ZONAL WAVE NUMBER VARIANCE SPECTRA OF STRATOSPHERIC MICROWAVE BRIGHTNESS TEMPERATURES


R. L. Martin(1) and J. L. Stanford, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011

(1) Applied Research Corporation, Landover, Maryland


J. Geophys. Res., 91, 13195-13200(1986)


Abstract

Well known theoretical predictions suggest that variances of large-scale atmospheric fluctuations, for scales somewhat shorter than those of the forcing mechanism, should obey a power law, k raised to the -b, where k is the horizontal wave number. The invariance of the exponent b with season, hemisphere, and latitude is tested using satellite-measured brightness temperatures. Global grids of TIROS-N Microwave Sounding Unit channel 4 measurements, which closely approximate the 30- to 150-mbar layer mean temperature, are constructed for January, March, and August 1979. These grids are zonally Fourier- transformed, and the resulting spectra are averaged over four 18 degree-wide latitude bands. Fits of a power law to these spectra over wavenumbers 10-36 give values of b which are independent of season, hemisphere, and latitude band, to within statistical uncertainties. The observed values of b are about 3.6, as compared to theoretical predictions of 3.