2001-2015年天山山区积雪时空变化及其与温度和降水的关系

采用2001-2015年MODIS积雪和陆表温度数据、中国高时空分辨率降水数据，基于趋势分析和相关分析方法，分析了天山山区积雪时空变化及其与温度和降水的关系。结果表明：（1）年内积雪面积变化受海拔影响，海拔≤4 000 m，呈单峰型分布，积雪面积冬季大，夏季小；海拔介于4 000~≤5 000 m，积雪面积分别在春季和秋季出现两次峰值；海拔>5 000 m，积雪面积变化与低海拔相反，在夏季达到最大，冬季最小。就年际变化而言，全区积雪面积呈略微减少趋势，其中秋季略微增加，春季变化不大，冬季和夏季明显减少。（2）积雪覆盖频率受水汽来向和地形影响，呈西高东低、北高南低分布格局，与海拔呈正相关。山区大部分区域积雪覆盖频率呈减少趋势，其中海拔介于3 600~≤4 600 m的积雪覆盖频率减少最为显著。（3）在春、夏季，温度是决定积雪面积变化的主要因素，与积雪面积呈负相关；在秋、冬季，降水对积雪面积变化的贡献大于温度，与积雪面积呈正相关。（4）积雪覆盖频率整体上与年均温度呈负相关，与降水呈低度正相关，相关程度及显著性水平在空间分布上存在差异，温度对积雪覆盖频率变化的贡献大于降水。

Spatial-temporal variation of snow cover in the Tianshan Mountains from 2001 to 2015,and its relation to temperature and precipitation

In this study, the spatial and temporal variation of snow cover in the Tianshan Mountains and its relation to temperature and precipitation were analyzed by using linear tendency estimate and correlation analysis, based on the Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover, MODIS land surface temperature data and China Meteorological Forcing Dataset during 2001-2015. The results demonstrated that:(1) There was obvious difference in monthly distribution of the snow cover percentage (SCP) for different elevation zones; the annual distribution of snow cover percentage presented a unimodal pattern below 4 000 m and over 5 000 m altitude; the maximum and minimum snow cover percentages occurred in winter and summer below 4 000 m, while the maximum and minimum values appeared in summer and winter over 5 000 m, respectively; the seasonal cycle of snow cover percentage exhibited a bimodal distribution between 4 000 m and 5 000 m altitude, with a peak in spring and autumn; during 2001-2015, there was a slight decreasing trend in annual mean snow cover percentage in Tianshan Mountains. However, there were differences in change trend of snow cover percentage in various seasons:there was a slight increasing trend in autumn, while a decreasing trend had been found in other seasons with more obvious in winter and summer. (2) The snow cover frequency (SCF) presented a spatial pattern from west high to east low and north high to south low due to water vapor sources and topography, and showed a positive correlation with elevation; the SCF had showed a decreasing trend during 2001-2015 in the Tianshan Mountains with more obvious in the altitude range between 3 600 m and 4 600 m. (3) In spring and summer, the temperature was the main cause of the change of snow cover percentage, and showed a negative correlation with snow; while in autumn and winter, precipitation was the main cause of the snow change, and had a positive correlation with snow. (4) Overall, the snow cover frequency showed a negative correlation with annual mean temperature and a positive correlation with precipitation; although there were great spatial differences in the degree of correlation and the significance level, the impact of temperature was larger than that of precipitation on SCF change.