Comparison study of raindrop size distribution in three regions of Shandong Province

To study the microphysical characteristics of precipitation in different regions of Shandong province-the Yellow River Delta, inland region and coastal region, the raindrop spectrum data at three sites (Kenli, Pingyin, and Jiaonan) from 2017 to 2020 were used to compare the raindrop size distribution (DSD) characteristics of different rain rates (R) and rainfall types (stratiform and convective rainfall). The results are as follows. (1) In 6 rain rate levels at 3 sites, there were certain degree of differences in the DSD spectral, the spectra width of mean DSD, and the contribution of different precipitation levels to the total precipitation amount. (2) In stratiform precipitation, the average DSD characteristics of Pingyin and Jiaonan were comparable to each other, but differences were found in convective precipitation at these 3 sites. (3) The distribution of the normalized Gamma spectral intercept parameter (log₁₀N_w) and the mass-weighted average diameter (D_m) showed that, log₁₀N_w of Kenli station was the lowest during stratiform precipitation. While the comparison with other national and international stations demonstrated that the distribution of log₁₀N_w versus D_m from Pingin agreed with the observations in Seoul, Korea. (4) The fitting curves of the shape parameter (μ) and slope parameter (λ) from the Gamma distribution exhibited localized characteristics. According to the trend of μ and λ with R at all 3 sites, R=10 mm·h^-1 can be used as a criterion for precipitation classification. At all three sites, when R increased greater than 100 mm·h^-1, the values of μ remained nearly constant towards 1~2, while the values of λ tend to 2. (5) The fitting results between the reflectivity factor (Z) and R (Z=AR^b) at 3 sites indicated that, the typical Z-R fitting formula (Z=300R^1.40) for weather radars overestimated the precipitation of Kenli and underestimated the precipitation of Jiaonan. The values of A and b in the Z-R fitting formula also exhibited differences between convective and stratiform precipitation.