Effects of temperature and precipitation on drought trends in Xinjiang, China

The characteristics of drought in Xinjiang Uygur Autonomous Region(Xinjiang),China have changed due to changes in the spatiotemporal patterns of temperature and precipitation,however,the effects of temperature and precipitation—the two most important factors influencing drought—have not yet been thoroughly explored in this region.In this study,we first calculated the standard precipitation evapotranspiration index(SPEI)in Xinjiang from 1980 to 2020 based on the monthly precipitation and monthly average temperature.Then the spatiotemporal characteristics of temperature,precipitation,and drought in Xinjiang from 1980 to 2020 were analyzed using the Theil-Sen median trend analysis method and Mann-Kendall test.A series of SPEI-based scenario-setting experiments by combining the observed and detrended climatic factors were utilized to quantify the effects of individual climatic factor(i.e.,temperature and precipitation).The results revealed that both temperature and precipitation had experienced increasing trends at most meteorological stations in Xinjiang from 1980 to 2020,especially the spring temperature and winter precipitation.Due to the influence of temperature,trends of intensifying drought have been observed at spring,summer,autumn,and annual scales.In addition,the drought trends in southern Xinjiang were more notable than those in northern Xinjiang.From 1980 to 2020,temperature trends exacerbated drought trends,but precipitation trends alleviated drought trends in Xinjiang.Most meteorological stations in Xinjiang exhibited temperature-dominated drought trend except in winter;in winter,most stations exhibited precipitation-dominated wetting trend.The findings of this study highlight the importance of the impact of temperature on drought in Xinjiang and deepen the understanding of the factors influencing drought.

Response of drought to climate extremes in a semi-arid inland river basin in China

Against the backdrop of global warming,climate extremes and drought events have become more severe,especially in arid and semi-arid areas.This study forecasted the characteristics of climate extremes in the Xilin River Basin(a semi-arid inland river basin)of China for the period of 2021–2100 by employing a multi-model ensemble approach based on three climate Shared Socioeconomic Pathway(SSP)scenarios(SSP1-2.6,SSP2-4.5,and SSP5-8.5)from the latest Coupled Model Intercomparison Project Phase 6(CMIP6).Furthermore,a linear regression,a wavelet analysis,and the correlation analysis were conducted to explore the response of climate extremes to the Standardized Precipitation Evapotranspiration Index(SPEI)and Streamflow Drought Index(SDI),as well as their respective trends during the historical period from 1970 to 2020 and during the future period from 2021 to 2070.The results indicated that extreme high temperatures and extreme precipitation will further intensify under the higher forcing scenarios(SSP5-8.5>SSP2-4.5>SSP1-2.6)in the future.The SPEI trends under the SSP1-2.6,SSP2-4.5,and SSP5-8.5 scenarios were estimated as–0.003/a,–0.004/a,and–0.008/a,respectively,indicating a drier future climate.During the historical period(1970–2020),the SPEI and SDI trends were–0.003/a and–0.016/a,respectively,with significant cycles of 15 and 22 a,and abrupt changes occurring in 1995 and 1996,respectively.The next abrupt change in the SPEI was projected to occur in the 2040s.The SPEI had a significant positive correlation with both summer days(SU)and heavy precipitation days(R10mm),while the SDI was only significantly positively correlated with R10mm.Additionally,the SPEI and SDI exhibited a strong and consistent positive correlation at a cycle of 4–6 a,indicating a robust interdependence between the two indices.These findings have important implications for policy makers,enabling them to improve water resource management of inland river basins in arid and semi-arid areas under future climate uncertainty.

A CMIP6-based assessment of regional climate change in the Chinese Tianshan Mountains

Climate warming profoundly affects hydrological changes,agricultural production,and human society.Arid and semi-arid areas of China are currently displaying a marked trend of warming and wetting.The Chinese Tianshan Mountains(CTM)have a high climate sensitivity,rendering the region particularly vulnerable to the effects of climate warming.In this study,we used monthly average temperature and monthly precipitation data from the CN05.1 gridded dataset(1961-2014)and 24 global climate models(GCMs)of the Coupled Model Intercomparison Project Phase 6(CMIP6)to assess the applicability of the CMIP6 GCMs in the CTM at the regional scale.Based on this,we conducted a systematic review of the interannual trends,dry-wet transitions(based on the standardized precipitation index(SPI)),and spatial distribution patterns of climate change in the CTM during 1961-2014.We further projected future temperature and precipitation changes over three terms(near-term(2021-2040),mid-term(2041-2060),and long-term(2081-2100))relative to the historical period(1961-2014)under four shared socio-economic pathway(SSP)scenarios(i.e.,SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).It was found that the CTM had experienced significant warming and wetting from 1961 to 2014,and will also experience warming in the future(2021-2100).Substantial warming in 1997 was captured by both the CN05.1 derived from interpolating meteorological station data and the multi-model ensemble(MME)from the CMIP6 GCMs.The MME simulation results indicated an apparent wetting in 2008,which occurred later than the wetting observed from the CN05.1 in 1989.The GCMs generally underestimated spring temperature and overestimated both winter temperature and spring precipitation in the CTM.Warming and wetting are more rapid in the northern part of the CTM.By the end of the 21st century,all the four SSP scenarios project warmer and wetter conditions in the CTM with multiple dry-wet transitions.However,the rise in precipitation fails to counterbalance the drought induced by escalating temperature in the future,so the nature of the drought in the CTM will not change at all.Additionally,the projected summer precipitation shows negative correlation with the radiative forcing.This study holds practical implications for the awareness of climate change and subsequent research in the CTM.

Spatio-Temporal Agricultural Drought Quantification in a Rainfed Agriculture, Athi-Galana-Sabaki River Basin

This study employs a quantitative approach to comprehensively investigate the full propagation process of agricultural drought, focusing on pigeon peas (the most grown crop in the AGS Basin) planting seasonal variations. The study modelled seasonal variabilities in the seasonal Standardized Precipitation Index (SPI) and Standardized Agricultural Drought Index (SADI). To necessitate comparison, SADI and SPI were Normalized (from −1 to 1) as they had different ranges and hence could not be compared. From the seasonal indices, the pigeon peas planting season (July to September) was singled out as the most important season to study agricultural droughts. The planting season analysis selected all years with severe conditions (2008, 2009, 2010, 2011, 2017 and 2022) for spatial analysis. Spatial analysis revealed that most areas in the upstream part of the Basin and Coastal region in the lowlands experienced severe to extreme agricultural droughts in highlighted drought years. The modelled agricultural drought results were validated using yield data from two stations in the Basin. The results show that the model performed well with a Pearson Coefficient of 0.87 and a Root Mean Square Error of 0.29. This proactive approach aims to ensure food security, especially in scenarios where the Basin anticipates significantly reduced precipitation affecting water available for agriculture, enabling policymakers, water resource managers and agricultural sector stakeholders to equitably allocate resources and mitigate the effects of droughts in the most affected areas to significantly reduce the socioeconomic drought that is amplified by agricultural drought in rainfed agriculture river basins.

Characteristics of Dry and Wet Climate in Shandong Province Based on Standardized Precipitation Index

Based on the monthly precipitation data of 116 meteorological stations in Shandong Province during 1970-2021,standardized precipitation index(SPI)was calculated,and the methods of linear fitting,mutation test and Morlet wavelet analysis were used to analyze the change trend and temporal and spatial distribution characteristics of SPI index in the past 52 years.The results show that there were more normal years in Shandong Province,and the frequency reached 38.46%.There was severe drought in the 1980s and more wet years after 2003.SPI index showed an upward trend in spring,summer and winter but a weak arid trend in autumn.In addition,intense dry weather was more frequent in summer.Spatially,the climate was normal or humid in most areas of Shandong Province.The regions with more wet years were located in the central and northeast Shandong and the peninsula,while the climate was normal in the southwest and north of Shandong.The areas with more dry years were mainly located in the northwest of Shandong Province.There was mainly local and global drought in Shandong Province,and the arid area showed a decreasing trend.In the past 52 years,Shandong Province experienced quasi-4 times of alternation between dry and wet climate.The long period of 21 a was the first main period,and the climate would be still wet in Shandong Province in the future.In terms of mutation,the climate in Shandong Province became humid after 2003,and 2003 was the mutation point.After the abrupt change,the climate changed from gradually drying to wetting.

Levant Drought Occurrence, Lebanon Case

Rainfall data is probably one of the longest-recorded climatic parameters in Lebanon. On the central coast of Lebanon, the Beirut weather station started collecting rainfall data in 1876. However, the recorded data is not available at one data provider source. Published data is found in historical documents but it reaches the early 1970s and then appears a data gap till 1990. Still the data is available, but it might be found to be saved privately. This study investigated the SPI variability on annual time scale between the years 1876 and 2021. The SPI was computed using R-Stat software to compare every year between 1876 and 2021. The majority (about 70% of the years) of the years are near normal in the precipitation rate. The Standardized Precipitation Index (SPI) demonstrated a normal distribution of years. Dry and wet years constitute about 15% of the total 146 years (1876-2021). Extremely dry years might appear in two consecutive years between 50 to 60 years count. After 1991, there were no wet years it was only near normal and few dry years. The last 30 years showed a trend of increasing drought years without any occurrence of wet years. This study demonstrated the importance of keeping records of at least rainfall data and it must be recorded on a daily basis or intensity on time. It is highly important on a managerial basis and for water security reasons to understand the drought event occurrence and investigate the changes in rainfall rates. Climate change scenarios always forecast a decrease in rainfall rates which will not appear without such studies.

Spatiotemporal Characteristics of Droughts and Floods in Shandong Province,China and Their Relationship with Food Loss

Mastering the pattern of food loss caused by droughts and floods aids in planning the layout of agricultural production,determining the scale of drought and flood control projects,and reducing food loss.The Standardized Precipitation Evapotranspiration Index is calculated using monthly meteorological data from 1984 to 2020 in Shandong Province of China and is used to identify the province’s drought and flood characteristics.Then,food losses due to droughts and floods are estimated separately from disaster loss data.Finally,the relationship between drought/flood-related factors and food losses is quantified using methods such as the Pearson correlation coefficient and linear regression.The results show that:1)there is a trend of aridity in Shandong Province,and the drought characteristic variables are increasing yearly while flood duration and severity are decreasing.2)The food losses caused by droughts in Shandong Province are more than those caused by floods,and the area where droughts and floods occur frequently is located in Linyi City.3)The impact of precipitation on food loss due to drought/flood is significant,followed by potential evapotranspiration and temperature.4)The relationship between drought and flood conditions and food losses can be precisely quantified.The accumulated drought duration of one month led to 1.939×10^(4)t of grain loss,and an increase in cumulative flood duration of one month resulted in1.134×10^(4)t of grain loss.If the cumulative drought severity and average drought peak increased by one unit,food loss due to drought will increase by 1.562×10^(4)t and 1.511×10^(6)t,respectively.If the cumulative flood severity and average flood peak increase by one unit,food loss will increase by 8.470×103t and 1.034×10^(6)t,respectively.

Future meteorological drought conditions in southwestern Iran based on the NEX-GDDP climate dataset

Investigation of the climate change effects on drought is required to develop management strategies for minimizing adverse social and economic impacts.Therefore,studying the future meteorological drought conditions at a local scale is vital.In this study,we assessed the efficiency of seven downscaled Global Climate Models(GCMs)provided by the NASA Earth Exchange Global Daily Downscaled Projections(NEX-GDDP),and investigated the impacts of climate change on future meteorological drought using Standard Precipitation Index(SPI)in the Karoun River Basin(KRB)of southwestern Iran under two Representative Concentration Pathway(RCP)emission scenarios,i.e.,RCP4.5 and RCP8.5.The results demonstrated that SPI estimated based on the Meteorological Research Institute Coupled Global Climate Model version 3(MRI-CGCM3)is consistent with the one estimated by synoptic stations during the historical period(1990-2005).The root mean square error(RMSE)value is less than 0.75 in 77%of the synoptic stations.GCMs have high uncertainty in most synoptic stations except those located in the plain.Using the average of a few GCMs to improve performance and reduce uncertainty is suggested by the results.The results revealed that with the areas affected by wetness decreasing in the KRB,drought frequency in the North KRB is likely to increase at the end of the 21st century under RCP4.5 and RCP8.5 scenarios.At the seasonal scale,the decreasing trend for SPI in spring,summer,and winter shows a drought tendency in this region.The climate-induced drought hazard can have vast consequences,especially in agriculture and rural livelihoods.Accordingly,an increasing trend in drought during the growing seasons under RCP scenarios is vital for water managers and farmers to adopt strategies to reduce the damages.The results of this study are of great value for formulating sustainable water resources management plans affected by climate change.

Meteorological Drought Detection and Forecast Using Standardized Precipitation Index and Univariate Distribution Models: Case Study of Bamako, Mali

As an extended period of unusually dry weather conditions without sufficient rain, drought poses enormous risk on societies. Characterized by the absence of precipitation for long periods of time, often resulting in water scarcity, droughts are increasingly posing significant environmental challenges. Drought is therefore considered an important element in the management of water resources, especially groundwater resources during drought. This study therefore sought to investigate the rainfall variability and the frequency of drought for the period 1991 to 2020 in Bamako based on monthly rainfall data from Bamako-Senou gauge station. The standardized precipitation index (SPI) for 12-month, 6-month and 3-month timescales and the SPI for annual totals were used to characterized drought in the study area (Bamako). Univariate parametric probability distributions such as Normal, Log-normal, Gumbel type I and Pearson type III (P3) distributions were fitted with drought variables (severity and duration) for future planning and management. Non-parametric test such as Mann-Kendall trend test was also used to detect trend in annual rainfall data. The results showed that based on 12-month SPI, Bamako experienced two (02) extreme droughts one in July 2002 (SPI = -2.2165) and another in June 2015 (SPI = -2.0598 QUOTE SPI=-2.0598 ). Drought years represented 46.67% for the overall periods according to the SPI for annual totals. The result further indicated that based on the goodness of fit test, the P3 distribution represents the best fitted distribution to both drought severity and duration over Bamako. Bamako is expected to experience several severe severities with higher and shorter duration in the future. Severities with 1, 2, 6, and 10-month duration had return periods ranged from 2.4 to 3.8 years, while 5, 10, 20, 25, 50, and 100-year return periods had 18.51, 26.08, 33.25, 35.50, 42.38, and 49.14 severities, respectively, and durations associated to these severities were 19.8, 26.9, 33.5, 35.6, 42, and 48.2 months, respectively.

Assessment of Climate Variability and Agricultural Activities in the Area of Tadla Plain

The variations in both precipitation and temperature have far-reaching effects on agricultural activities and the accessibility of water resources. These climatic parameters are pivotal in determining the availability of both groundwater and surface water for agricultural use. The aim of this study was to evaluate the variations in climate parameters, focusing on precipitation and temperature, alongside changes in cultivated land area and crop yields in the Tadla area (Béni Mellal Khénifra region, Morocco);additionally, our research looks at the changes in water inflow into two dams and four aquifers. Trends were assessed over the period of 2010-2020 using the standardized precipitation index (SPI) method, as well as the parametric regression method and nonparametric Mann-Kendall and Sen’s slope test. This analysis can be a preliminary step in demonstrating the effects of climate variability on water resource availability and its adverse impacts on agriculture in the region. The results showed a decreasing trend for some yield crops despite the increase in the cultivated area. The results of the groundwater levels and inflow dams showed a significant upward evolution. The analysis of the obtained SPI values and temperatures has revealed a notable and consistent upward trendencies. This upward trajectory indicates that both the SPI values, which reflect precipitation patterns and the temperatures, have been on the rise over the examined period. These results prompt reflection on the effects of climate variability on water resources in the region and economic activities, particularly agriculture.

Spatio-Temporal Analysis of Drought in the North-Eastern Coastal Region of Vietnam Using the Standardized Precipitation Index (SPI)

Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.

Assessing Vulnerability to Drought Based on Exposure,Sensitivity and Adaptive Capacity:A Case Study in Middle Inner Mongolia of China

In this paper,we proposed a framework for evaluating the performance of ecosystem strategies prepared for enhancing vulnerability reduction in the face of hazards due to climate change.The framework highlights the positive effects of human activities in the coupled human and natural system(CHANS) by introducing adaptive capacity as an evaluation criterion.A built-in regional vulnerability to a certain hazard was generated based upon interaction of three dimensions of vulnerability:exposure,sensitivity and adaptive capacity.We illustrated the application of this framework in the temperate farming-grazing transitional zone in the middle Inner Mongolia of the northern China,where drought hazard is the key threat to the CHANS.Specific indices were produced to translate such climate variance and social-economic differences into specific indicators.The results showed that the most exposed regions are the inner land areas,while counties located in the eastern part are potentially the most adaptive ones.Ordos City and Bayannur City are most frequently influenced by multiple climate variances,showing highest sensitivity.Analysis also indicated that differences in the ability to adapt to changes are the main causes of spatial differences.After depiction of the spatial differentiations and analysis of the reasons,climate zones were divided to depict the differences in facing to the drought threats.The climate zones were shown to be similar to vulnerability zones based on the quantitative structure of indexes drafted by a triangular map.Further analysis of the composition of the vulnerability index showed that the evaluation criteria were effective in validating the spatial differentiation but potentially ineffective because of their limited time scope.This research will be a demonstration of how to combine the three dimensions by quantitative methods and will thus provide a guide for government to vulnerability reduction management.

Assessment of Future Drought in Southwest China Based on CMIP5 Multimodel Projections

In the last decade, a series of severe and extensive droughts have swept across Southwest China, resulting in tremendous economic losses, deaths, and disruption to society. Consequently, this study is motivated by the paramount importance of as- sessing future changes in drought in Southwest China. Precipitation is likely to decrease over most parts of Southwest China around the beginning of the century, followed by widespread precipitation increases; the increase in potential evapotran- spiration （PET）, due to the joint effects of increased temperature and surface net radiation and decreased relative humidity, will overwhelm the whole region throughout the entire 21st century. In comparative terms, the enhancement of PET will outweigh that of precipitation, particularly under Representative Concentration Pathway （RCP） 8.5, resulting in intensified drought. Generally, the drying tendency will be in the southeast portion, whereas the mountainous region in the northwest will become increasingly wetter owing to abundant precipitation increases. Droughts classified as moderate/severe according to historical standards will become the norm in the 2080s under RCP4.5/RCP8.5. Future drought changes will manifest different characteristics depending on the time scale： the magnitude of change at a time scale of 48 months is nearly twice as great as that at 3 months. Furthermore, we will see that not only will incidences of severe and extreme drought increase dramatically in the future, but extremely wet events will also become more probable.

Future Changes of Drought and Flood Events in China under a Global Warming Scenario

This study investigates the impact of global warming on drought/flood patterns in China at the end of the 21st century based on the simulations of 22 global climate models and a regional climate model(RegCM3) under the SRES(Special Report on Emissions Scenarios) A1B scenario.The standardized precipitation index(SPI),which has well performance in monitoring the drought/flood characteristics(in terms of their intensity,duration,and spatial extent) in China,is used in this study.The projected results of 22 coupled models and the RegCM3 simulation are consistent.These models project a decrease in the frequency of droughts in most parts of northern China and a slight increase in the frequency in some parts of southern China.Considering China as a whole,the spatial extents of droughts are projected to be significantly reduced.In contrast,future flood events over most parts of China are projected to occur more frequently with stronger intensity and longer duration than those prevalent currently.Additionally,the spatial extents of flood events are projected to significantly increase.

SPEI_(PM)-based research on drought impact on maize yield in North China Plain

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（SPEI PM）. This improvement increased the applicability of SPEI in North China Plain（NCP）. The historic meteorological data during 1962–2011 were used to calculate SPEI PM. 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 SPEI PM was mentioned as SPEI PMk-j（k=time scale, 1, 2, 3, 4,…, 24 mon; j=month, 1, 2, 3,..., 12）, among which SPEI PM3-8 reflected the water condition from June to August, a period of heavy precipitation and vigorous growth of maize in NCP. SPEI PM3-8 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 SPEI PM3-8 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.

Spatio-temporal variation of hydrological drought under climate change during the period 1960–2013 in the Hexi Corridor, China

In recent years, climate change has been aggravated in many regions of the wodd. The Hexi Corridor is located in the semiarid climate zone of Northwest China, which is parUculady affected by climate change. Climate change has led to the spatial and temporal variations of temperature and precipitation, which may result in hydrological drought and water shortage. Thus, it is necessary to explore and assess the drought characteristics of river systems in this area. The patterns of hydrological drought in the Hexi Corridor were identified using the streamflow drought index （SDI） and standardized precipitation index at 12-month timescale （SPI12） from 1960 to 2013. The evolution of drought was obtained by the Mann-Kendall test and wavelet transform method. The results showed that both the mean annual SDI and SPI12 series in the Hexi Corridor exhibited an increasing trend during the study period. According to the results of wavelet analysis, we divided the study period into two segments, i.e. before and after 1990. Before 1990, the occurrence of droughts showing decreased SDI and SPI12 was concentrated in the northern part of the corridor and shifted to the eastern part of the corridor after 1990. The probability of drought after 1990 in Shule River basin decreased while increased in Shiyang River basin. The wavelet analysis results showed that Shiyang River basin will be the first area to go through the next drought period. Additionally, the relationships between drought pattern and climate indices were analyzed. The enhanced westedy winds and increased precipitation and glacier runoff were the main reasons of wet trend in the Hexi Corridor. However, the uneven spatial variations of precipitation, temperature and glacier runoff led to the difference of hydrological drought variations between the Shule, Heihe and Shiyang River basins.

Drought analysis in Antakya-Kahramanmaras Graben,Turkey

The most parts of the Earth experience precipitation variability as a part of their normal climates over both short- and long-time periods. These variations of precipitation will have unpredictable and perhaps unexpectedly extreme consequences（such as drought and flood） with respect to frequency and intensity for many regions of the Earth. Because of high precipitation fluctuations, the Mediterranean region is also the areas of the world sensitive to precipitation changes which often involve frequent drought conditions in Turkey. In this study, drought conditions at annual, seasonal and monthly time scales over the period of 1975–2010 were examined for Antakya-Kahramanmara？ Graben which is located in the eastern part of the Mediterranean region of Turkey. Application of appropriate measures to analyze and monitor droughts is recognized as a major challenge to scientists involved in atmospheric studies. Standardized Precipitation Index（SPI） and cumulative deviation curve techniques were used to determine drought conditions. Results indicated that the study area presented a cyclic pattern of variations with alternating drier and wetter years. From analyses of annual, seasonal and monthly drought series it can be seen that precipitation characteristic of the area is changing. By the results, apparent wet and dry periods can be distinguished. This study also indicated that precipitation totals of winter, spring and summer seasons were slightly decreased during the study period. Drought frequency was increased especially for the northern part of the area in the last ten years. Drought periods were divided into 1982–1985, 1999–2002 and 2004–2008, respectively. According to our analyses, the time scale of 1999–2002 was the driest period in the most of the graben area. The study area, which covers agriculturally important fertile alluvial plains, will experience increasing pressure on its water resources because of its growing population and industry, ever-larger demands for intensive agricultural activities, and frequent drought events.

Impact of Meteorological Drought on Streamflow Drought in Jinghe River Basin of China

Under global climate change, drought has become one of the most serious natural hazards, affecting the ecological environment and human life. Drought can be categorized as meteorological, agricultural, hydrological or socio-economic drought. Among the different categories of drought, hydrological drought, especially streamflow drought, has been given more attention by local governments, researchers and the public in recent years. Identifying the occurrence of streamflow drought and issuing early warning can provide timely information for effective water resources management. In this study, streamflow drought is detected by using the Standardized Runoff Index, whereas meteorological drought is detected by the Standardized Precipitation Index. Comparative analyses of frequency, magnitude, onset and duration are conducted to identify the impact of meteorological drought on streamflow drought. This study focuses on the Jinghe River Basin in Northwest China, mainly providing the following findings. 1) Eleven meteorological droughts and six streamflow droughts were indicated during 1970 and 1990 after pooling using Inter-event time and volume Criterion method. 2) Streamflow drought in the Jinghe River Basin lagged meteorological drought for about 127 days. 3) The frequency of streamflow drought in Jinghe River Basin was less than meteorological drought. However, the average duration of streamflow drought is longer. 4) The magnitude of streamflow drought is greater than meteorological drought. These results not only play an important theoretical role in understanding relationships between different drought categories, but also have practical implications for streamflow drought mitigation and regional water resources management.

Analysis of spatio-temporal evolution of droughts in Luanhe River Basin using different drought indices

Based on the monthly precipitation and air temperature from 1960 to 1989 in the Luanhe River Basin, the standardized precipitation evapotranspiration index （SPEI） and standardized precipitation index （SPI） at three- and six-month time scales and the self-calibrating Palmer drought severity index （sc-PDSI） were calculated to evaluate droughts in the study area. Temporal variations of the drought severity from 1960 to 1989 were analyzed and compared based on the results of different drought indices, and some typical drought events were identified. Spatial distributions of the drought severity according to the indices were also plotted and investigated. The results reveal the following： the performances of different drought indices are closely associated with the drought duration and the dominant factors of droughts; the SPEI is more accurate than the SPI when both evaporation and precipitation play important roles in drought events; the drought severity shown by the sc-PDSI is generally milder than the actual drought severity from 1960 to 1989; and the evolution of the droughts is usually delayed according to the scPDSI. This study provides valuable references for building drought early warning and mitigation systems in the Luanhe River Basin.

Drought variability and its connection with large-scale atmospheric circulations in Haihe River Basin

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 PenmaneMonteith 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.©2021 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).