Observing Mesospheric Turbulence With Specular Meteor Radars: A Novel Method for Estimating Second‐Order Statistics of Wind Velocity

Abstract

There are few observational techniques for measuring the distribution of kinetic energy within the mesosphere with a wide range of spatial and temporal scales. This study describes a method for estimating the three‐dimensional mesospheric wind field correlation function from specular meteor trail echoes. Each radar echo provides a measurement of a one‐dimensional projection of the wind velocity vector at a randomly sampled point in space and time. The method relies on using pairs of such measurements to estimate the correlation function of the wind with different spatial and temporal lags. The method is demonstrated using a multistatic meteor radar data set that includes ≈105 meteor echoes observed during a 24‐hr time period. The new method is found to be in good agreement with the well‐established technique for estimating horizontal mean winds. High‐resolution correlation functions with temporal, horizontal, and vertical lags are also estimated from the data. The temporal correlation function is used to retrieve the kinetic energy spectrum, which includes the semidiurnal mode and a 3‐hr period wave. The horizontal and vertical correlation functions of the wind are then used to derive second‐order structure functions, which are found to be compatible with the Kolmogorov prediction for spectral distribution of kinetic energy in the turbulent inertial range. The presented method can be used to extend the capabilities of specular meteor radars. It is relatively flexible and has a multitude of applications beyond what has been shown in this study.

Four‐Dimensional Quantification of Kelvin‐Helmholtz Instabilities in the Polar Summer Mesosphere Using Volumetric Radar Imaging

“…Although we have focused on just one KHI event, we are certain that many more events and not only KHI can be characterized with the type of PMSE volumetric imaging shown in this work. Given that not all the time one can separate easily the contributions of gravity waves and turbulence, one could quantify statistically such contributions by exploiting the multidimensional data with second-order statistics of the radial velocities, as it has been proposed by Vierinen et al (2019). This work was supported by the Deutsche Forschunggemeinschaft (DFG, German Research Foundation) under SPP 1788 (CoSIP)-CH1482/3-1.…”

Study of second-order wind statistics in the mesosphere and lower thermosphere region from multistatic specular meteor radar observations during the SIMONe 2018 campaign

“…This paper utilizes a gradient approach to estimate the mean winds and its gradients (Chau et al, 2017) and the frequency spectra of each wind component are obtained with a Fourier analysis. The second method uses second-order statistics of Doppler frequencies from SMR echoes, to obtain correlation, structure functions and spectra (Vierinen et al, 2019). The latter has been implemented here to characterize the MLT fluctuations (due to the interplay of GWs and turbulence) on different horizontal scales.…”

Mesospheric gravity wave activity estimated via airglow imagery, multistatic meteor radar, and SABER data taken during the SIMONe–2018 campaign

“…The winds used in this work have been obtained with a gradient method, i.e., besides the mean horizontal and vertical winds, the gradients of the horizontal components have also been obtained (Chau et al, 2017). Data from one day of this campaign has been used to test a second-order statistics approach by Vierinen et al (2019). More details of the SIMONe-2018 campaign as well as results of second-order statistics are given in the accompanying paper of this publication (see Asokan et al, 2020).…”

“…With the objective of bridging these gaps in gravity wave dynamics while estimating their momentum flux, an observation campaign named SIMONe-2018 (Spread-spectrum Interferometric Multi-static meteor radar Observing Network) was carried out in early Nov. 2018, to collect a large number of specular meteor echoes from several locations (e.g., Vierinen et al, 2019;Asokan et al, 2020). Also, an all-sky airglow imager system running out of the Leibniz Institute of Atmospheric Physics, Kühlungsborn, Germany, was observing the region in parallel to provide image data of the mesosphere and the horizontal structure of atmospheric oscillations during the campaign.…”