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

Kaskaoutis, D. G. ; Kalapureddy, M. C. R. ; Krishnamoorthy, K. ; Devara, P. C. S. ; Nastos, P. T. ; Kosmopoulos, P. G. ; Kambezidis, H. D. (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. ISSN 1680-7316

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Official URL: http://www.atmos-chem-phys.net/10/4893/2010/acp-10...

Related URL: http://dx.doi.org/10.5194/acp-10-4893-2010


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. Observed day-to-day variability in the aerosol load and Correspondence to: M. C. R. Kalapureddy (kalapureddy1@gmail.com) optical properties are direct consequence of the local winds and air-mass trajectories along with the position of the ship.

Item Type:Article
Source:Copyright of this article belongs to European Geosciences Union.
ID Code:17220
Deposited On:16 Nov 2010 08:11
Last Modified:17 May 2016 01:53

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