OBJECTIVE ANALYSIS OF A TWO-DIMENSIONAL DATA FIELD BY THE CUBIC SPLINE TECHNIQUE

Abstract

A procedure to use the spline interpolation technique on an arbitrarily prescribed two-dimensional data field is described. For using this technique, one must obtain an initial approximation to the data at the grid points. This is achieved by fitting spherical surfaces to the data. Bidirectional spline interpolation is then applied repeatedly on the grid point estimates of the data to produce convergence to the true surface. The spline interpolation technique and another objective analysis technique developed by Cressman are tested against an exact solution, and the resulting analyses are compared. Real temperature, geopotential height, and wind data for various pressure surfaces are analyzed by the spline method; and the results are compared to subjective analyses of the same data.