This chapter presents variabilities in the vertical structure of precipitation over the Indonesian maritime continent (IMC), which were inferred from the gradients of the radar reflectivity (dBZ) below the freezing level and were gathered from the latest 2A25 TRMM–Precipitation Radar product over a 17-year time span (1998–2014). In general, the downward increasing (DI) pattern of dBZ toward the surface is more dominant than the downward decreasing (DD) pattern, which has a ratio of 1.3. The DI is frequently observed over the ocean, and the higher prevailing rain top heights over land are associated with DD, in most cases. Shallow convective rains have the largest ratio of DI to DD (>4), followed by deep convective rains. The largest ratio is observed during December–January–February (DJF) when wetter conditions are dominant over the IMC, which is a favorable condition for raindrop growth. The stratiform rains show a dominant DD in which the ratio of DD to DI is greater than 1.6 for each season. The spatial distribution of the stratiform gradient is more complex than that of convective rain and does not show a robust land-ocean contrast. The diurnal variation in the reflectivity gradient for stratiform rain is less pronounced. With convective rain, DD is more dominant in the afternoon and evening over a large island, indicates a decrease in the raindrop concentration due to the evaporation and updraft associated with the intense convection.
Part of the book: Engineering and Mathematical Topics in Rainfall