Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

Abstract

Abstract. Mesospheric gravity wave (GW) momentum flux estimates using data from multibeam Buckland Park MF radar (34.6 • S, 138.5 • E) experiments (conducted from July 1997 to June 1998) are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions). The received beams were analysed with hybrid Doppler interferometry (HDI) (Holdsworth and Reid, 1998), principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997), later re-introduced by Hocking (2005) and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and verticalbeam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010) of the accuracy of the meteor radar technique.

VHF radar measurements of momentum flux using summer polar mesopause echoes

“…Rather than using individual combinations of beams as we have just described, it is possible to include all of the radial velocities in a least-squares inversion to determine the mean wind components and the various covariance terms of the Reynolds stress tensor. Spargo et al (2017) did this, following the approaches of Thorsen et al (1997) and Hocking (2005), to determine the six components of the density-normalized Reynolds stress tensor, to the BPMF radar operating in a five-beam (E, W, N, S and V) Doppler mode. In principle, this technique can be applied to the six-beam arrangement used here to determine the various Reynolds stress terms.…”

“…However, these components need to be removed from the radial velocity time series, and so we describe the approach used to calculate and remove them and note a few details. To calculate the mean and tidal winds, we follow the approach used by Spargo et al (2017) for the BPMF Doppler radar (Reid et al 1995; operating in Hybrid Doppler Interferometer (HDI) mode, and which is similar to that applied by Andrioli et al (2013) to meteor radar radial velocities. Briefly, the radial velocities were partitioned into non-oversampled windows of width 1 h, and the three wind components (u, v, w) were estimated using a standard least-squares formulation (e.g.…”

“…by Hocking (2005). Except for recent work by Spargo et al (2017), the former technique has not been actively pursued. The approach described by Hocking has attracted much investigation, but no definitive experimental validation against an accepted measurement of momentum flux (see, e.g.…”

“…Placke et al 2015). For the various parts of the arguments for and against using the meteor technique for measuring momentum flux, see for example, the discussions in Vincent et al (2010), Fritts et al (2012), Riggin et al (2016), and Spargo et al (2017).…”

Multistatic meteor radar observations of gravity-wave–tidal interaction over southern Australia

“…by a bistatic receiver corresponds to the projection of the 3-D wind velocity onto e (which is in the same direction as the Bragg vector in e.g. Stober and Chau, 2015), in turn projected onto b. Mathematically, this velocity is expressed as…”