ABSTRACT
Wind derived quantities such as streamfunctions and velocity potential have introduced a great simplicity in the expression of the governing equations of the atmospheric motion and constitutes the basic predictors for many numerical weather prediction models. It is, therefore, desirable to develop a transform pair which computes these potential functions given the observed wind field. The inverse transform would provide the wind field from the streamfunctions and velocity potential. This chapter describes two powerful and commonly used methods for the obtention of the streamfunction and velocity potential from the analyzed wind field are proposed. The wind field is assumed to be known on a regularly spaced grid array. Boundary conditions represent a major problem for the solutions of these equations, especially for the determination of the streamfunction. In this case, the assumption that the outward normal velocity at the boundary can be corrected to yield a net zero outward mass flux is made.
