Predictability of the wintertime Arctic Oscillation based on autumn circulation

摘要

A statistical method for 1-month lead prediction of the wintertime Arctic Oscillation (AO) is suggested in the study. Predictors, independently constructed for each forecast based on October geopotential height of the 500 hPa surface (Z500), indicate that the strongest impact of October circulation on the wintertime AO originates from a Z500 anomaly over the Taymyr Peninsula which causes an anomalous October advection of the cold (warm) air to the central Arctic and warm (cold) air to the East Asia prior to winters of the positive (negative) AO polarity. Independent verification assessments based on the series of 30 forecasts of the December-February (DJF) AO index (AOI) reveal a high skill of the developed method, with correlation coefficient between the predicted and observed DJF AOI being 0.61 and mean square skill score being 0.37.