Peripheral Cloud System Structure and Precipitation Characteristics of Typhoon Bebinca(1816)

Abstract

Based on radar and raindrop disdrometer observations, the evolution of microphysical features and raindrop size distribution of the precipitation in different peripheral cloud system structures during Typhoon Bebinca(1816) affecting Hainan Island are compared at Haikou and Tunchang stations. The results show that, convective cloud system in Haikou area strengthens with the development of precipitation cloud system, while in Tunchang area stratiform cloud precipitation is dominant, which causes some differences between raindrop size distributions. During the entire precipitaion process, the average raindrop size distribution of Haikou and Tunchang stations are unimodal spectrum, the number concentration of 1 mm raindrops at Tunchang Station is larger, while there are more large raindrops at Haikou Station. The raindrops observed at Haikou and Tunchang stations are mainly with a diameter of less than 1 mm, and the raindrop number concentration accounts for over 50% of the total concentration, but its contribution to the rain intensity is 3.7% and 17.15%, respectively. The raindrops with a diameter of 1-3 mm at Tunchang Station contributes the most to the rain intensity, reaching 79.84%. The raindrop number concentration of Haikou Station decreases with the increase of raindrop diameter, but its contribution to the rainfall intensity increases, and the contribution of raindrops with diameter greater than 3 mm to the total rainfall intensity reaches 56.61%. Comparing the evolution of microphysical parameters, the characteristic parameter curve of Haikou Station is unevenly distributed in time, showing paroxysmal heavy precipitation, while the characteristic parameter curve of Tunchang Station has little fluctuation, and the precipitation is smaller, uniform, and continuous than that of Haikou Station. In the time evolution of raindrop size distribution, Haikou Station is always in the form of single peak with a wider spectrum, while at Tunchang Station it is mainly single peak, with fewer double peaks. When the rainfall intensity increases, the raindrop size distribution at both stations increases in the diameter range of 1 mm, the spectrum width expands rapidly, and the large-scale raindrops will increase in number, especially the large scale raindrops with a diameter of more than 3 mm at Haikou Station. However, the increase in the number concentration of small-scale raindrops does not lead to an increase in rainfall intensity. The raindrop size distribution conforms to Gamma distribution, and the slope parameter and shape parameter comply with binomial relationship.

Keywords

• cloud system structure
• raindrop size distribution