Influence of continental advection on aerosol characteristics over Bay of Bengal (BoB) in winter: results from W-ICARB cruise experiment
Kharol, S. K.
Badarinath, K. V. S.
Kaskaoutis, D. G.
Sharma, A. R.
The transport of aerosols and pollutants from continental India to the
adjoining oceanic areas is a major topic of concern and several experimental
campaigns have been conducted over the region focusing on aerosol
characteristics and their climate implications. The present study analyzes
the spectral aerosol optical depth (AOD) variations over Bay of Bengal (BoB)
during Winter-Integrated Campaign for Aerosols, gases and Radiation Budget
(W-ICARB) from 27 December 2008 to 30 January 2009 and
investigates the influence of the adjoining landmass to the marine aerosol
field. High AOD<sub>500</sub> values (>0.7) occurred over northern BoB due to
outflow of aerosols and pollutants from the densely populated Indo-Gangetic
Plains (IGP); low AOD<sub>500</sub> (0.1–0.2) was observed in central and southern
BoB, far away from the mainland. The Angstrom exponent "α" was observed
to be high (>1.2) near coastal waters, indicating relative abundance of
accumulation-mode continental aerosols. On the other hand, over southern BoB
its values dropped below ~0.7. National Center for Environmental
Prediction (NCEP) reanalysis data on winds at 850 and 700 hPa, along with
air-mass trajectories calculated using Hybrid Single Particle Lagrangian
Integrated Trajectory (HYSPLIT) model, suggested transport of continental
aerosols from central and northern India over the BoB. On the other
hand, when the ship was crossing the eastern BoB, the aerosol loading was
strongly affected by air-masses originating from Southeast Asia, causing an
increase in AOD and α. Biomass-burning episodes over the region
played an important role in the observed aerosol properties. Terra/Aqua
Moderate Resolution Imaging Spectroradiometer (MODIS) AOD<sub>550</sub> and cruise
measured AOD<sub>550</sub> showed good agreement (<I>R</I><sup>2</sup> = 0.86 and 0.77,
respectively) over BoB, exhibiting similar AOD and α spatio-temporal