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| Titel |
Impact of satellite viewing-swath width on global and regional aerosol optical thickness statistics and trends |
| VerfasserIn |
P. R. Colarco, R. A. Kahn, L. A. Remer, R. C. Levy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 7 ; Nr. 7, no. 7 (2014-07-31), S.2313-2335 |
| Datensatznummer |
250115860
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| Publikation (Nr.) |
 copernicus.org/amt-7-2313-2014.pdf |
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| Zusammenfassung |
| We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite
aerosol optical thickness (AOT) product to assess the impact of reduced swath
width on global and regional AOT statistics and trends. Along-track and
across-track sampling strategies are employed, in which the full MODIS
data set is sub-sampled with various narrow-swath (~ 400–800 km) and
single pixel width (~ 10 km) configurations. Although view-angle
artifacts in the MODIS AOT retrieval confound direct comparisons between
averages derived from different sub-samples, careful analysis shows that with
many portions of the Earth essentially unobserved, spatial sampling
introduces uncertainty in the derived seasonal–regional mean AOT. These AOT
spatial sampling artifacts comprise up to 60% of the full-swath AOT
value under moderate aerosol loading, and can be as large as 0.1 in some
regions under high aerosol loading. Compared to full-swath observations,
narrower swath and single pixel width sampling exhibits a reduced ability to
detect AOT trends with statistical significance. On the other hand, estimates
of the global, annual mean AOT do not vary significantly from the full-swath
values as spatial sampling is reduced. Aggregation of the MODIS data at
coarse grid scales (10°) shows consistency in the aerosol trends
across sampling strategies, with increased statistical confidence, but
quantitative errors in the derived trends are found even for the full-swath
data when compared to high spatial resolution (0.5°) aggregations.
Using results of a model-derived aerosol reanalysis, we find consistency in
our conclusions about a seasonal–regional spatial sampling artifact in AOT.
Furthermore, the model shows that reduced spatial sampling can amount to
uncertainty in computed shortwave top-of-atmosphere aerosol radiative forcing
of 2–3 W m−2. These artifacts are lower bounds, as possibly other
unconsidered sampling strategies would perform less well. These results
suggest that future aerosol satellite missions having significantly less than
full-swath viewing are unlikely to sample the true AOT distribution well
enough to obtain the statistics needed to reduce uncertainty in aerosol
direct forcing of climate. |
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