## 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.