Climate Fact: Indian Monsoon and Aerosols
The Indian Monsoon is a system of winds that travel from the relatively cool ocean to the relatively warm continent during the summer months (the wet season) and from the cool continent to the warm ocean during the winter months (the dry season). A greater temperature contrast between the ocean and the land makes a stronger seasonal precipitation contrast more likely. Increases in atmospheric aerosol concentrations since the 1970′s have resulted in increased deposition of these aerosols onto the ice that covers the Himalayas. The Himalayas are the largest ice-covered region outside the poles and Himalayan glaciers feed the rivers that serve about 900 million people. As more aerosols have been deposited on this ice, the ice has become darker, allowing it to absorb more light and making it more prone to melting. As the ice melts, it exposes more of the rocky substrate. Rocky surfaces absorb more light than ice does, resulting in a regional warming. This warming trend has been particularly pronounced during the pre-monsoon month of May, which is now on average 4.9 degrees Fahrenheit warmer than it was in the late 1970′s. The Indian Ocean warmed to a much lesser extent during this period, enhancing the temperature gradient between the ocean and the land.
Seasons: Spring
Source: Gautam, R et al. “Enhanced pre-monsoon warming over the Himalayan-Gangetic region from 1979 to 2007.” Geophysical Research Letters 36 (2009): L07704.
