Evaluation of Subseasonal Prediction Skill Using the Global FIM-HYCOM Coupled Model

A coupled atmosphere (FIM) and ocean (HYCOM) modeling system FIM-HYCOM is being developed for subseasonal to seasonal prediction, where both component models are operating on a common icosahedral horizontal grid without the need for a flux coupler, and using an adaptive near-isentropic vertical coordinates. Once-per-week subseasonal hindcasts with 4 time-lagged ensemble members over a 16-year period have been carried out with this model at 30km and 60km horizontal resolution, respectively. Preliminary results from these multi-year hindcasts indicate that forecast skill of week-3-4 from FIM-HYCOM is comparable to that of the operational model CFSv2. Moreover, there is no significant improvement in the average performance when horizontal resoltion is increased from 60km to 30km. We will also discuss in detail the model's sensitivity to different cloud parameterizations.