Regional variability of summertime raindrop size distribution from a network of disdrometers in Beijing

Abstract

Regional raindrop size distribution (DSD) features are poorly understood due to the lack of observations. Here we investigate the regional variability of summertime DSD in Beijing, using the DSD observations from ten disdrometer sites from April to September 2017. The characteristics of DSD are analyzed for both convective and stratiform precipitation, mainly classified by rain rate (R). The shape (μ) and slope (λ) parameters follow a second-degree polynomial regression relationship for both stratiform and convective precipitation. On average, stratiform precipitation is found to have larger values of μ and λ than convective precipitation, whereas convective precipitation has a larger mass-weighted mean diameter (Dm) and a generalized intercept parameter (Nw). Interestingly, the north of Beijing has larger values of μ and λ, as opposed to Dm and Nw that exhibit greater values in the south, which could probably be attributed to terrain differences. The rain rate dependence on DSD is analyzed as well. In general, the Dm-R and Nw-R relationships follow a power-law distribution, and both Dm and Nw increase significantly with R. As the rain rate increases, Dm keeps increasing to around 1.5 mm until an equilibrium state is reached. The findings obtained here could provide useful reference for better estimations of rainfall using the remote sensing techniques.