2003—2020年新疆北部积雪因子时空变化分析

积雪作为冰冻圈的活跃因子之一，对气候环境的敏感性使其能够快速反映出与气温、降水等气候因素的关系变化，并影响着全球水文变化。本文基于Google Earth Engine（GEE）云平台，对北疆地区2003年6月-2021年6月的MODIS逐日积雪数据进行去云处理，并基于像元计算了积雪覆盖比例（SCP）、积雪覆盖日数（SCD）、积雪开始时间（SOD）和积雪结束时间（SED）。实验结果如下：（1）基于GEE的去云处理方法使得积雪产品相对于气象站点数据的总精度达到91.47%，有利于提高对积雪因子的时空变化分析。（2）北疆地区SCD空间分布差异较大，SCD随海拔的升高而增加，SOD随海拔升高而提前，主要在11-12月出现；SED随海拔升高而推迟，主要在2-3月出现；夏季平均SCD最少，主要分布于天山中部以及阿尔泰山北部区域，约占3.35%，冬季平均SCD最为明显，大于60天的区域占46.3%；而SCP在1月达到最大，7、8月最小。（3）趋势变化上，SCD、SOD以及SED均无明显变化趋势，SCD整体西部呈弱上升趋势，占51.72%，东部呈弱下降趋势，占48.28%；北疆西部SOD呈提前趋势，东部SOD呈推迟趋势，SED整体呈提前趋势。（4）温度对SCD的影响大于降水量；春夏季，SCD与温度、降水量无明显相关性，仅准葛尔盆地东部春季平均SCD与温度呈强正相关；秋冬季，SCD与降水量、温度分别呈现较强的正负相关性。

Analysis of spatial-time variation of snow factors in Northern Xinjiang from 2003 to 2020 based on GEE cloud platform

As one of the active factors of the cryosphere, snow, because of its sensitivity to the climatic environment, changes in relationship with climate factors such as temperature and precipitation can be reflected rapidly and affect global hydrological changes. In this paper, based on Google Earth Engine (GEE) cloud platform, MODIS day-by-day snow data from June 2003 to June 2021 in the northern border area are de-clouded and snow cover percentage (SCP), snow cover days (SCD), snow onset day (SOD) and snow end day (SED) are calculated based on image elements. The experimental results are as follows: (1) The GEE-based de-clouding method results in a total accuracy of 91.47% for snow product relative to meteorological station data, which is conducive to improving the analysis of space-time changes in snow factors.(2) The spatial distribution of SCD varies greatly in northern Xinjiang, with SCD increasing with elevation, SOD advancing with elevation and appearing mainly in November-December; SED postponing with elevation and appearing mainly in February-March; the least average SCD in summer, mainly distributed in the central Tianshan Mountains and the northern Altai Mountains , accounting for about 3.35%, and the average SCD is most obvious in winter, with 46.3% of regions with more than 60 days; while SCP reaches its maximum in January and minimum in July and August.(3) In terms of trend changes, no significant change trend in SCD, SOD and SED, weak ascending trend of SCD is presented in the western, accounting for 51.72%, weak descending trend is presented in the eastern, accounting for 48.28%; advance trend of SOD is presented in the northern border western, delayed trend of SOD is presented in the eastern, and advance trend of SED is presented in the overall area. (4) The effect of temperature on SCD is greater than precipitation, in spring and summer, there is no obvious correlation between SCD and temperature and precipitation, and strong positive correlations are only presented in the eastern part of the Junggar Basin in spring mean SCD and temperature; in autumn and winter, strong positive and negative correlations are found between SCD and precipitation and temperature, respectively.