Aerosol-induced intensification of cooling effect of clouds during Indian summer monsoon is a collaborative study between University of Hyderabad (Dr. Vijay Kanawade and Mr. Abin Thomas), IIT Kanpur (Prof. Sachchida Nand Tripathi and Dr. Chandan Sarangi) and IIT Delhi (Dr. Dilip Ganguly) and it has been now published in the prestigious Nature Communications. It can be accessed at the website https://www.nature.com/articles/s41467-018-06015-5
The long-term satellite data (2002-2016) and a global reanalysis modelled data supported with a detailed cloud-resolving numerical modeling provided robust evidence of aerosol-induced cloud modifications during the Indian Summer Monsoon. Aerosols (suspended solid or liquid particles in air) influence the cloud physical, microphysical, and radiative properties. However, the effect of aerosols on clouds from continental mesoscale convective cloud systems during Indian Summer monsoon had been unknown.
Authors find that aerosol interactions with clouds induce changes to the cloud structure and thereby have an intensified net cooling effect at the surface. Under high aerosol loading, clouds tend to have smaller droplets which instead of falling down as rain gets lofted up with the cloud parcels. This leads to enhanced formation of ice mass in these developing convective clouds. The increased formation of ice particles further releases more latent heat of freezing and invigorates the vertical development of convective clouds until they reaches the tropopause. The thermal capping at tropopause expands these vertically growing clouds horizonatlly leading to formation to thick stratiform cloud layers as opposed to much thinner anvil clouds otherwise. Enhancement in formation of these thick stratiform anvil clouds cause enhanced reflection of shortwave radiation from top of the clouds, leading to increased cooling. The longer lifetime of the thicker stratiform anvil clouds eventually intensifies a net cooling effect of clouds. The rate of net cooling effect of clouds during Indian summer monsoon is higher compared to previous studies in USA and China owing to higher aerosol emission rates at the surface over Indian subcontinent. The cooling effect may further stabilize the lower troposphere, leading the reduction in planetary boundary layer height. This may lead to enhanced accumulation of aerosols within the planetary boundary layer which can further decrease the turbulence in the lower troposphere. This may have climatic affect on moisture transport as well as spatial distribution of clouds and surface rainfall during Indian summer monsoon.
Prof. Appa Rao Podile, Vice-Chancellor, University of Hyderabad (UoH) appreciated the efforts of the young faculty member (Dr. Vijay Kanawade) for showing the path to others.
Dr. Kanawade, the corresponding author of the paper works at Centre for Earth, Ocean & Atmospheric Sciences, University of Hyderabad and can be contacted on email: firstname.lastname@example.org