In this study,the monthly and seasonal teleconnection intensity indices of the Pacific/North American(PNA), Western Atlantic(WA),Western Pacific(WP),Eastern Atlantic(EA)and Eurasian(EU)patterns for the period from 195...In this study,the monthly and seasonal teleconnection intensity indices of the Pacific/North American(PNA), Western Atlantic(WA),Western Pacific(WP),Eastern Atlantic(EA)and Eurasian(EU)patterns for the period from 1951 through 1990 are calculated.On this basis,their climatic variations and the relationship between the five teleconnection intensity indices and the El Nino events are examined.It is noted that when El Nino is at its mature stage (winter),the weak WP pattern is mainly characteristic of the circulation and the strong PNA pattern is the next.In summer when El Nino occurs and develops,the strong EU,weak WP and weak WA patterns are the main characteris- tics without the PNA circulation anomalies.Finally,by the nonlinear mapping method a nonlinear mapping diagram is established for diagnosing El Nino using three summer teleeonuection intensity indices and May and August Southern Oscillation Indices(SOIs).Thus,the El Nino phenomenon occurring in 1991 is diagnosed.Besides,the winter atmos- pheric circulation of the 1991/1992 El Nino is found to be the weak WP pattern and the PNA pattern is also weak.展开更多
One of the most serious droughts in last century occurred in eastern Sichuan Basin in the summer of 2006(hereinafter called the Drought).The response of Moderate Resolution Imaging Spectroradiometer(MODIS,boarding on ...One of the most serious droughts in last century occurred in eastern Sichuan Basin in the summer of 2006(hereinafter called the Drought).The response of Moderate Resolution Imaging Spectroradiometer(MODIS,boarding on NASA satellites of Terra and Aqua)to the Drought was analyzed in order to reach one practicable monitoring solution for regional soil moisture.Temporal process and spatial extension of the Drought were firstly estimated with ground meteorological and hydrological observations.Then,for the whole region of Sichuan and Chongqing,the remotely sensed Normalized Difference Water In-dex(NDWI)for the summers of 2001―2006 were calculated based on 8-day composite MODIS products,which were further used to construct a new water index(Normalized Difference Water Deviation Index,NDWDI)to examine the sensitivity of remote sensing in the Drought.The study showed that the NDWDI is more sensitive to regional drought than other absolute-soil-moisture-based indices.With the new index,the study extracted the spatial-temporal characteristics of the 2006 Drought,and explored its developing and withdrawing processes,which agreed with related statistics.Compared with ground method of drought observation,the NDWDI-based remote sensing solution of this paper is more pref-erable and practicable in that the local soil properties of water consumption and supply are implicitly taken into account,and the spatial representativity limit of ground observation is circumvented to a degree as satellite remotely senses the earth surface in a way of two-dimensional pixel matrix.So,the NDWDI-based method can be used to monitor regional soil water stress situation more practically and efficiently.展开更多
基金sponsored by the National Natural Science Foundation and Monsoon Research Funds
文摘In this study,the monthly and seasonal teleconnection intensity indices of the Pacific/North American(PNA), Western Atlantic(WA),Western Pacific(WP),Eastern Atlantic(EA)and Eurasian(EU)patterns for the period from 1951 through 1990 are calculated.On this basis,their climatic variations and the relationship between the five teleconnection intensity indices and the El Nino events are examined.It is noted that when El Nino is at its mature stage (winter),the weak WP pattern is mainly characteristic of the circulation and the strong PNA pattern is the next.In summer when El Nino occurs and develops,the strong EU,weak WP and weak WA patterns are the main characteris- tics without the PNA circulation anomalies.Finally,by the nonlinear mapping method a nonlinear mapping diagram is established for diagnosing El Nino using three summer teleeonuection intensity indices and May and August Southern Oscillation Indices(SOIs).Thus,the El Nino phenomenon occurring in 1991 is diagnosed.Besides,the winter atmos- pheric circulation of the 1991/1992 El Nino is found to be the weak WP pattern and the PNA pattern is also weak.
基金the National Natural Science Foundation of China(Grant No.40705037)Commonweal Fund of Changjiang Scientific Research Institute(Grant No.YWF0713/ZY05)
文摘One of the most serious droughts in last century occurred in eastern Sichuan Basin in the summer of 2006(hereinafter called the Drought).The response of Moderate Resolution Imaging Spectroradiometer(MODIS,boarding on NASA satellites of Terra and Aqua)to the Drought was analyzed in order to reach one practicable monitoring solution for regional soil moisture.Temporal process and spatial extension of the Drought were firstly estimated with ground meteorological and hydrological observations.Then,for the whole region of Sichuan and Chongqing,the remotely sensed Normalized Difference Water In-dex(NDWI)for the summers of 2001―2006 were calculated based on 8-day composite MODIS products,which were further used to construct a new water index(Normalized Difference Water Deviation Index,NDWDI)to examine the sensitivity of remote sensing in the Drought.The study showed that the NDWDI is more sensitive to regional drought than other absolute-soil-moisture-based indices.With the new index,the study extracted the spatial-temporal characteristics of the 2006 Drought,and explored its developing and withdrawing processes,which agreed with related statistics.Compared with ground method of drought observation,the NDWDI-based remote sensing solution of this paper is more pref-erable and practicable in that the local soil properties of water consumption and supply are implicitly taken into account,and the spatial representativity limit of ground observation is circumvented to a degree as satellite remotely senses the earth surface in a way of two-dimensional pixel matrix.So,the NDWDI-based method can be used to monitor regional soil water stress situation more practically and efficiently.
