On the scattering and reflection mechanisms contributing to clear air radar echoes from the troposphere, stratosphere, and mesophere

Publisher Website
Google Scholar
Abstract
With the advent of the MST (mesosphere‐stratosphere‐troposphere) radar technique the atmosphere from 0 to 100 km can be observed with a single radar system. Several different mechanisms have been identified as causing the echoes observed by MST radars. Two primary mechanisms are scattering from turbulent irregularities and Fresnel (or partial) reflection from horizontal strata. Two additional mechanisms that apply primarily to the upper mesosphere are meteor scatter and thermal (or incoherent or Thomson) scatter. Below the stratopause the refractive index structure responsible for the echoes arises solely from neutral atmosphere fluctuations; above the stratopause the radar cross section of such fluctuations is enhanced by the presence of free electrons (moreover, in the absence of small‐scale neutral fluctuations the electrons alone can provide the scattered signal). This paper is an attempt to unify the scattering and reflection theories in the light of observational studies.