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| Titel |
Heterogeneity in pre-monsoon aerosol types over the Arabian Sea deduced from ship-borne measurements of spectral AODs |
| VerfasserIn |
D. G. Kaskaoutis, M. C. R. Kalapureddy, K. Krishna Moorthy, P. C. S. Devara, P. T. Nastos, P. G. Kosmopoulos, H. D. Kambezidis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 10 ; Nr. 10, no. 10 (2010-05-26), S.4893-4908 |
| Datensatznummer |
250008484
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| Publikation (Nr.) |
 copernicus.org/acp-10-4893-2010.pdf |
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| Zusammenfassung |
| 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 Ångström 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 lnτλ 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
optical properties are direct consequence of the local winds and air-mass
trajectories along with the position of the ship. |
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