Comparison of Raindrop Size Distributions in a Midlatitude Continental Squall Line during Different Stages as Measured by Parsivel over East China

摘要

The characteristics of raindrop size distributions (DSDs) during a midlatitude continental squall line on 30 July 2014 in east China are studied, and the different life stages are observed by OTT second-generation Particle Size Velocity (Parsivel 2) disdrometers at Chuzhou during the mature stage and Nanjing during the declining stage. The observed rainfall is classified into convective line, transition, and stratiform regions based on the structure of the radar reflectivity Z and rainfall intensity R. The results show that the DSD characteristics of the different precipitation types and different squall-line stages are very different. The convective center has the largest number concentration and quantity of large drops corresponding to the highest rain rate; the rain rates in the trailing edge and stratiform regions are similar, although a lower concentration of small drops is present in the latter. Between the two stages, the drop size and number concentration for the convective center decrease, although the leading edge during the declining stage has more numerous larger drops; the number concentration is similar in the stratiform rainfall, but the drops become much smaller. For the normalized distribution, the scaled spectra for the convective center are closer to an exponential distribution, and the mu value during the declining stage is larger than that during the mature stage for the stratiform region and similar during both stages for the convective center. The declining stage has a larger exponent b and smaller coefficient A in the Z-R relationship based on fits for the entire dataset. Moreover, the R(Z(H), Z(DR)) estimator is more accurate than that when using the Z-R relation algorithm.