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.

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.

Drought and flood characteristics in the farmingpastoral ecotone of northern China based on the Standardized Precipitation Index

The farming-pastoral ecotone of northern China(FPENC)provides an important ecological barrier which restrains the invasion of desert into Northwest China.Studying drought and flood characteristics in the FPENC can provide scientific support and practical basis for the protection of the FPENC.Based on monthly precipitation data from 115 meteorological stations,we determined the changes in climate and the temporal and spatial variations of drought and flood occurrence in the FPENC during 1960-2020 using the Standardized Precipitation Index(SPI),Morlet wavelet transform,and inverse distance weighted interpolation method.Annual precipitation in the FPENC showed a slightly increasing trend from 1960 to 2020,with an increasing rate of about 1.15 mm/a.The interannual SPI exhibited obvious fluctuations,showing an overall non-significant upward trend(increasing rate of 0.02/a).Therefore,the study area showed a wetting trend in recent years.Drought and flood disasters mainly occurred on an interannual change cycle of 2-6 and 9-17 a,respectively.In the future,a tendency towards drought can be expected in the FPENC.The temporal and spatial distribution of drought and flood differed in the northwestern,northern,and northeastern segments of the FPENC,and most of the drought and flood disasters occurred in local areas.Severe and extreme drought disasters were concentrated in the northwestern and northeastern segments,and severe and extreme flood disasters were mainly in the northeastern segment.Drought was most frequent in the northwestern segment,the central part of the northeastern segment,and the northern part of the northern segment.Flood was most frequent in the western part of the northwestern segment,the eastern part of the northeastern segment,and the eastern and western parts of the northern segment.The accurate evaluation of the degrees of drought and flood disasters in the FPENC will provide scientific basis for the regional climate study and critical information on which to base decisions regarding environmental protection and socio-economic development in this region.

Drought trend analysis in a semi-arid area of Iraq based on Normalized Difference Vegetation Index, Normalized Difference Water Index and Standardized Precipitation Index

Drought was a severe recurring phenomenon in Iraq over the past two decades due to climate change despite the fact that Iraq has been one of the most water-rich countries in the Middle East in the past.The Iraqi Kurdistan Region(IKR)is located in the north of Iraq,which has also suffered from extreme drought.In this study,the drought severity status in Sulaimaniyah Province,one of four provinces of the IKR,was investigated for the years from 1998 to 2017.Thus,Landsat time series dataset,including 40 images,were downloaded and used in this study.The Normalized Difference Vegetation Index(NDVI)and the Normalized Difference Water Index(NDWI)were utilized as spectral-based drought indices and the Standardized Precipitation Index(SPI)was employed as a meteorological-based drought index,to assess the drought severity and analyse the changes of vegetative cover and water bodies.The study area experienced precipitation deficiency and severe drought in 1999,2000,2008,2009,and 2012.Study findings also revealed a drop in the vegetative cover by 33.3%in the year 2000.Furthermore,the most significant shrinkage in water bodies was observed in the Lake Darbandikhan(LDK),which lost 40.5%of its total surface area in 2009.The statistical analyses revealed that precipitation was significantly positively correlated with the SPI and the surface area of the LDK(correlation coefficients of 0.92 and 0.72,respectively).The relationship between SPI and NDVI-based vegetation cover was positive but not significant.Low precipitation did not always correspond to vegetative drought;the delay of the effect of precipitation on NDVI was one year.

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.

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.

Using leaf area index(LAI) to assess vegetation response to drought in Yunnan province of China

Climatic extremes such as drought have becoming a severe climate-related problem in many regions all over the world that can induce anomalies in vegetation condition. Growth and CO2 uptake by plants are constrained to a large extent by drought.Therefore, it is important to understand the spatial and temporal responses of vegetation to drought across the various land cover types and different regions. Leaf area index(LAI) derived from Global Land Surface Satellite(GLASS) data was used to evaluate the response of vegetation to drought occurrence across Yunnan Province, China(2001-2010). The meteorological drought was assessed based on Standardized Precipitation Index(SPI)values. Pearson's correlation coefficients between LAI and SPI were examined across several timescales within six sub-regions of the Yunnan. Further, the drought-prone area was identified based on LAI anomaly values. Lag and cumulative effects of lack of precipitation on vegetation were evident, with significant correlations found using 3-, 6-, 9-and 12-month timescale. We found 9-month timescale has higher correlations compared to another timescale.Approximately 29.4% of Yunnan's area was classified as drought-prone area, based on the LAI anomaly values. Most of this drought-prone area was distributed in the mountainous region of Yunnan.From the research, it is evident that GLASS LAI can be effectively used as an indicator for assessing drought conditions and it provide valuable information for drought risk defense and preparedness.

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.

Drought analysis using multi-scale standardized precipitation index in the Han River Basin,China

Regional drought analysis provides useful information for sustainable water resources management.In this paper,a standardized precipitation index(SPI) at multiple time scales was used to investigate the spatial patterns and trends of drought in the Han River Basin,one of the largest tributaries of Yangtze River,China.It was found that,in terms of drought severity,the upper basin of the Han River is the least,while the growing trend is the most conspicuous;a less conspicuous growing trend can be observed in the middle basin;and there is an insignificant decreasing trend in the lower basin.Meanwhile,the impact of drought on the Middle Route of the South-to-North Water Transfer Project was investigated,and it is suggested that water intake must be reduced in times of drought,particularly when successive or simultaneous droughts in the upper and middle basins of the Han River Basin occur.The results can provide substantial information for future water allocation schemes of the South-to-North Water Transfer Project.

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.

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.

Detecting Agro-Droughts in Southwest of China Using MODIS Satellite Data

The normalized difference vegetation index （NDVI） has proven to be typically employed to assess terrestrial vegetation conditions. However, one limitation of NDVI for drought monitoring is the apparent time lag between rainfall deficit and NDVI response. To better understand this relationship, time series NDVI （2000-2010） during the growing season in Sichuan Province and Chongqing City were analyzed. The vegetation condition index （VCI） was used to construct a new drought index, time-integrated vegetation condition index （TIVCI）, and was then compared with meteorological drought indices-standardized precipitation index （SPI）, a multiple-time scale meteorological-drought index based on precipitation, to examine the sensitivity on droughts. Our research findings indicate the followings： （1） farmland NDVI sensitivity to precipitation in study area has a time lag of 16-24 d, and it maximally responds to the temperature with a lag of about 16 d. （2） We applied the approach to Sichuan Province and Chongqing City for extreme drought monitoring in 2006 and 2003, and the results show that the monitoring results from TIVCI are closer to the published China agricultural statistical data than VCI. Compared to VCI, the best results from TIVCI3 were found with the relative errors of -4.5 and 6.36% in 2006 for drought affected area and drought disaster area respectively, and 5.11 and -5.95% in 2003. （3） Compared to VCI, TIVCI has better correlation with the SPI, which indicates the lag and cumulative effects of precipitation on vegetation. Our finding proved that TIVCI is an effective indicator of drought detection when the time lag effects between NDVI and climate factors are taken into consideration.

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 Impacts on Vegetation Indices and Productivity of Terrestrial Ecosystems in Southwestern China During 2001–2012

Drought, as a recurring extreme climate event, affects the structure, function, and process of terrestrial ecosystems. Despite the increasing occurrence and intensity of the drought in the past decade in Southwestern China, the impacts of continuous drought events on vegetation in this region remain unclear. During 2001–2012, Southwestern China experienced the severe drought events from 2009 to 2011. Our aim is to characterize drought conditions in the Southwestern China and explore the impacts on the vegetation condition and terrestrial ecosystem productivity. The Standardized Precipitation Index(SPI) was used to characterize drought area and intensity and a light-use efficiency model was used to explore the effect of drought on the terrestrial ecosystem productivity with Moderate Resolution Imaging Spectrometer(MODIS) data. The SPI captured the major drought events in Southwestern China during the study period, indicated that the 12-year period of this study included both ‘normal' precipitation years and two severe drought events in 2009–2010 and 2011. Results showed that vegetation greenness(Normalized Difference Vegetation Index, NDVI and Enhanced Vegetation Index, EVI) both declined in 2009/2010 drought, but the 2011 drought resulted in less declines of vegetation greenness and productivity due to shorten drought duration and rising temperature. Meanwhile, it was about 5 months lapse between drought events and maximum declines in vegetation greenness for 2009/2010 drought events. In addition, forest, grassland and cropland revealed significant different ecosystem responses to drought. It indicated that grassland showed an early sensitivity to drought, while cropland was the most sensitive to water deficit and forest was more resilient to drought. This study suggests that it is necessary to detect the difference responses of ecosystem to drought in a regional area with satellite data and ecosystem model.

Retrieving Multi-Scale Climatic Variations from High Dimensional Time-Series MODIS Green Vegetation Cover in a Tropical/Subtropical Mountainous Island

【Title】There are knowledge gaps in our understanding of vegetation responses to multi-scale climate-related variables in tropical/subtropical mountainous islands in the Asia-Pacific region. Therefore, this study investigated inter-annual vegetation dynamics and regular/irregular climate patterns in Taiwan. We applied principal component analysis （PCA） on 11 years （2001~2011） of high-dimensional monthly photosynthetically active vegetation cover （PV） derived from the Moderate Resolution Imaging Spectroradiometer （MODIS） and investigated the relationships between spatiotemporal patterns of the eigenvectors and loadings of each component through time and multi-scale climate-related variations. Results showed that the first five components contributed to 96.4% of the total variance. The first component （PC1, explaining 94.5% of variance） loadings, as expected, were significantly correlated with the temporal dynamics of the PV （r = 0.94）, which was mainly governed by regional climate. The temporal loadings of PC2 and PC3 （0.8% and 0.6% of variance, respectively） were significantly correlated with the temporal dynamics of the PV of forests （r = 0.72） and the farmlands （r = 0.80）, respectively. The low-order components （PC4 and PC5, 0.3% and 0.2% of variance, respectively） were closely related to the occurrence of drought （r = 0.49） and to irregular ENSO associated climate anomalies （r = -0.54）, respectively. Pronounced correlations were also observed between PC5 and the Southern Oscillation Index （SOI） with one to three months of time lags （r = -0.35 ~ -0.43, respectively）, revealing biophysical memory effects on the time-series pattern of the vegetation through ENSO-related rainfall patterns. Our findings reveal that the sensitivity of the ecosystems in this tropical/subtropical mountainous island may not only be regulated by regional climate and human activities but also be susceptible to large-scale climate anomalies which are crucial and comparable to previous large scale analyses. This study demonstrates that PCA can be an effective tool for analyzing seasonal and inter-annual variability of vegetation dynamics across this tropical/subtropical mountainous islandin the Pacific Ocean, which provides an opportunity to forecast the responses and feedbacks of terrestrial environments to future climate scenarios.

Response of hydrological drought to meteorological drought in the eastern Mediterranean Basin of Turkey

The hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area.The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they occur in this basin.Pearson’s correlation coefficient was used to show the correlation between standardized precipitation index(SPI)and standardized streamflow index(SSI)values on different time scales.Data from five meteorological stations and seven stream gauging stations in four sub-basins of the eastern Mediterranean Basin were analyzed over the period from 1967 to 2017.The correlation between SSI and SPI indicated that in response to meteorological drought,hydrological drought experiences a one-year delay then occurs in the following year.This is more evident at all stations from the mid-1990 s.The main factor causing hydrological drought is prolonged low precipitation or the presence of a particularly dry year.Results showed that over a long period(12 months),hydrological drought is longer and more severe in the upper part than the lower part of the sub-basins.According to SPI-12 values,an uninterrupted drought period is observed from 2002–2003 to 2008–2009.Results indicated that among the drought events,moderate drought is the most common on all timescales in all sub-basins during the past 51 years.Long-term dry periods with moderate and severe droughts are observed for up to 10 years or more since the late 1990 s,especially in the upper part of the sub-basins.As precipitation increases in late autumn and early winter,the stream flow also increases and thus the highest and most positive correlation values(0.26–0.54)are found in January.Correlation values(ranging between–0.11 and–0.01)are weaker and negative in summer and autumn due to low rainfall.This is more evident at all stations in September.The relation between hydrological and meteorological droughts is more evident,with the correlation values above 0.50 on longer timescales(12-and 24-months).The results presented in this study allow an understanding of the characteristics of drought events and are instructive for overcoming drought.This will facilitate the development of strategies for the appropriate management of water resources in the eastern Mediterranean Basin,which has a high agricultural potential.

Comprehensive drought monitoring in Yunnan Province, China using multisource remote sensing data

Development of drought monitoring techniques is important for understanding and mitigating droughts and for rational agricultural management. This study used data from multiple sources, including MOD13 A3, TRMM 3 B43, and SRTMDEM, for Yunnan Province, China from 2009 to 2018 to calculate the tropical rainfall condition index(TRCI), vegetation condition index(VCI), temperature condition index(TCI), and elevation factors. Principal component analysis(PCA) and analytic hierarchy process(AHP) were used to construct comprehensive drought monitoring models for Yunnan Province. The reliability of the models was verified, following which the drought situation in Yunnan Province for the past ten years was analysed. The results showed that:(1) The comprehensive drought index(CDI) had a high correlation with the standardized precipitation index, standardized precipitation evapotranspiration index, temperature vegetation dryness index, and CLDAS(China Meteorological Administration land data assimilation system), indicating that the CDI was a strong indicator of drought through meteorological, remote sensing and soil moisture monitoring.(2) The droughts from 2009 to 2018 showed generally consistent spatiotemporal changes. Droughts occurred in most parts of the province, with an average drought frequency of 29% and four droughtprone centres.(3) Monthly drought coverage during 2009 to 2014 exceeded that over 2015 to 2018. January had the largest average drought coverage over the study period(61.92%). Droughts at most stations during the remaining months except for October exhibited a weakening trend(slope > 0). The CDI provides a novel approach for drought monitoring in areas with complex terrain such as Yunnan Province.

Characterization of Drought and Its Assessment over Sindh,Pakistan During 1951-2010

Drought is one of the complex meteorological disasters affecting water resources, agriculture, livestock, and socioeconomic patterns of a region. Although drought prediction is difficult, it can be monitored based on climatological information. In this study, we provide high spatiotemporal resolution drought climatology, using observational, gridded precipitation data （0.5°×0.5°） from the Global Precipitation Climatological Center and soil moisture data from the Climate Prediction Center for the 60-yr period 1951-2010. The standardized precipitation index （SPI） based on a fitted Gamma distribution and Run method has been calculated from the regional drought identification model （ReDIM） for 3, 6, 9, 12, and 24 months. The results show strong temporal correlations among anomalies of precipitation, soil moisture, and SPI. Analysis of long-term precipitation data reveals that the drought vulnerability concentrates on monsoon season （July- September）, which contributes 72.4% and 82.1% of the annual precipitation in northern and southern Sindh, respectively. Annual and seasonal analyses show no significant changes in the observed precipitation. The category classification criteria are defined to monitor/forecast drought in the selected area. Further analysis identifies two longest episodes of drought, i.e., 1972 1974 and 2000 2002, while 1969, 1974, 1987, and 2002 are found to be the most severe historical drought years. A drought hazard map of Sindh was developed, in which 10 districts are recognized as highly vulnerable to drought. This study helps to explain the time, duration, intensity, and frequency of meteorological droughts over Sindh as well as its neighboring regions, and provides useful information to disaster management agencies and forecasters for assessing both the regional vulnerabilitv of drought and its seasonal predictability in Pakistan.

Estimation of total water storage changes in India

Long-term droughts significantly impact surface and groundwater resources in India,however,observed changes in major river basins have not been well explored.Here we use Standardized Precipitation Index(SPI)and Standardized Precipitation Evapotranspiration Index(SPEI)at three different time scales(24,48,and 60 months)to identify long-term droughts in India for the observed record of 1951-2015.Drought characteristics(extent,events,frequency,and intensity)are analyzed for different river basins in India.Increasing trend in the areal extent of droughts is observed in two methods with three time scales in the maximum area(63.66%)in India.We use the data from the Gravity Recovery and Climate Experiment(GRACE)to estimate the changes in the terrestrial water storage(TWS)during the period 2002-2015.We identify that major long-term droughts in India occurred from 1966 to 1969,1972,1986-1987,and 2002-2004.The all-India average TWS shows a negative trend from 2002 to 2015 with prominent decline in north Indian river basins and positive trend in south Indian river basins.SPI and SPEI at longer time scales are positively associated with TWS indicating the adverse impacts of droughts on surface and groundwater resources in such a populated region.

Role of Anthropogenic Climate Change in Autumn Drought Trend over China from 1961 to 2014

Understanding the impact of anthropogenic climate change on drought is of great significance to the prevention of its adverse effects.Two drought indices,standardized precipitation index(SPI)and standardized precipitation evapotranspiration index(SPEI),are used here for the detection and attribution of autumn droughts in China,and for the exploration of the role played by the anthropogenic climate change.SPI is only related to precipitation,but SPEI involves both precipitation and potential evapotranspiration.For their trend’s spatial patterns,the historical simulations(including all forcings,noted as ALL)from 11 models of the Coupled Model Intercomparison Project phase 6,as an ensemble,are able to reproduce their observational counterpart.SPI shows wetting trend in the north of 35°N and drying trend in the south.SPEI shows drying trend in almost whole China.The drying trend in historical simulations ALL is significantly stronger,compared with the counterpart from the accompanying simulations(called NAT)with only natural forcings implemented.This result clearly indicates that anthropogenic climate change plays a dominant role in the enhancement of autumn drought in China.A more rigorous detection work is also performed with the signal’s fingerprint of ALL(and NAT)projected onto the observation and assessed with the background noise from no external-forcing control simulations.The trend pattern signal in ALL is significantly detected in observation for both SPI and SPEI,with a more pronounced signal in SPEI than in SPI,while the signal of NAT is not detected for neither SPI nor SPEI.Finally,extreme droughts(with indices beyond-2)are assessed in terms of probability ratio between ALL and NAT.It is shown that the anthropogenic precipitation change plays a leading role in the south of 35°N,while the anthropogenic temperature change leads in the north.