Observation Study On The Physical Mechanism For Convective Precipitation Over Leizhou Peninsula

In order to investigate the physical mechanism diversity of precipitation between different synoptic systems and different parts of cloud, the measurement precision of Particle Size and Velocity (Parsivel) optical disdrometer were analyzed in the first place, and the data observed from two Parsivels were analyzed to research the physical mechanism for convective precipitation under the effect of subtropical high's strengthening westwards or shrinking eastward(SH) and tropical synoptic systems(TC) with the data from automatic weather station and Doppler radar over Leizhou Peninsula from July to August, 2007. Three cases were selected to realize the evolvement of physics, such as the mean diameter, root-mean-square diameter, root-cube-diameter, mean volume diameter, maximum diameter, rainfall and radar echo intensity, and the characteristics of raindrop size distribution. The results indicated that: the rainfall estimate by Parsivel appeared good agreement with the data from automatic weather station; the duration of TC was commonly longer than SH, and the range of variety of number density and liquid water content under TC were centralized, with smaller values than that under SH, however, the variety range of the mean diameter, root-mean-square diameter, root-cube-diameter, mean volume diameter, maximum diameter under TC were larger than SH with smaller values. The values of rainfall, liquid water content, raindrop size and number density under the part in cloud which had strong convection with wider raindrop size distributions were higher than that under the part which had weak convection. The evolvement of maximum diameters was agreed with radar echo intensity. The mean volume diameters D₀ were constant basically when the value of rainfall I is larger; when I was smaller, the evolvement of D₀ appeared agree with I; and D₀ became oscillate acutely when the precipitation starting or ending. The distribution parameterμand were agree with a quadratic polynomial. The coefficient A, b in Z-I relationship were obtained for every precipitation, and the relationship under SH and TC over Zhangjiang were Z=225I^1.6 and Z=177I^1.5, respectively; and Z=225I^1.6 and Z=204I^1.5 over Suixi, respectively.