An Objective Isobaric/Isentropic Technique for Upper Air Analysis

An objective meteorological analysis technique was 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 point is performed on an isentropic surface that passes through the grid point. The vertical analyses are based upon all surrounding radiosonde data and are not confined to a line of stations. They are calculated in the same manner as the horizontal analyses, except that the grid points lie in a vertical plane. The objective analyses were evaluated by comparing the computer-generated results of two different versions (A and B) with subjective hand analyses. 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 satisfactory results, producing cross-sectional analyses of stability and divergence which are compatible with the frontal surface.