Vertical Structure of Aerosols and Mineral Dust Over the Bay of Bengal From Multisatellite Observations

The vertical distribution of aerosol and dust extinction coefficient over the Bay of Bengal is examined using the satellite observations (Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) and Moderate Resolution Imaging Spectroradiometer (MODIS)) for the period from 2006 to 2017. Distinct seasonal pattern is observed in the vertical structure of both aerosol and dust over the Bay of Bengal with an enhancement of 24% in the aerosol extinction above 1km from winter (December, January and February) to premonsoon (March, April, and May). Significant contribution of dust is observed over the northern Bay of Bengal during premonsoon season where 22% of the total aerosol extinction is contributed by dust aerosols transported from the nearby continental regions. During winter, dust transport is found to be less significant with fractional contribution of similar to 10%-13% to the total aerosol optical depth over the Bay of Bengal. MODIS-derived dust fraction (fine mode based) shows an overestimation up to twofold compared to CALIOP dust fraction (depolarization based), whereas the Goddard Chemistry Aerosol Radiation and Transport-simulated dust fraction underestimates the satellite-derived dust fractions over the Bay of Bengal. Though the long-term variation in dust aerosol showed a decreasing trend over the Bay of Bengal, the confidence level is insufficient in establishing the robustness of the observed trend. However, significant dust-induced heating is observed above the boundary layer during premonsoon season. This dust-induced elevated heating can affect the convection over the Bay of Bengal which will have implication on the monsoon dynamics over the Indian region.