Environmental Conditions and Development Mechanism of Convection Bands over the Korean Peninsula

A significant portion of the annual precipitation over the Korean peninsula is produced by heavy precipitation systems (HPSs) during summer. HPSs over the Korean peninsula were classified into four major types (convection bands, cloud clusters, isolated thunderstorms, and squall lines) by phenomenological analysis. Among four major types of HPSs, convection bands (CBs) tend to concentrate a large amount of rainfall over limited area due to their linear organization and quasi-stationary behavior for several hours. Convective cells embedded in CB move along the band and new cells are continuously formed in the upstream of the band.

In this study, an attempt is made to understand the relationship between CBs and their environmental conditions and clarify the development mechanism of CBs. The data used for this study includes radar and satellite images, weather charts, rainfall data, thermodynamic charts, and NCEP Climate Forecast System Reanalysis data. Twenty-four CB cases occurred during 2001-2010 were selected.

Most of CBs generally developed under some typical synoptic situations: 1) meso-low propagating toward the northwestern flank of the western Pacific subtropical high (WPSH), 2) stationary monsoon front, and 3) large-scale convergence between synoptic-scale low and WPSH. Environmental conditions of CBs were characterized by strong low-level vertical shear along the parallel direction of CBs, low-level convergence and predominant band-parallel mean flow in the lower-troposphere. Thermodynamic condition of southern area of CBs was much more unstable compared to that of northern area of CBs. Averaged mCAPE over southern area and northern area of CBs were 1273 m² s^-2 and 329 m² s^-2, respectively.

The Weather Research and Forecasting (WRF) model was used for simulating representative CB cases. Especially, development mechanism of convection bands consisting of narrow convective cells with no stratiform clouds will be given.