Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbaniz...Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbanized slope regions, especially those considered high-risk areas. Various other factors contribute to the process;thus, it is essential to analyze the causes of such incidents in all possible ways. Soil moisture plays a critical role in the Earth’s surface-atmosphere interaction systems;hence, measurements and their estimations are crucial for understanding all processes involved in the water balance, especially those related to landslides. Soil moisture can be estimated from in-situ measurements using different sensors and techniques, satellite remote sensing, hydrological modeling, and indicators to index moisture conditions. Antecedent soil moisture can significantly impact runoff for the same rainfall event in a watershed. The Antecedent Precipitation Index (API) or “retained rainfall,” along with the antecedent moisture condition from the Natural Resources Conservation Service, is generally applied to estimate runoff in watersheds where data is limited or unavailable. This work aims to explore API in estimating soil moisture and establish thresholds based on landslide occurrences. The estimated soil moisture will be compared and calibrated using measurements obtained through multisensor capacitance probes installed in a high-risk area located in the mountainous region of Campos do Jordão municipality, São Paulo, Brazil. The API used in the calculation has been modified, where the recession coefficient depends on air temperature variability as well as the climatological mean temperature, which can be considered as losses in the water balance due to evapotranspiration. Once the API is calibrated, it will be used to extrapolate to the entire watershed and consequently estimate soil moisture. By utilizing recorded mass movements and comparing them with API and soil moisture, it will be possible to determine thresholds, thus enabling anticipation of landslide occurrences.展开更多
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 w...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.展开更多
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 ...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.展开更多
To better understand soil moisture dynamics in the Yangtze River Estuary (YRE) and predict its variation in a simple way, a field monitoring experiment was carried out along the north branch of the Yangtze River, wh...To better understand soil moisture dynamics in the Yangtze River Estuary (YRE) and predict its variation in a simple way, a field monitoring experiment was carried out along the north branch of the Yangtze River, where seawater intrusion was strong and salt-water variation is one of the limiting factors of local agriculture. In present paper, relation between antecedent precipitation index (API) and soil water content is studied, and effects of groundwater depth on soil water content was analyzed. A relatively accurate prediction result of soil water content was reached using a neural network model. The impact analysis result showed that the variation of the API was consistent with soil water content and it displayed significant correlations with soil water content in both 20 and 50 cm soil layer, and higher correlation was observed in the layer of 20 cm. Groundwater impact analysis suggested that soil moisture was affected by the depth of groundwater, and was affected more greatly by groundwater at depth of 50 cm than that at 20 cm layer. By introducing API, groundwater depth and temperature together, a BP artificial network model was established to predict soil water content and an acceptable agreement was achieved. The model can be used for supplementing monitoring data of soil water content and predicting soil water content in shallow groundwater areas, and can provide favorable support for the research of water and salt transport in estuary area.展开更多
Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR ...Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.展开更多
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 Kurdi...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.展开更多
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 pro...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.展开更多
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 patter...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.展开更多
Spatial and temporal characteristics of standardized precipitation index (SPI), which is widely used for drought/flood monitoring, are investigated in this study. The purpose is to obtain a reasonable primary scheme...Spatial and temporal characteristics of standardized precipitation index (SPI), which is widely used for drought/flood monitoring, are investigated in this study. The purpose is to obtain a reasonable primary scheme of zoning on the basis of drought/ wetness conditions in the study area. Spatio-temporal distributions of SPI with the time scales of 3 months and 12 months are investigated with the datasets of precipitation in the Taihu basin during past decades (1951-2000). Results indicate that SPI series of 3 months show random fluctuation while that of 12 months behaves like I/f noise. SPI series of 3 months show little trend while that of 12 months show significant trend at several stations. Drought magnitude (DM) is also estimated on the basis of SPI values to assess drought condition. No trend is detected in DMs with time scales of both 3 months and 12 months. Spatial variability of DM is analyzed by mapping the DM with 12 months for extreme drought and wetness, and regional characteristics are analyzed for DM.展开更多
Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors,especially in developing countries.This study attempts to examine the spatial and temporal characteristics of drought a...Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors,especially in developing countries.This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin(KRB)in Nepal,using the standardized precipitation evapotranspiration index(SPEI)over the period from 1987 to 2017.The Mann-Kendall test was used to explore the trends of the SPEI values.The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period.Spatially,the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales,especially in summer and winter.The mountain region also showed a significant increasing drought trend in winter.The drought characteristic analysis indicated that the maximum duration,intensity,and severity of drought events were observed in the KRB after 2000.The Terai region presented the highest drought frequency and intensity,while the hill region presented the longest maximum drought duration.Moreover,the spatial extent of drought showed a significant increasing trend in the hill region at the monthly(drought station proportion of 7.6%/10 a in August),seasonal(drought station proportion of 7.2%/10 a in summer),and annual(drought station proportion of 6.7%/10 a)scales.The findings of this study can assist local governments,planners,and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.展开更多
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 M...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.展开更多
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...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.展开更多
In order to give guidelines for the execution of countermeasures in response to extreme precipitation events.the tempo-spatial variation characteristics of extreme precipitationare are analyzed by 11 extreme precipita...In order to give guidelines for the execution of countermeasures in response to extreme precipitation events.the tempo-spatial variation characteristics of extreme precipitationare are analyzed by 11 extreme precipitation indexes during the past 60 years(1955-2015)in Shijiazhuang City.The results showed that the extreme precipitation of Shijiazhuang City generally showed a downward trend in the past 60 years,and the wet day precipitation(PRCPTOT)exhibited the most obvious downward trend.There were significant spatial differences in the trend of extreme precipitation indexes.According to the spatial superposition of the historical trend of extreme precipitation index and Hurst index,the extreme precipitation intensity indexes in most areas of Shijiazhuang city will continue to decline in the future,and the extreme precipitation intensity indexes in some central areas will continue to rise.展开更多
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...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.展开更多
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...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.展开更多
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 Standardiz...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.展开更多
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 unexpec...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.展开更多
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 ch...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.展开更多
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 thre...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.展开更多
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 betw...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.展开更多
文摘Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbanized slope regions, especially those considered high-risk areas. Various other factors contribute to the process;thus, it is essential to analyze the causes of such incidents in all possible ways. Soil moisture plays a critical role in the Earth’s surface-atmosphere interaction systems;hence, measurements and their estimations are crucial for understanding all processes involved in the water balance, especially those related to landslides. Soil moisture can be estimated from in-situ measurements using different sensors and techniques, satellite remote sensing, hydrological modeling, and indicators to index moisture conditions. Antecedent soil moisture can significantly impact runoff for the same rainfall event in a watershed. The Antecedent Precipitation Index (API) or “retained rainfall,” along with the antecedent moisture condition from the Natural Resources Conservation Service, is generally applied to estimate runoff in watersheds where data is limited or unavailable. This work aims to explore API in estimating soil moisture and establish thresholds based on landslide occurrences. The estimated soil moisture will be compared and calibrated using measurements obtained through multisensor capacitance probes installed in a high-risk area located in the mountainous region of Campos do Jordão municipality, São Paulo, Brazil. The API used in the calculation has been modified, where the recession coefficient depends on air temperature variability as well as the climatological mean temperature, which can be considered as losses in the water balance due to evapotranspiration. Once the API is calibrated, it will be used to extrapolate to the entire watershed and consequently estimate soil moisture. By utilizing recorded mass movements and comparing them with API and soil moisture, it will be possible to determine thresholds, thus enabling anticipation of landslide occurrences.
文摘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.
文摘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.
基金financially supported by the Ecological and Environmental Monitoring Project (JJ[2011]-017)funded by the Executive Office of the Three Gorges Project Construction Committee of the State Council of China+1 种基金the National Non-Profit Research Program of China (200903001)the National Basic Research Program of China(2010CB429001)
文摘To better understand soil moisture dynamics in the Yangtze River Estuary (YRE) and predict its variation in a simple way, a field monitoring experiment was carried out along the north branch of the Yangtze River, where seawater intrusion was strong and salt-water variation is one of the limiting factors of local agriculture. In present paper, relation between antecedent precipitation index (API) and soil water content is studied, and effects of groundwater depth on soil water content was analyzed. A relatively accurate prediction result of soil water content was reached using a neural network model. The impact analysis result showed that the variation of the API was consistent with soil water content and it displayed significant correlations with soil water content in both 20 and 50 cm soil layer, and higher correlation was observed in the layer of 20 cm. Groundwater impact analysis suggested that soil moisture was affected by the depth of groundwater, and was affected more greatly by groundwater at depth of 50 cm than that at 20 cm layer. By introducing API, groundwater depth and temperature together, a BP artificial network model was established to predict soil water content and an acceptable agreement was achieved. The model can be used for supplementing monitoring data of soil water content and predicting soil water content in shallow groundwater areas, and can provide favorable support for the research of water and salt transport in estuary area.
基金supported by the projectof the National Basic Research Program of China (GrantNo. 2009CB421401)the Key Technologies R&D Program (Grant No. 2009BAC51B02)+2 种基金the Special Scientific Research Fund of the Meteorological Public Welfare Profession of China (Grant No. GYHY200906018)the National Natural Science Foundation of China (Grant No.40705039)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. IAP07415)
文摘Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River (YHR) were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes: a region-wide flood over the entire YHR (RWF); a region-wide drought over the entire YHR (RWD); a flood in the south with a drought in the northern region of the Yangtze River (FS-DN); and a drought in the south with a flood in the northern region of the Yangtze River (DS-FN). Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High (WPSH), and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.
文摘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.
基金This study was financially supported by the National Natural Science Foundation of China(41871097).
文摘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.
基金Project supported by the National Natural Science Foundation of China (No.50809058)the International Science and Technology Cooperation Program of China (No.2010DFA24320)
文摘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.
基金Supported by the Major Special Science and Technology Projects on Water Pollution Control and Management (2008ZX07526-001)"Jingshi Scholar" Leading Professor Program of Beijing Normal University
文摘Spatial and temporal characteristics of standardized precipitation index (SPI), which is widely used for drought/flood monitoring, are investigated in this study. The purpose is to obtain a reasonable primary scheme of zoning on the basis of drought/ wetness conditions in the study area. Spatio-temporal distributions of SPI with the time scales of 3 months and 12 months are investigated with the datasets of precipitation in the Taihu basin during past decades (1951-2000). Results indicate that SPI series of 3 months show random fluctuation while that of 12 months behaves like I/f noise. SPI series of 3 months show little trend while that of 12 months show significant trend at several stations. Drought magnitude (DM) is also estimated on the basis of SPI values to assess drought condition. No trend is detected in DMs with time scales of both 3 months and 12 months. Spatial variability of DM is analyzed by mapping the DM with 12 months for extreme drought and wetness, and regional characteristics are analyzed for DM.
基金funded by the CAS(Chinese Academy of Sciences)Overseas Institutions Platform Project(Grant No.131C11KYSB20200033)the NSFC-ICIMOD Joint Research Project(Grant No.41661144038)。
文摘Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors,especially in developing countries.This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin(KRB)in Nepal,using the standardized precipitation evapotranspiration index(SPEI)over the period from 1987 to 2017.The Mann-Kendall test was used to explore the trends of the SPEI values.The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period.Spatially,the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales,especially in summer and winter.The mountain region also showed a significant increasing drought trend in winter.The drought characteristic analysis indicated that the maximum duration,intensity,and severity of drought events were observed in the KRB after 2000.The Terai region presented the highest drought frequency and intensity,while the hill region presented the longest maximum drought duration.Moreover,the spatial extent of drought showed a significant increasing trend in the hill region at the monthly(drought station proportion of 7.6%/10 a in August),seasonal(drought station proportion of 7.2%/10 a in summer),and annual(drought station proportion of 6.7%/10 a)scales.The findings of this study can assist local governments,planners,and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.
基金supported by the National Natural Science Foundation of China(42261026,41971094,42161025)the Gansu Provincial Science and Technology Program(22ZD6FA005)+1 种基金the Higher Education Innovation Foundation of Education Department of Gansu Province(2022A041)the open foundation of Xinjiang Key Laboratory of Water Cycle and Utilization in Arid Zone(XJYS0907-2023-01).
文摘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.
文摘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.
基金The National Key R&D Plan(2016YFC0401404)Sino-Dutchlow impact development Cooperation Project。
文摘In order to give guidelines for the execution of countermeasures in response to extreme precipitation events.the tempo-spatial variation characteristics of extreme precipitationare are analyzed by 11 extreme precipitation indexes during the past 60 years(1955-2015)in Shijiazhuang City.The results showed that the extreme precipitation of Shijiazhuang City generally showed a downward trend in the past 60 years,and the wet day precipitation(PRCPTOT)exhibited the most obvious downward trend.There were significant spatial differences in the trend of extreme precipitation indexes.According to the spatial superposition of the historical trend of extreme precipitation index and Hurst index,the extreme precipitation intensity indexes in most areas of Shijiazhuang city will continue to decline in the future,and the extreme precipitation intensity indexes in some central areas will continue to rise.
文摘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.
文摘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.
基金Under the auspices of the National Social Science Foundation of China (No.19CGL045)。
文摘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.
文摘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.
基金supported by the National Natural Science Foundation of China(91125005,41271083,41201062)the Incubation Foundation for Special Disciplines of the National Natural Science Foundation of China(J1210003/J0109)the Open Fund Project of the State Key Laboratory of Frozen Soil Engineering of China(SKLFSE201412)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.41171220)the Program for Changjiang Scholars and Innovative Research Team in University of the Ministry of Education of China(Grant No.IRT13062)+2 种基金the Programme of Introducing Talents of Discipline to Universities(the 111 Project,Grant No.B08048)the Jiangsu Provincial Collaborative Innovation Center for World Water Valley and Water Ecological Civilizationthe National Cooperative Innovation Center for Water Safety and Hydro-Science
文摘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.
基金supported by the National Key Technologies R&D Program of China (2011BAD32B01)the Ph D Programs Foundation of Ministry of Education of China (20100101110035)
文摘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.