汉江流域NDVI与水热指数时空变化及相关性分析

The correlation analysis and space-time changes of NDVI and hydro-thermal index in Hanjiang basin

文章提出水热指数的概念和计算模型,运用经验正交函数和奇异值分解法对汉江流域1999-2010年的归一化植被指数及38个气象站点的气温和降水资料进行分析。结果表明:①汉江流域植被覆盖具有明显的空间差异,地形和农耕活动是最主要原因。②水热指数的空间分布也具有明显的规律,气温的纬度差异和雨带季节推移是根本原因;大地貌单元和季风气候是重要原因。其时间系数具有明显的冬夏差异,冬半年时间系数的绝对值及变率均较夏半年小,即水热组合冬半年差异小,夏半年差异大。③NDVI与水热指数之间呈现出高度正相关,但人类通过各种方式改变着地表覆盖和水热组合,使得两者之间的高度正相关在局部地区受到影响。

This paper put forward the concept of hydro-thermal index and its calculation model. It used empirical orthogonal function and singular value decomposition method to analyze the data of the normalized difference vegetation index and temperature and rainfall data of 38 meteorological sites in Hanjiang river basin from 1999 to 2010. The conclusions were obtained as follows. （1） Vegetation coverage in Hanjiang river basin was obviously different in spatial distribution due to different topographical features and farming activities. （2） The spatial distribution of hydro-thermal index also had an obvious regular pattern. The primary reasons were temperature difference in different latitudes and the movement of the rainbelt with the seasons, and the difference of big landform elements and the monsoon climate were the main reasons. Time coefficient of hydro-thermal index had obvious differences both in winter and summer. In winter-half year, the absolute value and the variable rate of time coefficient were smaller than those in summer-half year, namely the difference of water hot combination was small in winter-half year and big in summer-half year. （3） NDVI and hydro-thermal index presented a highly positive correlation, while humans changed the surface coverage and hot-water by various means, which led to the fact that the highly positive correlation was influenced in local areas.