The Effect of Eurasian Snow Cover on the Indian Monsoon

Abstract

The authors successfully model and simulate the observed evidence that anomalously high winter/spring Eurasian snow cover is linked to weak rainfall in the following summer Indian monsoon. It is shown that excessive snow cover in February reduces June to September precipitation over India. The excessive snow cover is associated with a weak monsoon characterized by higher sea level pressure over India, a weaker Somali jet, weaker lower tropospheric westerlies, and weaker upper tropospheric easterlies. The weak monsoon is also associated with weaker secondary circulations. The remote response to excessive Eurasian snow cover is to reduce the strength of trade winds in the eastern equatorial Pacific Ocean. Energy used in melting excessive snow reduces the surface temperature over a broad region centered around the Tibetan Plateau. Reduced surface sensible heat flux reduces the midtropospheric temperature over the Tibetan Plateau. The result is to reduce the midtropospheric meridional temperature gradient over the Indian peninsula, which weakens the monsoon circulation.