Modification of Air-Sea momentum flux parameterization considering non-local effects

Abstract

The air-sea momentum flux is an important component in air-sea interactions. In climate models, the estimation of air-sea momentum flux mainly relies on bulk flux parameterization based on the Monin-Obukhov Similarity Theory. However, the bulk flux parameterization has significant biases under light wind conditions. To reduce these inaccuracies, this study analyzed observational data from marine stations. The results showed that the non-local effects, which are overlooked by the traditional Monin-Obukhov Similarity Theory, are a significant factor contributing to inaccuracies in the air-sea momentum flux parameterization. Based on this finding, this study proposed a modification equation associated with non-local effects to improve the parameterization of air-sea momentum flux under near-neutral conditions. Furthermore, the modification equation was extended to non-neutral conditions, enabling its integration into air-sea momentum flux parameterization schemes and climate models. To evaluate the applicability and effectiveness of this modification, offline and online tests were conducted using two observational datasets and the Community Atmosphere Model version 6. Assessed by the comprehensive evaluation metric DISO, it was demonstrated that the non-local effects modification evidently enhanced the calculation accuracy of air-sea momentum flux and significantly improves the simulation performance in climate models.