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| Titel |
Ground-based remote sensing of thin clouds in the Arctic |
| VerfasserIn |
T. J. Garrett, C. Zhao |
| 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 ; 6, no. 5 ; Nr. 6, no. 5 (2013-05-14), S.1227-1243 |
| Datensatznummer |
250017890
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| Publikation (Nr.) |
 copernicus.org/amt-6-1227-2013.pdf |
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| Zusammenfassung |
| This paper describes a method for using interferometer measurements of
downwelling thermal radiation to retrieve the properties of single-layer
clouds. Cloud phase is determined from ratios of thermal emission in three
"micro-windows" at 862.5 cm−1, 935.8 cm−1,
and 988.4 cm−1 where absorption by water vapour is particularly
small. Cloud microphysical and optical properties are retrieved from thermal
emission in the first two of these micro-windows, constrained by the
transmission through clouds of primarily stratospheric ozone emission at 1040 cm−1. Assuming a cloud does not approximate a blackbody, the
estimated 95% confidence retrieval errors in effective radius re,
visible optical depth τ, number concentration N, and water path WP
are, respectively, 10%, 20%, 38% (55% for ice crystals), and
16%. Applied to data from the Atmospheric Radiation Measurement programme
(ARM) North Slope of Alaska – Adjacent Arctic Ocean (NSA-AAO) site near
Barrow, Alaska, retrievals show general agreement with both ground-based
microwave radiometer measurements of liquid water path and a method that uses
combined shortwave and microwave measurements to retrieve re, τ
and N. Compared to other retrieval methods, advantages of this technique
include its ability to characterise thin clouds year round, that water vapour
is not a primary source of retrieval error, and that the retrievals of
microphysical properties are only weakly sensitive to retrieved cloud phase.
The primary limitation is the inapplicability to thicker clouds that radiate
as blackbodies and that it relies on a fairly comprehensive suite of ground
based measurements. |
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