Sastrugi sea ice than on multiyear ice. First-year ice is smoother than multiyear ice, which allows the wind to pass uniformly over the surface without topographic obstructions. Except during the melt season, snow is dry and light in climates cold enough for sea ice, allowing the snow to be easily blown and create sastrugi parallel to the wind direction. The locations of sastrugi are fixed by March in the northern hemisphere and may be linked to the formation of melt ponds. Melt ponds are more likely to form in the depressions between zastrugi on first-year ice. Sastrugi Sastrugi, or zastrugi, are
Surface wave detection by animals to test certain wave properties. Wave characteristics are measured optically. This is done by shining a laser (often helium-neon) at the water surface. Reflections and distortions of the laser’s beam are picked up by a photodiode. Fishes' movements are videotaped with a high-speed camera from above the testing tank so that the precise timing and nature of their responses’ to stimuli can be reviewed. "Aplocheilus lineatus" assumes a hunting posture at the water surface in which it holds the top of its head within 200 μm of the water surface. On perception of appropriate wave stimuli, fish first turn towards