Seasonal variation of microphysical characteristics for different rainfall types in the Tianshan Mountains of China

Abstract

Three-year (2020−2022) raindrop size distribution (DSD) measurements from a second-generation PARSIVEL disdrometer deployed at Zhaosu, which is located in the Tianshan Mountains of China, are analyzed to investigate the seasonal variability of microphysical characteristics of two types of rainfall. Rainfall at Zhaosu is classified as stratiform rainfall and convective rainfall in the normalized intercept parameter–median volume diameter (log10Nw–D0) and log10Nw–mass-weighted mean diameter (log10Nw–Dm) spaces, respectively. Both stratiform rainfall and convective rainfall samples in the log10Nw–D0 space are more than three times those in the log10Nw–Dm space, accompanied by smaller mean rainfall rate (R). Rainfall in summer (spring) has the lowest (highest) concentration of small-size raindrops, while rainfall in fall (summer) has the lowest (highest) concentration of mid- and large-size raindrops, accompanied by the largest (smallest) mean Dm and D0 values and the smallest (largest) mean log10Nw values in summer (spring). Convective rainfall exhibits more significant seasonal variation in microphysical parameters and DSD than stratiform rainfall, whether in the log10Nw–D0 space or the log10Nw–Dm space. The convective rainfall in spring is more like maritime cluster, whereas that in summer is more like continental cluster in the log10Nw–Dm space. Furthermore, in the log10Nw–D0 and log10Nw–Dm spaces, localized relationships of radar reflectivity factor – R (Z–R) and shape parameter – slope parameter (μ–∧) are derived across seasons for different rainfall types. The results indicate that there are significant seasonal variations in the microphysical characteristics of rainfall in the Tianshan Mountains of China for the two rainfall types. This study further emphasizes that different classification schemes for rainfall types can lead to significant differences in the characteristics of DSD, Z–R, and μ–∧ relationships for different rainfall types.