GEOS-5 Seasonal Forecast System: ENSO Prediction Skill and Bias

The Goddard Earth Observing System (GEOS) Atmosphere-Ocean General Circulation Model, Version 5 (GEOS-5 AOGCM) Seasonal-to-Interannual Forecast System has been used routinely by the GMAO since 2008, the current version since 2012. A coupled reanalysis starting in 1980 provides the initial conditions for the 9-month experimental forecasts. Once a month, a suite of 11 ensemble forecasts is generated. The seasonal forecast output data includes surface fields, atmospheric and ocean fields, as well as sea ice thickness and area, and soil moisture variables.

GEOS-5 coupled seasonal forecast system prediction skill and bias of the equatorial Pacific Ocean sea surface temperature (SST) indices (Niño 1+2, 3, 3.4, 4) over the period 1981-2015 is presented. The system's performance during the earlier and later halves of this time period is compared and contrasted to better understand the impact of initial conditions, observations availability and model's shortcomings on the ENSO forecast.