Abstract
The distributions of monthly-mean zonal root mean square (r.m.s.) relative geostrophic vorticity, ξg, are useful in determining the locations, seasonal migrations and other properties of jet streams, and hence are valuable in general circulation studies, as shown by Srivatsangam (1974).
In this paper the distributions of zonal r.m.s. ξg as obtained from radiosonde and Satellite Infra Red Spectrometer (SIRS) data are compared. The differences between the two distributions are shown to be partially due to the over-estimation of geopotential heights made by the SIRS observations in the presence of clouds, and the under-estimates made in the clear regions. The estimation errors result from the nature of the least squares regression method used in deriving geopotential heights from radiosonde data, as well as the subsequent interpolation of clear-area data into cloudy areas (where no SIRS-derived data are often available).
