Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administrat...Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administration (NOAA-AVHRR)'s Leaf Area Index (LAI) satellite images. Results suggest that from 1982 to 2000 global climate change has contributed to an increase in vegetation cover in the Qinghai-Tibet Plateau. The correlation between rainfall and LAI EOF PC1 and PC2 indicates that rainfall is the major climatic factor influencing interannual variations of average vegetation cover throughout the entire Plateau. However, annual mean vegetation cover trends in the Qinghai-Tibet Plateau are mainly out of phase with air temperature increasing, which is primarily responsible for nonsynchro- nous changes of vegetation cover. In the southern ridge of the Qinghai-Tibet Plateau, recent warming trends contribute to humid weather and favorable conditions for vegetation growth. By contrast, higher temperatures have led to arid conditions and insufficient rainfall in the northern part of the Plateau, leading to drought and other climatic conditions which are not conducive to increased vegetation cover.展开更多
The term "westerlies-dominated climatic regime" describes the pattern of precipitation/moisture variations between westerliesdominated arid Central Asia(ACA) and mid-latitude monsoon-dominated Asia on decada...The term "westerlies-dominated climatic regime" describes the pattern of precipitation/moisture variations between westerliesdominated arid Central Asia(ACA) and mid-latitude monsoon-dominated Asia on decadal to multi-millennial time scales. However, no attempts have been made to define its core region and the possible physical mechanisms responsible during the period of instrumental observations. The present study investigates the spatiotemporal variations of summer and winter precipitation on interannual to decadal time scales over mid-latitudes of the Eurasian continent using Empirical Orthogonal Function(EOF) analysis. Our results suggest the existence of an opposing pattern of summer precipitation variations between ACA and mid-latitude monsoon-dominated Asia and Mediterranean on decadal time scales. Based on these results, the core region influenced by the westerlies is outlined, including arid central Asia and Xinjiang in China(36°–54°N, 50°–90°E). By using monthly NCEP-NCAR reanalysis, the relationship between the "westerlies-dominated climatic regime" and atmospheric circulation were also analyzed. The combination of the zonal climatic teleconnection pattern and anomalous Indian Summer Monsoon Precipitation(ISMP) causes the precipitation characteristics of the "westerlies-dominated climatic regime" precipitation pattern. In addition, the Atlantic Multidecadal Oscillation(AMO) may also have an important effect on the "westerlies-dominated climatic regime".展开更多
基金the National Basic Research Program of China (Grant No. 2006CB403607)the National Natural Science Foundation of China (Grant Nos. 40675047 and 40605023)+1 种基金the Key Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-219)a Western Washington University summer research grant
文摘Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administration (NOAA-AVHRR)'s Leaf Area Index (LAI) satellite images. Results suggest that from 1982 to 2000 global climate change has contributed to an increase in vegetation cover in the Qinghai-Tibet Plateau. The correlation between rainfall and LAI EOF PC1 and PC2 indicates that rainfall is the major climatic factor influencing interannual variations of average vegetation cover throughout the entire Plateau. However, annual mean vegetation cover trends in the Qinghai-Tibet Plateau are mainly out of phase with air temperature increasing, which is primarily responsible for nonsynchro- nous changes of vegetation cover. In the southern ridge of the Qinghai-Tibet Plateau, recent warming trends contribute to humid weather and favorable conditions for vegetation growth. By contrast, higher temperatures have led to arid conditions and insufficient rainfall in the northern part of the Plateau, leading to drought and other climatic conditions which are not conducive to increased vegetation cover.
基金supported by National Basic Research Program of China(Grant No.2010CB950202)National Natural Science Foundation of China(Grant No.41130102)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20120211130001)Fundamental Research Funds for the Central Universities(Grant No.LZUJBKY-2014-119)the Open Foundation of MOE Key Laboratory of Western China’s Environmental System,Lanzhou University(Grant No.LZUJBKY-2013-BT01)
文摘The term "westerlies-dominated climatic regime" describes the pattern of precipitation/moisture variations between westerliesdominated arid Central Asia(ACA) and mid-latitude monsoon-dominated Asia on decadal to multi-millennial time scales. However, no attempts have been made to define its core region and the possible physical mechanisms responsible during the period of instrumental observations. The present study investigates the spatiotemporal variations of summer and winter precipitation on interannual to decadal time scales over mid-latitudes of the Eurasian continent using Empirical Orthogonal Function(EOF) analysis. Our results suggest the existence of an opposing pattern of summer precipitation variations between ACA and mid-latitude monsoon-dominated Asia and Mediterranean on decadal time scales. Based on these results, the core region influenced by the westerlies is outlined, including arid central Asia and Xinjiang in China(36°–54°N, 50°–90°E). By using monthly NCEP-NCAR reanalysis, the relationship between the "westerlies-dominated climatic regime" and atmospheric circulation were also analyzed. The combination of the zonal climatic teleconnection pattern and anomalous Indian Summer Monsoon Precipitation(ISMP) causes the precipitation characteristics of the "westerlies-dominated climatic regime" precipitation pattern. In addition, the Atlantic Multidecadal Oscillation(AMO) may also have an important effect on the "westerlies-dominated climatic regime".
