Studies of Clouds Produced by Low Level Jets and Mountain Waves

Abstract

Two kinds of special billow clouds were detected by photographic observation. These clouds were in two different layers at altitude estimated to be 1700 and 3000m. The photographs were taken at Numanohata in Southern Hokkaido in July 1963 during a field project on Artificial Fog Dispersal. Analysis revealed that the upper altostratus billow was a lee wave cloud produced by the Hidaka range with a prevailing east wind. The lower stratocumulus billow was in rows in the statically unstable layer of moist unsaturated air. This effect was produced by the wind shear above and below the cloud layer. The direction of this wind shear was nearly perpendicular to the axes of the rows. The distance between each element of the upper altostratus billow was not the same. In some instances, the distance between the elements was nearly twice the wave length. This suggests that a lee wave is not only a simpe sinusoidal wave, but may be distorted, with different amplitudes at each wave crest.