干旱区植被生态系统对气候变化极为敏感,并且干旱区的植被变化研究对全球碳循环具有重要意义。然而近几十年来,中亚干旱区植被对气候变化的响应机制尚不甚明朗。利用归一化植被指数NDVI数据集和MERRA(Modern-Era Retrospective Analysis...干旱区植被生态系统对气候变化极为敏感,并且干旱区的植被变化研究对全球碳循环具有重要意义。然而近几十年来,中亚干旱区植被对气候变化的响应机制尚不甚明朗。利用归一化植被指数NDVI数据集和MERRA(Modern-Era Retrospective Analysis for Research and Applications)气象数据,采用经验正交函数(EOF,Empirical Orthogonal Function)和最小二乘法等方法系统分析了31a(1982—2012年)来中亚地区NDVI在不同时间尺度的时空变化特征。进一步分析和研究NDVI与气温和降水的相关性,结果表明:1982—2012年,中亚地区年NDVI总体呈现缓慢增长趋势,而1994年以后年NDVI呈现明显下降趋势,尤其在哈萨克斯坦北部草原地区下降趋势尤为突出。这可能是由于过去30年间,中亚地区降水累计量的持续减少造成的。NDVI的季节变化表明春季NDVI增长最为明显,冬季则显著下降。与平原区相比,中亚山区的NDVI值增长幅度最大,并且山区年NDVI与季节NDVI呈现显著增加趋势(P<0.05)。中亚地区年NDVI与年降水量正相关,而年NDVI与气温变化存在弱负相关。年NDVI和气温的正相关中心在中亚南部地区,负相关中心则出现在哈萨克斯坦的西部和北部地区;NDVI和降水的相关性中心刚好与气温相反。此外,在近30年间的每年6月至9月,中亚地区NDVI与气温存在近一个月的时间延迟现象。本研究为中亚干旱区生态系统变化和中亚地区碳循环的估算提供科学依据。展开更多
The vulnerable ecosystem of the arid and semiarid region in Central Asia is sensi- tive to precipitation variations. Long-term changes of the seasonal precipitation can reveal the evolution rules of the precipitation ...The vulnerable ecosystem of the arid and semiarid region in Central Asia is sensi- tive to precipitation variations. Long-term changes of the seasonal precipitation can reveal the evolution rules of the precipitation climate. Therefore, in this study, the changes of the sea- sonal precipitation over Central Asia have been analyzed during the last century （1901-2013） based on the latest global monthly precipitation dataset Global Precipitation Climatology Centre （GPCC） Full Data Reanalysis Version 7, as well as their relations with El Ni~_o- Southern Oscillation （ENSO）. Results show that the precipitation in Central Asia is mainly concentrated in spring and summer seasons, especially in spring. For the whole study period, increasing trends were found in spring and winter, while decreasing trends were detected in summer and fall. Inter-annual signals with 3-7 years multi-periods were derived to explain the dominant components for seasonal precipitation variability. In terms of the dominant spatial pattern, Empirical orthogonal function （EOF） results show that the spatial distribution of EOF-1 mode in summer is different from those of the other seasons during 1901-2013. Moreover, significant ENSO-associated changes in precipitation are evident during the fall, winter, spring, and absent during summer. The lagged associations between ENSO and seasonal precipitation are also obtained in Central Asia. The ENSO-based composite analy- ses show that these water vapor fluxes of spring, fall and winter precipitation are mainly generated in Indian and North Atlantic Oceans during El Nino. The enhanced westerlies strengthen the western water vapor path for Central Asia, thereby causing a rainy winter.展开更多
基金supported by The National Natural Science Foundation of P.R.China(10961022,10901130)The Scientific Research Programmes of Colleges in Xinjiang(XJEDU2007G01,XJEDU2008S10)
文摘干旱区植被生态系统对气候变化极为敏感,并且干旱区的植被变化研究对全球碳循环具有重要意义。然而近几十年来,中亚干旱区植被对气候变化的响应机制尚不甚明朗。利用归一化植被指数NDVI数据集和MERRA(Modern-Era Retrospective Analysis for Research and Applications)气象数据,采用经验正交函数(EOF,Empirical Orthogonal Function)和最小二乘法等方法系统分析了31a(1982—2012年)来中亚地区NDVI在不同时间尺度的时空变化特征。进一步分析和研究NDVI与气温和降水的相关性,结果表明:1982—2012年,中亚地区年NDVI总体呈现缓慢增长趋势,而1994年以后年NDVI呈现明显下降趋势,尤其在哈萨克斯坦北部草原地区下降趋势尤为突出。这可能是由于过去30年间,中亚地区降水累计量的持续减少造成的。NDVI的季节变化表明春季NDVI增长最为明显,冬季则显著下降。与平原区相比,中亚山区的NDVI值增长幅度最大,并且山区年NDVI与季节NDVI呈现显著增加趋势(P<0.05)。中亚地区年NDVI与年降水量正相关,而年NDVI与气温变化存在弱负相关。年NDVI和气温的正相关中心在中亚南部地区,负相关中心则出现在哈萨克斯坦的西部和北部地区;NDVI和降水的相关性中心刚好与气温相反。此外,在近30年间的每年6月至9月,中亚地区NDVI与气温存在近一个月的时间延迟现象。本研究为中亚干旱区生态系统变化和中亚地区碳循环的估算提供科学依据。
基金International Cooperation Fund of Ecological Effects of Climate Change and Land Use/Cover Change in Arid and Semiarid Regions of Central Asia in the Most Recent 500 Years,No.41361140361The Western Scholars of the Chinese Academy of Sciences,No.2015-XBQN-B-20+1 种基金National Natural Science Foundation of China,No.41471340,No.41605055Hong Kong Baptist University Faculty Research,No.FRG2/17-18/030
文摘The vulnerable ecosystem of the arid and semiarid region in Central Asia is sensi- tive to precipitation variations. Long-term changes of the seasonal precipitation can reveal the evolution rules of the precipitation climate. Therefore, in this study, the changes of the sea- sonal precipitation over Central Asia have been analyzed during the last century （1901-2013） based on the latest global monthly precipitation dataset Global Precipitation Climatology Centre （GPCC） Full Data Reanalysis Version 7, as well as their relations with El Ni~_o- Southern Oscillation （ENSO）. Results show that the precipitation in Central Asia is mainly concentrated in spring and summer seasons, especially in spring. For the whole study period, increasing trends were found in spring and winter, while decreasing trends were detected in summer and fall. Inter-annual signals with 3-7 years multi-periods were derived to explain the dominant components for seasonal precipitation variability. In terms of the dominant spatial pattern, Empirical orthogonal function （EOF） results show that the spatial distribution of EOF-1 mode in summer is different from those of the other seasons during 1901-2013. Moreover, significant ENSO-associated changes in precipitation are evident during the fall, winter, spring, and absent during summer. The lagged associations between ENSO and seasonal precipitation are also obtained in Central Asia. The ENSO-based composite analy- ses show that these water vapor fluxes of spring, fall and winter precipitation are mainly generated in Indian and North Atlantic Oceans during El Nino. The enhanced westerlies strengthen the western water vapor path for Central Asia, thereby causing a rainy winter.
