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Atmospheric Structure Simulation: An ARMA Model for Smooth Isotropic Two-Dimensional Geophysical Power Spectra
PHILLIPS LAB HANSCOM AFB MA
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Geophysical phenomena are often characterized by smooth continuous power spectral densities having a negative power law slope. Frequently, Fourier transform analysis has been employed to generate synthetic scenes from pseudorandom arrays by passing the stochastic data through a Fourier filter having the desired power spectral dependency. This report examines the possibility of producing two-dimensional synthetic structure by invoking autoregressivemoving average analysis, as contrasted with the Fourier method. Computations that apply multidimensional fast Fourier transforms to large data arrays consume enormous resources and time. An alternative method is needed to reduce the computational burden, achieve circular symmetry, account for correlations in all directions, and lend itself to producing non-stationary scenes. Future editions of the Phillips Laboratory Strategic High Altitude Atmospheric Radiance Code SHARC will feature an ability to calculate structured radiance. The method explored herein provides a process to construct a non-stationary database for SHARC that accurately simulates symmetric two-dimensional geophysical power spectra and takes into account correlations along the line of sight that existing methods approximate. Atmospheric structure, ARMA Modeling, Power spectral density analysis, Two dimensional power spectra.
APPROVED FOR PUBLIC RELEASE