Advances and Features of Meteor Radar Techniques for M-L-T Region Neutral Wind Characterization

One of the current frontiers in understanding neutral-ion coupling within the atmosphere lies in a much better observational specification of neutral wind structure. This need is critical for providing quantitative information that can help refine and advance whole atmosphere model representations of interlocked mesosphere-ionosphere energy interchange pathways. Such mechanisms, such as stratospheric warming effects on ionospheric structure, have been recognized as essential to understanding not only climatology but also space weather variability of atmospheric parameters. Specular radio reflections from ionized meteor trails have been a long established technique for monitoring neutral winds. Recently, exciting new capabilities have been added to this observing method through the use of multi static, multi frequency transmit/receive architectures and advanced coded continuous waveforms as described by e.g. Stober and Chau [Radio Science, 2015]. The power of this technique has recently been advanced further through the use of stochastic process regression techniques to fit sparse projected wind observations from a meteor radar network and predict a vector wind field with minimal assumptions and rigorous uncertainties. This latter feature is very important in order to enable future model-data assimilative studies in a comprehensive, statistical manner. Further analysis from the vector wind fields can address many terms in the full continuity equations, such as horizontal divergence and relative vorticity [Chau et al, 2017]. We highlight recent advances in analysis for MIMO meteor wind observing systems, discussing in particular the techniques that lead to minimal constraint, rigorous uncertainty determination. We present several examples of complex wind fields observed at mid to high latitudes and use them to conclude with a targeted discussion of the particular mesosphere-lower thermosphere science that can be unlocked by continuous application of the technique.