Strengths and limitations of MST radar measurements of middle-atmosphere winds

摘要

Radars have been used successfully for manyyears to measure atmospheric motions over a wide range of altitudes, from groundlevel up to heights of several hundred kilometres into the ionosphere. In thispaper we particularly wish to concentrate on the accuracy of these measurementsfor winds in the middle atmosphere (i.e. 10–100-km altitude). We begin bybriefly reviewing the literature relating to comparisons between radar methodsand other techniques. We demonstrate where the radar data are most and leastreliable and then, in parallel with a discussion about the basic principles ofthe method, discuss why these different regimes have the different accuraciesand precisions they do. This discussion is used to highlight the strengths andweaknesses of radar methods. Issues like radar volume, aspect sensitivity,gravity wave effects and scatterer intermittency in producing wind biases, andthe degree by which the intermittent generation of scatterers at quasi-randompoints in space could skew the radar measurements, are all considered. We alsoinvestigate the possibility that MF radar techniques can be contaminated byE-region scatter to heights as low as 92–95-km altitude (i.e. up to 8–10 kmbelow the ionospheric peak echo). Within all these comments, however, we alsorecognize that radar methods still represent powerful techniques which have animportant future at all levels of the atmosphere.