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近40年新疆植被指数变化趋势及其气象因子相关性分析

Interdecadal Trend of NDVI in Xinjiang over the Past 40 Years and its Correlation Analysis with Climatic Factors

  • 摘要: 基于我国新疆地区1981~2020年的60个气象国家站的降水量日值观测数据,NOAA的归一化植被指数(NDVI)的卫星遥感数据,以及2000~2020年NOAA的积雪分布的卫星遥感数据,对该地区植被覆盖的时空分布变化特征进行分析,并进一步通过相关性分析探讨相关气象因子。结果表明:1981~2020年新疆7~8月整体NDVI呈现上升趋势;2000~2020年NDVI的增加趋势有所放缓。年均日降水量的逐年变化率的量级在±0.1 mm (10 a)−1之间,且在不同地域和季节之间存在明显差异。南疆地区的积雪融化率在2000~2020年呈现普遍下降趋势,而北疆地区则呈现较弱的上升趋势。相关性分析表明该区域在不同时间段内,降水量与NDVI之间的相关性有较大的差异,其中地形平坦区域的多数站点NDVI的变化率与非冬季降水量的相关性较高,而另外一些站点的NDVI主要与冬季降水量和积雪融化率具有较高的相关性,且这些站点普遍位于高山山麓区域。由此可知,一方面该地区植被指数受降水量的影响较为显著,符合干旱半干旱地区气候与植被的关系;另一方面对于山麓地区冬季降雪和山地融雪同样对植被生长具有重要影响。根据本研究的结果推测,近40年来年内融雪量的增加趋势可能是导致这些地区植被覆盖逐年改善的重要原因之一。本研究成果可从植被覆盖的角度为新疆气候变化相关研究提供一定的观测论据。

     

    Abstract: Based on daily precipitation data from 60 national meteorological stations in Xinjiang, China, from 1981 to 2020, satellite remote sensing data of the normalized difference vegetation index (NDVI) from NOAA (National Oceanic and Atmospheric Administration), and satellite remote sensing data of snow cover distribution from NOAA from 2000 to 2020, this study analyzes the spatiotemporal distribution characteristics of vegetation cover in the region. Furthermore, correlation analysis is conducted to explore relevant climatic factors. The results show that the overall NDVI in Xinjiang in July and August exhibited an upward trend from 1981 to 2020, with the increasing trend slowing down during 2000–2020. The annual average daily precipitation rate varied between ±0.1 mm (10 a)−1, with substantial differences across areas and seasons. The annual snowmelt rate (SMR) in southern Xinjiang exhibited a downward trend in general during 2000–2020, while northern Xinjiang exhibited a weak upward trend. Correlation analysis indicated substantial variations in the correlation between precipitation and NDVI across different time periods. In flat terrain areas, the NDVI change rate at most stations exhibited a higher correlation with nonwinter precipitation; however, at other stations, NDVI was observed to be mainly correlated with winter precipitation and SMR, with these stations generally located at the foothills of mountains. This indicates that, on the one hand, the vegetation index in this region is substantially influenced by precipitation, consistent with the relationship between climate and vegetation in arid and semi-arid regions. On the other hand, winter snowfall and mountain snowmelt also play an important role in vegetation growth in foothill areas. Based on this study’s results, we speculate that the increasing trend of annual snowmelt during the past 40 years may be one of the important reasons for the annual improvement in vegetation cover in these areas. The findings of this study provide observational evidence from the perspective of vegetation cover for climate change research in Xinjiang.

     

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