[A-AS02] From weather predictability to controllability

[AAS02-09] Response of convection to forcing that creates a cold pool

*Masaki Satoh^1,2, Shunnosuke Nakai¹, Jun Hiraiwa¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Typhoon Science and Technology Research Center, Yokohama National University)

Keywords:convection, cold pools, typhoons, eyewalls

It is known that the dynamics of cold pools generated by the evaporation of raindrops in the atmospheric mixed layer play an important role in the excitation of cumulus convection in the atmosphere. In this study, assuming non-adiabatic cooling due to the evaporation of raindrops, we investigate the convection response when a cooling source is forced into the mixed layer by numerical simulations. 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 boundary condition domain, with a uniform forcing near the center in the x-direction and the y-direction. The forcing provides a constant cooling source - 1 K/h in the region below 1 km height. The forcing width varies from 1, 2, 4, and 6 km. The results 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. When the forcing width is 1 km, the convective suppression area is generally limited to half of the region. The case of a circular forcing in the region's center was also examined. The area of convective suppression was found to extend approximately 5-10 times the forcing size. The temperature drop at the lowest level of the atmosphere in the forcing region is a few degrees, and the temperature distribution in the cold pool is determined by the mass transport by the forcing and the sensible heat supply from the sea surface. The balance between the strength of the mass flux and the heat supply from the sea surface determines the area of expansion of the cold pool. A similar forcing was applied to Typhoon Nanmadol in 2022 using the stretch-NICAM. A circular region of force is applied to a fixed position. The changes in the internal structure of the typhoon concerning the size and location of the region of force are investigated. Preliminary experimental results show that the forcing applied to the central region of the typhoon weakened in intensity due to thermodynamic effects. The nature of the forcing that effectively affects the typhoon wall cloud and the spiral band will be investigated. This research was supported by JST Moonshot R&D Grant Number JPMJMS2282.