Verification and Improvement of the Ability of CFSv2 to Predict the Antarctic Oscillation in Boreal Spring

The boreal spring Antarctic Oscillation (AAO) has a significant impact on the spring and summer climate in China. This study evaluates the capability of the NCEP Climate Forecast System Version 2 (CFSv2) model in predicting the boreal spring AAO for period 1983−2015. The results indicate that the CFSv2 has a poor skill in predicting the spring AAO, failing to predict the zonal symmetric spatial pattern of AAO, with an insignificant correlation of 0.02 between the predicated and observed AAO Index (AAOI). Considering the interannual increment approach can amplify the prediction signals, we firstly establish a dynamical-statistical model to improve the interannual increment of AAOI (DY_AAOI), with two predictors of CFSv2-forecasted concurrent spring sea surface temperatures (SSTs) and observed preceding autumn sea ice. This dynamical-statistical model demonstrates a good capability in predicting the DY_AAOI, with a significant correlation coefficient of 0.58 between the observation and prediction during 1983−2015 in the two-year-out cross-validation. Then, we get the improved AAOI by adding the improved DY_AAOI to the preceding observed AAOI. The improved AAOI shows a significant correlation coefficient of 0.45 with the observed AAOI during 1983−2015. Moreover, the unrealistic atmospheric response to preceding fall sea ice in CFSv2 may be the possible cause for the failure AAO prediction of CFSv2. This study gives a new clue for AAO prediction and the short-term climate prediction.