ユーラシア大陸の積雪とＥＮＳＯ 雪氷・大気・海洋結合系の提唱

Abstract

The winter snow cover area anomaly over Eurasia has been noted for about a century as a precursor of the succeeding Indian monsoon rainfall anomaly. This snow cover anomaly is shown to be associated with the particular atmospheric teleconnection pattern called Eurasian pattern. Indian monsoon rainfall is shown, in turn, to be tightly linked with the sea surface temperature in the equatoriol Pacific in the following autumn and winter. The global analysis of atmospheric circulation anomalies also demonstrates that the significant Eurasian pattern with anomalous snow cover is greatly responsible for producing anomalous sure gradient along the equatorial Indian Ocean therough the western Pacific, which trigggers the E1 Nino event over the eastern equatorial Pacific. These anomalous condition seem to be caused by the anti-E1 Nino condition over the western Pacific in combination with the polarity of the teleconnection pattern (NAO) over the northern Atlantic through the Arctic region.These observational evidences strongly suggest that the ENSO cycle with a time scale of several year period should be taken as oscillation in the coupled cryosphere/atmosphere/ocean climate system over the globe, rather than that in the coupled atmosphere/ocean system in the tropical Pacific.