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| Titel |
Validation of MODIS derived aerosol optical depth and an investigation on aerosol transport over the South East Arabian Sea during ARMEX-II |
| VerfasserIn |
M. Aloysius, M. Mohan, S. Suresh Babu, K. Parameswaran, K. Krishna Moorthy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 6 ; Nr. 27, no. 6 (2009-06-08), S.2285-2296 |
| Datensatznummer |
250016544
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| Publikation (Nr.) |
 copernicus.org/angeo-27-2285-2009.pdf |
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| Zusammenfassung |
| The influence of wind and humidity on aerosol optical depth (AOD)
over the Arabian sea is being investigated using MODIS (Moderate
Resolution Imaging Spectroradiometer) Level 3 (Collection-5) and
NCEP (National Centres for Environmental Prediction) reanalysis data
for the second phase of the Arabian Sea Monsoon Experiment
(ARMEX-II) over the South East Arabian Sea (SEAS) in the pre-monsoon
period (14 March–10 April 2003). In order to qualify MODIS data for
this study, MODIS aerosol parameters were first compared with ship
borne Microtops measurements. This showed correlations 0.96–0.97 in
the case of spectral AODs and a correlation 0.72 for the angstrom
exponents. The daily AOD data from MODIS and winds from NCEP reveal
that the ship observed episodic enhancement and decay of AOD at the
TSL (Time Series Location) during 23 March–6 April 2003 was
caused by the southward drift of an aerosol pocket driven by an
intensification and reduction of surface pressure in the North
Western Arabian Sea with a low altitude convergence prevailing over
SEAS. The AOD increase coincided with a decrease in the Angstrom
exponent and the fine mode fraction suggesting the pocket being
dominated by coarse mode particles. A partial correlation analysis
reveals that the lower altitude wind convergence is the most
influential atmospheric variable in modulating AOD over the ARMEX-II
domain during the TSL period. However, surface winds at a distant
zone in the north/north west upwind direction also had a moderate
influence, though with a lag of two days. But this effect was minor
since the winds were not strong enough to produce marine aerosols
matching with the high AODs over the ARMEX-II domain. These findings
and the similarity between MODIS column mass concentration and the
ship borne QCM (Quartz Crystal Microbalance) measured coarse mode
mass concentration, suggest that the aerosol pocket was mostly
composed of coarse mode mineral dust in the lower atmospheric
altitudes transported from the Arabian deserts. |
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