Response of Convection to Forcing That Creates a Cold Pool

The cold pool dynamics generated by the evaporation of raindrops in the planetary boundary layer leads to the excitation and organization of convection in the atmosphere. In this study, assuming non-adiabatic cooling due to the evaporation of raindrops, we use numerical simulations to investigate the convection response when a cooling source is forced into the planetary boundary layer. The numerical model SCALE is used to drive a radiative-convective equilibrium state with a horizontal grid spacing of 1 km in a 96 km × 96 km double-period domain. The forcing provides a constant cooling source of 1 K h−1 in the region below a height of 1 km. We show that for a forcing width of 2 km or more, convection is localized at both ends of the region in the x-direction, indicating that the effect of the forcing extends over the entire region. The case of a circular forcing also showed a wider response compared to the forcing radius. A simple model showed that the heat balance between the strength of the mass flux and the heat exchange from the sea surface and the surrounding ambient air determines the area of expansion of the cold pool.