博斯腾湖面积定量遥感

Quantitative Detection of Bosten Lake Area Using NOAA/AVHRR Data

采用NOAA/AVHRR资料,利用水体与地物光谱特性的差异,结合通道2方案和通道2/通道1方案,对4月博斯腾湖水体进行判识,而利用通道2、通道2/通道1并结合通道4的方案判识了10月博斯腾湖水体,在此基础上利用线性混合模式对混合像元做了处理,定量估算了1990—1998年4月和10月博斯腾湖的面积,调研了9年来博斯腾湖面积变化情况,表明9年间博斯腾湖面积呈增加趋势。进一步采用主成分分析方法对博斯腾湖面积增大原因做了初步的气候分析,表明1988年以来博斯腾湖地区气温升高、蒸发量减少、降水有所增加,而人类活动用水和出流稳定并有减少是博斯腾湖面积增加的主要原因。而博斯腾湖及上游地区季节性积雪的特征,使冬季积雪水资源注入博斯腾湖,导致春季博斯腾湖面积较秋季大。

To estimate the area of Bosten Lake and the area change since 1990, the threshold values of the channel reflectance and bright temperature of NOAA/AVHRR data are used to distinguish water body from other objects. For channel 2, water body indicates lower reflectance than vegetation and other land covers. The ratio of Channel 2 to Channel 1 can enhance the difference between water body and land, and decrease the effects of cloud and vegetation to a certain extent. For the image in April, the water body is identified by the reflectance of Channel 2 and the ratio of channel 2 to channel 1. The pixels are identified as water body if the reflectance in channel 2 is lower than the threshold T1, as the land if it is higher than T2（threshold）, and as mixed pixels if it is between T1 and T2. Based on the histograms of channel 2 and the ratio of channel 2 to channel 1, the threshold values of the T1 and T2 are found, and they are fixed on the different satellite images. In October, the water body in the south-east of the Lake is identified with bright temperature of channel 4 because the region is covered by vegetation. But, in the east of the Lake, the water body is still identified by the reflectance of channel 2 and the ratio of channel 2 to channel 1. The threshold value of channel 4 is also determined according to the histogram. The linear mixed model is used to calculate the area of mixed pixels at the edge of lake. The area of Bosten Lake in April and October from 1990 to 1998 are calculated, and the area changes of Bosten Lake during the nine years are detected. The result shows that the area of Bosten Lake has been increasing from 1990 to 1998 due to the increasing of the temperature/precipitation and the decreasing of evaporation, and the water utilization by mankind and the water exiting has been stable, even has decreased since 1988. Furthermore, the area of Bosten Lake is bigger in spring than that in autumn due to the supplying of the melt water of snow after the winter.