 |
| Titel |
Accounting for the effects of sastrugi in the CERES clear-sky Antarctic shortwave angular distribution models |
| VerfasserIn |
J. Corbett, W. Su |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-10), S.3163-3175 |
| Datensatznummer |
250116522
|
| Publikation (Nr.) |
 copernicus.org/amt-8-3163-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Cloud and the Earth's Radiant Energy System (CERES) instruments on NASA's
Terra, Aqua and Soumi NPP satellites are used to provide a long-term
measurement of Earth's energy budget. To accomplish this, the radiances
measured by the instruments must be inverted to fluxes by the use of a
scene-type-dependent angular distribution model (ADM). For permanent snow
scenes over Antarctica, shortwave (SW) ADMs are created by compositing radiance
measurements over the full viewing zenith and azimuth range. However, the
presence of small-scale wind blown roughness features called sastrugi cause
the BRDF (bidirectional reflectance distribution function) of the snow to vary significantly based upon the solar azimuth angle
and location. This can result in monthly regional biases between −12 and 7.5 Wm−2 in the inverted TOA (top-of-atmosphere) SW flux. The bias is assessed
by comparing the CERES shortwave fluxes derived from nadir observations with
those from all viewing zenith angles, as the sastrugi affect fluxes inverted
from the oblique viewing angles more than for the nadir viewing angles. In
this paper we further describe the clear-sky Antarctic ADMs from
Su et al. (2015). These ADMs account for the sastrugi effect by using
measurements from the Multi-Angle Imaging Spectro-Radiometer (MISR)
instrument to derive statistical relationships between radiance from
different viewing angles. We show here that these ADMs reduce the bias and
artifacts in the CERES SW flux caused by sastrugi, both locally and
Antarctic-wide. The regional monthly biases from sastrugi are reduced to
between −5 and 7 Wm−2, and the monthly-mean biases over
Antarctica are reduced by up to 0.64 Wm−2, a decrease of 74 %. These
improved ADMs are used as part of the Edition 4 CERES SSF (Single Scanner Footprint) data. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|