The Implications for Radiative Cloud Forcing via the Link Between Shallow Convection and Planetary Boundary Layer Mixing

Abstract

In this study, the role of shallow convection and its links with planetary boundary layer (PBL) mixing is analyzed using a global atmospheric model. All of the simulations are conducted with the Korean Integrated Model (KIM), which is a next-generation operational global model for Korea Meteorological Administration. The simulation results show that the direct effect of shallow convection enhances additional vertical mixing inside the shallow convective layer, whereas its indirect effect reduces vertical mixing inside the PBL by changing the PBL height, thus vertical mixing strength. It is also found that the impact of shallow convection on low-level clouds is tightly related to the overlapping between PBL and shallowing convection. When the PBL height is located in the higher (lower) part of the shallow convective layer, the mixing across the top of the PBL becomes smaller (larger). Therefore, the diffusivity profile of KIM shallow convection scheme is modified according to the overlapping pattern of PBL mixing and shallow convection. The systematic bias of downward solar radiation at the surface of KIM is improved with the revised diffusivity profile of the shallow convection scheme proposed in this study.