基于不同方法的中国天山山区降水形态分离研究

基于天山山区1950s-1979年27个气象站点的日平均气温及标注的各类型降水资料,运用频率求交法和概率保证法并结合海拔高程,研究并分析了各站点降水形态转化的临界气温及固液态降水分离的阈值温度空间分布特征及原因,预测了天山山区1980-2014年雪雨比变化。结果表明:天山山区各站点降水形态转化的临界气温及固液态降水分离的阈值温度其空间分布上整体呈现出北坡小于南坡而雪雨比南坡小于北坡的变化规律,且三者均随着海拔高程的增加而增大,两种方法获得的结果基本一致。深入明晰了天山山区降水形态随温度变化特征,为天山山区水文模型中有关参数的选取提供科学的参考。

Separation of precipitation forms based on different methods in Tianshan mountainous area,Northwest China

Tianshan mountainous area is located in the alpine region,Northwest China,where solid precipitation plays an important role in total precipitation volume.Separating precipitation into rain and snow is very signifi-cant to estimate whether precipitation is available for runoff,soil infiltration and evaporation.And it is also critical for water balance calculation and hydrologic simulation process in alpine regions.Based on daily mean temperature and precipitation labeled with different types from 27 meteorological stations in Tianshan mountainous area during 1950s-1979,combined with altitude,this paper analyzed the spatial distribution of critical temperature (CT) of precipitation transformation using frequency intersection method and threshold temperature (TT) which separate solid from liquid precipitation using probability guarantee method.Then the ratios of snowfall to rainfall from 1980 to 2014 were predicted in this area.The results showed that different stations had different CT values and TT values in a certain temperature range during 1950s-1979.The range of CT values observed in Tianshan mountainous area was found from 1.57 ℃ to 5.70 ℃ while TT values from 1.36 ℃ to 5.48 ℃.As a whole,CT and TT values in the north slope of Tianshan mountainous area were less than that in the south slope.And the ratios of snowfall to rainfall in the north slope were generally larger than that in the south slope.All three of them increased with the rising of altitude.But the altitude was not the only factor which impact the change of TT,and other meteorological factors such as atmospheric pressure,atmospheric humidity may impact on it.It is also shown that CT values based on the frequency intersection method were similar to TT values based on the probability guarantee method.Through an in-depth comparative analysis of the spatial distribution of CT and TT values,this study could provide reference for the selection of parameters in the hydrological modelling in Tianshan mountainous area.