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Heterogeneity in pre-monsoon aerosol types over the Arabian Sea deduced from ship-borne measurements of spectral AODs

Kaskaoutis, DG and Kalapureddy, MCR and Krishna Moorthy, K and Devara, PCS and Nastos, PT and Kosmopoulos, PG and Kambezidis, HD (2010) Heterogeneity in pre-monsoon aerosol types over the Arabian Sea deduced from ship-borne measurements of spectral AODs. Atmospheric Chemistry and Physics, 10 (10). pp. 4893-4908.

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Abstract

Ship-borne sunphotometer measurements obtained in the Arabian Sea (AS) in the pre-monsoon season (18 April-10 May 2006) during a cruise campaign (ICARB) have been used to retrieve the Aerosol Optical Depth (AOD; τ ) and the Angstrom wavelength exponent (α). The continents surrounding the AS produce natural and anthropogenic aerosols that have distinctive influences on α and its spectral distribution. The α values were estimated by means of the least-squares method over the spectral bands 340-1020 nm and 340-870 nm. The spectral distribution of AOD in logarithmic co-ordinates could be fit using a 2nd order polynomial with higher accuracy in the wavelength band 340- 1020 nm than in the 340-870 nm band. A polynomial fit analytically parameterizes the observed wavelength dependencies of AOD with least errors in spectral variation of α and yields accurate estimates of the coefficients (a1 and a2). The coarse-mode (positive curvature in the lnτ λ vs. lnλ ) aerosols are mainly depicted in the Northern part of the AS closely associated with the nearby arid areas while fine-mode aerosols are mainly observed over the far and coastal AS regions. In the study period the mean AOD at 500 nm is 0.25±0.11 and the α340-1020 is 0.90±0.19. The α340-870 exhibits similar values (0.92±0.18), while significant differences revealed for the constant terms of the polynomial fit (a1 and a2) proportionally to the wavelength band used for their determination.

Item Type: Article
Additional Information: Copyright of this article belongs to European Geosciences Union
Uncontrolled Keywords: accuracy assessment; aerosol; air mass; heterogeneity; least squares method; monsoon; optical depth; parameterization; particle size; shipborne measurement; size distribution; spatial distribution; spectral analysis; wavelength; wind direction; wind velocity, Arabian Sea; Indian Ocean
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 22 May 2015 11:33
Last Modified: 22 May 2015 11:33
URI: http://moeseprints.incois.gov.in/id/eprint/790

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