Microphysical Characteristics and Types of Precipitation for Different Seasons over North Taiwan

Abstract

 In this work, long-term (10 years) raindrop size distribution (RSD) measurements from the Joss–Waldvogel Disdrometer (JWD) installed at the National Central University (NCU) (24°58′6″N, 121°11′27″E), Taiwan, and the vertical profile of radar reflectivity were used to analyze the variations in the gamma parameters of six seasons (winter, spring, mei-yu, summer, typhoon, and autumn) and types of precipitation. The normalized gamma distribution of RSD revealed that the highest mean D_m (mass-weighted average diameter) values occurred in the summer, whereas the highest mean log₁₀ N_w (normalized intercept parameter) values were found in the winter. Furthermore, most of the rain falling at a rate of less than 20 mm h⁻¹ occurs in Northern Taiwan. In this study, we used radar reflectivity to differentiate between convective and stratiform systems. It was revealed that the mean D_m values are higher in convective systems, whereas the mean log₁₀ N_w values are higher in stratiform systems. The structure of RSD in stratiform systems remains constant in all seasons; however, convection is similar to maritime type. The microphysical characteristics that are responsible for the different RSD features in different seasons and types of precipitation are illustrated with the help of contoured frequency by altitude diagrams of radar reflectivity.