The Effects of Wave-Dependent Surface Fluxeson CESM2 Climate Simulations

• Main Authors: Shi, Xiaoming, Li, Qing, Lestari, Diah Valentina, Lin, Shangfei, Su, Hui
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2024
• Subjects: Pacific; Southern Ocean
• Online Access: http://dx.doi.org/10.22541/essoar.171137007.70394880/v1

Processes at the air-sea interface govern the climate mean state and climate variability by determining the exchange of momentum, heat, and water between the atmosphere and ocean. Traditional climate models compute those exchanges across the air-sea interface by assuming an ocean surface with roughness determined by wind and stability conditions, essentially assuming ocean surface waves are in equilibrium states. In reality, that is rarely the case. Such effects have been emphasized in numerical weather predictions for weather systems like tropical cyclones. An accurate representation of ocean surface waves requires a prognostic ocean surface wave model. The addition of WAVEWATCH III (WW3) to the Community Earth System Model 2 (CESM2) makes it possible to parameterize the impacts of ocean surface waves on momentum and energy exchange. This study documents our implementation of a wave-state-dependent surface flux scheme in CEMS2. Our scheme considers the effects of waves on ocean surface roughness and those of sea spray on surface sensible and latent heat. We found that the new scheme significantly impacts the mean atmospheric circulation and the upper ocean. The errors in mean atmospheric circulation and surface temperature patterns are reduced. The modified surface flux lowers the eddy-driven jet speed and weakens the Hadley circulation. Global mean sea surface temperature (SST) warm bias is reduced due to the cooling of the Southern Ocean and eastern boundary currents. In particular, the eastern Pacific exhibited a weak cooling trend in the historical simulation for the recent decades, reducing the existing SST trend bias in CESM2.