Impact of aerosols from the Asian Continent on the adjoining oceanic environments |
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Authors: | K Parameswaran Sandhya K Nair K Rajeev |
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Institution: | (1) Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram, 695 022, India |
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Abstract: | Aerosol optical depth (AOD) at 630 nm wavelength over the oceanic regions adjoining the Asian Continent is examined using
a seven-year long data base derived from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA satellite to study
the mean spatial and temporal variations as well as to understand the impact of aerosols advecting from the continent. Depending
on the prevailing meteorological conditions and nature of synoptic circulation, the AOD over the oceanic region shows a systematic
annual variation. This annual pattern inturn also shows an inter-annual variability because of the corresponding variations
in the meteorological features over the continent as well as small-scale deviations in the nature of synoptic circulation.
The annual variation over the oceanic regions also shows a pronounced spatial heterogeneity depending on the influence of
continental aerosols. Making use of the wind speed dependence of sea-salt AOD at far-oceanic environments and monthly mean
wind speeds at small grids of size 5° × 5°, the annual variation of sea-salt AOD at different locations is studied to understand
the spatial heterogeneity of this component. The residual component obtained by subtracting this from the measured AOD is
the non-oceanic component due to advection from continent. The source regions for major continental advections are delineated
from the analysis of air-mass back trajectories at appropriate locations identified from the annual pattern of non-oceanic
component. The long-term effect of the continental impact is examined from the mean trend of AOD over the three major oceanic
regions. This study shows that the continental influence is most significant over the Arabian Sea, followed by the Bay of
Bengal and is almost insignificant in most of the regions over the Southern Hemispheric Indian Ocean, except for the effect
of smoke aerosols over a few locations near Indonesia and Madagascar. |
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Keywords: | Atmospheric Sciences aerosols remote sensing |
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