Washington: Dust and soot transported from the deserts of the Middle East settle on the snow cover of the Himalaya mountain range and affect the intensity of the summer monsoon in India, a study has found. Using a powerful NASA-developed atmospheric model, researchers from University of Maryland in the US found that large quantities of dark aerosols — airborne particles such as dust and soot that absorb sunlight — settle on top of the Tibetan Plateau’s snowpack in spring before the monsoons begin.
These dark aerosols cause the snow to absorb more sunlight and melt more quickly. The findings suggest that, among these dark aerosols, windblown dust from the Middle East has the most powerful snow-darkening effect. More than a century ago, British meteorologist Henry Blanford noted a connection between springtime Himalaya snow cover and the intensity Indian monsoons. “Blanford knew that snow cover on the Tibetan Plateau wasn’t the only phenomenon that influenced the monsoon, but he knew it was important,” said William Lau, a research scientist who led the study. “The relationship between snow cover and the monsoon is useful enough that the India Meteorological Department still uses it to develop its annual summer monsoon forecast,” Lau said.
Researchers used the Goddard Earth Observing System Model to simulate 100 years’ worth of springtime snow cover and it influence on the yearly summer monsoon cycle. To test the effect of dust blown in from the Middle East, the researchers ran the same simulations again, with an added software package that incorporates the snow-darkening effects of dust, soot and other dark aerosols deposited atop the Tibetan Plateau. Adding dark aerosol deposition to the model substantially increased the amount of sunlight absorbed by the snow, accelerating the rate of melting.