High-resolution modeling study of an isolated convective storm over Seoul Metropolitan area

Abstract

The ability of a high-resolution (500 m) Weather Research and Forecasting (WRF) model to simulate an isolated convective precipitation event over Seoul metropolitan area on August 16, 2015 was investigated. To understand the effects of micro- and mesoscale forcing on the initiation of convective rainfall under large-scale conditions, we performed sensitivity tests using different initial times. Despite simulating the same case, the quantitative precipitation forecast and the timing of moist convection varied widely among the experiments. Mesoscale features such as outflow and low-level convergence are different in location and intensity among the experiments. When assimilation of surface observations and radar data was performed, the simulation reproduced the low-level convergence and, hence, the location and amount of rainfall reasonably well within the first 6 h of simulation period. The timing differences of convective rainfall among the experiments were examined in terms of the atmospheric boundary layer (ABL) growth. Rapid growth of the ABL enabled moist convection to occur early in the presence of an outflow. An overestimated maximum ABL height by the model also led to earlier collapse of the ABL as compared to observations, which contributed to a reduction of convective available potential energy over the urban area in late afternoon. The results of this study demonstrate that accurate simulation of ABL growth is important for predicting the timing and intensity of isolated convective storms.