The fog/low stratus clouds in the Arctic: detection with multispectral satellite imagery

            The safe operation of aviation and shipping, particularly in areas of insufficient coverage of automatic meteorological stations in the Arctic requires accurate interpretation of satellite images. Operational detection of fog and low stratus clouds and recognizing of them on the background of snow and ice cover and cloudiness of the upper layer is very important challenge. 

           The verified images obtained by Aqua and Terra satellites with a scanning radiometer MODIS, which operates in 36 spectral bands, with wavelengths from 0.4 µm to 14.4 µm, were collected.  With the Beam VISAT 5.0 software, which was designed to work with satellite data in raster format, thematic digital techniques of satellite multispectral information, based on difference in the values of the integral brightness of the images, both in optical and far-infrared ranges of the spectrum, have been developed.  These techniques, models of additive color synthesis, improve the quality of interpretation of fogs and low stratus clouds in terms of the complex structure of cloudiness and underlying surface in polar regions. Developed RGB combinations, which are based on the selected MODIS bands are:

1. RGB (1.6 µm; 0.8 µm; 0.6 µm)
2. RGB (0.8 µm; 3.9-8.7 µm; 10.8 µm)
3. RGB (0.8 µm; 1.6 µm; 3.9-8.7 µm)
4. RGB ((0-12)-(0-11) µm, (0-11)-(0-3.8) µm, (0-11) µm)

          Analysis of the obtained images has shown that the developed models of color synthesis help to distinguish the fog/low stratus clouds under different conditions of cloudiness and underlying surface accurately.

Key words: remote sensing, satellite imagery, additive color synthesis, fog, low stratus clouds, polar regions