The Influence of Eurasian Snow Extent on the Northern Extratropical Stratosphere in a QBO Resolving Model

E-ISSN： 2169-8996|123|1|315-328

ISSN： 2169-897x

Source： JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES, Vol.123, Iss.1, 2018-01, pp. : 315-328

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Abstract

AbstractThe European Centre/Hamburg version 6 atmospheric model with a well‐defined stratosphere and an internally generated Quasi‐biennial oscillation (QBO) was used to study the relationship between the autumn Eurasian snow extent and the wintertime climate of the northern hemisphere. A positive snow cover anomaly was imposed over Eurasia in early autumn and held constant until spring. One hundred years of the snow anomaly run was compared with a 100 year control run. A dynamical response to the snow anomaly is seen in the northern polar stratosphere and troposphere during autumn and early winter, in line with previous modeling studies, and the monthly progression of the atmospheric anomalies follows the size of the surface forcing. However, this response is weaker, and occurs earlier in season, than that seen in observations. Considering the effect of QBO, we find a stratospheric vortex weakening during the easterly phase; however, the effect is weaker than that seen in observations. The strongest response of the polar vortex is found when both factors—the snow anomaly and the QBO phase—are considered together, with the response being close to an additive combination of the responses to the individual forcings. Although our study confirms the ability of snow cover variability to significantly influence the large‐scale circulation, it also demonstrates that the inclusion of a well‐resolved stratosphere is not a sufficient condition for reproducing the intensity and timing of the circulation response appearing in observations.