Flux Adjustment on Seasonal-Scale Sea Surface Temperature Drift in NICOCO

抄録

 High-resolution atmosphere–ocean coupled models are the primary tool for sub-seasonal to seasonal-scale (S2S) prediction. Seasonal-scale sea surface temperature (SST) drift is, however, inevitable because of the imbalance between the model components, which may deteriorate the prediction skill. Here, we examine the performance of a simple flux adjustment method specifically designed to suppress seasonal-scale SST drift through case studies. The Nonhydrostatic Icosahedral Atmospheric Model (NICAM)–Center for Climate System Research Ocean Component Model (COCO) coupled weather/climate model, named as NICOCO, was employed for wintertime 40-day integrations with a horizontal resolution of 14 km for the atmosphere and 0.25° for the ocean components. The coupled model with no flux adjustment suffers SST drift of typically -1.5–2°C in 40 days over the tropical, subtropical, and Antarctic regions. It is found that simple flux adjustment sufficiently suppressed the SST drift. Nevertheless, the lead-lag correlation analysis suggests that air–sea interactions are likely to be appropriately represented under flux adjustment. Thus, high-resolution coupled models with flux adjustment can substantially improve S2S prediction.