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

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.