BENGALURU: Black carbon aerosols (similar to soot) have reduced rainfall in south India during the pre-monsoon season. Research studies by the Indian Institute of Science have revealed the presence of ‘elevated aerosol layers’ over central and northern areas that is impacting rainfall distribution over India.
Black aerosols constitute only a small fraction of the atmospheric mass but they have the ability to alter climate by absorbing sunlight rather than reflecting it. If natural aerosols scatter light and are a cooling agent, black carbon aerosols are highly absorbing and therefore, a warming agent. Setting up measurement studies from air, ship and ground-based platforms and analysing satellite observations, Indian’s pioneering climate scientist Prof Satheesh conducted field experiments on light aerosols and has broken many myths on their impact on climate change. For this work, he is the recipient of 2018 Infosys Prize in Physical Sciences category.
According to Prof S K Satheesh, Centre for Atmospheric and Ocean Sciences, IISc, since the atmosphere is thin at higher levels, even a small amount of black carbon can cause intense warming. “We have shown that this leads to strong north-south gradients in aerosol-induced warming at high atmospheric levels. Model simulation studies indicate that such a scenario can affect the atmospheric circulation pattern and so impact the regional rainfall distribution over the country,” he said.
Research has indicated that elevated heating, due to black carbon aerosols during pre-monsoon, causes enhanced rain over the north-east and some parts of central India but reduction of rain over south.
“This gives a signature of aerosol heating induced migration of rain bands from north to northeast. This is not just limited to land but also affects the amount of rainfall occurring over the northern Indian Ocean and Bay of Bengal,” he said.