We analyzed the Normalized Difference Vegetation Index （NDVI） from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand t...We analyzed the Normalized Difference Vegetation Index （NDVI） from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand the eco-hydrological effect of atmospheric precipitation and its relationship with vegetation. First,we analyzed its general spatio-temporal distribution using its mean,standard deviation and linear trend. Then,we used the Empirical Orthogonal Functions （EOF） method to decompose the NDVI and precipitation data into spatial and temporal modes. We selected four leading modes based on North and Scree test rules and analyzed the synchronous seasonal and inter-annual variability between the vegetation index and precipitation,distinguishing time-lagged correlations between EOF modes with the correlative degree analysis method. According to our detailed analyses,the vegetation index and precipitation exhibit a prominent correlation in spatial distribution and seasonal variation. At the 90% confidence level,the time lag is around 110 to 140 days,which matches well with the seasonal variation.展开更多
The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observati...The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observational analysis indicates that Vicente influenced distant heavy rainfall by transporting water vapor northward to the Beijing area. This moisture transport was mainly driven by the interaction between Vicente and the western Pacific subtropical high（WPSH） associated with the formation of a low-level southeasterly moisture channel. A set of numerical sensitivity experiments were performed with prescribed typhoons of different intensities to investigate the interaction between Vicente and the WPSH and its effects on this rainstorm process. The results indicate that the WPSH interacting with typhoons of different intensities may exert varying degrees of influence on the development of a southeasterly moisture channel, resulting in a change in rain rate and location over the Beijing area. Specifically, in the presence of an enhanced typhoon,the WPSH shows remarkable withdrawal to the east, which is favorable for a northward extension of the southeasterly moisture channel, thereby increasing moisture supply for the rainstorm. The WPSH tends to stretch westward in a zonal pattern if the typhoon is weakened or removed, hindering the northward extension of the moisture channel. Thus, the rainfall area may be expected to expand or contract, with corresponding increases or decreases in rain rate over the Beijing area with a strengthened or weakened typhoon, respectively.展开更多
准确估算区域降水对水文过程评价和水资源管理意义重大。为评估TRMM 3B42V7降水产品在海河流域南系的估算精度及其在土壤和水评估模型(Soil and Water Assessment Tool,SWAT)中的适用性,利用28个气象站降水观测数据(2007-2016年)和101...准确估算区域降水对水文过程评价和水资源管理意义重大。为评估TRMM 3B42V7降水产品在海河流域南系的估算精度及其在土壤和水评估模型(Soil and Water Assessment Tool,SWAT)中的适用性,利用28个气象站降水观测数据(2007-2016年)和101个雨量站观测数据(2010-2016年)开展研究。研究表明:站点尺度上,3B42V7降水产品对月降水估算的均方根误差小于15 mm,平均误差小于8.5 mm;在湿润季节的估算精度更好。流域尺度上,日降水估算精度较差,相关系数小于0.6。分区尺度上,3B42V7能够很好地捕捉到不同等级降水强度,但对微量降雨有所低估;山区和平原的年降水量均出现高估现象,平原区较为突出;此外,3B42V7能够较好地捕捉到研究区内极端降水的时间和空间分布。分2种情景进行水文模拟,利用月平均流量对模型进行校准和验证,在情景Ⅰ中,验证期模拟结果较好,决定系数在0.56~0.96之间,纳什效率系数在-11.09~0.94之间。TRMM 3B42V7可为海河流域及其类似区域的水资源管理提供参考。展开更多
Drought is one of the most frequent and widespread natural disasters and has tremendous agricultural,ecological,societal,and economic impacts.Among the many drought indices,the standardized precipitation index(SPI)bas...Drought is one of the most frequent and widespread natural disasters and has tremendous agricultural,ecological,societal,and economic impacts.Among the many drought indices,the standardized precipitation index(SPI)based on monthly precipitation data is simple to calculate and has multiscale characteristics.To evaluate the applicability of high spatiotemporal resolution satellite precipitation products for drought monitoring,based on the Tropical Rainfall Measuring Mission(TRMM)products and station-based meteorological data,the SPI values at different time scales(1,3,6,and 12 months)were calculated for the period of 1998-2016 in the middle and lower reaches of the Yangtze River Basin(MLRYRB).The temporal correlations show that there is a high degree of consistency between calculations at the different time scales(1,3,6 and 12 months)based on the two data sources and that the amplitude of fluctuations decreases with increasing time scale.In addition,the Mann-Kendall(MK)test method was applied to analyze the trends from 1998 to 2016,and the results suggest that wetting trends clearly prevailed over drying trends.Moreover,a correlation analysis of the two data sources based on 60 meteorological stations was performed with the SPI values at different time scales.The correlation coefficients at the short time scales(1,3,and 6 months)are all greater than 0.7,and the correlation coefficient at the long time scale(12 months)is greater than 0.5.In summary,the results demonstrate that the TRMM 3B43 precipitation product provides a new data source that can be used for reliable drought monitoring in the MLRYRB.展开更多
The snowmelt runoff model （SRM） has been widely used in simulation and forecast of streamflow in snow-dominated mountainous basins around the world. This paper presents an overall review of worldwide applications of...The snowmelt runoff model （SRM） has been widely used in simulation and forecast of streamflow in snow-dominated mountainous basins around the world. This paper presents an overall review of worldwide applications of SRM in mountainous watersheds, particularly jn data-sparse watersheds of northwestern China. Issues related to proper selection of input climate variables and parameters, and determination of the snow cover area （SCA）using remote sensing data in snowmelt runoff modeling are discussed through extensive review of literature. Preliminary applications of SRM in northwestern China have shown that the model accuracies are relatively acceptable although most of the watersheds lack measured hydro-meteorological data. Future research could explore the feasibility of modeling snowmelt runoff in data-sparse mountainous watersheds in northwestern China by utilizing snow and glacier cover remote sensing data, geographic information system （GIS） tools, field measurements, and innovative ways of model parameterization.展开更多
In this study,the characteristics and preliminary causes of tropical cyclone remote precipitation(TRP)over China during the period from 1979 to 2020 are investigated.Results indicated that approximately 72.42%of tropi...In this study,the characteristics and preliminary causes of tropical cyclone remote precipitation(TRP)over China during the period from 1979 to 2020 are investigated.Results indicated that approximately 72.42%of tropical cyclones(TCs)in the Western Pacific produce TRP over China.The peak months for TRP are July and August.The four key regions of TRP are the adjacent areas between the Sichuan and Shaanxi Provinces,the northern coast of the Bohai Sea,the coast of the Yellow Sea,and the southern coast area.The typical distance between the station with TRP and the TC center ranges from 1500 to 2500 km.Most of these stations are situated north to 60°west of north of the TC.The south–west water vapor transportation on the west side of the TC is crucial to TRP.TRP has a decreasing trend because of the decrease in the number of TCs that generate TRP.From the perspective of large-scale environmental conditions,a decrease in the integrated horizontal water vapor transport in China' Mainland,the weakening of upward motion at approximately 25°–35°N,which is inconducive to convection,and an increase in low-level vertical wind shear,which is unfavorable for the development of TC in areas with high frequencies of TRP-related TCs,are the factors that result in the decreasing trend of TRP.展开更多
基金Foundation： National Natural Science Foundation of China, No.40701172 No.40671122+2 种基金 The International Program for Cooperation in Science and Technology, No.2007DFA20040 National Science and Technology Supporting Item, No.2008BAC34B01 The Beijing Municipal Science and Technology Plan, No.D08040600580801
文摘We analyzed the Normalized Difference Vegetation Index （NDVI） from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand the eco-hydrological effect of atmospheric precipitation and its relationship with vegetation. First,we analyzed its general spatio-temporal distribution using its mean,standard deviation and linear trend. Then,we used the Empirical Orthogonal Functions （EOF） method to decompose the NDVI and precipitation data into spatial and temporal modes. We selected four leading modes based on North and Scree test rules and analyzed the synchronous seasonal and inter-annual variability between the vegetation index and precipitation,distinguishing time-lagged correlations between EOF modes with the correlative degree analysis method. According to our detailed analyses,the vegetation index and precipitation exhibit a prominent correlation in spatial distribution and seasonal variation. At the 90% confidence level,the time lag is around 110 to 140 days,which matches well with the seasonal variation.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB452804 and 2009CB421504)National Natural Science Foundation of China(91215302,41175063,41275066,and 41475055)
文摘The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observational analysis indicates that Vicente influenced distant heavy rainfall by transporting water vapor northward to the Beijing area. This moisture transport was mainly driven by the interaction between Vicente and the western Pacific subtropical high（WPSH） associated with the formation of a low-level southeasterly moisture channel. A set of numerical sensitivity experiments were performed with prescribed typhoons of different intensities to investigate the interaction between Vicente and the WPSH and its effects on this rainstorm process. The results indicate that the WPSH interacting with typhoons of different intensities may exert varying degrees of influence on the development of a southeasterly moisture channel, resulting in a change in rain rate and location over the Beijing area. Specifically, in the presence of an enhanced typhoon,the WPSH shows remarkable withdrawal to the east, which is favorable for a northward extension of the southeasterly moisture channel, thereby increasing moisture supply for the rainstorm. The WPSH tends to stretch westward in a zonal pattern if the typhoon is weakened or removed, hindering the northward extension of the moisture channel. Thus, the rainfall area may be expected to expand or contract, with corresponding increases or decreases in rain rate over the Beijing area with a strengthened or weakened typhoon, respectively.
文摘准确估算区域降水对水文过程评价和水资源管理意义重大。为评估TRMM 3B42V7降水产品在海河流域南系的估算精度及其在土壤和水评估模型(Soil and Water Assessment Tool,SWAT)中的适用性,利用28个气象站降水观测数据(2007-2016年)和101个雨量站观测数据(2010-2016年)开展研究。研究表明:站点尺度上,3B42V7降水产品对月降水估算的均方根误差小于15 mm,平均误差小于8.5 mm;在湿润季节的估算精度更好。流域尺度上,日降水估算精度较差,相关系数小于0.6。分区尺度上,3B42V7能够很好地捕捉到不同等级降水强度,但对微量降雨有所低估;山区和平原的年降水量均出现高估现象,平原区较为突出;此外,3B42V7能够较好地捕捉到研究区内极端降水的时间和空间分布。分2种情景进行水文模拟,利用月平均流量对模型进行校准和验证,在情景Ⅰ中,验证期模拟结果较好,决定系数在0.56~0.96之间,纳什效率系数在-11.09~0.94之间。TRMM 3B42V7可为海河流域及其类似区域的水资源管理提供参考。
基金National Key Research and Development Program of China,No.2017YFA0603704National Natural Science Foundation of China,No.51339004。
文摘Drought is one of the most frequent and widespread natural disasters and has tremendous agricultural,ecological,societal,and economic impacts.Among the many drought indices,the standardized precipitation index(SPI)based on monthly precipitation data is simple to calculate and has multiscale characteristics.To evaluate the applicability of high spatiotemporal resolution satellite precipitation products for drought monitoring,based on the Tropical Rainfall Measuring Mission(TRMM)products and station-based meteorological data,the SPI values at different time scales(1,3,6,and 12 months)were calculated for the period of 1998-2016 in the middle and lower reaches of the Yangtze River Basin(MLRYRB).The temporal correlations show that there is a high degree of consistency between calculations at the different time scales(1,3,6 and 12 months)based on the two data sources and that the amplitude of fluctuations decreases with increasing time scale.In addition,the Mann-Kendall(MK)test method was applied to analyze the trends from 1998 to 2016,and the results suggest that wetting trends clearly prevailed over drying trends.Moreover,a correlation analysis of the two data sources based on 60 meteorological stations was performed with the SPI values at different time scales.The correlation coefficients at the short time scales(1,3,and 6 months)are all greater than 0.7,and the correlation coefficient at the long time scale(12 months)is greater than 0.5.In summary,the results demonstrate that the TRMM 3B43 precipitation product provides a new data source that can be used for reliable drought monitoring in the MLRYRB.
基金supported by the National Natural Science Foundation of China(Grant No51069017)the Special Fund for Public Welfare Industry of Ministry of Water Resources of China(Grant No201001065)+1 种基金the Open-End Fund of Key Laboratory of Oasis Ecology,Xinjiang University(Grant No XJDX0206-2010-03)the Open-End Fund of the China Institute of Water Resources and Hydropower Research(Grant NoIWHR-SKL-201104)
文摘The snowmelt runoff model （SRM） has been widely used in simulation and forecast of streamflow in snow-dominated mountainous basins around the world. This paper presents an overall review of worldwide applications of SRM in mountainous watersheds, particularly jn data-sparse watersheds of northwestern China. Issues related to proper selection of input climate variables and parameters, and determination of the snow cover area （SCA）using remote sensing data in snowmelt runoff modeling are discussed through extensive review of literature. Preliminary applications of SRM in northwestern China have shown that the model accuracies are relatively acceptable although most of the watersheds lack measured hydro-meteorological data. Future research could explore the feasibility of modeling snowmelt runoff in data-sparse mountainous watersheds in northwestern China by utilizing snow and glacier cover remote sensing data, geographic information system （GIS） tools, field measurements, and innovative ways of model parameterization.
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province (No.KYCX22_1136)the National Natural Scientific Foundation of China (No.42275037)+2 种基金the Basic Research Fund of CAMS (No.2023Z016)the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province (No.SCSF202202)supported by the Jiangsu Collaborative Innovation Center for Climate Change。
文摘In this study,the characteristics and preliminary causes of tropical cyclone remote precipitation(TRP)over China during the period from 1979 to 2020 are investigated.Results indicated that approximately 72.42%of tropical cyclones(TCs)in the Western Pacific produce TRP over China.The peak months for TRP are July and August.The four key regions of TRP are the adjacent areas between the Sichuan and Shaanxi Provinces,the northern coast of the Bohai Sea,the coast of the Yellow Sea,and the southern coast area.The typical distance between the station with TRP and the TC center ranges from 1500 to 2500 km.Most of these stations are situated north to 60°west of north of the TC.The south–west water vapor transportation on the west side of the TC is crucial to TRP.TRP has a decreasing trend because of the decrease in the number of TCs that generate TRP.From the perspective of large-scale environmental conditions,a decrease in the integrated horizontal water vapor transport in China' Mainland,the weakening of upward motion at approximately 25°–35°N,which is inconducive to convection,and an increase in low-level vertical wind shear,which is unfavorable for the development of TC in areas with high frequencies of TRP-related TCs,are the factors that result in the decreasing trend of TRP.
