 |
| Titel |
Remote sensing of sea ice: advances during the DAMOCLES project |
| VerfasserIn |
G. Heygster, V. Alexandrov, G. Dybkjær, W. Hoyningen-Huene, F. Girard-Ardhuin, I. L. Katsev, A. Kokhanovsky, T. Lavergne, A. V. Malinka, C. Melsheimer, L. Toudal Pedersen, A. S. Prikhach, R. Saldo, R. Tonboe, H. Wiebe, E. P. Zege |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1994-0416
|
| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 6, no. 6 ; Nr. 6, no. 6 (2012-12-03), S.1411-1434 |
| Datensatznummer |
250003875
|
| Publikation (Nr.) |
 copernicus.org/tc-6-1411-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| In the Arctic, global warming is particularly pronounced so that we need to
monitor its development continuously. On the other hand, the vast and
hostile conditions make in situ observation difficult, so that available
satellite observations should be exploited in the best possible way to
extract geophysical information. Here, we give a résumé of the sea
ice remote sensing efforts of the European Union's (EU) project DAMOCLES
(Developing Arctic Modeling and Observing Capabilities for Long-term
Environmental Studies). In order to better understand the seasonal variation
of the microwave emission of sea ice observed from space, the monthly
variations of the microwave emissivity of first-year and multi-year sea ice
have been derived for the frequencies of the microwave imagers like AMSR-E
(Advanced Microwave Scanning Radiometer on EOS) and sounding frequencies of
AMSU (Advanced Microwave Sounding Unit), and have been used to develop an
optimal estimation method to retrieve sea ice and atmospheric parameters
simultaneously. In addition, a sea ice microwave emissivity model has been
used together with a thermodynamic model to establish relations between the
emissivities from 6 GHz to 50 GHz. At the latter frequency, the emissivity
is needed for assimilation into atmospheric circulation models, but is more
difficult to observe directly. The size of the snow grains on top of the sea
ice influences both its albedo and the microwave emission. A method to
determine the effective size of the snow grains from observations in the
visible range (MODIS) is developed and demonstrated in an application on the
Ross ice shelf. The bidirectional reflectivity distribution function (BRDF)
of snow, which is an essential input parameter to the retrieval, has been
measured in situ on Svalbard during the DAMOCLES campaign, and a BRDF model
assuming aspherical particles is developed. Sea ice drift and deformation is
derived from satellite observations with the scatterometer ASCAT (62.5 km
grid spacing), with visible AVHRR observations (20 km), with the synthetic
aperture radar sensor ASAR (10 km), and a multi-sensor product (62.5 km)
with improved angular resolution (Continuous Maximum Cross Correlation, CMCC
method) is presented. CMCC is also used to derive the sea ice deformation,
important for formation of sea ice leads (diverging deformation) and
pressure ridges (converging). The indirect determination of sea ice
thickness from altimeter freeboard data requires knowledge of the ice
density and snow load on sea ice. The relation between freeboard and ice
thickness is investigated based on the airborne Sever expeditions conducted
between 1928 and 1993. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|