The six main pastoral areas (Xinjiang, Tibet, Qinghai, Sichuan, Gansu, and Inner Mongolia) are the important production base of animal husbandry in China, and also the frequent snow disaster areas. To obtain snow conditions of these pastoral areas timely and accurately is valuable for disaster prevention and reduction. With higher spatial resolution and stronger interpretation, optical remote sensing is better for snow cover identification, but it is vulnerable to cloudy weather. Microwave remote sensing is not easy affected by cloud, but identification accuracy is not high. In this paper, we integrated the two kinds of data to identify snow covers. The MODIS data (optical) are used in cloud-free areas, while AMSR-E data (microwave) are used in the rest areas. According to the method, each single day is defined as monitoring unit, and every ten days compose the image combining unit. The monitoring area covers the six main pastoral areas of China. The monitoring duration is from October 1st, 2008 to March 31st, 2009. The main conclusions are as follows: 1) The grasslands Northern Xinjiang, eastern Tibet, south-west of Qinghai, central Gansu, northern Sichuan, the Xilin Gol, and Hulunbeier of Inner Mongolia are the areas with frequent snow cover. 2) The monitoring area possesses the smallest snow cover in December 10th to 20th, while it has the biggest snow cover in January 1st to 10th. 3) During the monitoring period, the fluctuation of snow-cover area can be concluded in three types: Xinjiang and Inner Mongolia have the single peaks, Tibet and Qinghai have three peaks and three valleys, and Sichuan and Gansu are relatively stable.
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