[Objective] The research aimed to simplify the operating process of agricultural drought monitoring and assessment product,and improve fine level of monitoring and assessment map.[Method] By comprehensively using GIS ...[Objective] The research aimed to simplify the operating process of agricultural drought monitoring and assessment product,and improve fine level of monitoring and assessment map.[Method] By comprehensively using GIS and mathematics,meteorology,management science,computer science,the monitoring and assessment of drought were as the core,the monitoring and assessment system of agricultural drought based on GIS technology was studied.[Result] The drought in Guangxi on November 4,2006 was monitored by using the system,and the actual situation was used to test.The result proved that the good monitoring effect was obtained.[Conclusion] The monitoring and assessment system of agricultural drought based on GIS realized the organic combination of GIS and professional monitoring,assessment model.The flexible HCI interface and visualization expression were provided.The monitoring and assessment function of agricultural drought was realized.It had the good practicality and advancement.展开更多
Using Moderate Resolution Imaging Spectroradiometer(MODIS) data from the dry season during 2010–2012 over the whole Yunnan Province, an improved temperature vegetation dryness index(iTVDI), in which a parabolic dry-e...Using Moderate Resolution Imaging Spectroradiometer(MODIS) data from the dry season during 2010–2012 over the whole Yunnan Province, an improved temperature vegetation dryness index(iTVDI), in which a parabolic dry-edge equation replaces the traditional linear dry-edge equation, was developed, to reveal the regional drought regime in the dry season. After calculating the correlation coefficient, root-mean-square error, and standard deviation between the iTVDI and observed topsoil moisture at 10 and 20 cm for seven sites, the effectiveness of the new index in depicting topsoil moisture conditions was verified. The drought area indicated by iTVDI mapping was then compared with the drought-affected area reported by the local government. The results indicated that the iTVDI can monitor drought more accurately than the traditional TVDI during the dry season in Yunnan Province. Using iTVDI facilitates drought warning and irrigation scheduling, and the expectation is that this new index can be broadly applied in other areas.展开更多
The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought...The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.展开更多
It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorolog...It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorological stations of the Pearl River Basin,the Standardized Precipitation Evapotranspiration Index（ SPEI） at different time scales was calculated. Based on the SPEIs of 1- 12 months,a newly proposed index for drought--Joint Drought Index（ JDI） was established under the multi-scale perspective through the copula function. Since short-term SPEIs are essential for the identification of emerging droughts and long-term SPEIs are useful for prolonged droughts,the JDI,which integrates all the usefull informations of drought and can thus form an overall judgement,is superior than the single SPEI in drought monitoring. By the forcast evaluation system and comparison to the actual drought,the accuracy and effectiveness of JDI in drought monitoring were verified. In general,JDI can be used as a new ideal index for future drought monitoring and assessment. Additionly,we analyzed the spatio-temperal characteristics of drought across the Pearl River Basin using the JDI. The results indicate that mild drought was the most frequent drought occurred in the Pearl River Basin over the past half century,and moderate drought followed. Severe drought and extreme drought would appear occasionally while exceptional drought could hardly be found. A dry-wet-dry interdecadal variation pattern had been found from the 1960 s to the 2000 s. Since the 21 stcentury,an obvious trend toward drought can be observed in the whole basin,especially in the Xijiang subbasin,which,consequently,poses an increasing challenge for the water resource planning and management.展开更多
Togo’s economy is heavily dependent on rainfed agriculture. Therefore, anomalies in precipitation can have a significant impact on crop yields, affecting food production and security. Thus, monitoring anomalous clima...Togo’s economy is heavily dependent on rainfed agriculture. Therefore, anomalies in precipitation can have a significant impact on crop yields, affecting food production and security. Thus, monitoring anomalous climate conditions in Togo through the combination of precipitation satellite-based data and Standard Precipitation Index (SPI) help anticipate the development of drought scenarios or excessive rainfall, allowing farmers to adjust their strategies and minimize losses. Continuous and adequate spatial monitoring of these climate anomalies provided by satellite-based products can be central to an effective early warning system (EWS) implementation in Togo. Precipitation satellite-based products have been presented invaluable tools for assessing droughts and , offering timely and comprehensive data that supports a wide range of applications. In this study, we applied the Integrated Multi-satellite Retrievals for GPM (IMERG) rainfall product, a unified satellite global precipitation product developed by NASA, to identify and characterize the severity of dry and wet climate events in Togo during the period from 2001 to 2019. The Standard Precipitation Index (SPI), as the main index recommended by the World Meteorological Organization to monitor drought wide world, was selected as the reference index to monitor dry and wet climate events across Togo regions. The results show two distinct major climate periods in Togo in the timeframe analyzed (2001-2019), one dominated by wet events from 2008 to 2010, and a second marked by severe and extreme dry events from 2013 to 2015;MERG rainfall and SPI combination were able to capture these events consistently.展开更多
The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing ...The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing the latest Version-7 TRMM Multi-satellite Precipitation Analysis （TMPA 3B42V7） data for drought condition monitoring in the Weihe River Basin （0.135×10^6 km2）. The accuracy of the monthly TMPA 3B42V7 satellite precipitation data was firstly evaluated against the ground rain gauge observations. The statistical characteristics between a short period data series （1998-2013） and a long period data series （1961-2013） were then compared. The TMPA 3B42V7-based SPI （Standardized Precipitation Index） sequences were finally validated and analyzed at various temporal scales for assessing the drought conditions. The results indicate that the monthly TMPA 3B42V7 precipitation is in a high agreement with the rain gauge observations and can accurately capture the temporal and spatial characteristics of rainfall within the Weihe River Basin. The short period data can present the characteristics of long period record, and it is thus acceptable to use the short period data series to estimate the cumulative probability function in the SPI calculation. The TMPA 3B42V7-based SPI matches well with that based on the rain gauge observations at multiple time scales （i.e., 1-, 3-, 6-, 9-, and 12-month） and can give an acceptable temporal distribution of drought conditions. It suggests that the TMPA 3B42V7 precipitation data can be used for monitoring the occurrence of drought in the Weihe River Basin.展开更多
Drought research requires data on precipitation and actual soil moisture of fields because precipitation is variable among years and the soil textures differ with crop fields. Measurement of soil water content in the ...Drought research requires data on precipitation and actual soil moisture of fields because precipitation is variable among years and the soil textures differ with crop fields. Measurement of soil water content in the field is simple but labor-intensive. A prototype of an automatic field data monitoring system has been recently developed to collect data more efficiently. Using this system, data of soil water contents was successfully transmitted onto the personal computer approximately 700 m away from wheat field plots, for the period from March to May which was critical for soil drying and wheat growth. In addition, sample data of soil water content and grain yield was obtained from field plots of three bread wheat genotypes.展开更多
Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Pa...Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park(TNP),Serbia,we monitored defoliation and mortality of individual trees in permanent experimental plots.Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress.The two sets of data were combined to determine the impact of climatic events,primarily drought periods,on the desiccation of forests.Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests(ICP Forests)with TNP data helped relate forest desiccation to climate events.Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots,and then assessed for their influence on tree desicca-tion in the entire national park.The standardized precipita-tion evapotranspiration index(SPEI)was used for a more detailed analysis of the drought period.Despite the lack of climate data for a certain period,the SPEI index revealed a link between climate variables and the defoliation and desic-cation of forests.Furthermore,the desiccation of trees was preceded by a long drought period.Although mixed conifer-ous-deciduous forests are often considered less vulnerable to natural influences,this study suggests that forest ecosystems can become vulnerable regardless of tree species composi-tion due to multi-year droughts.These findings contribute to a better understanding of important clues for predicting pos-sible future desiccation of forests.Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.展开更多
Agricultural drought,characterized by insufficient soil moisture crucial for crop growth,poses significant chal lenges to food security and economic sustainability,particularly in water-scarce regions like Senegal.Thi...Agricultural drought,characterized by insufficient soil moisture crucial for crop growth,poses significant chal lenges to food security and economic sustainability,particularly in water-scarce regions like Senegal.This study addresses this issue by developing a comprehensive geospatial monitoring system for agricultural drought using the Regional Hydrologic Extremes Assessment System(RHEAS).This system,with a high-resolution of 0.05°,effectively simulates daily soil moisture and generates the Soil Moisture Deficit Index(SMDI)-based agricultural drought monitoring.The SMDI derived from the RHEAS has effectively captured historical droughts in Senegal over the recent 30 years period from 1993 to 2022.The SMDI,also provides a comprehensive understanding of regional variations in drought severity(S),duration(D),and frequency(F),through S-D-F analysis to identify key drought hotspots across Senegal.Findings reveal a distinct north-south gradient in drought conditions,with the northern and central Senegal experiencing more frequent and severe droughts.The study highlights that Senegal experiences frequent short-duration droughts with high severity,resulting in extensive spatial impact.Addition ally,increasing trends in drought severity and duration suggest evolving climate change effects.These findings emphasize the urgent need for sustainable interventions to mitigate drought impacts on agricultural productiv ity.Specifically,the study identifies recurrent and intense drought hotspots affecting yields of staple crops like maize and rice,as well as cash crops like peanuts.The developed high-resolution drought monitoring system for Senegal not only identifies hotspots but also enables prioritizing sustainable approaches and adaptive strategies,ultimately sustaining agricultural productivity and resilience in Senegal’s drought-prone regions.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
Meteorological drought is a natural hazard that can occur under all climatic regimes. Monitoring the drought is a vital and important part of predicting and analyzing drought impacts. Because no single index can repre...Meteorological drought is a natural hazard that can occur under all climatic regimes. Monitoring the drought is a vital and important part of predicting and analyzing drought impacts. Because no single index can represent all facets of meteorological drought, we took a multi-index approach for drought monitoring in this study. We assessed the ability of eight precipitation-based drought indices（SPI（Standardized Precipitation Index）, PNI（Percent of Normal Index）, DI（Deciles index）, EDI（Effective drought index）, CZI（China-Z index）, MCZI（Modified CZI）, RAI（Rainfall Anomaly Index）, and ZSI（Z-score Index）） calculated from the station-observed precipitation data and the Ag MERRA gridded precipitation data to assess historical drought events during the period 1987–2010 for the Kashafrood Basin of Iran. We also presented the Degree of Dryness Index（DDI） for comparing the intensities of different drought categories in each year of the study period（1987–2010）. In general, the correlations among drought indices calculated from the Ag MERRA precipitation data were higher than those derived from the station-observed precipitation data. All indices indicated the most severe droughts for the study period occurred in 2001 and 2008. Regardless of data input source, SPI, PNI, and DI were highly inter-correlated（R^2=0.99）. Furthermore, the higher correlations（R^2=0.99） were also found between CZI and MCZI, and between ZSI and RAI. All indices were able to track drought intensity, but EDI and RAI showed higher DDI values compared with the other indices. Based on the strong correlation among drought indices derived from the Ag MERRA precipitation data and from the station-observed precipitation data, we suggest that the Ag MERRA precipitation data can be accepted to fill the gaps existed in the station-observed precipitation data in future studies in Iran. In addition, if tested by station-observed precipitation data, the Ag MERRA precipitation data may be used for the data-lacking areas.展开更多
To develop a suitable method for monitoring wheat yield loss caused by drought for dry farming areas in northwestern China, daily ET0 and ETC were calculated using KC and FAO- PM from 1961 to 2000, and wheat evapotr...To develop a suitable method for monitoring wheat yield loss caused by drought for dry farming areas in northwestern China, daily ET0 and ETC were calculated using KC and FAO- PM from 1961 to 2000, and wheat evapotranspiration with an interval of 10 days was estimated with soil water balance equation for the mountainous areas in southern Ningxia, China. Actual water consumption and water requirements of wheat during growing season was calculated using soil water balance equation by correcting leakage of soil water and run-off of precipitation every year. A model for estimation of yield loss by drought was established based on crop growth-water consumption function and yield potential. The results show that it is an effective method for monitoring drought and estimating yield loss. This method is suitable for monitoring drought and estimating yield loss of wheat in dry farming areas in northwestern China.展开更多
Background:Snags(standing dead trees)are important biological legacies in forest systems,providing numerous resources as well as a record of recent tree mortality.From 1997 to 2017,we monitored snag populations in dro...Background:Snags(standing dead trees)are important biological legacies in forest systems,providing numerous resources as well as a record of recent tree mortality.From 1997 to 2017,we monitored snag populations in drought-influenced mixed-conifer and ponderosa pine(Pinus ponderosa)forests in northern Arizona.Results:Snag density increased significantly in both forest types.This increase was driven largely by a pulse in snag recruitment that occurred between 2002 and 2007,fol owing an extreme drought year in 2002,with snag recruitment returning to pre-pulse levels in subsequent time periods.Some later years during the study also were warmer and/or drier than average,but these years were not as extreme as 2002 and did not trigger the same level of snag recruitment.Snag recruitment was not equal across tree species and size classes,resulting in significant changes in species composition and size-class distributions of snag populations in both forest types.Because trees were far more abundant than snags in these forests,the effect of this mortality pulse on tree populations was far smal er than its effect on snag populations.Snag loss rates increased over time during the study,even though many snags were newly recruited.This may reflect the increasing prevalence of white fir snags and/or snags in the smal er size classes,which general y decay faster than snags of other species or larger snags.Thus,although total numbers of snags increased,many of the newly recruited snags may not persist long enough to be valuable as nesting substrates for native wildlife.Conclusions:Increases in snag abundance appeared to be due to a short-term tree mortality"event"rather than a longerterm pattern of elevated tree mortality.This mortality event fol owed a dry and extremely warm year(2002)embedded within a longer-term megadrought.Climate models suggest that years like 2002 may occur with increasing frequency in the southwestern U.S.Such years may result in additional mortality pulses,which in turn may strongly affect trajectories in abundance,structure,and composition of snag populations.Relative effects on tree populations likely wil be smal er,but,over time,also could be significant.展开更多
基金Supported by National Natural Science Foundation of Guangxi(Guikezi0832205)National Science and Technology Support Plan Project of China(2008BAK50B02-02)Science Research and Technology Development Plan Project of Guangxi(Guikegong10123009-4)~~
文摘[Objective] The research aimed to simplify the operating process of agricultural drought monitoring and assessment product,and improve fine level of monitoring and assessment map.[Method] By comprehensively using GIS and mathematics,meteorology,management science,computer science,the monitoring and assessment of drought were as the core,the monitoring and assessment system of agricultural drought based on GIS technology was studied.[Result] The drought in Guangxi on November 4,2006 was monitored by using the system,and the actual situation was used to test.The result proved that the good monitoring effect was obtained.[Conclusion] The monitoring and assessment system of agricultural drought based on GIS realized the organic combination of GIS and professional monitoring,assessment model.The flexible HCI interface and visualization expression were provided.The monitoring and assessment function of agricultural drought was realized.It had the good practicality and advancement.
基金supported by the National Key Research and Development Program of China (2016YFA0601601)National Natural Science Foundation of China (Grants Nos. U1502233,41405001)+1 种基金the Jiangsu Collaborative Innovation Center for Climate ChangePh.D. Programs Foundation of Ministry of Education of China (20135301120010)
文摘Using Moderate Resolution Imaging Spectroradiometer(MODIS) data from the dry season during 2010–2012 over the whole Yunnan Province, an improved temperature vegetation dryness index(iTVDI), in which a parabolic dry-edge equation replaces the traditional linear dry-edge equation, was developed, to reveal the regional drought regime in the dry season. After calculating the correlation coefficient, root-mean-square error, and standard deviation between the iTVDI and observed topsoil moisture at 10 and 20 cm for seven sites, the effectiveness of the new index in depicting topsoil moisture conditions was verified. The drought area indicated by iTVDI mapping was then compared with the drought-affected area reported by the local government. The results indicated that the iTVDI can monitor drought more accurately than the traditional TVDI during the dry season in Yunnan Province. Using iTVDI facilitates drought warning and irrigation scheduling, and the expectation is that this new index can be broadly applied in other areas.
基金Under the auspices of National Natural Science Foundation of China(No.41071221)National Science Technology Support Program(No.2008BAC34B06)China Postdoctoral Science Foundation(No.20110490200)
文摘The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.
基金Supported by National Natural Science Foundation,China(41371498)Comprehensive Process Observation and Test Platform Construction of Natural Geography in Marina Small Watershed,Sun Yat-sen University,China
文摘It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorological stations of the Pearl River Basin,the Standardized Precipitation Evapotranspiration Index（ SPEI） at different time scales was calculated. Based on the SPEIs of 1- 12 months,a newly proposed index for drought--Joint Drought Index（ JDI） was established under the multi-scale perspective through the copula function. Since short-term SPEIs are essential for the identification of emerging droughts and long-term SPEIs are useful for prolonged droughts,the JDI,which integrates all the usefull informations of drought and can thus form an overall judgement,is superior than the single SPEI in drought monitoring. By the forcast evaluation system and comparison to the actual drought,the accuracy and effectiveness of JDI in drought monitoring were verified. In general,JDI can be used as a new ideal index for future drought monitoring and assessment. Additionly,we analyzed the spatio-temperal characteristics of drought across the Pearl River Basin using the JDI. The results indicate that mild drought was the most frequent drought occurred in the Pearl River Basin over the past half century,and moderate drought followed. Severe drought and extreme drought would appear occasionally while exceptional drought could hardly be found. A dry-wet-dry interdecadal variation pattern had been found from the 1960 s to the 2000 s. Since the 21 stcentury,an obvious trend toward drought can be observed in the whole basin,especially in the Xijiang subbasin,which,consequently,poses an increasing challenge for the water resource planning and management.
文摘Togo’s economy is heavily dependent on rainfed agriculture. Therefore, anomalies in precipitation can have a significant impact on crop yields, affecting food production and security. Thus, monitoring anomalous climate conditions in Togo through the combination of precipitation satellite-based data and Standard Precipitation Index (SPI) help anticipate the development of drought scenarios or excessive rainfall, allowing farmers to adjust their strategies and minimize losses. Continuous and adequate spatial monitoring of these climate anomalies provided by satellite-based products can be central to an effective early warning system (EWS) implementation in Togo. Precipitation satellite-based products have been presented invaluable tools for assessing droughts and , offering timely and comprehensive data that supports a wide range of applications. In this study, we applied the Integrated Multi-satellite Retrievals for GPM (IMERG) rainfall product, a unified satellite global precipitation product developed by NASA, to identify and characterize the severity of dry and wet climate events in Togo during the period from 2001 to 2019. The Standard Precipitation Index (SPI), as the main index recommended by the World Meteorological Organization to monitor drought wide world, was selected as the reference index to monitor dry and wet climate events across Togo regions. The results show two distinct major climate periods in Togo in the timeframe analyzed (2001-2019), one dominated by wet events from 2008 to 2010, and a second marked by severe and extreme dry events from 2013 to 2015;MERG rainfall and SPI combination were able to capture these events consistently.
基金jointly supported by the National Key Research and Development Program approved by Ministry of Science and Technology,China(2016YFA0601504)the Program of Introducing Talents of Discipline to Universities by the Ministry of Education and the State Administration of Foreign Experts Affairs,China(B08048)+1 种基金the National Natural Science Foundation of China(41501017,51579066)the Natural Science Foundation of Jiangsu Province(BK20150815)
文摘The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing the latest Version-7 TRMM Multi-satellite Precipitation Analysis （TMPA 3B42V7） data for drought condition monitoring in the Weihe River Basin （0.135×10^6 km2）. The accuracy of the monthly TMPA 3B42V7 satellite precipitation data was firstly evaluated against the ground rain gauge observations. The statistical characteristics between a short period data series （1998-2013） and a long period data series （1961-2013） were then compared. The TMPA 3B42V7-based SPI （Standardized Precipitation Index） sequences were finally validated and analyzed at various temporal scales for assessing the drought conditions. The results indicate that the monthly TMPA 3B42V7 precipitation is in a high agreement with the rain gauge observations and can accurately capture the temporal and spatial characteristics of rainfall within the Weihe River Basin. The short period data can present the characteristics of long period record, and it is thus acceptable to use the short period data series to estimate the cumulative probability function in the SPI calculation. The TMPA 3B42V7-based SPI matches well with that based on the rain gauge observations at multiple time scales （i.e., 1-, 3-, 6-, 9-, and 12-month） and can give an acceptable temporal distribution of drought conditions. It suggests that the TMPA 3B42V7 precipitation data can be used for monitoring the occurrence of drought in the Weihe River Basin.
文摘Drought research requires data on precipitation and actual soil moisture of fields because precipitation is variable among years and the soil textures differ with crop fields. Measurement of soil water content in the field is simple but labor-intensive. A prototype of an automatic field data monitoring system has been recently developed to collect data more efficiently. Using this system, data of soil water contents was successfully transmitted onto the personal computer approximately 700 m away from wheat field plots, for the period from March to May which was critical for soil drying and wheat growth. In addition, sample data of soil water content and grain yield was obtained from field plots of three bread wheat genotypes.
基金supported by the Ministry of Science,Technological Development and Innovation(Contract No.451-03-66/2024-03/200027)the Ministry of Agriculture,Forestry,and Water Management of the Republic of Serbia’s Forest Directorate within the project“Monitoring and Assessment of Air Pollution Impacts and its Effects on Forest Ecosystems in Republic of Serbia-Forest Condition Monitoring”.
文摘Forest ecosystems within national parks are threatened by various biotic and abiotic factors.To deter-mine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park(TNP),Serbia,we monitored defoliation and mortality of individual trees in permanent experimental plots.Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress.The two sets of data were combined to determine the impact of climatic events,primarily drought periods,on the desiccation of forests.Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests(ICP Forests)with TNP data helped relate forest desiccation to climate events.Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots,and then assessed for their influence on tree desicca-tion in the entire national park.The standardized precipita-tion evapotranspiration index(SPEI)was used for a more detailed analysis of the drought period.Despite the lack of climate data for a certain period,the SPEI index revealed a link between climate variables and the defoliation and desic-cation of forests.Furthermore,the desiccation of trees was preceded by a long drought period.Although mixed conifer-ous-deciduous forests are often considered less vulnerable to natural influences,this study suggests that forest ecosystems can become vulnerable regardless of tree species composi-tion due to multi-year droughts.These findings contribute to a better understanding of important clues for predicting pos-sible future desiccation of forests.Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.
基金supported by the NASA(Grant No.80NSSC21K0403)USAID Kansas State University subcontract KSU-A20-0163-S035 with Michigan State University.
文摘Agricultural drought,characterized by insufficient soil moisture crucial for crop growth,poses significant chal lenges to food security and economic sustainability,particularly in water-scarce regions like Senegal.This study addresses this issue by developing a comprehensive geospatial monitoring system for agricultural drought using the Regional Hydrologic Extremes Assessment System(RHEAS).This system,with a high-resolution of 0.05°,effectively simulates daily soil moisture and generates the Soil Moisture Deficit Index(SMDI)-based agricultural drought monitoring.The SMDI derived from the RHEAS has effectively captured historical droughts in Senegal over the recent 30 years period from 1993 to 2022.The SMDI,also provides a comprehensive understanding of regional variations in drought severity(S),duration(D),and frequency(F),through S-D-F analysis to identify key drought hotspots across Senegal.Findings reveal a distinct north-south gradient in drought conditions,with the northern and central Senegal experiencing more frequent and severe droughts.The study highlights that Senegal experiences frequent short-duration droughts with high severity,resulting in extensive spatial impact.Addition ally,increasing trends in drought severity and duration suggest evolving climate change effects.These findings emphasize the urgent need for sustainable interventions to mitigate drought impacts on agricultural productiv ity.Specifically,the study identifies recurrent and intense drought hotspots affecting yields of staple crops like maize and rice,as well as cash crops like peanuts.The developed high-resolution drought monitoring system for Senegal not only identifies hotspots but also enables prioritizing sustainable approaches and adaptive strategies,ultimately sustaining agricultural productivity and resilience in Senegal’s drought-prone regions.
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.
文摘Meteorological drought is a natural hazard that can occur under all climatic regimes. Monitoring the drought is a vital and important part of predicting and analyzing drought impacts. Because no single index can represent all facets of meteorological drought, we took a multi-index approach for drought monitoring in this study. We assessed the ability of eight precipitation-based drought indices（SPI（Standardized Precipitation Index）, PNI（Percent of Normal Index）, DI（Deciles index）, EDI（Effective drought index）, CZI（China-Z index）, MCZI（Modified CZI）, RAI（Rainfall Anomaly Index）, and ZSI（Z-score Index）） calculated from the station-observed precipitation data and the Ag MERRA gridded precipitation data to assess historical drought events during the period 1987–2010 for the Kashafrood Basin of Iran. We also presented the Degree of Dryness Index（DDI） for comparing the intensities of different drought categories in each year of the study period（1987–2010）. In general, the correlations among drought indices calculated from the Ag MERRA precipitation data were higher than those derived from the station-observed precipitation data. All indices indicated the most severe droughts for the study period occurred in 2001 and 2008. Regardless of data input source, SPI, PNI, and DI were highly inter-correlated（R^2=0.99）. Furthermore, the higher correlations（R^2=0.99） were also found between CZI and MCZI, and between ZSI and RAI. All indices were able to track drought intensity, but EDI and RAI showed higher DDI values compared with the other indices. Based on the strong correlation among drought indices derived from the Ag MERRA precipitation data and from the station-observed precipitation data, we suggest that the Ag MERRA precipitation data can be accepted to fill the gaps existed in the station-observed precipitation data in future studies in Iran. In addition, if tested by station-observed precipitation data, the Ag MERRA precipitation data may be used for the data-lacking areas.
文摘To develop a suitable method for monitoring wheat yield loss caused by drought for dry farming areas in northwestern China, daily ET0 and ETC were calculated using KC and FAO- PM from 1961 to 2000, and wheat evapotranspiration with an interval of 10 days was estimated with soil water balance equation for the mountainous areas in southern Ningxia, China. Actual water consumption and water requirements of wheat during growing season was calculated using soil water balance equation by correcting leakage of soil water and run-off of precipitation every year. A model for estimation of yield loss by drought was established based on crop growth-water consumption function and yield potential. The results show that it is an effective method for monitoring drought and estimating yield loss. This method is suitable for monitoring drought and estimating yield loss of wheat in dry farming areas in northwestern China.
基金provided by the USDA Forest Service Rocky Mountain Research Station。
文摘Background:Snags(standing dead trees)are important biological legacies in forest systems,providing numerous resources as well as a record of recent tree mortality.From 1997 to 2017,we monitored snag populations in drought-influenced mixed-conifer and ponderosa pine(Pinus ponderosa)forests in northern Arizona.Results:Snag density increased significantly in both forest types.This increase was driven largely by a pulse in snag recruitment that occurred between 2002 and 2007,fol owing an extreme drought year in 2002,with snag recruitment returning to pre-pulse levels in subsequent time periods.Some later years during the study also were warmer and/or drier than average,but these years were not as extreme as 2002 and did not trigger the same level of snag recruitment.Snag recruitment was not equal across tree species and size classes,resulting in significant changes in species composition and size-class distributions of snag populations in both forest types.Because trees were far more abundant than snags in these forests,the effect of this mortality pulse on tree populations was far smal er than its effect on snag populations.Snag loss rates increased over time during the study,even though many snags were newly recruited.This may reflect the increasing prevalence of white fir snags and/or snags in the smal er size classes,which general y decay faster than snags of other species or larger snags.Thus,although total numbers of snags increased,many of the newly recruited snags may not persist long enough to be valuable as nesting substrates for native wildlife.Conclusions:Increases in snag abundance appeared to be due to a short-term tree mortality"event"rather than a longerterm pattern of elevated tree mortality.This mortality event fol owed a dry and extremely warm year(2002)embedded within a longer-term megadrought.Climate models suggest that years like 2002 may occur with increasing frequency in the southwestern U.S.Such years may result in additional mortality pulses,which in turn may strongly affect trajectories in abundance,structure,and composition of snag populations.Relative effects on tree populations likely wil be smal er,but,over time,also could be significant.
