中文摘要：

基于2001—2015年MOD10A1/MYD10A1、MOD13Q1以及相关气象数据,采用积雪持续时间比率法,监测了天山山区的季节雪线高程,分析了其变化特征及影响因子。结果表明：（1）近15年天山山区雪线整体呈显著上升趋势,平均高程3 680 m左右,其中,北坡、伊犁河谷、南坡季节雪线的稳定性依次减弱,平均高程分别为3 620 m、3 390 m及3 820 m;空间上雪线高程呈现南高北低、东高西低的纬度地带性分布特点。（2）年际尺度上,气温是影响天山山区雪线高程的主控因素,呈显著正相关,南北坡与之相同,但伊犁河谷则降水是影响其变化的主控因素,呈显著负相关;季节尺度上,夏季气温、冬季降水是影响雪线高程的主控因素,降水与其呈负相关,但气温较高的地区,夏秋季降水会促进积雪融化,使雪线高程上升;月尺度上,7月气温、1月降水对其影响最明显,且存在一定的滞后反应。（3）天山山区雪线高程比零度层低800 m左右,两者呈较好正相关;雪线高程与NDVI（Normalized Difference Vegetation Index）呈负相关,植被覆盖较好区域,同年NDVI与雪线高程相关性较好,植被覆盖较差区域,前一年NDVI与其相关性较好。

英文摘要：

We monitored the seasonal snowline elevation on Tianshan Mountains and analyzed its changing character- istics and impact factors by adopting the snow cover duration ratio method, based on MOD10A1/MYD10A1, MOD13Q1 and related meteorological data from 2001 to 2015. The results show that： （1） The overall snowline on Tian- shan Mountains have been on the rise significantly in the recent 15 years, with average elevation of about 3 680 meters, wherein the stability of the snow lines on the northern slope of Tianshan Mountains, Yili River Valley and the southern slope of Tianshan Mountains has weakened successively, the average elevations of which are 3 620, 3 390 and 3 820 meters respectively; the snowline elevation in space shows the latitudinal zonality distribution charac- teristics of being high in the south and low in the north and high in the east and low in the west. （2） On the interannual scale, temperature is the main controlling factor which influences the snowline elevation of Tianshan Mountains, with significant positive correlation, so are the case on the south and north slopes of the Tianshan Mountains, while in Yili River Valley, precipitation is the main controlling factor that influences its change, with significant negative correla- tion; on the seasonal scale, the temperature in summer and the precipitation in winter are the main controlling factors which influence the snowline elevation, precipitation assumes negative correlation with it, while in areas with higher temperature, the precipitation in summer and autumn can facilitate snow melting, which makes the snowline elevation rise; on the monthly scale, the temperature in July and the precipitation in January are most obvious in affecting it, and there exists a certain lag in response. （3） The snowline elevation of Tianshan Mountains is about 800 meters lower than the zero degree layer, the two have a good positive correlation; snowline elevation shows negative correlation with NDVI, in areas with good vegetation cover, NDVI and sn