An Objective Isobaric/Isentropic Technique for Upper Air Analysis

Abstract

An objective meteorological analysis technique has been developed to provide both horizontal and vertical (cross-sectional) upper air analyses. The horizontal analyses are made at grid points that lie on isobaric levels in a conventional manner. However, the interpolation of values other than temperature at a grid paint is performed on an isentropic surface that passes through the grid point. The vertical analyses are based on all surrounding radiosonde data and are not confined to a line of stations. They are calculated in an equivalent manner as the horizontal analyses, except that the grid points lie in a vertical plane. The objective analyses have been evaluated by comparing the computer-generated results of two different versions (A and B) with subjective hand analysts. Comparisons for one test case are presented in this paper. The computer analyses show good agreement with the subjective analyses, and depict the baroclinic features of both the temperature and wind fields. In particular, the B version, which uses a second-order polynomial to interpolate grid-point values, gives very satisfactory results, producing cross-sectional analyses of stability and divergence that are compatible with the frontal surface.