Radar interferometer observations of mesospheric echoing layers at Jicamarca

Abstract

VHF radar observations at Jicamarca show that the most intense mesospheric echoes at the equator are returned from thin horizontal layers with lifetimes ranging from tens of minutes to many hours. A few such layers may be present at a time, typically separated in altitude by a few kilometers. Interferometric studies of radar returns from these layers indicate that the characteristic widths of the corresponding Doppler spectra are usually determined by the spatial integration effect due to finite size scattering volumes. Radar returns from lower mesospheric layers appear to be due to randomly distributed scatterers convected through the observation volume by nonturbulent wind fields. The scatterers in question may possibly be specularity points or glints on corrugated refractive index surfaces. Higher mesospheric layer echoes, however, imply the existence of turbulent flow fields in the vertical plane, with dominant eddy motions at scale sizes comparable with the scattering volume dimensions of about a kilometer.