Improved sea ice monitoring for the Baltic Sea - Summary of first two years
Leif E.B. Eriksson(1), Karin Borenäs(2), Wolfgang Dierking(3), Per Pemberton(2) and Henrik Lindh(4)
(1) Chalmers University of Technology, Dept. of Radio and Space Science, SE-41296 Göteborg, Sweden
(2) Swedish Meteorological and Hydrological Institute, Sven Källfelts gata 15, SE-42671 Västra Frölunda, Sweden
(3) Alfred Wegener Inst. for Polar and Marine Research, Bussestrasse 24, D-27570 Bremerhaven, Germany
(4) Swedish Meteorological and Hydrological Institute, Folkborgsvägen 1, SE-60176 Norrköping, Sweden
Since many years SAR data from satellites are used for operational monitoring of sea ice. In January 2007 a project started in Sweden that will assess if monitoring and forecasting capabilities can be improved by the use of SAR data from new, more advanced satellites. The main objective is to evaluate how multi-polarisation SAR data from L-band (ALOS), C-band (Envisat and Radarsat-2) and X-band (TerraSAR-X and COSMO-SkyMed) can improve determination of sea ice concentration, classification of ice types and detection of ice ridges. The intention is also to investigate the possibilities to use ALOS ScanSAR data as a complement and backup for the Radarsat ScanSAR data that currently is used for operational sea ice monitoring.
Data acquisitions have been granted for three consecutive ice seasons and field campaigns were conducted in February to April 2007 and in March 2008. The campaigns, named “Bothnia Ice Sar experiment 2007 and 2008” (BothnIS-2007 and BothnIS-2008), took place along the coast between the cities Umeå and Luleå in northern Sweden. A number of helicopter flights were flown with cameras for the visual and thermal infrared regimes. In this way location and structure of the ice edge, new ice, melt ponds and ice ridges could be documented for large areas. These observations were complemented by weather data and measurements on the ice. In 2007 only data from ALOS PALSAR and Envisat ASAR were available. In 2008 the first TerraSAR-X images were acquired and in 2009 we expect to receive data also from Radarsat-2 and COSMO-SkyMed.
A comparison between ScanSAR images from ALOS and Envisat shows that the main ice features can be seen in both image types, indicating that ALOS ScanSAR data can be used as a complement to the C-band data that is used currently. The analysis of polarimetric L-band data clearly showed the advantage of the cross-polarized channel for reduction of the wind sensitivity of open water surfaces. Results from the data collected in 2008 is currently being analysed and will be presented at the symposium.