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Project for estimation of long-term variability in ice concentration


To develop an improved ice concentration / ice edge algorithm for
use on passive microwave data as well as a physical model of the
atmospheric forcing of the ice edge to obtain a better explanation
of interannual variability in the sea ice extent record for the

Improvement of the ice concentration / ice edge algorithm will be
based on digital data for case study regions (Weddell and
Bellingshausen Seas, 1986, 1992, 1993) including cloud-free
coverage by visible/infrared sensors (AVHRR, OLS). The accuracy
of sea ice extent derived from passive microwave observations will
be estimated by comparison with the higher resolution VIS/IR data.
Validation and calibration of VIS/IR ice concentration estimates
will require with coincident Landsat images (1986 case studies)
and radar and line-scan camera images (1992, 1993 case studies).
Coincident surface temperature data over the ice (buoys, ECMWF
model) and pressure fields at the surface and 500 mb (ECMWF) will
then be examined to study the effect of weather and surface
condition variability (regional and seasonal) on algorithm
performance. Accounting for regional and seasonal differences in
ice conditions will entail primarily parameterizing meteorological
data in the calculation of algorithm coefficients.

To develop a model of the atmospheric forcing, the relationship
between atmospheric circulation and ice extent will be examined on
interseasonal and iterannual time scales. This will entail
determining depression tracks and a meridional forcing index from
model fields and comparing them to ice extent derived from
satellite data. For the latter passive microwave ice extents and
estimates of ice edge motion from multi-temporal AVHRR images will
be used. The primary meteorological data set for this work will
be the digitized daily Australian surface and upper air analyses
covering the period from the mid 1970's to the present. Analysis
of the effects of individual atmospheric systems on sea ice extent
will be carried out on a limited number of case studies. Storm
centers, surface wind speed, and surface temperature will be
related to ice edge position as depicted in individual AVHRR
scenes obtained during 1992 and 1993. Effects in the Weddell and
Bellingshausen Seas will be contrasted.

Using the improved algorithm ice extent around the Antarctic from
1978 to the present will be derived from the passive microwave
data set. The application of the atmospheric forcing model to the
ice extent record should help explain the observed interannual
variability in term of atmospheric cycles.

Aufforderung zur Vorschlagseinreichung

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Universität Bremen
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28334 Bremen

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Beteiligte (3)