Three-to-six day oscillation caused by air-sea interaction

Ehud Strobach1, Andrea Molod2, Atanas l Trayanov3, Gael Forget4, Jean-Michel Campin5, Christopher N Hill6, Dimitris Menemenlis7 and Patrick Heimbach4, (1)University of Maryland College Park, College Park, MD, United States, (2)Global Modeling and Assimilation Office, NASA GSFC, Greenbelt, MD, United States, (3)Science Systems and Applications, Inc., Lanham, United States, (4)Massachusetts Institute of Technology, Cambridge, MA, United States, (5)M.I.T./EAPS, Cambridge, United States, (6)MIT, Cambridge, United States, (7)NASA Jet Propulsion Laboratory, Pasadena, United States
Recent studies have shown that oceanic mesoscale and submesoscale variability has large-scale and long-term impacts both on the atmospheric and oceanic circulations. This includes impact on storm track intensity, atmospheric blocking, monsoon rainfall, and net vertical ocean heat flux. Representing processes underlying the impact of mesoscale eddies in climate models requires high-resolution coupled ocean-atmosphere models, which are rare and computationally expensive. Understanding the effect of ocean eddies on the climate system using high-resolution global coupled models can inform subgrid-scale parameterizations in lower-resolution models and hence help improve climate predictions.

Analysis of output from a global, high-resolution (~10km horizontal grid spacing), coupled ocean-atmosphere simulation revealed an ubiquitous interaction in the air-sea interface, with a cyclic nature characterized by a period of several days. Using a set of simulations, we found that the interaction is governed by air-sea coupling and by model resolution. We discuss the results from this set of simulations, including the results from a new, global, coupled ~5km simulation. We suggest a possible mechanism for this interaction, which is controlled by feedback between the Sea Surface Temperature (SST) in the ocean and surface wind speed in the atmosphere.