Investigation of stream functions obtained through second-order geostrophic approximations.

Abstract

By using the geostrophic approximation in various of the horizontal acceleration terms in the Eulerian equations for horizontal flow, wind components are computed from which relative vorticity is determined. The problem of obtaining a stream function is then reduced to solving a Poisson-type equation, thus avoiding the use of the balance equation. Tow different computation schemes for the x,y components of the 500-mb wind are investigated. The stream functions obtained from these methods are then compared with those obtained through the solution of the balance equation. The results of forecasts for 24 and 48 hours using the various stream functions with the barotropic model are also presented.