A study of 15-year aerosol optical thickness and direct shortwave aerosol radiative effect trends using MODIS, MISR, CALIOP and CERES
By combining Collection 6 Moderate Resolution and Imaging Spectroradiometer (MODIS) and Version 22 Multi-angle Imaging Spectroradiometer (MISR) aerosol products with Cloud and Earth's Radiant Energy System (CERES) flux products, the aerosol optical thickness (AOT, at 0.55 µm) and shortwave...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/13849/2017/acp-17-13849-2017.pdf |
| Summary: | By combining Collection 6 Moderate Resolution and Imaging
Spectroradiometer (MODIS) and Version 22 Multi-angle Imaging
Spectroradiometer (MISR) aerosol products with Cloud and Earth's
Radiant Energy System (CERES) flux products, the aerosol optical
thickness (AOT, at 0.55 µm) and shortwave (SW) aerosol
radiative effect (SWARE) trends are studied over ocean for the near-full Terra (2000–2015) and Aqua (2002–2015) data records. Despite
differences in sampling methods, regional SWARE and AOT trends are
highly correlated with one another. Over global oceans, weak SWARE
(cloud-free SW flux) and AOT trends of 0.5–0.6 W m<sup>−2</sup>
(−0.5 to −0.6 W m<sup>−2</sup>) and 0.002 AOT decade<sup>−1</sup>
are found using Terra data. Near-zero AOT and SWARE trends are also
found for using Aqua data, regardless of the angular distribution models
(ADMs) used. Regionally, positive AOT and cloud-free SW flux (negative SWARE) trends are found over the Bay of Bengal, the Arabian Sea, the Arabian/Persian Gulf and the
Red Sea, while statistically significant negative trends are derived
over the Mediterranean Sea and the eastern US coast. In addition,
the global mean instantaneous SW aerosol direct forcing efficiencies
are found to be ∼ −60 W m<sup>−2</sup> AOT<sup>−1</sup>, with
corresponding SWARE values of ∼ −7 W m<sup>−2</sup> from both
Aqua and Terra data, again regardless of CERES ADMs
used. Regionally, SW aerosol direct forcing efficiency values of
∼ −40 W m<sup>−2</sup> AOT<sup>−1</sup> are found over the southwest
coast of Africa where smoke aerosol particles dominate in
summer. Larger (in magnitude) SW aerosol direct forcing efficiency
values of −50 to −80 W m<sup>−2</sup> AOT<sup>−1</sup> are found over
several other dust- and pollutant-aerosol-dominated regions. Lastly,
the AOT and SWARE trends from this study are also intercompared
with aerosol trends (such as active-based ones) from several previous
studies. Findings suggest that a cohesive understanding of the
changing aerosol skies can be achieved through the analysis of
observations from both passive- and active-based analyses, as well
as from both narrowband and broadband datasets. |
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| ISSN: | 1680-7316 1680-7324 |