The First Operational Version of Taiwan Central Weather Bureau’s One-tier Global Atmosphere-Ocean Coupled Forecast System for Seasonal Prediction

Abstract The first version of the Taiwan Central Weather Bureau one-tier (TCWB1T) fully coupled global atmospheric and oceanic modeling forecast system had been developed and implemented as a routine operation for seasonal prediction at Central Weather Bureau (CWB) in 2017, with a minor revision in 2020. Based on NCEP CFSv1, the global atmospheric model in NCEP CFSv1 was replaced by CWB’s atmospheric global spectral model (GSM) and coupled with the GFDL MOM3. Several parameters have been tested and tuned in the CWB atmospheric GSM, achieving an optimal configuration with better sea surface temperature (SST) predictions for integration more than one year. Using NCEP CFSR as the initial condition, TCWB1T conducted hindcast from 1982 to 2011 and forecast from 2012 to 2019 for analyzing its performance. The results of hindcast and forecast show that the TCWB1T has useful predictions as verified to the observation of OISST, ERSST, CFSR, and GPCP based on the methods of EOF, RMSE, anomaly correlation, RPSS, RD, and ROC. And TCWB1T has the same level of skill scores as compared to NCEP CFSv2 and/or ECMWF SEAS5, based on EOF, APC, climatological bias, RMSE, temporal correlation, and anomaly correlation percentage of forecast skill. TCWB1T shows forecast skills which are better in winter than summer. Overall, it indicates that TCWB1T can be used for seasonal ENSO predictions.