A segment on a graphical or digital ice chart connecting the location of an ice cover point at successive moments of time. For subsequent analysis and calculations, the observed drift vector field is
usually interpolated to regular grid points with a step size chosen as required. The vectors at the regular grid points can also be obtained by means of model calculations.
Snow that has been moved by wind and collected into snowdrifts. A wind speed of about 13 mph will move light surface snow. In weather reports, snow lifted less than 6 ft above the surface is drifting
snow, more than 6 ft is blowing snow.