The Interannual Variability of Surface Winds in Antarctica and the Surrounding Oceans: A Climatological Analysis Using the ERA-Interim Reanalysis Data

摘要

Season-dependent interannual variability of surface winds across Antarctica and the Southern Ocean is investigated using European Centre for Medium-Range Weather Forecasts Interim (ERA-Interim) reanalysis for 1979-2017 and the empirical orthogonal function (EOF) technique. The first three EOF modes, which account for 18-23%, 11-15%, and 8-10% of the total variances for the four austral seasons, are related to several known modes of Southern Hemisphere large-scale circulation including the southern annular mode, Pacific South American (PSA), and Zonal Wave 3 (ZW3) and to sea surface temperature anomalies in eastern (Ni?o 3) and central (Ni?o 4) tropical Pacific Ocean. Specifically, EOF1 and EOF2 are significantly correlated with southern annular mode in all seasons except for autumn EOF2. Neither EOF1 nor EOF2 are significantly correlated to Ni?o 3, but Ni?o 4 is significantly correlated to winter EOF1 and to EOF2 in all seasons but winter. EOF1 is significantly related to ZW3 for all seasons but summer; however, no significant connection is found between EOF2 and ZW3. Significant correlations exist between spring and winter EOF2 and PSA1 and between spring EOF1 and PSA2. EOF3 is significantly correlated with Ni?o 3, Ni?o 4, and PSA2 in all seasons but summer. The spatial patterns of all three modes can be largely explained by the anomalous mean sea level pressure fields that strengthen or weaken climatological winds in different regions of the Antarctica and the Southern Ocean, although variations in katabatic forcing also plays a role in the variations of surface winds especially in East Antarctica and during winter season where and when katabatic forcing dominates.