Characteristics of Global Light Rain System From GPM/DPR Measurements

Abstract

Understanding the microphysical and macrophysical characteristics of global light rain (0.2–2.5 mm/hr) is important for modeling the hydrological cycle and enhancing the cloud-related parameterization in the numerical weather prediction (NWP) model. To understand the characteristics of light rain systems, this study classified global light rain events using the Global Precipitation Measurement Dual-frequency Precipitation Radar measurements over the 8–years period. As a result, global light rain systems were identified into four types based on microphysical (mass-weighted mean diameter (D_m) and normalized intercept parameter (logN_w)) and macrophysical (cloud-echo-top height (CETH)) parameters. The four classified types are (a) Type 1: light rain dominant in tropics and mid-latitude, (b) Type 2: light rain linked to atmospheric deep convection, (c) Type 3: light rain from humid oceanic inflow blocked by topography, and (d) Type 4: light rain associated with subtropical high-pressure systems. Type 2 shows the largest D_m and the smallest logN_w, while Type 4 exhibited opposite patterns. Type 3 has the highest CETH and vertically stretching radar reflectivity profiles. Type 1 showed similar distributions of D_m and logN_w with Type 3 and radar reflectivity with Type 4 but different distributions of hydrometeor phase with Types 3 and 4. To clarify the characteristics of Type 1, a detailed analysis was conducted, showing larger D_m and logN_w, higher radar reflectivity, and stronger seasonality in tropical regions compared to mid-latitudes. This study provides valuable insights into geospatial/statistical characteristics of global light rain, which is expected to enhance the accuracy of cloud parameterization in the NWP model.