Air-Sea Interactions and Earth System Modeling: An Unified Wave Interface

Shuyi S Chen, University of Washington, Atmospheric Sciences, Seattle, WA, United States
Air-sea fluxes of mass, heat, and momentum are critically important for global weather and climate. Water evaporated from the tropical oceans is a major source of moisture for global precipitation, and salt and organic aerosols from the oceans provide cloud nucleation sites and affect microphysical processes. Transfer of heat and momentum between the atmosphere and ocean drives the atmospheric and ocean circulations and modulates the global water and energy cycle. Although the air-sea transfer processes occur on small scales, their impact on weather and climate is global and across all scales. Progress toward accurate modeling of air-sea fluxes has been limited in part because of the complex physical processes controlling the air-sea fluxes and the lack of observations, especially in high-wind conditions, in which extreme wind-induced surface waves and sea spray push the existing air-sea flux formulations into untested territories. These are not well understood and poorly represented in current weather prediction and Earth system models.

The goal of this study is to develop an unified air-sea interface for new generation Earth system models. The coupling framework has been developed and tested in the Unified Wave INterface-Coupled Model (UWIN-CM, Chen et al. 2013; Chen and Curcic 2016). This air-sea interface module is now built to be compatible with the NASA GMAO modeling framework, with the intent of eventually being incorporated into GMAO modeling system to make Earth System model predictions. The model simulations with the new air-sea fluxes module are evaluated and validated using NASA satellite data, e.g., surface wind products of the Ocean Vector Winds Science Team (OVWST), gridded air-sea fluxes (OAFlux), and surface waves data from the Cyclone Global Navigation Satellite System (CYGNSS), and on-going aircraft measurements.

The new air-sea interface module is fully tested in the regional high-resolution coupled atmosphere-wave-ocean model, i.e., UWIN-CM simulations of high-impact weather systems such as hurricanes and winter storms, and tested in the global GMAO GEOS model for simulations up to 1-2 months. The air-sea flux module will also be designed to facilitate future augmentation with additional physics. A review of the progress and chalenges in air-sea interaction in context of tropical convection and prediction across scales from hours to subseasonal including examples from tropical cyclones to the MJO. A fully coupled atmoshere-wave-ocean modeling framework and need for in situ and satellite observations going forward will be discussed.