Integrated changes in tropical precipitation and circulation under global warming: moist static energy budget and the role of sea surface warming pattern

This study uses the outputs of 24 models from CMIP6 to investigate the underlying mechanisms that determine the spatial pattern of the changes in annual-mean tropical precipitation (ΔP) and circulation (Δω) under global warming. The spatial pattern of ΔP is determined by the combined contributions from the dynamic and thermodynamic components in the simplified moisture or dry static energy budgets. Furthermore, the connection between Δω and the changes in the vertical structure of moist static energy (MSE) is revealed through the MSE budget simplified by the three-layer model. In this model, Δω is further separated into two components that are symmetric (Δωsym) and antisymmetric (Δωasym) about the mid-troposphere based on the vertical structure of Δω over the tropics. Notably, on the other hand, the changes in the vertical structure of MSE exhibit two features, namely the increased atmospheric instability determined by the SST pattern change and the deepening of mid-tropospheric MSE minimum relative to the surface. We further investigate the mechanisms for the spatial patterns of Δωsym and Δωasym based on the circulation decomposition framework. Specifically, the pattern of Δωsym is controlled by the mean advection of stratification change (MASC) mechanism throughout the tropics and the increased moist instability over the equatorial Pacific and northern Indian ocean. On the other hand, the pattern of Δωasym is controlled by the MASC mechanism throughout the tropics and the decreased surface convergence over the eastern Pacific intertropical convergence zone. The increased moist instability and the decreased surface convergence are further induced by the relative SST warming pattern and the change in Laplacian of SST, respectively. Moreover, it is found that the intermodel uncertainty in Δωsym dominates that in ΔP, which is influenced by the local SST change and the changes in the zonal tropical Pacific SST gradient simultaneously. These results contribute to a better understanding of the processes that determine future hydrological changes, particularly with regards to the future pattern of the dynamic part (Δω).