In this chapter, we discuss various extended, and in some cases unusual, applications of MST radar. These may be special cases of general MST techniques, or specific applications of the technique applied to special cases, or even quite unusual applications which are a substantial deviation from “normal” MST standard practices. If such a topic fits well in another chapter, it may appear there – if it is somewhat of an exception, or has a sightly unusual methodology, or is not really an operational technique, it may appear here. Polar mesosphere summer echoes are an example of an “extended” application. While the techniques used to study these unusual echoes are really the same as for other MST studies, the unusual physics associated with the scatterers that produce these echoes makes them of particular interest. Lightning study is an example of a slightly “miscellaneous” application, in that the techniques are a little unusual (high PRFs, and the events are very short lived). Meteor study is an example of a slightly non-standard application that has grown into a substantial field all of its own. Differential absorption is a technique developed early in the days of radar in the 1960s and 1970s which has had a rebirth in the last decades, and deserves a brief mention here. Precipitation study with MST radars is a relatively mature field, but is still a secondary application, so is also included here.
Each of these fields has a significant role in its own right, but extended discussion of them would simply take up too much space, and would spread the intended application of this book beyond its original goals. Hence the topics are summarized briefly in this chapter – maybe too briefly for some, but we have tried to give sufficient references that interested readers may expand their knowledge through these references.
This book is intended to concentrate on experimental and analysis techniques, and the underlying processes (both geophysical and technical) that guide the experiments and their design. Examples of the latter include the basic theory of turbulence, and the theory behind gravity waves (see the next chapter, and also some small discussion in Chapter 2).