Abstract: The Qilian Mountains is located on the northeastern edge of the Qinghai-Xizang Plateau.It has always been known as the ice source reservoir and is the source of life that supports the water resources of the Hexi Corridor.Based on MODIS snow cover products,the temporal and spatial variation characteristics of snow cover and snow line in Qilian Mountains from 2011 to 2020 were analyzed,and the dominant climatic factors affecting their changes were analyzed in combination with temperature and precipitation data.Research results show that: ①The Qilian Mountains are dominated by short-day snow areas,and the annual snow areas are mainly distributed in the western part of the Qilian Mountains.②The spatial distribution of the whole year snow area and the permanent snow line is obviously different.The western section is larger than the eastern section in the basin,and the altitude shows the characteristics of normal distribution.The area of the whole year snow area in the northeast slope direction is higher than that in the southwest slope direction,and the height of the permanent snow line is lower than that in the southwest slope direction.③The annual variation of seasonal snow cover area generally shows a trend of decreasing first and then increasing.The changes of seasonal temperature and precipitation are significantly correlated with the changes of seasonal snow cover.④The influence of temperature change on snow cover in the high-altitude mountainous area of the western section is weak,and the snow accumulation caused by precipitation has a more significant impact on the annual snow cover area and the permanent snow line.The snow cover in the low altitude area of the eastern section is difficult to accumulate all year round,and the influence of solar radiation and rain erosion during the snow melting period on the annual snow cover area and the permanent snow line is more significant.

Key words: Qilian Mountains, snow cover, snow line, spatio-temporal variation, MODIS