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基于星载测雨雷达探测资料的青藏高原东南坡降水个例分析

Case study of precipitation over southeast slope of Tibetan Plateau based on TRMM PR data

  • 摘要: 针对青藏高原东南坡降水云内大气温湿结构缺乏认知的情况,利用TRMM PR资料、ERA5再分析资料和IGRA等资料,分析了青藏高原东南坡三个降水个例水平分布特征、垂直结构特征及天气背景特征。结果表明:(1) 高原东南坡以冰云及混合云降水为主,近地表降水率及回波顶高度分布不均;地表雨强越大,回波顶高度越高,云顶温度越低。虽然对流降水样本数较少,但其降水强度集中在10~50 mm·h-1,对总降水量的贡献较大。(2) 从降水垂直结构来看,降水率自高空至6 km高度较为均匀的增大,体现了粒子的碰并增长过程,在4—6 km高度,降水释放潜热最大,粒子尺寸也更大,大于40 dBz的反射率因子多分布在此高度范围内。(3) 雷达反射率因子的垂直变率在5 km附近有一狭长大值区,反映了融化层的存在,融化层会随着回波顶高度的变化表现出轻微的抬升或下降。(4) 三个降水个例均发生在低层辐合高层辐散的流场中,降水落区水汽充沛,且云体对流有效位能较大,有利于降水系统的产生和发展。

     

    Abstract: In light of the lack of cognition of the vertical structure of temperature and humidity inside the precipitating clouds over southeast slope of Tibetan Plateau, characteristics of horizontal distribution, vertical structure and weather background of three precipitation cases are investigated based on datasets detected by TRMM PR, ERA5 data as well as IGRA data. The results indicate that: (1) The main precipitation type over southeast slope of Tibetan Plateau are ice cloud precipitation and mixed cloud precipitation. The distribution of near-surface rain rate and echo top height are uneven. The echo top height becomes higher with the increase of rain intensity, while the temperature of cloud top gets lower. Although there are few samples of convective precipitation, the precipitation intensity is mainly concentrated in 10—50 mm·h-1, and its contribution to the total precipitation is large. (2) The vertical profiles show that rain rate increases uniformly from high altitude to 6 km, which reflects the accretion process of particles. At 4—6 km height range, the latent heat released by precipitation is the largest, and the particle size is larger, and radar echoes that are larger than 40 dBz mostly appear in the range. (3) The vertical variability of reflectivity factor has a narrow high value region near 5 km, presenting the existence of melting layer; the melting layer will slightly rise or fall with the change of echo top height. (4) Three precipitation cases all occur in the flow field of convergence at the lower level and divergence at the upper level. The precipitation area is rich in water vapor, and the convective available potential energy is large, which is conducive to the generation and development of precipitation system.

     

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