Analysis of Terminal Velocity and VHF Backscatter of Precipitation Particles Using Chung-Li VHF Radar Combined with Ground-Based Disdrometer

Ching-Lun Su ； Yen-Hsyang Chu

《Terrestrial, Atmospheric and Oceanic Sciences》 18卷1期 (2007/03) Pp. 97-116

並列摘要

The backscatter from precipitation particles observed by the vertically pointed antenna beam of the Chung-Li VHF radar and the drop size distributions measured by a ground-based disdrometer co-located at the radar site are analyzed and studied in this article. We find that the disdrometermeasured drop size distribution can be well approximated to a Gamma distribution. On the basis of this property and a power law approximation to the fallspeed-diameter relation V(subscript D)=AD(superscript B), we derive the theoretical relation between terminal velocity V(subscript D) and range-corrected VHF backscatter P of the precipitation particles. We find that the V(subscript D)- P relation follows a power law in the form of V(subscript D)=α P(superscript β), where α and β are both the functions of the precipitation parameters. Chu et al. (1999) first found that the relation between α and β can be empirically approximated to an exponential form of α=Ae(superscript ξβ), where β is a function of B and ξ is a factor associated with precipitation. In this article, under the assumptions of the Gamma distribution of the drop size distribution and the power-law relation between V(subscript D) and D, we theoretically show that the analytical relation between α and β indeed follows an exponential form of α=Ae(superscript ξβ), where ξ is a function of the drop size distribution. The experimental results obtained by the Chung-Li VHF radar combined with the ground-based disdrometer measurements validate the exponential approximation to the α-β relation. The uses of the α-β relation for the investigations of the rainfall rate and properties of drop size distribution are presented and discussed.

並列關鍵字

VHF Radar ； Precipitation ； Terminal velovity ； Reflectivity