Abstract
This paper purports the results of a co mparative study conducted to investigate aerosol optical, microphysical and radiative characteristics over an Exclusive Econo mic Zone (EEZ) associated with pristine environment, and coastal regions influenced by human activities, during 2009-2011. The measurements over the EEZ of the Arabian Sea (AS) were carried out fro m Sagar Kanya (SK-226) ship while over the coastal locations (Mumbai and Goa); employing Sun-photometers. The aerosol optical thickness (AOT) at 500 n m was found to be in the range of 0.3-0.45 in the EEZ wh ile it was 0.45-0.75 in the coastal regions. The AOTs at all the three sites showed a good association with concurrent meteorological parameters. Angstrom parameters (alpha and beta, representative of aerosol size d istribution and loading, respectively) indicated opposite behavior in the pristine (EEZ) but similar trend in the polluted coastal regions. This feature reveals that the aerosol loading over the EEZ is contributed by coarse-mode particles while the fine-mode particles contribute to the loading over coastal regions. Abundance of fine-mode part icles over the coastal regions is also evidenced from the second order polynomial fit coefficients (a1 and a2) of alpha. This aspect corroborates the long-range transport of air-mass over the experimental sites fro m the western coast India.
Highlights
Aerosols are an integ ral part o f the at mosphere and oceans
The present paper focuses on the temporal, spatial and spectral variat ions of Aerosol Optical Thickness (AOT) over the Exclusive Econo mic Zone (EEZ) (Arabian Sea) and coastal locations[Mumbai and Goa], based on Sun-photometric measurements made on-board research vessel, Sagar Kanya; and near the coast over land and sea regions
Surface radiat ive cooling due to aerosols is found to be larger over the coastal Arabian Sea than that over the EEZ
Summary
Aerosols are an integ ral part o f the at mosphere and oceans. Along with g reenhouse gases, they can affect climate in several ways. There are a number of networks of ground-based Sun-photometers measuring AOT at different locations around the world. A ERONET Sun-photometers cannot be located everywhere, and every time AOT data are needed, such as during some field campaigns and other special events, as well as routine measurements applied to certain specific studies. During the months of December–Feb ruary, north-easterly wind over the Indian subcontinent carries aerosols from the land towards the oceanic atmosphere, affecting the coastal regions These months, become most ideal period to study the effect of continental aerosols and their dispersal in the oceanic at mosphere. The present paper focuses on the temporal, spatial and spectral variat ions of AOT over the EEZ (Arabian Sea) and coastal locations[Mumbai (formerly known as Bo mbay) and Goa], based on Sun-photometric measurements made on-board research vessel, Sagar Kanya; and near the coast over land and sea regions. The data points, which gave the best second-order polynomial fit between ln AOT versus ln λ[15,16] only, were considered for analysis in the present study
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