This Envisat image, acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 25 January 2010, captures the deep freeze that has gripped southeastern Europe in recent days. Along with Arctic temperatures, heavy snowfall has covered (counterclockwise from top right to bottom right) parts of the Ukraine, Moldova, Romania, Bulgaria, Greece and Turkey. The cold snap is a result of cold Arctic air sweeping across the region. The northerly wind is visible in the cloud formations over the Black Sea. Wind direction is reported by the direction from which it originates, so a northerly wind blows air from north to south.