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https://doi.org/10.5194/egusphere-2024-1892
https://doi.org/10.5194/egusphere-2024-1892
05 Jul 2024
 | 05 Jul 2024
Status: this preprint is open for discussion.

Spatial and temporal changes in autumn Eurasian snow cover and its relationship with the Arctic Oscillation

Gareth J. Marshall

Abstract. Previous studies have demonstrated that variations in the seasonal expansion of Eurasian snow cover (SC) can influence the following winter Arctic Oscillation (AO) and, consequently, affect mid-latitude weather. We examine changes in the extent and rate of autumn Eurasian SC advance and the temporal variability of the magnitude and sign of the SC-AO relationship. Novel aspects are (i) the use of the latest version of the 20th Century Reanalysis (20CR), allowing analysis back to 1836; (ii) adjusting the reanalysis SC through comparison with observations; and (iii) investigating spatial variation in the frequency of significant SC-AO relationships across Eurasia.

Over the past 50 years the snow advance indices (SAI) demonstrate a slowing and accelerating of snow advance in October and November (p < 0.01), respectively, corresponding to a greater contemporaneous decrease in SC extent in October than November and thus a postponement of SC onset. The most temporally robust spatial SC-AO relationship is a longitudinal dipole such that positive (negative) relationships between October SAI and the AO are more frequent in western (eastern) Eurasia. As the sum of the two regional correlations closely matches the correlation for Eurasia as a whole, an especially strong October SAI-AO relationship occurs when the sign of the relationship in one of these regions is reversed from climatology. Future work will aim to determine the exact linkages behind this new finding in the context of contemporaneous changes in regional atmospheric circulation and snow cover and the many additional factors observed to influence the SC-AO relationship.

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Gareth J. Marshall

Status: open (until 16 Aug 2024)

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Gareth J. Marshall

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Short summary
Eurasian autumn snow cover (SC) can influence Northern Hemisphere weather in the following winter by affecting the Arctic Oscillation (AO) mode of atmospheric variability. We find that the relationship between the rate of October snow advance and the AO is predominantly of opposite sign between east and west Eurasia. Periods when the SC advance is strongly related to the AO, and thus might be used for weather prediction, occur when the sign of the relationship is reversed in one of the regions.