Abstract
Abstract. We have studied the possibility of combining the high-resolution synthetic aperture radar (SAR) segmentation and ice concentration estimated by radiometer brightness temperatures. Here we present an algorithm for mapping a radiometer-based concentration value for each SAR segment. The concentrations are estimated by a multi-layer perceptron (MLP) neural network which has the AMSR-2 (Advanced Microwave Scanning Radiometer 2) polarization ratios and gradient ratios of four radiometer channels as its inputs. The results have been compared numerically to the gridded Finnish Meteorological Institute (FMI) ice chart concentrations and high-resolution AMSR-2 ASI (ARTIST Sea Ice) algorithm concentrations provided by the University of Hamburg and also visually to the AMSR-2 bootstrap algorithm concentrations, which are given in much coarser resolution. The differences when compared to FMI daily ice charts were on average small. When compared to ASI ice concentrations, the differences were a bit larger, but still small on average. According to our comparisons, the largest differences typically occur near the ice edge and sea–land boundary. The main advantage of combining radiometer-based ice concentration estimation and SAR segmentation seems to be a more precise estimation of the boundaries of different ice concentration zones.
Highlights
Ice concentration is defined as the ratio of the ice-covered area to the total area for a given sea region
We evaluated the algorithm results by comparing them to the Finnish Meteorological Institute (FMI) digitized ice chart grids, which have a nominal resolution of 1 km, and to the high-resolution (3.125 km)
We have developed an algorithm combining sea ice concentration estimates based on radiometer data and Synthetic aperture radar (SAR) segmentation to yield high-resolution ice concentration estimates
Summary
Ice concentration is defined as the ratio of the ice-covered area to the total area for a given sea region. Baltic Sea ice AMSR-2 brightness temperature mosaics from 23 January to 1 February 2014, and a test data set, consisting of daily cover has large annual and local variations. The ice and weather conditions in this Arctic area are different from the Baltic Sea. Typically the weather during the winter months is colder, usually clearly below 0 ◦C, and the snow cover is typically wet only during the melting period starting in May–June. The weather during the winter months is colder, usually clearly below 0 ◦C, and the snow cover is typically wet only during the melting period starting in May–June In this Arctic test area, the ice concentrations vary because the ice is moving in most parts of the Arctic test area. In the Baltic, it is typical that some areas melt and refreeze during the wintertime due to rapid temperature changes
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