Dependence of Model-Simulated Heavy Rainfall on the Horizontal Resolution during the Jakarta Flood Event in January-February 2007

Abstract

Time-lagged ensemble downscaling experiments with Japan Meteorological Agency-Nonhydrostatic model are performed to study the dependence of heavy precipitation simulated by the model on the horizontal resolution for five days during late January to early February 2007, when the Jakarta Flood event occurred. The model runs with horizontal resolutions of 2, 4, and 5 km downscaled from the model runs with a 20-km resolution demonstrate the ability to reproduce a region of strong convective activity to the north of Java Island during the event. Daily meridional propagation of enhanced precipitation signals is simulated in the model runs with 2- and 4-km resolutions.
Cumulative distribution functions of precipitation rate in the model are analyzed for four different regions: ocean, northern coast, mountain, and southern coast. The northern coast region shows the highest contribution of heavy precipitation compared to other regions for all the experiments as well as for satellite-based precipitation estimates. The statistics on the frequency of heavy precipitation show that the diurnal variation of heavy precipitation produced by the model with a 2-km resolution agrees well with that of satellite-based precipitation estimates.