The Swedish Meteorological and Hydrological Institute (SMHI) maps ice extent and type for shipping and weather prognoses (Table 6, #4.1). The ice extent at sea is of great importance for navigation, and assistance from an icebreaker is often needed, especially for harbors in the Bothnian Bay. Hence, ice conditions are mapped daily during the winter period, normally from the end of November until the end of May. Ice meteorologists take advantage of detailed reports about ice type and ice thickness from observers along the coast, e.g. pilots, special ice observers, and from the icebreakers passing through the ice-covered sea. Observations from helicopters are part of the regular icebreaking activities. Satellite images, especially from US weather satellites (NOAA-15, NOAA16 and NOAA-17), complement the ice reports and provide information on the large-scale ice situation on the scale 1 km x 1 km during clear sky conditions. More detailed ice information, down to the scale 20 m x 20 m, can be retrieved from a satellite-based instrument called Synthetic Aperture Radar (SAR). SAR sensors are also found onboard the Canadian RADARSAT (in operation since 1996) and on the European ENVISAT (since 2003) and provide information on the ice situation regardless of weather conditions and time of day. A good description of the ice situation is also needed as input data for weather prognosis models because the extent of sea ice has a major influence on weather (especially in coastal areas), and on temperature, cloudiness, and precipitation. Results from daily ice mapping are saved in a database from which e.g. climate statistics for the Baltic region may be generated.
Swedish Meteorological and Hydrological Institute (SMHI)