[A-AS03] 大規模な水蒸気場と組織化した雲システム

[AAS03-09] A stochastic lattice model for convective self-aggregation

★Invited Papers

*神野 拓哉¹、三浦 裕亮¹ (1.東京大学大学院理学系研究科)

キーワード：対流自己組織化、放射対流平衡

Self-aggregation of tropical convection is a universal feature which occurs in various environmental fields. Several preceding models conceptualized the self-aggregation as a phase transition driven by the collisions between cold pool gust fronts. However, the self-aggregation is controlled by various physical processes such as surface fluxes, radiation, moisture perturbations in planetary boundary layers, and it is unclear which process plays a dominant role. In this study, a simple stochastic lattice model for the pattern formation of deep convections is developed, inspired by two-dimensional Ising model. The current model incorporates the effect of clear-sky radiative cooling as an interaction between clouds, which suppresses deep convections. It also incorporates the effect of cold pool collisions, which triggers new convection. Our results show that by varying the intensity of clear-sky radiative cooling effects, the transition from the scattered to the aggregated cloud field is reproduced. It is implied that the feedback of longwave radiation also plays a key role in causing convective self-aggregation. The model also successfully explains the dependence of self-aggregation on several model parameters such as the experimental domain size and the characteristic size of cold pools.