Atmospheric Sensitivity and Validation Study of the Variable Terrain Radio Parabolic Equation Model (VTRPE)

The Variable Terrain Radio Parabolic Equation (VTRPE) computer model is a powerful and flexible program that provides calculations of the radar propagation conditions of the atmosphere. It is limited however, by the accuracy and resolution of the input data. This study quantifies the sensitivity of the VTRPE model to the accuracy and resolution of the atmospheric parameters that go into it. Also, two case studies are examined to test the utility of VTRPE in operational use. The sensitivity to measurements of pressure, temperature, and humidity was found to be dependent on the meteorological environment. In standard and subrefractive environments, average values of Root Mean Squared Error in calculating propagation pathloss were greatest for measurement errors in humidity. While the overall RMSE averaged only 0.5% to 5%, in certain regions the errors in calculating pathloss were as high as 20%. VTRPE was used to calculate possible height errors when birds were detected at long ranges from a WSR-88D radar in a ducting environment. While the radar assumes a standard atmosphere when calculating height, results from VTRPE suggest that this resulted in possible height errors of over 3 km. Another case study of detected anomalous propagation was examined to determine the effects of multiple soundings in the VTRPE calculation of propagation pathloss. In this example, the effect of assuming a homogeneous atmosphere resulted in propagation pathloss errors of up to 30%.Air Force Inst of Tech Wright-Patterson AFB OH is the author of 'Atmospheric Sensitivity and Validation Study of the Variable Terrain Radio Parabolic Equation Model (VTRPE)', published 1997 under ISBN 9781423567332 and ISBN 1423567331.