Structure analysis of heavy precipitation over the eastern slope of the Tibetan Plateau based on TRMM data

The horizontal and vertical structure of a heavy rainfall system occurred over the eastern slope of the Tibetan Plateau on 21 July 2013 has been studied by using TRMM data, NCEP-FNL operational global analysis data and ERA-Interim analysis data in combination with Doppler radar and other surface observational data.The result indicates that the heavy rainfall system, which was triggered by unstable stratification combined with 700 hPa shear line and surface convergence line, consisted of a main stratiform precipitation cloud cluster and several scattered convective precipitation clouds characterized by high precipitation intensity. Although the total amount of convective rainfall was less than that of the stratiform rainfall, averaged convective rainfall rate was 4.7 times larger than the stratiform rainfall rate and convective rainfall accounted for 25.6% of the total rainfall. The horizontal scale was about 20-50 km for a reference precipitation rate of 10 mm/h. The spectral distribution of convective rainfall intensity indicated that the rainfall intensity was largely concentrated within the range of 1-50 mm/h, and the rainfall with intensity of 20-30 mm/h made the greatest contribution to total rainfall. Meanwhile, almost 90% of the stratiform rainfall was below 10 mm/h. Vertically, the top of the heavy precipitation system could reach up to 12 km above the ground with a low core structure (below 6 km). Most precipitation occurred in the levels from ground to near 7 km and the distribution of precipitation rate in vertical was inhomogeneous. In general, precipitation decreased with increasing height, but within a certain range of height, convective precipitation increased with height. As a verification dataset and supplement for TRMM PR, Doppler radar observations also showed the characteristics of low precipitation center in this rainfall event.