The First Operational Version of the Taiwan Central Weather Bureau's One-tier Global Atmosphere-Ocean Coupled Forecast System for Seasonal Prediction / Dr Hann-Ming Henry Juang (Environmental Modeling Center, NOAA/NWS/NCEP) [莊漢明 博士 (NOAA/NWS/NCEP)]

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 CWB in 2017. Based on the NOAA NCEP CFSv1 package, the global atmospheric model in NOAA NCEP CFSv1 was replaced by CWB's global atmospheric spectral model with a horizontal resolution of wave number 119 in triangular truncation (T119) and a vertical resolution of 40 vertical layers and coupled with the NOAA GFDL MOM3. Several parameters have been tested and tuned in the CWB global atmospheric model, achieving an optimal configuration with better sea surface temperature (SST) predictions for more than a one-year integration.  Using NCEP CFSR as the initial condition, TCWB1T conducted a hindcast from 1982 to 2011. By analyzing the SST of hindcast data, it shows that Niño3.4 regional SST anomaly forecasts were well predicted for winter. The fraction of variance explained by EOF modes 1 through 5 for SST anomaly shows TCWB1T is close to the observed ERSST. The results of hindcast and forecast (during 2012-2019) from TCWB1T show that TCWB1T has useful predictions as compared to the observation of ERSST, has the same level of skill scores as compared to NCEP CFSv2 and ECMWF SEAS4/SEAS5 in hindcast period. Nevertheless, TCWB1T has better skill scores in the forecast period than NCEP CFSv2. TCWB1T shows predictability is better in winter than in summer. Overall, it indicates that TCWB1T can be used for seasonal El Niño-Southern Oscillation predictions.