Using measured variance of skywave radar sea-echo power spectra to estimate ionospheric Doppler broadening of mean spectra

A relation between ionospheric Doppler broadening of skywave sea—echo Doppler spectra and the normalized variance of such spectra is derived. It is shown that the normalized variance is largest at the first-order Bragg lines of the Doppler spectra, and varies with Doppler frequency in a way that depends on the ionospheric Doppler broadening. An accurate measurement of the mean Doppler spectrum and the mean variance spectrum would lead to an estimate of the ionospheric distortion and to its removal.