南疆西部降雪时空分布特征及其突变分析

Spatiotemporal Distribution and Abrupt Change of Snowfall in the West of South Xinjiang

利用新疆气象信息中心提供的南疆西部17个气象站1961-2010年的逐日降水资料，采用降水变率、降雪贡献率、线性趋势分析、R／S分析等方法，研究南疆西部近50a降雪空间分布、年际变化及其持续性。根据南疆西部独特的地理气候特征，将其分成平原西部、东部及山区3大区域，利用Morlet小波变换分析不同区域周期变化，采用Mann-Kendall突变检验研究不同区域突变特征，结合滑动T检验和信噪比检验确定近50a区域突变年份。结果表明：①南疆西部降雪空间分布不均匀，降雪呈现自西北向东南快速减少格局，降雪对年降水的贡献少，降雪年际波动明显，积雪不稳定。②南疆西部平均年降雪量呈增加趋势，年降雪日数呈减少趋势，平均年降雪量的增大主要与降雪强度有关。③空间上各站倾向率一0．01—0．16mm·a^-1，除巴楚站降雪呈弱的减少趋势外，其他站均为增加趋势；R／S分析显示，除伽师、岳普湖外，大部分测站降雪与过去变化一致，即南疆西部降雪保持持续增加趋势。④近50a小雪贡献率显著减少，中雪贡献率趋于稳定而大雪贡献率显著增加；与其同步，小雪日数减少而中雪、大雪日数缓慢增加；年平均雪量主要由大雪量增加所致，即冬半年降雪具有极端化趋势，易发雪灾。⑤不同区域低频周期特征相似，高频特征有差异，50a时间序列上确定1977年、2000年为平原西部突变年份，1995年为山区突变年份，平原东部突变特征不明显，主要以年际波动为主。

The spatiotemporal distribution, interannual variation and continuity of snowfall in the west of south Xinjiang in recent 50 years were studied using the methods of precipitation variability analysis, snowfall contribution analysis ,linear trend analysis and R/S analysis based on the daily precipitation data observed by 17 meteorological stations in the west of south Xinjiang during the period from 1961 to 2010 ,and the data were provided by Xinjiang Meteorology Information Center. According to the topographical and climatic conditions, the west of south Xinjiang was divided into three regions,i, e. the mountainous area, northwest and southeast plain. The periodicity variation of snowfall in different regions was analyzed with Morle wavelet transform. The abrupt change of snowfall was studied through the Man-Kendall abrupt change test. Combining with a sliding T-test and signal-to-noise ratio test, the abrupt change years were determined. Results are as follows： （1） The spatial distribution of snowfall was not uniform. In the west of south Xinjiang, snowfall decreased rapidly from the northwest to the southeast. Snowfall contributed less to the annual precipitation, and its contribution rate was very unstable. The interannual variation of snowfall was significant; （2） The average annual snowfall in the west of south Xinjiang was in an increase trend, which was related to the snowfall intensity, but the snowfall days were in a decrease trend; （3） Spatially, the tendency rates at the stations varied in a range of -0.01 -0.16 mm · a^-1. Snowfall at all the stations was in an increase trend except a slight decrease at Bachu Meteorological Station; （4） The contribution rate of slight snow decreased significantly, that of moderate snow was relatively stable, and that of heavy snow increased significantly. Moreover, the days of slight snow decreased, but those of moderate and heavy snow increased slowly ; （5） The periodicity of low frequency was similar among different regions, but that of high frequency was different. In recent 50 years, the abrupt change of snowfall occurred in 1977 and 2000 in the western plain,but in 1995 in the mountainous area.