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.

Due to the severe threat of tropical cyclones to human life, recent years have witnessed an increase in the investigations on raindrop size distributions of tropical cyclones to improve their quantitative precipitation estimation algorithms and modeling simulations. So far, the raindrop size distributions of tropical cyclones using disdrometer measurements have been conducted at coastal and inland stations, but such studies are still missing for oceanic locations. To the authors’ knowledge, the current study examines—for the first time—the raindrop size distributions of fourteen tropical cyclones observed (during 2003–2007) at an oceanic station, Aimeliik, located in the Palau islands in the Western Pacific. The raindrop size distributions of Western Pacific tropical cyclones measured in the Palau islands showed unlike characteristics between stratiform and convective clusters, with a larger mass-weighted mean diameter and smaller normalized intercept parameter in the convective type. The contribution of the drop diameters to the total number concentration showed a gradual decrease with the increase in drop diameter size. Raindrop size distributions of Western Pacific tropical cyclones measured in the Palau islands differed slightly from Taiwan and Japan. The helpfulness of empirical relations in raindrop size distribution in rainfall estimation algorithms of ground-based (Z–R, μ–Λ, D_m–R, and N_w–R) and remote-sensing (σ_m–D_m, μ_o–D_m, D_m–Z_ku, and D_m–Z_ka) radars are evaluated. Furthermore, the present study also related the rainfall kinetic energy of fourteen tropical cyclones with rainfall rate and mass-weighted mean diameter (KE_time–R, KE_mm–R, and KE_mm–D_m). The raindrop size distribution empirical relations appraised in this study offer a chance to: (1) enhance the rain retrieval algorithms of ground-based, remote sensing radars; and (2) improve rainfall kinetic energy estimations using disdrometers and GPM DPR in rainfall erosivity studies.