Numerical Analysis of Wind Field and its Application to the Numerical Weather Forecasting (Part II)

Abstract

In section 2, it is shown that we must consider the effect of friction in the numerical forecasting of the stream function in the lower atmosphere. The stream function, as well as the velocity potential, is easily obtained by use of the observed wind. By means of the so-called divergence equation we determined the frictional coefficient, assuming, for the sake of simplicity, that it is proportional to the wind speed. In our case, it is estimated about 4.2×10^-5sec^-1.
In section 3, we are interested in discussing the so-called ω-equation and the balance equation. The magnitude of the vertical velocity, obtained by the cu-equation, is about a half of that of the vertical velocity, obtained by using the observed wind. In the lower atmosphere, the stream function, which is obtained by the balance equation, is likely to overcompensate the sharpness of isobaric contour height. This fact leads to the result that near the ground surface the balance equation cannot safely be used as a first approximation of the divergence equation.