Differences in atmospheric environments can have a significant impact on microphysical processes of precipitation. Dominant warm (cold) rain processes in East Asia (southern Great Plains of USA) is implied by large (small or constant) gradient of reflectivity at low level in vertical reflectivity profiles. Long-term ground observations using two-dimensional video disdrometers were conducted in southern Korea (KOR) and Norman, Oklahoma, USA (OKL). Raindrop size distributions (RSD) and their moments in the two regions were analyzed in the framework of scaling normalized RSDs. Results show that the concentrations of small (big) raindrops were higher (smaller) in KOR than in OKL. KOR RSDs were also found to be characterized by relatively high characteristic number concentrations, , and a small characteristic diameters, when compared to OKL RSDs. The increases with increasing in both KOR and OKL at the lower Z with the opposite trend at higher Z. In addition, OKL RSDs with > 2.5 mm indicate the existence of an equilibrium between coalescence and break-up processes. Rainfall estimation relationships between the rain rate (R) and radar variables were retrieved from scattering simulations at S-, C-, and X-band wavelengths. KOR RSDs showed relatively small horizontal reflectivity and specific differential phase shift at the same R and same wavelength when compared to OKL RSDs. The regional dependency was significant due to the different microphysical process in KOR and OKL. The specific attenuation of KOR was however similar to that of OKL only at S-band, indicating an advantage of using specific attenuation in S-band in rainfall estimation.