Linkages between Eurasian snow cover and Northern Hemisphere winter-time climate variability

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2000.Includes bibliographical references (p. 107-112).Recently it has been shown that the Eurasian snow cover in the prior autumn (ESCSON) and the leading mode variability in the wintertime extratropical Northern Hemisphere (NH) atmospheric circulation have significant correlation. In this study, a linkage between the ESCSON and the following wintertime NH climate variability was investigated. Satellite data from the NOAA is used for snow cover, and NCEP/NCAR Reanalysis data are used for climate variables. The high latitudes sea-level pressure is quality-controlled by use of the IABP sea-level pressure dataset, which is derived from the buoy observations. Interannual variability of and association between ESCSON and winter climate variables were surveyed by use of linear statistical analysis techniques; Empirical Orthogonal Function (EOF) analysis, and correlation/regression analysis. The gravity current by the expansion of the cold, dense air over Siberia north- and westward remained one among the several possible mechanisms. The upper air mechanism may be active to connect the ESCSON and the leading mode of DJF surface pressure variability. It is also suggested that the DJF sea-level pressure variations associated with the ESCSON is considerably confined to the Atlantic side, and has only limited association with the linear trend and the Pacific side variations. Future work may include reexamination of the results using the possible, longer data of the observation. The mechanism connecting the ESCSON anomalies and the upper level circulation anomaly should be investigated further, for which one possible approach is analysis of the wave activity and energy propagation in the troposphere and stratosphere.by Kazuyuki Saito.S.M