the numerical sea ice forecast in finland in the winter 1993-94 ...

ERS-1 images were delivered with a resolution of 100 m, and a width of ca. 100 km. The cycles of 3
d were used during the 1994 experiment, which allowed two orbits: Helsinki - Bothnian Bay (“A”-
orbit) and Bothnian Bay - Stockholm (“Dl’-orbit) (Fig. 3).
In the analysis of the 1994 ERS- 1 images most of the problems encountered in the winter of 1992/93
(Seinä & Grönvall 1994, Herland et al. 1994) were avoided. Winter 1993 was a mild one having high
humidity areas, and the ice surface was bare or/and wet. In 1994 the air temperature was mostly under
freezing point and hence the analysing problems were avoided. At the end of experiment melted snow
caused some analysing problems in the Gulf of Finland. The field experiment, however, going on in
the area solved the calibration. For the classification of ice and open water the two scales contextual
classifier was used allowing classification in ten minutes (Similä 1994a).
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Fig. 3. “A” and “D” orbits of ERS- 1.
A field experiment was held during March 14-28 in the Bothnian Bay, the Bothnian Sea, and the Gulf
of Finland based aboard the research vessel Aranda.
Using a specially designed Swedish-Finnish icebreaker communication system (IRIS) some 30 % of
the images were delivered into active icebreakers almost in real-time. The icebreakers have
Macintosh-based image processors allowing satellite image handling together with ice charts and sea
charts in order to find out the best possible route for assisted vessels. All icebreaker officers have
expressed their enthusiasm for using SAR images in ice breaking activities. The ERS-1 resolution of
100 m compared to NOAA’s 1.1 km and the availability of ice information during storm conditions
were especially considered most important.
In Appendixes 1 and 2 the received ERS-1 SAR images are analysed using the method described in
Herland et al. (1994).
In the winter of 1992193 the main analysing problems occurred in ice/water-, ice edge- and undefined
areas -definitions as shown in the figure 4. Ice/water means the failure to define ice- or water-cover,
ice edge means failure in the definition of edges of different types of ice or between ice and water, and