Shear-induced roll structure of fog observed by a millimeter-wave scanning Doppler radar

[1] Three-dimensional fog roll structure induced by Kelvin-Helmholtz instability (KHI) is studied, based on observations made with a millimeter-wave scanning Doppler radar and a rawinsonde. Roll structure in a fog layer was observed below 150 m altitude when extremely large vertical shear (exceeding 100 m s−1 km−1) existed at 50–60 m altitude. The direction of the shear was perpendicular to the roll direction. The Richardson number was less than 0.25 at the shear altitude, which indicates that the fog roll structure was induced by KHI.