OBSERVATIONS OF THE UNAMBIGUOUS 2-DIMENSIONAL HORIZONTAL WAVE-NUMBER SPECTRUM OF OH INTENSITY PERTURBATIONS

The unambiguous 2-D horizontal wave number spectrum of gravity wave pe rturbations in OH emission intensities is computed from imager observa tions acquired on 2 Feb 1995 at the Starfire Optical Range, NM. The te chnique involves computing the (omega, k, l) = (omega, h, phi) spectru m of OH images collected over a several hour period, where k is the zo nal wave number, l is the meridional wave number, h = (k(2) + l(2))(1/ 2), phi = tan(-1) (k/l), and omega is the temporal frequency. The data are used to study the azimuthal distribution of wave energy propagati on and the separability of the (h, phi) spectrum. The h spectral indic es, computed from power-law fits of the 2-D spectrum over the wave num ber range 2 pi/(200 km) < h < 2 pi/(20 km), vary between -1.6 and -3.6 as a function of phi with a mean of -2.58. Consequently, the image sp ectrum is not separable in h and phi. We show that nonseparability is most likely associated with distortion of the wave perturbations cause d by the viewing geometry at large zenith angles.