Preprints
https://doi.org/10.5194/amt-2021-40
https://doi.org/10.5194/amt-2021-40

  26 Feb 2021

26 Feb 2021

Review status: this preprint is currently under review for the journal AMT.

Four-dimensional mesospheric and lower thermospheric wind fields using Gaussian process regression on multistatic specular meteor radar observations

Ryan Volz1, Jorge L. Chau2, Philip J. Erickson1, Juha P. Vierinen3, J. Miguel Urco2, and Matthias Clahsen2 Ryan Volz et al.
  • 1Haystack Observatory, Massachusetts Institute of Technology, USA
  • 2Leibniz Institute of Atmospheric Physics at the University of Rostock, Germany
  • 3UiT Arctic University of Norway, Norway

Abstract. Mesoscale dynamics in the mesosphere and lower thermosphere (MLT) region have been difficult to study from either ground- or satellite-based observations. For understanding of atmospheric coupling processes, important spatial scales at these altitudes range between tens to hundreds of kilometers in the horizontal plane. To date, this scale size is challenging observationally, and so structures are usually parameterized in global circulation models. The advent of multistatic specular meteor radar networks allows exploration of MLT mesocale dynamics on these scales using an increased number of detections and a diversity of viewing angles inherent to multistatic networks. In this work, we introduce a four dimensional wind field inversion method that makes use of Gaussian process regression (GPR), a non-parametric and Bayesian approach. The method takes measured projected wind velocities and prior distributions of the wind velocity as a function of space and time, specified by the user or estimated from the data, and produces posterior distributions for the wind velocity. Computation of the predictive posterior distribution is performed on sampled points of interest and is not necessarily regularly sampled. The main benefits of the GPR method include this non-gridded sampling, the built-in statistical uncertainty estimates, and the ability to horizontally-resolve winds on relatively small scales. The performance of the GPR implementation has been evaluated on Monte Carlo simulations with known distributions using the same spatial and temporal sampling as one day of real meteor measurements. Based on the simulation results we find that the GPR implementation is robust, providing wind fields that are statistically unbiased and with statistical variances that depend on the geometry and are proportional to the prior velocity variances. A conservative and fast approach can be straightforwardly implemented by employing overestimated prior variances and distances, while a more robust but computationally intensive approach can be implemented by employing training and fitting of model parameters. The latter GPR approach has been applied to a 24-hour data set and shown to compare well to previously used homogeneous and gradient methods. Small scale features have reasonably low statistical uncertainties, implying geophysical wind field horizontal structures as low as 20–50 km. We suggest that this GPR approach forms a suitable method for MLT regional and weather studies.

Ryan Volz et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-40', Anonymous Referee #1, 15 Mar 2021 reply
    • AC1: 'Reply on RC1', Ryan Volz, 30 Apr 2021 reply
  • CC1: 'Comment on amt-2021-40', Chris Meek, 27 Mar 2021 reply
    • AC2: 'Reply on CC1', Ryan Volz, 01 May 2021 reply
      • CC2: 'Reply on AC2', Chris Meek, 03 May 2021 reply
        • AC3: 'Reply on CC2', Ryan Volz, 06 May 2021 reply
  • CC3: 'Comment on amt-2021-40', Gunter Stober, 18 Jun 2021 reply
    • AC4: 'Reply on CC3', Ryan Volz, 24 Jun 2021 reply
      • CC4: 'Reply on AC4', Gunter Stober, 25 Jun 2021 reply
        • CC5: 'Reply on CC4', Gunter Stober, 25 Jun 2021 reply
        • AC5: 'Reply on CC4', Ryan Volz, 25 Jun 2021 reply
          • CC6: 'Reply on AC5', Gunter Stober, 28 Jun 2021 reply
      • CC7: 'Reply on AC4', Aaron Smith, 29 Jun 2021 reply

Ryan Volz et al.

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Short summary
We introduce a new way of estimating winds in the upper atmosphere (about 80 to 100 kilometres altitude) from the observed Doppler shift of meteor trails using a statistical method called Gaussian process regression. Wind estimates and, critically, the uncertainty of those estimates can be evaluated smoothly (i.e. not gridded) in space and time. The effective resolution is set by provided parameters, which are limited in practice by the number density of the observed meteors.