为研究高原地区降水相态变化特征,利用西藏自治区39个气象站点降水和温度等观测资料,分析了该区域1979-2013年的降雪/降水天数比例特征,结果表明:西藏地区(9月-次年5月)平均雪水天水比为19.29％,其比值空间分布不均,西藏东部及腹地偏小,北、西、南3面各站偏大;指数关系可以较好的拟合西藏地区雪水比率与温度、海拔的关系,可对缺少观测资料的高原地区雪水比天数特征进行初步估算;近35年西藏地区雪水天数比总体呈现显著下降趋势,其倾向率为-1.27％/10a,除西藏南部小部分区域站点呈增加趋势外,其余站点雪水比率均呈减小趋势,其春、秋季下降最为显著,高海拔地区(海拔＞4500 m)雪水比率下降最为显著.%In order to study the characteristics of precipitation phase in plateau area,the observation data from 39 stations in Tibet during 1929-2013 were used,and the changes of snowfall/precipitation (SD/PD) ratio studied.The main conclusions obtained are as follows:main conclusions obtained are as follows:the average of SD/PD ratio in Tibet is 19.29 ％,and its spatial distribution is uneven.The value of SD/PD is low at east and hinterland of Tibet,while at north/west/south boundary of Tibet is high;the relationship between SD/PD and temperature and latitude is described accurately by exponential functions,and it will benefit places in Tibet which is lack of observational data.SD/PD ratio in Tibet has decreased distinctly during the recent 35 years,and the tendency rate is-1.27 ％/10a.Except for few stations in south of Tibet,the SD/PD ratio is decreasing,and it is more significant in spring and autumn.The ratio of high latitude stations (＞4500 m) has faster decline than others.
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