Influence of Eurasian snow cover in spring on the Indian Ocean Dipole

Abstract

The Indian Ocean Dipole (IOD) shows a significant negative correlation with the extent of Eurasian snow cover in spring. The anomalies in the land-sea temperature contrast, which are induced by the anomalies of Eurasian snow cover in spring, reverse the patterns of convection activ- ity anomalies over the western and eastern tropical Indian Ocean in summer. Moreover, for heavier and lighter than normal Eurasian snow cover in spring, anomalies in the vertical zonal circulation over the tropical Indian Ocean (Walker circulation) and in the vertical meridional circulation between the Indian Ocean and the Eurasian continent (Hadley circulation) occur in summer. The Walker and Hadley circulation anomalies probably play an important role in the occurrence and duration of IOD events. Eurasian snow cover in spring is presumably one of the factors that trigger IOD events. These results provide a basis for further investigation of the mechanisms linking snow cover, the Indian monsoon, atmospheric circulation, and sea surface temperature.