Indian monsoon carrier of pollutants: Study

Using satellite images and sophisticated computer models, an international team of researchers  found that pollutants from India, China and Indonesia are being wafted up to the stratosphere during the monsoon season.

The study suggests that the impact of Asian pollutants on the stratosphere – which in turn is linked to global climatic health – may increase in coming decades because of the growing industrial activity in China, India and other Asian nations.

The monsoon circulation provides an effective pathway for polluting particles to enter into global circulation within the atmosphere, the researchers report on the Friday’s issue of “Science”.

Monsoon a pathway

“The monsoon is one of the most powerful atmospheric circulation systems on the planet, and it happens to form right over a heavily polluted region. As a result the monsoon provides a pathway for transporting pollutants up to the stratosphere,” says principal investigator William Randel from the US’ National Centre for Atmospheric Research in Boulder, Colorado.

Once in the stratosphere, the pollutants circulate around the globe for several years. Some eventually descend back into the lower atmosphere, while others break apart.
What could be the impact of these pollutants? Randel admits that more research is required even though the study seems to suggest that Asian pollutants will create harmful chemicals that will gobble up the protective ozone layer.

Indian disagreement

Indian researchers, however, do not agree with this suggestion.
“Had it been the case, we would have seen ozone depletion in the tropics as well. But it was never our problem,” Gufran Beig, a senior scientist from Indian Institute of Tropical Meteorology, Pune told Deccan Herald.

“If Asian pollutants have a significant role in mid-latitudes, then ozone recovery in the mid-latitude would not have started in the last 5-7 years,” said Beig.

The NCAR team with colleagues from Canada and UK modeled summertime circulation pattern in the tropics to show monsoon provides rapid transport to black carbon, sulfur dioxide, nitrogen oxides, and other pollutants to ascend into the stratosphere, about 20-25 miles above the Earth’s surface.

This was deduced after tracing the movement of a chemical pollutant known as hydrogen cyanide, a byproduct of biomass burning and forest fire.

The researchers say when sulfur rises into the stratosphere, it can lead to the creation of small aerosol particles that are known to influence the ozone layer.