[A-CG32] Land-Atmosphere interactions and Asian monsoon precipitation (LAMos)

[ACG32-05] On the sensitivity of land-atmosphere coupling to the model mesh sizesduring the Indian summer monsoon:Based on high-resolution regional climate simulations

*Rakesh Teja Konduru¹, Hiroshi G. Takahashi¹ (1.Department of Geography, Tokyo Metropolitan University)

Keywords:Land-atmosphere coupling, Indian summer monsoon, surface energy fluxes, precipitation, model resolution, regional climate model

Land surface interacts with the atmosphere by the exchange of energy and momentum to induce convection. Generally, land-surface possesses several features per se, vegetation, topography, settlements, and land use. These land surface features appear across various spatial dimensions and do not change on convective short time scales. These features we considered as static land surface features. Under such spatial and temporal scales, static land surface features interact differently with the atmosphere by controlling the exchange of energy and momentum. Therefore, it is essential to represent the static land surface features in the climate models accurately. Considering the heterogeneous nature of land surface over the Indian region, static surface features representation is crucial for effective land-atmosphere interactions. It is required to study the spatial scale sensitivity of these interactions.

This study investigated the spatial scale dependency of the land-atmosphere interactions by using a regional climate model. To perform this investigation, we have performed 5 regional climate experiments with different model mesh sizes (25, 12.5, 6.25, 3.125, and 1 km) during the summer monsoon by using Weather Research and Forecasting (WRFv3.9.1.1) model. Significant spatial differences were observed in the surface static features, temperatures, energy fluxes, and roughness lengths between coarse and fine model horizontal resolutions. Experiments with fine model resolution generated a large surface temperature, sensible heat flux, and deep planetary boundary layer compared to coarse resolutions. This increase in sensible heat flux influenced the land-atmosphere coupling to become strong (weak) in fine (coarse) model horizontal resolutions over central and south India. Such a dependency of the land-atmosphere coupling on model resolution also changed the monsoon precipitation characteristics. This investigation revealed that the land-atmosphere coupling linearly increases with the resolution of static land features, but their spatial distribution is heterogeneous.