A team of researchers used computer modelling to examine the impact that aerosols – in the form of pollution, sea salt and dust – has on global rainfall. The scientists wanted to get to the bottom of an observed positive correlation between aerosols over North Africa, West Asia and the Arabian Sea, and rainfall over India.
After running simulations with and without the various aerosol types, the team concluded that the rise of dust in North Africa and the Arabian peninsula had the greatest impact. They suggested that the dust absorbs warmth from sunlight, drawing moist air from the tropics and increasing the intensity of the prevailing winds that transport moisture from the Arabian Sea into India, where it falls as rain.
‘The difference between a monsoon flood year or a dry year is about ten per cent of the average summer rainfall in central India. Variations driven by dust may be strong enough to explain some of that year-to-year variation,’ said one of the study’s authors, Phil Rasch of the US Department of Energy’s Pacific Northwest National Laboratory.
This story was published in the May 2014 edition of Geographical Magazine