Assessment of ENSO Skill in Forced Global HYCOM

Coupled ocean/atmosphere variability in the tropical Pacific, through El Niño/Southern Oscillation (ENSO), is a major contributor to fluctuations in North American and global rainfall and temperature, including tropical cyclones, extreme rainfall events, and droughts. Prediction of ENSO beyond the few months between the occurrence of westerly wind events in the western Pacific and the equatorial warming that triggers the Bjerknes feedback has been a major challenge. The long-term goal of this project is to contribute to the development and testing of a global fully coupled prediction system for the operational US Navy. The target time scales of this system will be seasonal through interannual; an essential capability of this system will be to forecast ENSO conditions with a reasonable degree of certainty. OBJECTIVES The project objective is to assess the skill of forced global Hybrid Coordinate Ocean Model (HYCOM) in reproducing ENSO events. In order for coupled prediction to be successful, both the ocean and atmospheric components must first show skill in the uncoupled mode. APPROACH To address this goal, we are assessing the skill of a suite of forced coupled HYCOM/CICE (sea ice) simulations: two are configured on a global 0.72 ° grid that telescopes at the equator to roughly 0.5° and are forced with different atmospheric reanalysis fluxes, while the third is configured on a global fine-resolution (0.08°) grid. The latter is forced with the same atmospheric fluxes as those used in on