Multiscale Processes in Air-Sea Coupling: Observations and Modeling of High-Impact Weather

Air-sea exchanges 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 have not been well understood and are poorly represented in current weather prediction and Earth system models.

Coherent observations in the atmospheric boundary layer and upper ocean across the air-sea interface from field campaigns have cumulatively provided valuable insight into air-sea interactive processes. This study will use observations from CBLAST 2003-04, RAINEX 2005, ITOP 2010, DYNAMO 2011-12, and CPEX-AW 2021 to show case the multiscale air-sea interactions in hurricanes and the MJO. The recent advancements in coupled atmosphere-wave-ocean models with increased resolution, e.g., ~O(1 km) grid spacing in regional and O(10 km) in global models, have made it possible to develop and test various new model physics at the air-sea interface with relatively realistic environmental conditions across time scales from hours to subseasonal time scales and beyond. This talk will present an overview of the progress and challenges in air-sea coupling in context of high-impact weather such as tropical cyclones and the Madden-Julian Oscillation (MJO) and their prediction across scales. A fully coupled atmosphere-wave-ocean Earth system modeling framework and need for in situ and satellite observations going forward will be discussed.