Evaluation of Simplified Evaporation Duct Refractivity Models for Inversion Problems

A radar system’s performance on any given day requires detailed knowledge of the current meteorological conditions because atmospheric refractivity depends on thermodynamic properties such as temperature, water vapor, and pressure.  Because of the significant challenges involved in obtaining this data, recent efforts have focused on development of methods to obtain the refractivity structure inversely using radar measurements and radar wave propagation models.  Inversion techniques usually require the use of simplified refractivity models in order to reduce the parameter space of the solution.  We examine simple refractivity models and we optimize the models and evaluate their performance using atmospheric measurements and radar wave propagation simulations.  Results to-date of this study suggest that the best log-linear model formulation of an evaporation duct for an inversion problem would be a two-layer model that contains at least three parameters: duct height, duct curvature, and mixed layer slope.  This functional form permits a reasonably accurate fit to atmospheric measurements as well as embodies key features of the profile required for correct propagation prediction with as few parameters as possible.

Publications

Saeger, J.T., N.G. Grimes, H.E. Rickard, and E.E. Hackett, 2015, Evaluation of simplified evaporation duct refractivity models for inversion problems, Radio Science, 50, doi:10.1002/2014RS005642.

Rickard, H.E., J.T. Saeger, and E.E. Hackett, 2015, Similarity and dissimilarity measures for comparison of propagation patterns, Proceedings of the IEEE AP-S and North American URSI Meeting, Vancouver, Canada.