Weak monsoon could be linked to air pollution

Hyderabad: Excessive aerosol concentration in the Bay of Bengal between March and May could be affecting the Southwest monsoon, according to meteorological scientists.

Experts say data over the past decade and half shows that years with higher concentrations of aerosols have been deficient monsoon years.

Aerosols are suspended particulate matter that could consist of particles such as dust, soot or sulphates from industrial and vehicular emissions that together form a mist in the higher atmosphere.

Black carbon aerosols consist of suspended carbon in various forms and are an urban phenomenon. The Asian Brown Cloud is a much studied phenomenon occurring from November to March every year after which it is washed away by rain caused by the southwest monsoon.

It even appears in satellite images as a black mark over parts of India.

Scientists from the Indian Institute of Tropical Meteorology (IITM) have studied the correlation between aerosol haze formation over the Bay and Bengal in the pre-monsoon months and subsequent intensity of the southwest monsoon.

“A significant negative relationship between  aerosol loading over the Bay of Bengal region in the  pre-monsoon months i.e. March to May and the forthcoming monsoon rainfall has been observed through analysis of 15 years,” said Dr S.D. Patil, a retired scientist from IITM

Scientists explain that aerosol loading occurs every year, in varying proportions.

In years with higher levels of aerosol concentration there was a weaker southwest monsoon.  Those years with lower concentrations of aerosols in the atmosphere had a stronger monsoon.