祁连山区能量场特征与降水分布的关系分析

Analyses of Energy Field Characteristics and Precipitation in Qilian Mountains

采用祁连山地形云野外观测的资料,分西南气流移动、西南气流阻塞、西北和平直西风气流型,用三维插值方法分型计算湿静力总温度Tσ场和总降水场,分析了不同的大尺度流型下冷龙岭西段降水分布与能量场特征的关系.对比山脉南北坡与山外同高度Tσ的日变化,发现山坡Tσ全天高于山外,山脉呈高能岛其外围有能量锋,不同流型下南北坡能量锋强度和Tσ垂直廓线有明显差异,其与地形云降水有较好的对应关系.在局地环境因子中,冷龙岭南北坡平均日雨量与对流不稳定度指数(ΔTσ=地面Tσ-500 hPaTσ)的负相关最高,其次是地面至300 hPa平均Tσ呈正相关.可看出,高能弱对流不稳定时日雨量最大,反之低能强对流不稳定时多为小雨或无雨;冷龙岭南北坡的能量锋强度与日雨量相关不明显.

In this paper,using observation data of orographic cloud over the Qilian Mountains,the air current was divided into southwest air current moving pattern,southwest air current obstruction pattern,northwest air current pattern and straight westerly pattern.Wet static total temperature T-σ field and total precipitation field have been calculated with three-dimensional interpolation method.For different macro scale circulation pattern,the relation between precipitation distribution and energy field characteristics in the western Lenglong Range has been analyzed.Contrasting the daily variations of T-σ between the north and south slopes of the range and at the same altitude outside the range,it is found that T-σ inside the range is always higher that outside the range,with a high energy island over the range and energy fronts outside the range.Energy front intensity and T-σ vertical profile are very different for different circulation patterns,corresponding to orographic cloud precipitation very well.The daily mean precipitation has maximum negative correlation with convective instability index（ΔT-σ=surface T-σ subtracts T-σ at 500 hPa）.However,it has positive correlation with the T-σ averaged from the surface to 300 hPa.One can see that weak convective instability day with high energy has maximum daily precipitation,whereas strong convective instability day with low energy has less precipitation or not.There is not obvious relationship between energy front intensity and daily precipitation.