VORTICITY DISTRIBUTION AND ADVECTION IN THE LOWER AND MIDDLE TROPOSPHERE

Abstract

The three-dimensional distribution of relative vorticity in the lower 25,000 feet of the atmosphere, and over a three-day period of time, is presented and discussed. Absolute-vorticity centers are advected at seven levels for six twelve-hour periods with use of mean observed winds. The actual movement of the centers is compared with the movement dictated by the mean wind, and the differences are noted. It is found that the truest advection, with regard to both direction and speed, took place in the layer where the mean divergence was smallest; in this case at about 8000 ft. An observed-wind method of computing the vorticity is compared with a geostrophic method which employs the LaPlacian of the contour field. It is found that the deviation of individual computed maps from the mean map is about four times as great in the case of the geostrophic method as it is in the observed-wind method.