• Contrary to the general notion that pre-monsoon aerosol loading results in decrease in seasonal rainfall, a long-term (2002-2013) satellite observational study and model-based analysis by researchers from the Indian Institute of Technology (IIT) Kanpur has found that higher aerosol loading results in delayed but more rainfall over Central and Northern India.
• Higher aerosol loading changes cloud properties in terms of size (both height and width) and microphysics, which results in more rainfall.

Size matters

• Fourteen microns is the agreed raindrop size, and until it reaches this size, the growth of droplets in the cloud is primarily driven by condensation. When aerosol particles are higher, the number of nucleation sites increases resulting in far too many number of droplets.

More Facts on the Study:

• Fourteen microns is the agreed raindrop size, and until it reaches this size, the growth of droplets in the cloud is primarily driven by condensation.
• When aerosol particles are higher, the number of nucleation sites increases resulting in far too many number of droplets.
• In the absence of cloud, aerosol particles tend to absorb solar radiation and this leads to warming or less decrease in temperature with height. As a result, there is suppression of convection leading to further suppression of cloud formation.
• Till now scientists have shown that presence of more aerosol in pre-monsoon season may lead to reduction in total monsoon rainfall due to aerosol-solar radiation interactions.
• The aerosol-cloud microphysical feedback suggests that higher aerosol loading can enhance the strength of convective rainfall and increase the frequency and intensity of extreme rainfall during Indian summer monsoon.

Source: The Hindu