Washington: Scientists have helped to explain why heavy snowfall over the Himalayas in winter and spring can lead to drought over India, especially in the early part of the summer monsoon.
As far back as the 1880s scientists have known that increased snow over the Himalayas can be linked with weaker summer monsoon rains over India. However, the mechanisms explaining this link were never properly understood.
New research shows that greater snowfall reflects more sunlight and produces a cooling over the Himalayas.
This means a weakening of the monsoon winds that bring rain to India. The relationship is strongest in the absence of warm (El Nino) or cold (La Nina) conditions in the tropical Pacific, because these are normally the dominant control over Indian rains.
Andy Turner, lead study author, from the Walker Institute at the University of Reading says: "Our work shows how, in the absence of a strong influence from the tropical Pacific, snow conditions over the Himalayas and Tibetan Plateau could be used to help forecast seasonal monsoon rainfall for India, particularly over northern India during the onset month of June.”
"The onset timing of the monsoon is very important for agriculture; a lack of rainfall early in the growing season can have a devastating impact on crops," Turner said.
Previous studies have also found links between snowfall over a much larger area of northern Eurasia but this study suggests that the Himalayan region has a stronger influence on Indian rainfall.
The monsoon rains over India and the rest of South and East Asia are relied on by more than a third of the world's population, says a University of Reading release.
This study shows in detail the mechanisms linking heavy snowfall over the Himalayas and Tibet in winter and spring with summer monsoon drought, particularly in the early part of the season (June).
These findings were published in Climate Dynamics.
First Published: Saturday, April 24, 2010, 11:40