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| Titel |
Comparison of MODIS 3 km and 10 km resolution aerosol optical depth retrievals over land with airborne sunphotometer measurements during ARCTAS summer 2008 |
| VerfasserIn |
J. M. Livingston, J. Redemann, Y. Shinozuka, R. Johnson, P. B. Russell, Q. Zhang, S. Mattoo, L. Remer, R. Levy, L. Munchak, S. Ramachandran |
| 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 ; 14, no. 4 ; Nr. 14, no. 4 (2014-02-21), S.2015-2038 |
| Datensatznummer |
250118420
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| Publikation (Nr.) |
 copernicus.org/acp-14-2015-2014.pdf |
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| Zusammenfassung |
| Airborne sunphotometer measurements acquired by the NASA Ames Airborne
Tracking Sunphotometer (AATS-14) aboard the NASA P-3 research aircraft are
used to evaluate dark-target over-land retrievals of extinction aerosol
optical depth (AOD) from spatially and temporally near-coincident
measurements by the Moderate Resolution Imaging Spectroradiometer (MODIS)
during the summer 2008 Arctic Research of the Composition of the Troposphere
from Aircraft and Satellites (ARCTAS) field campaign. The new MODIS
Collection 6 aerosol data set includes retrievals of AOD at both 10 km × 10 km
and 3 km × 3 km (at nadir) resolution. In this paper we compare MODIS and AATS
AOD at 553 nm in 58 10 km and 134 3 km retrieval grid cells. These AOD
values were derived from data collected over Canada on four days during
short time segments of five (four Aqua and one Terra) satellite overpasses
of the P-3 during low-altitude P-3 flight tracks. Three of the five
MODIS–AATS coincidence events were dominated by smoke: one included a P-3
transect of a well-defined smoke plume in clear sky, but two were confounded
by the presence of scattered clouds above smoke. The clouds limited the
number of MODIS retrievals available for comparison, and led to MODIS AOD
retrievals that underestimated the corresponding AATS values. This happened
because the MODIS aerosol cloud mask selectively removed 0.5 km pixels
containing smoke and clouds before the aerosol retrieval. The other two
coincidences (one Terra and one Aqua) occurred during one P-3 flight on the
same day and in the same general area, in an atmosphere characterized by a
relatively low AOD (< 0.3), spatially homogeneous regional haze from
smoke outflow with no distinguishable plume. For the ensemble data set for
MODIS AOD retrievals with the highest-quality flag, MODIS AOD agrees with
AATS AOD within the expected MODIS over-land AOD uncertainty in 60% of
the retrieval grid cells at 10 km resolution and 69% at 3 km resolution.
These values improve to 65 % and 74%, respectively, when the
cloud-affected case with the strongest plume is excluded. We find that the
standard MODIS dark-target over-land retrieval algorithm fails to retrieve
AOD for thick smoke, not only in cloud-contaminated regions but also in
clear sky. We attribute this to deselection, by the cloud and/or bright
surface masks, of 0.5 km resolution pixels that contain smoke. |
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