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

Abstract

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 1 km 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 ~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.

Radiative Impacts of Aerosols During COVID-19 Lockdown Period Over the Indian Region

“…During spring, anthropogenic and dust aerosols are transported from the Indo-Gangetic Plain and Myanmar region to the Bay of Bengal (Nair et al, 2016). In agreement with our results, past studies show evidence of anthropogenic (Satheesh et al, 2001;Kumar et al, 2014;Nair et al, 2016) and dust (Lakshmi et al, 2017) aerosol loading over the Bay of Bengal during the spring season. Trajectory analysis-based studies also show that anthropogenic aerosols over the Bay of Bengal are associated with transport from the Indian region (Nair et al, 2016).…”

Sensitivity of aerosol radiative forcing to various aerosol parameters over the Bay of Bengal

“…The majority of the aerosol loading was closer to the surface during January and above 1 km during May. The aerosol loading is similar to the one observed by Lakshmi et al (2017)…”

“…The BL height for winter and pre-monsoon over the BoB has been found to be varying from 500 m to 1 km (Subrahamanyam et al 2012;Lakshmi et al 2017). Since the present study is a model analysis of factors affecting the aerosol forcing, two profiles representing aerosols within the BL (during winter -January) and aerosols above the BL (during premonsoon -May) have been used (figure 1a).…”

Aerosol Induced Changes in Sea Surface Temperature Over the Bay of Bengal Due to COVID-19 Lockdown

“…The high population density and numerous industries over the region mean that emissions over these source regions are relatively high. Northwesterly winds during the period further act as conduits transporting these aerosols to the BoB (Lakshmi et al, 2017). Southern BoB is affected by the surrounding coastal regions and aerosols from the Arabian Sea, which is less affected by anthropogenic activities leading to lower AOD (Nair et al, 2009).…”