利用NOAA-CHAIN监测近10a来中国西北土地覆盖的变化

Change in Land Coverage in Northwest China During the Past Decade Monitored by NOAA-CHAIN

近 10a来 ,中国西北地区土地覆盖发生显著的变化 .利用基于遥感的中国西北土地覆盖动态监测系统NOAAAVHRRProcessingChain (NOAA CHAIN) ,预处理 1990年 7～ 8月和 1999年 7～ 8月NOAAAVHRR影像资料 ,对预处理过程的大气纠正和几何纠正方法及有关参数的计算进行详细的介绍 .对计算的参数NDVI进行统计 ,获取两个时期土地覆盖变化的数据 .从NDVI差值分布图可以看出中国西北植被指数普遍减小 ,植被退化严重 ,严重退化的地区主要分布在青海东部农牧交错区、新疆的天山地区和塔里木河下游的“绿色走廊”地带等 ;中度退化地区分布在青海的柴达木盆地、新疆的准葛尔盆地和塔里木盆地南部、甘肃的民勤地区、陕西北部和甘肃庆阳地区北部等 .植被增加的地区主要分布在伊利河流域、新疆北部、青海南部。

During the past ten years, the land coverage has changed a lot in Northwest China. Using the Land Coverage Dynamic Monitoring System NOAACHAIN, the NOAAAVHRR image data of Northwest China in August 1990 and 1999 is pre-processed. In this article the detail processes of atmosphere correction and geo-correction, and the calculation of system parameters are described. Through the statistics of vegetation index NDVI, the change in land coverage is obtained between these two periods. The results showed that the NDVI decreases in the whole Northwest China, and the vegetation degeneration is serious. The July NDVI peak difference is {-0.1439} with a decreasing area of 1^77 10 6 km 2 and an increasing area of 0^46 10 6 km 2. The August NDVI peak difference is {-0.1528} with a decreasing area of 2^01 10 6 km 2 and an increasing area of 0^402 10 6 km 2. The most serious degradation areas are distributed in the agri-herd interleaving areas in eastern Qinghai Province, the Tianshan Mountains and the lower reaches of the Tarim River in Xinjiang Region. And the more serious degradation areas are distributed in the Qaidam Basin in Qinghai Province, the Junggar Basin and southern Tarim Basin in Xinjiang Region, the northern Shaanxi Province, and the Minqin County and Qingyang Prefecture in Gansu Province. At the same time, the NDVI increases in some areas, such as, the Ili River Basin in northern Xinjiang Province, southern Qinghai Province, Lanzhou City of Gansu Province and the Qinling Mountains. NOAACHAIN is a pre-processing system of NOAAAVHRR data. As the result of the pre-processing, the NDVI can efficiently show the change in land coverage in Northwest China. Also the system exhibits a rather perfect stability. The key steps for NOAACHAIN are the confirmation and calculation of the parameters for atmosphere correction and the number of the GCPs for geo-correction.