Michael R. Dobry
Dept. of Mech. Eng., New Mexico State Univ., Box 30001-3501, Las Cruces, NM 88004
Robert P. Hansen
U.S. Military Academy, West Point, NY
David H. Marlin
U.S. Army Res. Lab., White Sands Missile Range, NM
A sensitivity analysis was performed on the Green's function parabolic equation (GFPE) model to determine parameter bounds which maintain model validity. To determine these bounds, inverse theory was used to determine the ``best'' combination of input parameters over a two-dimensional domain using a normalized sum of squared residuals. A two-dimensional version of the fast field program (FFP), a widely accepted atmospheric propagation model, was used as comparison. Plots of the error surface were then made to show sensitivity bounds. Upward and downward refracting atmospheres were considered for a range of frequencies. The GFPE model was found to require a height increment parameter of about 0.05 wavelengths while the range increment parameter extended from 10 to 120 wavelengths depending on atmospheric profile and frequency. The thickness of the attenuation layer was found to be frequency dependent and ranged from 50 to over 200 wavelengths. The surface wave integral height was found to be a minimum of 30 and 13 wavelengths for the upward and downward atmospheres, respectively. The CPU time for the GFPE model ranged from 10 to 60 s, depending on frequency, and was approximately 60--1000x faster than the two-dimensional FFP.