Changes in the sub-decadal covariability between Northern Hemisphere snow cover and the general circulation of the atmosphere

摘要

Details of the sub-decadal covariability relationship between continental snow cover extent anomalies and the dominant mode of atmospheric variability, referred to as the Arctic oscillation (AO) or North Atlantic oscillation (NAO), for the period 1971-2001 are explored. On the seasonal time scale, the winter AO is found to be significantly correlated with the preceding autumn Eurasian snow cover (SNC_(EUR)) throughout the period observed. Consistent with this finding, SNC_(EUR) variability led the AO variability on the sub-decadal time scale in the early half of the record. However, starting in the mid 1980s, the AO and SNC_(EUR) vary in phase. Analyses of the seasonal relationship and persistence of snow and atmospheric variables illustrate a phase shift in the sub-decadal variability between the AO and SNC_(EUR) due to the loss of autumn-winter SNC_(EUR) autocorrelation replaced by a significant winter-spring persistence and the emergence of a concurrent SNC_(EUR)-AO connection in winter and spring. Similar analysis shows that the sub-decadal NAO variation is mostly described by the fluctuation in summer North American snow cover.