Characterization of synoptic environment for mesoscale convective systems over <scp>South Korea</scp> using <scp>ERA5</scp> reanalysis data

Abstract We performed a composite analysis using ERA5, the fifth‐generation reanalysis dataset from European Centre for Medium‐Range Weather Forecasts (ECMWF), to characterize the synoptic conditions for organizational modes of mesoscale convective systems (MCSs) in South Korea. The MCS modes are divided into four classes based on their morphological and propagation characteristics: convective cells (CC), mesoscale convective complex (MCC), forward‐propagating quasi‐linear convective system (FP QLCS), and stationary or back‐building QLCS (ST/BB QLCS). The reference time for the composite analysis was determined using the largest one‐hour accumulated rainfall. CC events primarily develop due to orographic lifting and surface heating under a moist low‐level environment that is favorable for convection. For MCC events, a mesoscale trough develops at the northwest edge of North Pacific High (NPH), and moisture transport by southwesterly winds results in convective instability at lower levels. The FP QLCS develops due to strong dynamical forcings from an upper‐level trough and an upper‐level jet. The baroclinic structure of cyclones, along with moisture transport in the warm sector, supports synoptic‐scale upward motion. In ST/BB QLCS events, the interaction between a continental low and the NPH provides a continuous supply of moisture over land. The persistent moisture transport forms a deep layer of convective instability, resulting in a narrow and long‐lasting rain region. In conclusion, we generalized the environmental conditions that are conducive to the development of each MCS mode based on the composite analysis. The insights from this study can serve as a starting point for understanding the mechanisms behind MCS formation and development, particularly in moisture‐rich environments.