Raindrop size distribution (RSD) characteristics of summer and winter seasons over north Taiwan are analyzed by using long‐term (~12 years) raindrop spectra from Joss‐Waldvogel disdrometer located at National Central University (24°58′N, 121°10′E), Taiwan. Along with the disdrometer data, radar reflectivity mosaic from six ground‐based radars, Tropical Rainfall Measuring Mission, Moderate Resolution Imaging Spectroradiometer, and ERA‐Interim data sets are used to establish the dynamical and microphysical characteristics of summer and winter rainfall. Significant differences in raindrop spectra of summer and winter rainfall are noticed. Winter rainfall has a higher concentration of small drops and a lower concentration of midsize and large drops when compared to summer rainfall. RSD stratified on the basis of rain rate showed a higher mass‐weighted mean diameter ( D _m ) and a lower normalized intercept parameter (log ₁₀ N _w ) in summer than winter. Similarly, diurnal variation of RSD showed higher D _m and lower log ₁₀ N _w values in summer as compared to winter rainfall. In addition, for both seasons, the mean value of D _m is higher in convective precipitation than stratiform. Radar reflectivity ( Z ) and rain rate ( R ) relations ( Z = A * R ^b ) showed a clear demarcation between summer and winter rainfall. Higher ground temperatures, deeply extended clouds with intense convective activity in summer modified the RSD through evaporation, drop sorting, and collision‐coalescence processes resulting with higher D _m and lower log ₁₀ N _w values in summer as compared to winter rainfall.

Raindrop size distribution (RSD) characteristics in summer season rainfall of two observational sites (Taiwan (24°58′N, 121°10′E) and Palau (7°20′N, 134°28′E)) in western Pacific are studied by using five years of impact type disdrometer data. In addition to disdrometer data, Tropical Rainfall Measuring Mission, Moderate Resolution Imaging Spectroradiometer, and ERA‐Interim data sets are used to illustrate the dynamical and microphysical characteristics associated with summer season rainfall of Taiwan and Palau. Taiwan and Palau's raindrop spectra showed a significant difference, with a higher concentration of middle and large drops in Taiwan than Palau rainfall. RSD stratified on the basis of rain rate showed a higher mass‐weighted mean diameter (D_m) and a lower normalized intercept parameter (log₁₀N_w) in Taiwan than Palau rainfall. Precipitation classification into stratiform and convective regimes showed higher D_m values in Taiwan than Palau. Furthermore, for both the locations, the convective precipitation has a higher D_m value than stratiform precipitation. The radar reflectivity‐rain rate relations (Z = A*R^b) of Taiwan and Palau showed a clear variation in the coefficient and a less variation in exponent values. Terrain‐influenced clouds extended to higher altitudes over Taiwan resulted with higher D_m and lower log₁₀N_w values as compared to Palau.

We made an effort to inspect the raindrop size distribution (RSD) characteristics of Indian Ocean and Pacific Ocean tropical cyclones (TCs) using ground-based disdrometer measurements from observational sites in India and Taiwan. Five TCs (2010-2013) from the Indian Ocean and six TCs (2014-2016) from the Pacific Ocean were measured using particle size and velocity disdrometers installed in south India and south Taiwan, respectively. Significant differences between the RSDs of Indian Ocean and Pacific Ocean TCs are noticed. For example, a higher number of small drops is observed in Indian Ocean TCs, whereas Pacific Ocean TCs have more mid-size and large drops. RSDs of Pacific Ocean TCs have higher mass-weighted mean diameter and lower normalized intercept parameter than Indian Ocean TCs. RSD values quantified based on rainfall rate and precipitation types also showed similar characteristics between Indian Ocean and Pacific Ocean TCs. The radar reflectivity and rainfall rate (Z-R) relations and shape and slope (μ-Λ) relations of both oceanic (Indian and Pacific) TCs are found to be distinctly different. Possible causes for the dissimilarities in RSD features between Indian Ocean and Pacific Ocean TCs are due to relative differences in water vapor availability and convective activity between TCs in these two oceanic basins.

Rainfall erosivity (or water erosion) has severe implications on agriculture, water, and land use management. Though, there were Rainfall erosivity studies on regional and global scale, tropical cyclones’ Rainfall erosivity is poorly assessed and have not been documented for one of the most cyclones affecting regions of the world like Taiwan. Here, using 15-years of raindrop size distributions (RSD) and 60-years of hourly rain gauges data, we estimated cyclones (also called typhoons) rainfall erosivity over Taiwan, and establish that typhoons’ mean rainfall erosivity is higher than the global mean rainfall erosivity. Moreover, regional variability of typhoons rainfall erosivity showed an increasing pattern from north to south (Taipei to Pingtung), with relatively higher values over eastern and southern parts of Taiwan. The annual mean erosivity of typhoons rainfall showed raising trends over eastern and southern Taiwan during 1958–2017. Our results provide an insight in assessing the land use and agricultural management for Taiwan.