河西地区绿洲NDVI的演变特征及与气候因子的关系分析

选取NOAA和NASAPathfinder AVHRR陆面资料中的1982-2000年中国区域的NDVI逐月数据,进行河西地区植被覆盖状况分析,探讨河西绿洲植被的演变规律,分析研究河西地区NDVI的年际变化特征,发现近20年来额济纳绿洲是明显退化的;临泽和民勤是明显的正值,金塔绿洲也为正值,但值较小。从时间段上来说,1982-1984年,NDVI处于相对高值段,各绿洲有所发展;1985-1989年是NDVI的低值段,绿洲退化;1990-1995是NDVI的高值段,绿洲的发展很明显;1996年开始,NDVI有所下降,绿洲有所退化。对1982-2000年河西绿洲的降水、气温、地温、及各内陆河的径流资料与河西绿洲中部临泽、民勤、金塔、额济纳旗四个绿洲的NDVI作了相关分析,研究了河西中部地区绿洲发展和气候变化及水资源的关系,发现河西中部地区绿洲NDVI与前期3、4月份的气温、降水、内陆河径流的关系较好,与5月份地气温差的相关关系较好。

Variation characteristics of oasis vegetation in Central Hexi in the late 20th Century

Basing on NDVI monthly data during 1982-2000 in China from NOAA,NASA,Pathfinder and AVHRR land surface data,the vegetation coverage condition is analyzed and the variation laws of oasis vegetation are inquired in this paper.Taking NDVI during the last-ten day of June for example,the annual variation characteristics of NDVI in Hexi area is studied;it can be found that oasis in Ejina degenerates obviously,oases in Linze and Minqin develop obviously and oasis in Jinta develops to some extent.From the point of temporal variation,NDVI was in relatively high stage from 1982 to1984 and every oasis developed more or less,NDVI was low between 1985 and 1989 and the oasis degenerated.NDVI was in high section between 1990 and 1995,and oasis developed obviously.While since 1996,NDVI has decreased and oasis has degenerated.The corresponding precipitation,air temperature,ground temperature and runoff data in each inland river are analyzed with regard to NDVI of the four oases in central Hexi,Linze,Minqin,Jinta and Ejina;the relationships of oasis development to climatic variation and water resource in central Hexi are studied.It can be found that oasis NDVI in central Hexi possesses a better relationship with the air temperature,precipitation,inland runoff in early March and April.And the correlative relationship between oasis NDVI and difference in temperature of air and ground is also significant.