SPEI, with Mansour Eddahbi Dam and Assaka recording the highest frequencies for SPI-3 and SPEI-3, respectively. [ABSTRACT FROM AUTHOR]

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Drought assessment is necessary for creating adaptation and resilience measures for the livelihoods of the affected communities. This study assessed drought trends in Kenya's Upper Ewaso Ng'iro River Basin (UENB) from 1981 to 2020. A Standardized Precipitation Index (SPI), a precipitation-based index, and a Standardized Precipitation Evapotranspiration Index (SPEI), a multivariate index that considers the difference between precipitation and potential evapotranspiration (PET), were used to evaluate drought severity and frequency over varying timescales. Monthly rainfall and temperature data for 10 stations within the basin were analyzed to calculate the SPI and SPEI time series values for 3, 6, and 12 months. The results demonstrate an alarming increase in the severity and frequency of drought events in the UENB since 1999. Additionally, the study reveals that the SPI and SPEI indices differ in identifying temporal and spatial drought characteristics, with longer timescales showing improved accuracy. Notably, the SPEI identifies more extensive and severe drought periods in the region compared to the SPI. The research findings are crucial in guiding policy decisions related to SDGs as they provide valuable information on drought trends necessary for implementing effective drought adaptation and resilience measures and promoting sustainable development in the UENB. HIGHLIGHTS The study describes the temporal and spatial evolution characteristics of meteorological drought in the region.; There has been an increase in drought frequency in the basin over the 40 years, and it has significantly increased since 2000.; The study shows the relationship between the SPI and SPEI in identifying drought events and that the SPEI performed better than the SPI in identifying drought.;

The increasing frequency of global drought events poses a significant threat to the stability of grassland ecosystems' functionality. The Inner Mongolian grasslands stand out as one of the world's most drought-prone regions, facing elevated drought risks compared to other biomes. An in-depth comprehension of the impact of drought on grassland ecosystems is paramount for their long-term sustainability. Using the Standardized Precipitation Evapotranspiration Index (SPEI) from 1982 to 2018, this study identified various drought events within the Inner Mongolian grasslands, encompassing moderate drought, severe drought, and extreme drought. The resistance of the vegetation to the different drought conditions, assessed through net primary productivity (NPP) as a metric (reflecting its capacity to maintain its original level during drought periods), was examined. The research findings indicated that the period from 2001 to 2018 witnessed a substantial increase in both the frequency and the extent of drought events compared to the period from 1982 to 2000, particularly concerning severe and extreme droughts. The areas most severely impacted by extreme drought were the Xilingol League and the Alxa League. From 1982–2000 to 2001–2018, under moderate drought conditions, vegetation resistance exhibited a minor decrease in the central and eastern regions but experienced a slight increase in the western region. In contrast, under severe drought conditions, the western region saw a significant decrease in vegetation resistance. Remarkably, under extreme drought conditions, the western region showed a substantial increase in vegetation resistance, while the central and eastern regions experienced a slight decrease. Across all three drought conditions, as precipitation levels declined, the resistance of the meadow–steppe–desert ecosystems demonstrated a high–low–high distribution pattern. The temperate desert steppe exhibited a minimal vulnerability to drought, boasting resistance levels exceeding 0.9. Notably, extreme drought had the most pronounced impact on the temperate meadow steppe, temperate steppe, and temperate desert steppe, particularly within the temperate meadow steppe category. Given these findings, the authorities responsible for grassland management should prioritize regions characterized by frequent drought occurrences and low drought resistance, such as Ulanqab City, the Xilingol League, and the western part of Hulun Buir City. Safeguarding steppe ecosystems is of paramount importance for stabilizing vegetation productivity and land carbon sinks, especially under the anticipated exacerbation of climate conditions in the future. [ABSTRACT FROM AUTHOR]

According to the Standardized Precipitation Evapotranspiration Index (SPEI), most extensive summer droughts in European Russia south of 55° N in 1950–2021 were observed during the extremely negative phases of the Eastern Atlantic/Western Russia (EAWR) and West Pacific (WP) atmospheric circulation patterns characterized by abnormal high atmospheric pressure and an increased frequency of the number of days with atmospheric blocking over European Russia. It is shown that the frequency of droughts in the study area in the years of the negative phases of both circulation indices and their extremes in the summer months as compared to other years was higher by five droughts per decade in the Volga and Central Chernozem regions and by three droughts per decade in the northwestern Caspian region. A statistically significant correlation was found between the EAWR in summer and the multidecadal variability of sea surface temperature in the North Atlantic. It was revealed that the increase in the drought frequency in the study area in recent decades has been caused by the restructuring of atmospheric circulation in the Euro-Atlantic sector accompanying the transition of the Atlantic Multidecadal Oscillation (AMO) to a positive phase. An increase in the stability of the EAWR and WP atmospheric circulation patterns was observed, as well as a related significant increase in the frequency of extensive droughts in the study area in 2010–2021. They were accompanied by the weakening of zonal atmospheric circulation in the Northern Hemisphere, the combination of the positive AMO phase and the effects of anthropogenic warming on the atmospheric circulation in the Northern Hemisphere, including those associated with blocking events. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Quantifying variation in precipitation and drought in the context of a changing climate is important to assess climate-induced changes and propose feasible mitigation strategies, particularly in agrarian economies. This study investigates the main characteristics and historical drought trend for the period 1980–2016 using the Standard Precipitation Index (SPI), Standard Precipitation Evaporation Index (SPEI), Run Theory and Mann–Kendall Trend Test at seven stations across the Upper Draa Basin. The results indicate that rainfall has the largest magnitude over the M’semrir and Agouim (>218 mm/pa) and the lowest in the Agouilal, Mansour Eddahbi Dam, and Assaka subregions (104 mm–134 mm/pa). The annual rainfall exhibited high variability with a coefficient of variation between 35−57% and was positively related to altitude with a correlation coefficient of 0.86. However, no significant annual rainfall trend was detected for all stations. The drought analysis results showed severe drought in 1981–1984, 2000–2001, and 2013–2014, with 2001 being the driest year during the study period and over 75% of both SPEI and SPI values returned drought. Conversely, wet years were experienced in 1988–1990 and 2007–2010, with 1989 being the wettest year. The drought frequency was low (

【Objective】 Global warming is expected to increase the frequency of extreme weathers such as flooding and drought. Understanding their spatiotemporal variation is important to help mitigate its detrimental impact. The purpose of this paper is to analyze the spatiotemporal variation of drought in Inner Mongolia of China. 【Method】 The analysis was based on meteorological data measured from 1951 to 2018 from 50 weather stations across the region. The occurrence and severity of the drought was quantified using the standardized precipitation evapotranspiration index (SPEI). 【Result】 An abrupt climate change occurred around 1979. Since then, most areas in the region have seen an ease of drought stress. Since 1996, however, western Inner Mongolian have seen a return of the drought. Spatially, severe droughts occurred mainly in central-western Inner Mongolia, and southern Chifeng and Tongliao. 【Conclusion】 SPEI can be used as an index to quantify drought at provincial scale. Its application to Inner Mongolia reveals that the province has undergone alternate drought and humidified climate since 1951. Drought occurred more frequently and severely in the central-western province than in other areas.

The current study evaluates the impact of drought on Pakistan's agriculture sector at national and provincial scales during 2000–2020 using the Standardized Precipitation Evapotranspiration Index (SPEI-3). Severe drought events were observed during 2001, 2003, 2006, 2007, 2008, 2012, 2017, and 2018, which are used to demonstrate the impact of drought on agriculture. Balochistan and Sindh provinces are severely affected by drought due to their arid/hyper-arid climate nature. Drought severity is relatively high in Kharif season (ranging from severe to moderate) compared with drought in Rabi season. The average SPEI-3 during Kharif (Rabi) season across KP, Punjab, Balochistan, and Sindh provinces are − 0.48 to − 1.02 (0.47 to − 0.83), − 1.33 to − 1.68 (− 0.93 to − 1.36), − 1.21 to − 1.54 (− 0.76 to − 1.30), and − 1.73 to − 2.07 (1.54 to − 1.96), respectively. The results showed that Punjab, Balochistan, and Sindh provinces are most vulnerable to drought. As the drought index becomes more positive, the maize yield increases at both national and provincial levels. Drought has mixed effects on the rice yield. Similarly, the decline in drought severity leads to an increase in sugarcane, tobacco and wheat yields. The decrease in drought severity has a positive impact on the irrigated area under canals, wells and tubewells at both national and provincial levels. Similarly, an increase in the drought index also leads to an increase in the total cultivated and cropped area. [ABSTRACT FROM AUTHOR]

The increasing frequency of global drought events poses a significant threat to the stability of grassland ecosystems’ functionality. The Inner Mongolian grasslands stand out as one of the world’s most drought-prone regions, facing elevated drought risks compared to other biomes. An in-depth comprehension of the impact of drought on grassland ecosystems is paramount for their long-term sustainability. Using the Standardized Precipitation Evapotranspiration Index (SPEI) from 1982 to 2018, this study identified various drought events within the Inner Mongolian grasslands, encompassing moderate drought, severe drought, and extreme drought. The resistance of the vegetation to the different drought conditions, assessed through net primary productivity (NPP) as a metric (reflecting its capacity to maintain its original level during drought periods), was examined. The research findings indicated that the period from 2001 to 2018 witnessed a substantial increase in both the frequency and the extent of drought events compared to the period from 1982 to 2000, particularly concerning severe and extreme droughts. The areas most severely impacted by extreme drought were the Xilingol League and the Alxa League. From 1982–2000 to 2001–2018, under moderate drought conditions, vegetation resistance exhibited a minor decrease in the central and eastern regions but experienced a slight increase in the western region. In contrast, under severe drought conditions, the western region saw a significant decrease in vegetation resistance. Remarkably, under extreme drought conditions, the western region showed a substantial increase in vegetation resistance, while the central and eastern regions experienced a slight decrease. Across all three drought conditions, as precipitation levels declined, the resistance of the meadow–steppe–desert ecosystems demonstrated a high–low–high distribution pattern. The temperate desert steppe exhibited a minimal vulnerability to drought, boasting resistance levels exceeding 0.9. Notably, extreme drought had the most pronounced impact on the temperate meadow steppe, temperate steppe, and temperate desert steppe, particularly within the temperate meadow steppe category. Given these findings, the authorities responsible for grassland management should prioritize regions characterized by frequent drought occurrences and low drought resistance, such as Ulanqab City, the Xilingol League, and the western part of Hulun Buir City. Safeguarding steppe ecosystems is of paramount importance for stabilizing vegetation productivity and land carbon sinks, especially under the anticipated exacerbation of climate conditions in the future.

【Objective】 Global warming has been resulting in more extreme weather events such as drought and flooding, and understanding their severity and frequency is important for improving management to mitigate their detrimental impact. Taking Shandong province as an example, this paper analyzes the spatiotemporal variation of droughts over the past 40 years in the province. 【Method】 Monthly temperature and precipitation measured from 1981 to 2020 at 25 meteorological stations across the province were collected. Standardized precipitation evapotranspiration index (SPEI) at each station was calculated at both seasonal and annual scales, from which we calculated the spatiotemporal variation of droughts in the province using linear regression, Tyson polygon, spatial interpolation and wavelet analysis. 【Result】 ①Summer precipitation had been in decline while annual precipitation had been in increase, though neither was at significant level. Meanwhile, seasonal and annual temperature had both been in increase at significant level. ②At seasonal and annual scales, dry and wet weather occurred alternately, and the summer alternation annual alternation remained almost unchanged over the 40 years. ③The areas suffering spring and summer droughts had been in increase while areas hit by autumn and winter throughs had been in decline, though neither was at significant level. ④The frequency of spring drought increased gradually from the southwest-southeast to the north, though spatial difference in summer and annual droughts across the province was small. The frequency of autumn drought increased gradually from the north to the south, while the frequency of winter drought increased gradually from the southwest to the northwest-southeast. ⑤Seasonally, the identified drought periods are 10, 29, 4 and 17 a in spring, 20, 4, 7 and 10 a in summer, 14, 6, 25, 8 and 3 a in autumn, 5, 24, 16 and 10 a in winter. Annually, the periods were 23, 14, 4, 10 and 7 a. 【Conclusion】 Temperature rise in Shandong province was significant, but the change in precipitation was not significant, with dry and wet occurring alternately.

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Drought research is of great importance for planning and management of water resources, due to the great impact that droughts have on society and ecosystems. In this study, the effect that using different models for calculating evapotranspiration has on the analysis of droughts in the semiarid region of North Central Mexico is investigated, using climatological information from 14 meteorological stations. Drought was analyzed using the Reconnaissance Drought Index (RDI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at the scales of 3, 6 and 12 months. Eight evapotranspiration models were used: those of Thornthwaite, Hargreaves – Samani, Droogers – Allen, Allen, Dorji, Priestley – Taylor, Makkink and Irmak. According to three of the efficiency indices that were used – the root mean squared error (RMSE), the medium absolute error (MAE) and the concordance index – the Hargreaves – Samani model yields the best evapotranspiration results as compared to the Penman–Monteith model, whereas the models of Thornthwaite and Dorji are the least recommended for this purpose. The non-parametric Wilcoxon test, at a 5% significance level, leads to the conclusion that there are no statistically significant differences between the RDI and SPEI drought indices calculated using the Thornthwaite or the Hargreaves – Samani model. At the three scales of analysis, differences in the RDI index calculated using evapotranspiration estimated with the Thornthwaite or the Hargreaves – Samani model are minimal, but are slightly larger for the SPEI index. Drought events detected with the RDI and SPEI indices are more intense when the Thornthwaite model is used to calculate evapotranspiration instead of the Hargreaves – Samani model. These results may prove valuable in the analysis of droughts, especially in arid and semiarid regions. [ABSTRACT FROM AUTHOR]

Sawa Lake is a historical, cultural, and environmental landmark of great importance in education and tourism. Its unique advantages make it a potential global natural heritage and geopark in 2021. The current research is devoted to investigate and assess the actual reasons behind the rapid decline of the water level of Sawa Lake, which has begun to drop dramatically in an unprecedented situation. Landsat data are employed for interpreting the temporal and spatial changes of both water and vegetation covers. Shuttle Radar Topography Mission data are used for water volume estimation. Standardized Precipitation Evapotranspiration Index was used in comparing the rainfall rate to the changing of land use-land cover. Additionally, the Modified Normalized Difference Water Index and Normalized Difference Vegetation Index are established on the Landsat OLI imageries using ENVI 5.3 software. The data analysis showed that one of the most important reasons for the Sawa Lake water level drop is the massive pumping of the groundwater from a site located to the south of the lake to feed the Mamlahat Al-Samawa from which NaCl is extracted. [ABSTRACT FROM AUTHOR]

With the change of global climate, extreme weather events such as drought and flood disasters occur frequently. These have a great impact on crop yields. As an important main grain producing area, the impact of drought and flood on the agricultural production of the three provinces in three northeast provinces of China cannot be ignored. Based on historic meteorological data such as daily precipitation, maximum temperature, minimum temperature, 2 m average wind speed, sunshine hours and relative humidity, etc., the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) during 1988－2017 in three northeast provinces of China were calculated with different time scales. Through comparing with characterization of drought and flood disasters in history, SPEI was chosen to judge drought and flood in the growth season of spring maize. With the purpose of evaluating the effects of drought and flood on spring maize yield, based on the distance correlation analysis method, the index of reasonable time scale and key month were selected to analyze the relationship between the index and the relative meteorological yield of spring maize. The relationship between water conditions at different growth stages and the yield was also analyzed. The results showed that: (1) both SPI and SPEI could represent the drought and flood conditions in three northeast provinces of China. Compared with SPI, SPEI had higher correlation with the drought and flood disaster rate, and SPEI was more advantageous in characterizing the drought and flood conditions in the study area; (2) relative meteorological yield was significantly correlated with drought disaster rate in all three provinces (P

Drought is one of the most widespread and devastating extreme climate events when water availability is significantly below normal levels for a long period. In recent years, the Haihe River Basin has been threatened by intensified droughts. Therefore, characterization of droughts in the basin is of great importance for sustainable water resources management. In this study, two multi-scalar drought indices, the standardized precipitation evapotranspiration index (SPEI) with potential evapotranspiration calculated by the Penman–Monteith equation and the standardized precipitation index (SPI), were used to evaluate the spatiotemporal variations of drought characteristics from 1961 to 2017 in the Haihe River Basin. In addition, the large-scale atmospheric circulation patterns were used to further explore the potential links between drought trends and climatic anomalies. An increasing tendency in drought duration was detected over the Haihe River Basin with frequent drought events occurring in the period from 1997 to 2003. The results derived from both SPEI and SPI demonstrated that summer droughts were significantly intensified. The analysis of large-scale atmospheric circulation patterns indicated that the intensified summer droughts could be attributed to the positive geopotential height anomalies in Asian mid-high latitudes and the insufficient water vapor fluxes transported from the south.

As one of the extreme climate events, the frequency and intensity of drought’s change significantly affect the growth of regional vegetation. Drought events have occurred frequently in the Vegetation Region of Northwest China (VRNWC) in the past 20 years, but the spatiotemporal characteristics of drought lack discussion in VRNWC. Additionally, the response mechanism of vegetation activities to drought is unclear. In this study, the Theil-Sen median trend and Mann-Kendall test correlation analysis were combined to analyse the spatiotemporal characteristics of drought in VRNWC based on the Standardized Precipitation Evapotranspiration Index (SPEI) from 2000 to 2019. Morlet wavelet and Hurst (H) exponent were used to analyse the future prediction of drought in VRNWC. The effects of drought on vegetation change were further analysed using the Normalized Difference Vegetation Index (NDVI). The results showed that from 2000 to 2019, the SPEI in VRNWC increased at the rate of 0.0113/ a, and the drought slowed down, mainly distributed in northeastern Shaanxi, southern Gansu, southern Qilian Mountains, and western Xinjiang. However, there was extreme drought in the northwest of the Tarim Basin in 2007 and severe drought in the northern Qaidam Basin in 2014. In the past 20 years, the occurrence frequency, duration and percentage of drought grade of slight drought, moderate drought, and severe drought showed a downward trend. The VRNWC gradually developed to a wetting trend, but the overall frequency of slight drought was the highest, and the frequency of extreme drought was the lowest, while severe drought was mainly concentrated in the Qinghai Plateau. The drought in VRNWC had a periodicity of about 8a. Further, SPEI_Hurst indicated that the drought in the study area will probably increase in the future. Drought in VRNWC significantly impacted vegetation, and 72.36% of the regional SPEI was positively correlated with the NDVI. This study provides a theoretical basis and data support for ecological management and future ecological restoration in vegetation regions.

Copyright of Al-Ameed Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The climate system has both non-stationary and nonlinear characteristics. The non-stationary processes such as climate change and human activities have brought severe challenges to life, agriculture and ecology in arid areas. It is of great practical significance to study the spatiotemporal variation and non-stationary characteristics of drought in arid region for adopting the countermeasures to adapt to climate change. The traditional trend change and variation analysis method was used to study the drought change characteristics, which could not effectively identify the clustering phenomenon of drought and the spatial and temporal variation of drought in different time intervals. Therefore, the method of breaks for additive seasonal and trend (BFAST) was introduced to determine the non-stationary characteristics and spatial variation of drought. In this study, a typical inland arid area was taken as the study area, and the drought was quantified by standardized precipitation evapotranspiration index (SPEI). The results show that: (1) the study area was prone to light drought and moderate drought, and the duration and intensity of drought events increased significantly after 1996; (2) The spatial distribution of drought frequency and drought intensity in different seasons were significantly different; (3) The results of BFAST analysis showed that there were four discontinuities in SPEI12 time series, which indicated that the drought in the study area had obvious non-stationary characteristics. Through the analysis of the breakpoint and drought change characteristics in the study area, the occurrence time of the breakpoint in the northern region had a certain periodicity, and the climate was in a state of aridity. The results of this study have important guiding significance for further understanding the non-stationary characteristics of drought in inland arid areas, and will promote the management of water resources and the protection of ecological environment.

Drought is considered as a frequent environmental disaster that persists long enough to adversely influence economic and social development for the last few decades, particularly in Ethiopia. Here, we examined the occurrence of drought severity change in Ethiopia using standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), China Z Index (CZI) and percent of normal precipitation (PNP). Mann Kendal and Sen's method tests also used to compute trends and magnitudes of drought occurrences. The years 1953, 1961–1964, 1972–1976, 1984–1987, 2002–2004 and 2011–2014 were recorded as the most intense drought episodes ranging from − 1.58 to − 4.31. With some exceptions, the years 1984, 1986, 2002 and 2014/15 were the direst extreme drought occurrence across all locations. The interpolated spatial extent of drought frequency was highest in central, north and southern regions of the country, respectively. More extreme and severe droughts are identified from SPI and SPEI time series than CZI and PNP at many stations across the domain. In 3-month time scales, severe/extreme drought incidences are intra-annual and 12- and 24-month time scales are inter-annual. SPI and SPEI have stronger correlation than SPI and CZI at all timescales. This kind of inventory drought characterization can be used as a basis to quantitatively prioritize specific intervention at the regional level in responding to drought impacts due to climate change with available resources. By large, it will help to foster a vital shift in the way drought is perceived and coped in the region, taking into account the country's economic, social and environmental context. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Global reanalysis products are extensively used for hydrologic applications in sparse data regions. The establishment of some inputs for hydrologic modelling from global reanalysis requires prior scrutiny and assessment. Thus, the present study attempts to exploit Climate Forecast System Reanalysis datasets for the Mereb-Gash river basin in Eritrea, with the objective of preparing input data for future hydrological modelling efforts as well as climate characterization. The research activities include statistical analysis of reanalysis datasets, computation of potential evapotranspiration and drought indices using different approaches. Results show that there were predominantly significant monotonic trends in most of the data; precipitation and relative humidity exhibited significant decreasing trends, whereas increasing trends were detected in temperature and potential evapotranspiration. Three potential evapotranspiration estimation methods were employed out of which the Thornthwaite method showed a considerable dependence on elevation of a station. In most cases, Penman-Monteith provides higher estimates than Hargreaves and Thornthwaite equations. Besides, drought indices based on standardized precipitation evapotranspiration and rainfall anomaly demonstrate the presence of persistent dry conditions over the period 2000 to 2013 and predominantly humid conditions from 1979 through the end of 1990s. The findings of this study imply that presence of significant trends in most of the climatic variables and persistent drought conditions in recent years may ultimately be associated to human and climate influences on the environment. Thus, concerted and effective countermeasures should be executed in the study area to reverse the existing ecological imbalances. [ABSTRACT FROM AUTHOR]

Drought indices are widely used for drought quantification. The objective of this study is to introduce a hybrid drought index, the Precipitation Evapotranspiration Difference Condition Index (PEDCI), and to compare its performance in Oklahoma to existing drought indices. The PEDCI is based on a simple water balance model, which accounts for the difference between water supply (precipitation) and water demand (potential evapotranspiration). While it is similar in this respect to the Standardized Precipitation and Evapotranspiration Index (SPEI) and the Palmer Drought Severity Index, it uses a different method to normalize the index in time and space which was inspired by Vegetation Condition Index. The performance of the PEDCI is evaluated quantitatively using SPEI, soil moisture data, and crop yield data. The performance of the PEDCI is also evaluated qualitatively using six criteria. Results show that the PEDCI is highly correlated with SPEI and that it can represent drought conditions in Oklahoma as effectively as the SPEI. Correlations between the PEDCI and soil moisture/crop yield also demonstrate good correspondence. The qualitative evaluation of PEDCI shows that there are two key strengths in comparison to the SPEI. First, it is simple to calculate and interpret. Second, the normalization method does not require any empirical parameters or fitting a probability distribution function. The PEDCI can be used to characterize drought conditions on a variety of timescales and it has utility for monitoring agricultural and meteorological drought, especially in a changing climate.

New changing characteristics have emerged in the drought and its dominant meteorological factors in Northeast China, as the ecological impacts of global climate change in recent years. These impacts may bring unpredictable natural disaster risks to local agricultural production. In order to guide the prevention of agricultural drought and mitigation work, it is particularly important to explore the spatial and temporal patterns and evolution trends of drought in Northeast China under the background of climate change, thereby to reveal the meteorological driving factors of drought in the spring maize during growing season. Here, five meteorological factors, including wind speed precipitation, sunshine duration, air temperature, pressure and relative humidity, were interpolated month by month, particularly considering the geographical location and altitude. The data was taken from 105 meteorological stations in Northeast China, where the local DEM data was in the resolution of 30 meters. A Penman-Monteith method was used to calculate the potential evapotranspiration. A IDL program was also used to calculate the Standardized Precipitation Evapotranspiration Index (SPEI) at the 1, 3, 6, 12 and 24-month scales in 1989-2018, further to analyze the multi-scale characteristics of drought. As such, the change characteristic of each meteorological factor was determined in the spring maize during growing season. The high-incidence month and region of drought in the growing season were identified by the SPEI of 1-month scale, thereby to gain the trends of monthly average precipitation and reference evapotranspiration. A stepwise linear regression method was selected to extract the dominant meteorological factors driving drought in each month and the whole growing season. The results indicated that: 1) from 1989 to 2018, a light-serious-light trend of drought was showed in Northeast China in a 10-year cycle, particularly which the worst drought was found in 2000-2010. There was an obvious effect using the SPEI for the drought, as the time scale increased, but there can be a time lag at a certain degree. 2) In the spring maize during growing season, the drought was tend to occur in May, with a high probability in the west of Jilin, the east of Inner Mongolia and the southwest of Heilongjiang. 3) Meteorological variations in the spring maize during growing season in Northeast China were mainly characterized by the increase of air temperature, together with the decrease of air pressure and wind speed. The change rates of average temperature (Tmean), the maximum temperature (Tmax), the minimum temperature (Tmin), the air pressure (APS) and the wind speed (WV) were 0.41 ℃ /(10a), 0.42 ℃/(10a), 0.39 ℃/(10a), -0.05 kPa/(10a), and -0.08 m/(s·10 a), respectively. Other meteorological factors did not change significantly. 4) Dominant meteorological factors driving drought varied in the maize growth period in Northeast China. The significant factors were ranked in descend order: the precipitation (PRE), air relative humidity (RHU), Tmax and sunshine duration (SSD) in May, followed by the PRE, RHU, SSD and Tmin in June, the PRE, RHU and SSD in July, the PRE, Tmax and Tmean in August, and the PRE, RHU and Tmax in September. In the whole growth season, the main meteorological factors were the PRE, Tmax, SSD, and RHU. Specifically, the PRE played the most important role in drought in each month, compared with the other factors. The WV and APS showed the minimum influence on drought. This finding can offer a promising potential reference for the drought characteristics of the spring maize during growing season in Northeast China, and further to make the reasonable decisions for drought prevention. [ABSTRACT FROM AUTHOR]

Introduction. Drought is a natural phenomenon that occurs in all climates, and is one of the most relevant natural hazards, which propagates through the full hydrological cycle and affects large areas, often with long-term economic and environmental impacts. A prolonged deficit in precipitation over a defined region cause a meteorological drought, while the other types of drought describe secondary effects on specific ecological and economic compartments. Recent trends in the drought distribution and intensity shows that Europe splits into two big areas, in which the southern and western regions have positive trends of drought frequency, duration, and severity, and the northern and eastern regions show a decrease in this parameters. Regarding the long events, territory of Ukraine belongs to the areas in which a prominent decrease in drought frequency, duration and severity are fixed. But positive trends in the drought characteristics are observed on the Black Sea coast, also in the Carpathian region, many droughts occurred in the past three decades. The purpose of this study to examine the results of analysis of the spatiotemporal distribution of warm season droughts (April-October) across the administrative areas of Ukraine in 2021-2050 under the climate scenarios RCP4.5 and RCP6.0 with them comparing. Data and methods. Drought estimation was performed using the SPEI index (the Standardized Precipitation Evapotranspiration index). The inclusion of temperature through the potential evapotranspiration (PET) along with precipitation data allows SPEI to account for the impact of temperature regime on a drought situation. A drought episode for given time scale is defined as a period, in which SPEI is continuously negative and reaches a value of –1.0 or less. In this study, the gridded fields of monthly air temperature and precipitation intensity from multimodel sets of global CMP5 models are taken for calculations of SPEI. Data access was made through the Climate Explorer. All data were averaged over the area of each of 25 administrative regions of Ukraine. Research results. Analysis of the time series of the calculated SPEI index for both scenarios showed that in all regions of Ukraine there will be a tendency to transition from moderately wet conditions in 2021- 2035 to droughty conditions in 2037-2050. In the first half of the study period drought is expected near 2024, as well as in 2030-2033 almost in all provinces except southern areas. In the second half of the period prolonged seasonal drought is projected in 2044-2047 over all Ukraine and in some areas drought may reach an extreme intensity. Decade analysis of the SPEI7 time series showed that in both scenarios in all regions of Ukraine, the least number of dry seasons is expected from 2021 to 2030. The highest number of dry seasons in this period may reach up to 4-5 cases per 10 years in the western regions under RCP6.0 scenario. In other regions the number of dry warm seasons will be 2-3 cases per 10 years. In the period from 2031 to 2040, the number of dry seasons will increase substantially in all regions of Ukraine under RCP4.5 scenario, in which their number will be 5-6 cases per 10 years. Under RCP6.0 scenario, an increase in the number of droughts will be observed in all areas except the western regions, where will be from 2 to 4 dry seasons per 10 years. In the last decade from 2041 to 2050, in both scenarios, the number of dry seasons will increase throughout Ukraine compared to the previous decade. Under RCP6.0 scenario, the greatest increase is projected in the north of the country and in some other regions throughout Ukraine, where the maximum number of seasons with droughts will reached up 8-10 cases per 10 years. Conclusions. Comparison of the SPEI7 time series for both scenarios showed that under RCP6.0 scenario the transition from wet conditions to dry conditions is projected during long period from 2030 to the early 2040s. In this time, small interannual variations of the SPEI index across all regions are expected, and only in the last decade the dry seasons will prevail. In addition, in the RCP6.0 scenario, maxima of drought frequency are expected in few different regions of the country, compared with the RCP4.5 scenario, which indicates significant scenarios' differences in the predicted state of the regional atmospheric circulation determined the temperature and precipitation regimes in the future. [ABSTRACT FROM AUTHOR]

Located in the subtropical monsoon climate area of China, the Yangtze River Basin (YRB) had been frequently affected by drought events recently. Based on standardized precipitation evapotranspiration Index (SPEI) and enhanced vegetation index (EVI), the characteristics of drought in the YRB and the influence of drought on vegetation in different seasons were investigated by maximum correlation (Rmax) between 1981 and 2015. The results showed that: (a) Droughts occurred frequently but had no obvious regularity in the YRB from 1981 to 2015. The drought intensity in autumn and winter were slightly higher than that in spring and summer. The autumn droughts in Sichuan Basin were the most serious, followed by the spring droughts in the middle and lower reaches of the YRB; (b) Annual SPEI series at 102 stations exhibited a downward trend and 72 stations exhibited an upward trend. There was no station showing a significant downward trend and two stations showing a significant upward trend. There was a drying trend in autumn and winter, and a wetting trend in spring and summer. The eastern area of the YRB shows a more arid trend in spring and autumn, as well as in the southwest in winter; (c) 90% of YRB showed a significant positive correlation (p <.05) between SPEI and EVI during the growing season (March–October), and the vegetation was more sensitive to short‐term and medium‐term drought. However, there were spatial and seasonal differences in the impact of drought on vegetation. Different types of land cover had different responses to droughts. Grasslands and croplands were more sensitive to droughts, grasslands at low elevation was dominated by short‐term droughts, while at high elevation was influenced by medium‐long‐ and long‐term droughts. Croplands and woodlands were more vulnerable to short‐term droughts. [ABSTRACT FROM AUTHOR]

Potential change in the hydrological cycles may lead to changes in extreme events such as drought due to the changes in intensity, frequency, and seasonality of precipitation and evaporative demand. In this study, projected drought scenarios and associated uncertainties in the late 21st century over the Continental United States are analysed based on seven regional climate models (RCMs) contributing to the Coordinated Regional Climate Downscaling Experiment. Meteorological drought scenarios are analysed based on standardized precipitation evapotranspiration index (SPEI). Here, we propose a new multimodel ensemble approach based on the similarity of spectral power of different frequency components of the SPEI time series. The approach combines output from different RCMs based on their ability to produce the observed power spectra as well as convergence towards the average spectra from all participating RCMs in the future climate. Furthermore, to understand the SPEI variability associated with climate teleconnection, continuous wavelet transform‐based spectral coherency between the SPEI and two climate indices: the El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) is analysed. Results show that among‐model uncertainty is the dominant source of uncertainties in the projected drought scenarios with contributions as large as 97% to the total uncertainty. Fifteen to 20% more frequent droughts are projected in future climate due to a decrease in mean SPEI as well as an increase in the variability of SPEI. Observed SPEI variability is strongly associated with ENSO variability while PDO modulates the strength of correlation between the SPEI and the ENSO. Spectral analysis of future SPEI shows that the increase in the SPEI variability is due to an increase in interannual variability as well as an enhanced ENSO teleconnection over the study area. The results show the increased role of climatic variability and hence the enhanced predictability of drought scenarios in the future climate. [ABSTRACT FROM AUTHOR]

Reference crop evapotranspiration (ET0) estimation accuracy strongly affects the accuracy of drought monitoring using the standardized precipitation evapotranspiration index (SPEI). The FAO56 Penman–Monteith (the reference method here), Irmak, Berti, Priestley–Taylor, and Valiantzas methods were used to compute ET0 and subsequently SPEI at 1‐, 3‐, and 12‐month timescales during 1961–2016 at 763 weather stations in China. The spatiotemporal variations in the climatic variables and ET0, D (=P − ET0) and SPEI with five ET0 estimators (hereafter SPEIPM, SPEIIRA, SPEIPT, SPEIMHS, and SPEIVal) were investigated. The cumulative frequency and periods (using the Morlet wavelet analysis) of the annual SPEIs were analyzed. The results showed that, corresponding to the P, ET0, and D, drought severity was characterized by large seasonal and regional differences using SPEIPM, SPEIIRA, SPEIPT, SPEIMHS, or SPEIVal, especially in northwestern China, the Inner Mongolia region, and the Qinghai–Tibetan Plateau (P < 500 mm/yr). Additionally, the effects of the different ET0 equations on the minimum SPEI and frequency values were large in these drier subregions but generally small in other regions. Meanwhile, an increased ET0 prediction accuracy did not automatically lead to an improved SPEI accuracy in regions P > 500 mm/yr. With respect to the averaged values for Subregion 1 (P < 134 mm/yr), although the vibration intensities and spectra were visually similar for different SPEIs, the periodical signals differed. Regional climatic conditions have a significant impact on the SPEI estimates in regions characterized by P (<500 mm/yr); we therefore suggest that the ET0 equations for drought analysis with SPEI should be carefully selected. [ABSTRACT FROM AUTHOR]

Drought poses a threat to socio-economic activities across most East African river basins. While there are indications that global warming may continue to enhance evaporation from basins and intensify droughts, most drought projections over East Africa are based on rainfall alone. The present study combines rainfall and Potential Evapotranspiration (PET) to examine the impacts of global warming on droughts in East Africa, with a focus on four major river basins. We characterised the drought by means of two drought indices: the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI). While the SPEI is based on the Climate Water Balance (CWB) (precipitation minus evapotranspiration), SPI is based on only rainfall. Multi-ensemble simulations from the CORDEX (the Coordinated Regional Climate Downscaling Experiment) datasets were analysed for the study. The capability of the simulations to reproduce the relevant climate variables (temperature, precipitation, PET and water balance, SPEI and SPI) over the East Africa region and specifically across four river basins (Rufiji, Tana, Juba and Upper-Nile) was evaluated. The impacts of climate change on the drought indices were considered at four specific Global Warming Levels (GWLs) (i.e. 1.5 °C, 2.0 °C, 2.5 °C, and 3.0 °C) under the Representative Concentration Pathway (RCP) 8.5 scenario and a Self-Organizing Map (SOM) was used to classify the SPEI and SPI projections into 12 groups, based on their similarities. Our results show that the CORDEX models give a realistic simulation of the relevant climate variables (including the drought indices) over East Africa and the river basins. For most of the variables, the spatial correlations between the observed and the simulated variables are high (0.6 < r > 0.9). In the annual cycle over these basins, the observations fall within the simulation spreads, and the simulation ensemble mean closely follows the observations. However, the ensemble mean does not accurately reproduce the spatial distribution of the drought frequency in the region. The CORDEX simulations project an increase in the intensity and frequency of SPEI droughts over East Africa. The magnitude of the projection, which varies over the region, increases with increasing GWLs. In contrast to the SPEI projection, however, the SPI projects only a weak change for intensity and frequency of droughts, and the magnitude does not vary with the GWLs. The SOM classification shows that 90% of the simulations project more severe and more frequent droughts with SPEI than they do with SPI. Over the river basins, the SPEI projections are more robust than the SPI. Hence, using only rainfall for drought projections may underestimate the severity of future droughts, while incorporating PET may enhance the robustness of the projections. The results of the study have application in mitigating the impacts of droughts on socio-economic activities across the East African river basins. • We project future changes in SPEI and SPI drought characteristics over East Africa at different GWLs using CORDEX dataset. • The CORDEX dataset gives a remarkable simulation of all the climate variables for calculating the drought characteristics. • More intense and more frequent SPEI droughts are projected over East Africa; the magnitude of the change grows with GWLs. • The SPEI projection is higher and more robust than the SPI, which shows wetting at the equator and drying along the coast. [ABSTRACT FROM AUTHOR]

Groundwater aquifers around the world are experiencing stress due to the composite influence of climate change and excessive groundwater withdrawal. Despite this influence, there is still insufficient knowledge on climate-groundwater interaction dynamics in complex aquifers like Australia's Great Artesian Basin. This understanding can inform improved management, which can in turn, increase resilience of groundwater system to on-going groundwater withdrawal and climate change. The main aim of this research was to assess the impacts of climatic change on groundwater storage (GWS) changes over the Great Artesian Basin (GAB) using a range of multi-scale indicators, including Gravity Recovery and Climate Experiment (GRACE)-derived groundwater observations and standardized precipitation evapotranspiration indices (SPEI). Rotated principal component analysis (rPCA) was used to identify climatic hotspots (where GWS variation is particularly sensitive or vulnerable to the impacts of climate change), and correlation analyses were used to assess the relationship between these hotspots and changes in groundwater over space and time. The localized spatial pattern via rPCA was uncovered in the GAB's southeastern region, where annual variations in GWS exhibited conspicuous peaks in 2002, 2014, and 2015. Another finding was that the southeast region of the GAB experienced higher GWS variations as compared to other sub-basins during 2007–2008, which resulted in low groundwater recharge. These findings underscore the variations in GWS within the GAB, emphasizing its responsiveness to climatic variations (e.g., rainfall contributes to recharge of groundwater system and drought intensifies water extraction and restricts discharge). Moreover, this study found a substantial negative correlation (r = −0.7), between SPEI at 12-month scale and GWS variation in the southern GAB region. This relationship highlights the vulnerability of groundwater storage in the southern GAB region to prolonged drought conditions. Furthermore, this study identified positive correlations (r = 0.4 to 0.8), between key climate indices such as the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) with GWS anomalies in the southeast and northern GAB regions. These correlations underscore the pivotal roles played by ENSO and PDO in shaping GWS variations in these areas, highlighting the need to incorporate an understanding of these climatic processes into water resource management strategies. This consideration is crucial for ensuring sustainable water management practices that can adapt to the influence of these climate phenomena. These findings provide essential insights into the dynamics of groundwater in the face of changing environmental conditions, with implications for sustainable water management. • Hotspots of groundwater-climate interactions assessed in Great Artesian Basin. • Climate teleconnections drive changes in groundwater in the Great Artesian Basin. • Groundwater changes are sensitive to extreme climatic events (droughts and floods). • ENSO and PDO are key drivers of groundwater fluxes in the Great Artesian Basin. [ABSTRACT FROM AUTHOR]

Drought projections on seasonal to annual time scales are presented for Canada over the twenty-first century, based on the Standardized Precipitation Evapotranspiration Index (SPEI). Results make use of bias-corrected temperature and precipitation projections from 29 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5), and include three different forcing scenarios (RCP2.6, RCP4.5 and RCP8.5). Large differences in projected drought changes are observed among different regions. On the annual time scale, southwestern Canada and the Prairies may experience an increase in drying under a warmer climate. On the other hand, coastal regions, including northern Canada, the northwest Pacific coast and the Atlantic region, show a small increase in wetness. Winter and spring SPEI results depict an increase in wetting, reflecting the projected country-wide winter and spring precipitation increases under climate change. For the most part, autumn and summer show increases in drying. The largest relative changes in both summer drying and winter wetting were found over northern regions, but the offsetting seasonal effects typically balance out to yield various degrees of wetting on the annual scale for this region. The projected drought responses are relatively modest in the weak forcing scenario (RCP2.6) for most Canadian regions. In addition, even for regions most affected, a marked increase in surface water deficit might not occur until the second half of this century. Inter-model variation (a crude measure of projection uncertainty) typically increases with forcing intensity and lead time, and is generally greater in northern and western Canada. [ABSTRACT FROM AUTHOR]

In this study we assess future drought probabilities in the Greater Alpine Region based on four regional climate model simulations with COSMO-CLM forced by ECHAM5 and HadCM3 under different emission scenarios. As a drought indicator, the Standardized Precipitation Evapotranspiration Index is applied. The evaluation of a hindcast run show reasonable skill of the CCLM in simulating the evolution of dry and wet phases, although decreasing skill towards the East of the Alpine domain is apparent. The results of the scenario investigations indicate a considerably higher probability for droughts averaged over the study region, but with rather diverse patterns north and south of the Alps. This signal is mainly emerging from the warm season months, whereas in winter nearly no change is detected. By differentiating between precipitation and temperature as the driving forces of the considerable drying trends in summer we found precipitation as the relevant driver north of and in the Alps, whereas we detected that temperature, as a proxy for evapotranspiration, is the main factor for the southern and eastern areas.

Drought and extreme precipitation events can have major environmental and socioeconomic impacts. Yet, how drought and wetness are changing in China in the context of climate change is still under debate. Here, the standardized precipitation evapotranspiration index (SPEI) was calculated based on high-quality and more densely distributed daily meteorological observation data from 655 stations across China during the period of 1965–2017. National and regional trends in drought and wetness and their various characteristics, including intensity, duration, frequency, and percentage of area affected, were investigated at multiple timescales. We found that (1) China as a whole has undergone a significant (p < 0.01, trend significant at the level of 0.01) wetting trend, with an annual SPEI increase of 0.5 per decade from 1965 to 2017. A seasonal wetting trend was also observed, with summer being particularly significant (p < 0.01). (2) Regionally, each subregion also showed a wetting trend during the study period except for southwest China, and these wetting trends were significant in the western region of northwest China (p < 0.05, trend significant at the level of 0.05), the Tibetan Plateau (p < 0.05), and eastern China (p = 0.06). (3) Decadal trends in drought and wetness intensity, frequency, duration, and affected areas indicated that the drought events also became more severe and more frequent in the last two decades, and the areas showing drying trends were mainly located in southwest China (especially for the autumn drought) and the southwestern parts of eastern northwest China (spring drought). Our results highlight the fact that although a wetting trend was observed in most regions of China, the frequent occurrence of severe drought in southwest China and the southwestern parts of eastern northwest China still present a considerable threat to both the environment and society. Therefore, how to effectively coordinate the allocation of regional water resources to cope with drought risk under future climate change will be particularly important.

The calculation method of potential evapotranspiration (PET) was improved by adopting a more reliable PET estimate based on the Penman-Monteith equation into the standardized precipitation evapotranspiration index (SPEI) in this study (SPEIPM). This improvement increased the applicability of SPEI in North China Plain (NCP). The historic meteorological data during 1962–2011 were used to calculate SPEIPM. The detrended yields of maize from Hebei, Henan, Shandong, Beijing, and Tianjin provinces/cities of NCP were obtained by linear sliding average method. Then regression analysis was made to study the relationships between detrended yields and SPEI values. Different time scales were applied, and thus SPEIpm was mentioned as SPEIPMk-j (k=time scale, 1, 2, 3, 4, …, 24 mon; j=month, 1, 2, 3, …, 12), among which SPEIPM3-8 reflected the water condition from June to August, a period of heavy precipitation and vigorous growth of maize in NCP SPEIPM3-8 was highly correlated with detrended yield in this region, which can effectively evaluate the effect of drought on maize yield. Additionally, this relationship becomes more significant in recent 20 yr. The regression model based on the SPEI series explained 64.8% of the variability of the annual detrended yield in Beijing, 45.2% in Henan, 58.6% in Shandong, and 54.6% in Hebei. Moreover, when SPEIPM3-8 is in the range of −0.6 to 1.1, −0.9 to 0.8 and −0.8 to 2.3, the detrended yield increases in Shandong, Henan and Beijing. The yield increasing range was during normal water condition in Shandong and Henan, where precipitation was abundant. It indicated that the field management matched well with local water condition and thus allowed stable and high yield. Maize yield increase in these two provinces in the future can be realized by further improving water use efficiency and enhancing the stress resistance as well as yield stability. In Hebei and Beijing, the precipitation is less and thus the normal water condition cannot meet the high yield target. Increasing of water input and improving water use efficiency are both strategies for future yield increase. As global climate change became stronger and yield demands increased, the relationship between drought and maize yield became much closer in NCP too. The research of drought monitoring method and strategies for yield increase should be enhanced in the future, so as to provide strong supports for food security and agricultural sustainable development in China.

Copyright of Journal of Shenyang Agricultural University is the property of Journal of Shenyang Agricultural University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT: Enhancing the capability of both standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) for quantifying wet and dry events under distinct climate conditions is of paramount importance. The different recommendations of recent studies regarding the best distribution to calculate the SPEI and the lack of studies addressing the effect of different parameters estimation methods on the SPI motivated us to apply and adapt distinct testing methodologies to select candidate models for calculating these standardized drought indices (SDI). The study is based on two data sets. The first represents a tropical–subtropical region of Brazil. The second comprises the same weather stations that were used for developing the original version of the SPEI. The study also emphasized the performance of the models within the range of typical SDI values [−2.0 : 2.0]. Along with goodness‐of‐fit tests, we calculated the mean absolute errors between the indices values estimated from the candidate distributions, and their corresponding theoretical values derived from the standard normal distribution. The two‐parameter gamma and the generalized extreme value distributions are, respectively, recommended for general use in SPI and SPEI algorithms (1–12‐month timescales). The unbiased probability weighted moments are recommended to estimate the distributions parameters. The study also described a trade‐off between choosing the best model for the central part and for the tails of the distributions. This trade‐off suggests that the methodologies used to select models for the SDI algorithms may have to decide which part of the distribution (central or tails) should be emphasized. The behaviour of the errors among different wet/dry categories showed that both indices were only capable of representing drought and floods in a similar probabilistic way within the range [−2.0 : 2.0]. This feature supports our decision to emphasize model performances within such range. [ABSTRACT FROM AUTHOR]

Huai River Basin (HRB) is an important food and industrial production area and a frequently drought-affected basin in eastern China. It is necessary to consider the future drought development for reducing the impact of drought disasters. Three global circulation models (GCMs) from Coupled Model Intercomparison Project phase 5 (CMIP5), such as CNRM-CM5 (CNR), HadGEM2-ES (Had) and MIROC5 (MIR), were used to assessment the future drought conditions under two Representative Concentration Pathways (RCPs) scenarios, namely, RCP4.5 and RCP8.5. The standardized precipitation evapotranspiration index (SPEI), statistical method, Mann-Kendall test, and run theory were carried out to study the variations of drought tendency, frequency, and characteristics and their responses to climate change. The research showed that the three CMIP5 models differ in describing the future seasonal and annual variations of precipitation and temperature in the basin and thus lead to the differences in describing drought trends, frequency, and drought characteristics, such as drought severity, drought duration, and drought intensity. However, the drought trend, frequency, and characteristics in the future are more serious than the history. The drought frequency and characteristics tend to be strengthened under the scenario of high concentration of RCP8.5, and the drought trend is larger than that of low concentration of RCP4.5. The lower precipitation and the higher temperature are the main factors affecting the occurrence of drought. All three CMIP5 models show that precipitation would increase in the future, but it could not offset the evapotranspiration loss caused by significant temperature rise. The serious risk of drought in the future is still higher. Considering the uncertainty of climate models for simulation and prediction, attention should be paid to distinguish the effects of different models in the future drought assessment.

Drought is a natural hazard with critical societal and economic consequences to millions of people around the world. In this paper, we present the climatology of severe drought events that occurred during the 20th century in the region of Sao Paulo, Brazil. To account for the effects of rainfall deficit and changes in temperature at a climatic timescale, we chose the Standardized Precipitation Evapotranspiration Index (SPEI) to identify severe droughts over the city of Sao Paulo, and the eastern and central-western regions of the state. Events were identified using weather station data and European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis data, in order to assess the representation of drought periods in both datasets. Results show that the reanalysis seems suitable to represent the number of events and their mean duration, severity and intensity, but the timing and characteristics of individual events are not well reproduced. The correlation between observation and reanalysis SPEI time series is low to moderate in all cases. A linear trend analysis between 1901 and 2010 shows a tendency of increasing (decreasing) severe drought events in the central and western (eastern) Sao Paulo state, according to observational data. This is in agreement with previous findings, and the reanalysis presents this same signal. The weakened trend values in the reanalysis may be associated with issues in representing precipitation in this dataset.

In this paper, we provide a Lagrangian analysis of the anomalies in the moisture transport during two important drought events (1989/1990 and 2003) configured over the Danube River Basin (DRB) region. Firstly, we identified the drought episodes that occurred over the DRB in the period of 1980-2014 through the Standardized Precipitation Evapotranspiration Index (SPEI). SPEI was calculated using monthly Climatic Research Unit (CRU) Time-Series (TS) Version 3.23 precipitation and potential evapotranspiration (PET) datasets with a spatial resolution of 0.5 degrees. The monthly SPEI-1 index was applied to identify the drought episodes and their respective indicators, including duration, severity, and intensity. Two significant drought events were selected: 1989/1990 (presenting dry conditions during October 1989-March 1990) and 2003 (presenting dry conditions during April 2003-September 2003). These events were associated with the two most severe SPEI-1 episodes identified over the DRB during 1980-2014. Then, an analysis of anomalies in the moisture transport was conducted in order to verify possible changes in the moisture supply from the climatological sources for the DRB during these episodes. The moisture transport analysis was performed through a Lagrangian approach, which uses the outputs of the FLEXiblePARTicle dispersion model FLEXPART integrated with one of the reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF): the ECMWF Re-Analysis (ERA)-Interim dataset. The DRB receives moisture from seven different moisture source regions: the North Atlantic Ocean (NATL), North Africa (NAF), the Mediterranean Sea (MED), the Black Sea (BS), the Caspian Sea (CS), the DRB, and Central and Eastern Europe (Rest of Land (RestL)). The analysis of drought events shows that the precipitation and moisture supply from the selected sources weakened mainly during both drought events. Anomalous subsidence and an increased PET also prevailed over the DRB during these SPEI-1 episodes. RestL and MED registered the most intensive reduction in the moisture supply over the DRB during both periods. [ABSTRACT FROM AUTHOR]

This study aimed to characterize present and future drought changes over eastern China using observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations. We used the standardized precipitation evapotranspiration index (SPEI) to characterize droughts at the timescales of 3- and 12-month. We distinguished the spatial patterns of drought regimes (DRs) using the rotated empirical orthogonal function (EOF) on the SPEI. Our results identified three DRs centered in northern China (DR1), northeastern China (DR2), and southern China (DR3). Droughts in these regimes have increased in recent decades. Most CMIP5 models reproduce at least two of the DRs. The rotated EOF results indicate that the three DRs can jointly explain 46-68% of the SPEI variance (compared with approximately 60% in the observations). Among the 33 CMIP5 models analysed in this study, 13 simulated all three DRs well and showed a strong correlation pattern (>0.5). Further analysis indicated that both the external natural and greenhouse gas forcing experiments in CMIP5 reproduced the DRs, implying that natural variability and anthropogenic activity play important roles in the formation of these DRs. With continued climate warming, the three DRs over eastern China will persist. Despite the uncertainties in drought changes that mainly depend on the potential evapotranspiration methods, climate model results suggest that droughts would be aggravated under warming scenarios. The probability of severe droughts increase by the end of the century: 33% in DR1, 25% in DR2, 34% in DR3 in RCP4.5 and almost double in RCP8.5 scenario in Thornthwaite method based SPEI estimates. [ABSTRACT FROM AUTHOR]