Abstract
Abstract. An overview of the turbulent structures seen by MF, HF and VHF radars in the troposphere, stratosphere and mesosphere is presented, drawing on evidence from previous radar measurements, in situ studies, laboratory observations, observations at frequencies other than those under focus, and modelling studies. We are particularly interested in structures at scales less than one radar pulse length, and smaller than the beam width, and especially the degree of anisotropy of turbulence at these scales. Previous radar observations are especially important in regard to the degree of anisotropy, and we highlight the role that these studies have had in furthering our understanding in this area. The contrasts and similarities between the models of anisotropic turbulence and specular reflection are considered. The need for more intense studies of anisotropy at MF, HF and VHF is especially highlighted, since this is an area in which these radars can make important contributions to the understanding of atmospheric turbulence.Key words. Meteorology and atmospheric dynamics (turbulence) – Atmospheric composition and structure (instruments and techniques) – History of geophysics (atmospheric sciences)
Highlights
Radars depend on scatter or reflection from perturbations in radio refractive index in order for them to be able to function as tools for atmospheric studies
Our intention in this article is to develop a picture of the structure of turbulence as seen by MF, HF and VHF radars in the upper troposphere, the stratosphere and the mesosphere
We will draw our evidence from a variety of sources, especially concentrating on previous radar
Summary
Radars depend on scatter or reflection from perturbations in radio refractive index in order for them to be able to function as tools for atmospheric studies. The consequences of this structure are to produce more anisotropic scatterers or specular reflection at the edges, where the background temperature is horizontally stratified but highly fluctuating as a function of height ( containing large gradients), and to produce more isotropic scatterers towards the centre, where the temperature profile is closer to adiabatic This is illustrated by the central part of the figure, which shows anisotropy at the edges and more isotropy towards the centre. Sometimes the more intense turbulence layers can be the least seen with radar This fact was recently raised by Gibson-Wilde et al (2000) using computer simulations, these authors did not draw a parallel between their observations and the extensive references and types of discussions in the literature considered here
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