Aerosol optical depth trend over the Middle East
We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the moderate-resolution imaging spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2016-04-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/16/5063/2016/acp-16-5063-2016.pdf |
Summary: | We use the combined Dark Target/Deep Blue aerosol optical depth (AOD)
satellite product of the moderate-resolution imaging spectroradiometer
(MODIS) collection 6 to study trends over the Middle East between 2000 and
2015. Our analysis corroborates a previously identified positive AOD trend
over large parts of the Middle East during the period 2001 to 2012.<br><br>
We relate the annual AOD to precipitation, soil moisture and surface
winds to identify regions where these attributes are directly related to the AOD
over Saudi Arabia, Iraq and Iran. Regarding precipitation and soil moisture,
a relatively small area in and surrounding Iraq turns out to be of prime
importance for the AOD over these countries. Regarding surface wind speed,
the African Red Sea coastal area is relevant for the Saudi Arabian AOD.<br><br>
Using multiple linear regression we show that AOD trends and interannual
variability can be attributed to soil moisture, precipitation and surface
winds, being the main factors controlling the dust cycle. Our results confirm
the dust driven AOD trends and variability, supported by a decreasing
MODIS-derived Ångström exponent and a decreasing AERONET-derived fine
mode fraction that accompany the AOD increase over Saudi Arabia. The positive
AOD trend relates to a negative soil moisture trend. As a lower soil moisture
translates into enhanced dust emissions, it is not needed to assume growing
anthropogenic aerosol and aerosol precursor emissions to explain the
observations. Instead, our results suggest that increasing temperature and
decreasing relative humidity in the last decade have promoted soil drying,
leading to increased dust emissions and AOD; consequently an AOD increase is
expected due to climate change. |
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ISSN: | 1680-7316 1680-7324 |