Analyzing the Relationship between Terminal Velocity of Raindrops and VHF Backscatter from Precipitation

Abstract

β=− Aexp () , where A is the coefficient in the relation VA D B = , D is the diameter of the rain drop, and ξ is a factor related to radar parameters and precipitation intensity. An examination of this exponential relationship between α and β shows that the radar experimental result was in excellent agreement with the theoretical prediction. From the observational results made with the Chung-Li VHF radar, we find that the value of β varied in the range 0.02 - 0.14, which is significantly different from the theoretical value of 0.07143. In addition, the β value is found to be positively correlated with the vertical air velocity, which is variable in nature. We, therefore, presume that the vertical air velocity seems to play a crucial factor in governing the change in the β value to explain the large scatter of the observed β values. The application of ξ value to the estimation of the precipitation intensity is also discussed in the text.