Radar data objective analysis

The spherical geometry of weather radar scans results in a data distributio n wherein datapoint separation in one coordinate direction and/or in one pa rt of the analysis domain can differ widely from that in another. Objective analysis of the nonuniform radar data to a uniform Cartesian grid is desir able for many diagnostic purposes, For the benefit of the diagnostic data a nalyst as well as of users of these analyses, the authors evaluate properti es of techniques typically used for such objective analysis. This is done p artly through theoretical consideration of the properties of the schemes. b ut mostly by empirical resting. In terms of preservation of the phase and a mplitude of the input data, predictability of th; degree of smoothing and f iltering, and relative insensitivity to input data unsteadiness or spatial characteristic, the isotropic Gaussian or Barnes-type weight function with constant smoothing parameter appears to be the most desirable of the scheme s considered. Modification of this scheme so that the weight function varie s spatially, with the datapoint spacing, results in an improved analysis, a ccording to some commonly used measures of error. Interpretation of analyse s based on such a modified scheme can be affected, however. For example, an alyses of unsteady input fields suffer from a convolution of the temporal e volution of the data with spatial variations of the weight function. As a c onsequence, unambiguous assessment of physical evolution is precluded.