Horizontal Wavenumber Spectra of Vertical Vorticity and Horizontal Divergence of Mesoscale Dynamics in the Mesosphere and Lower Thermosphere Using Multistatic Specular Meteor Radar Observations

• Published in: Earth and space science (Hoboken, N.J.) N.J.), 2022-09, Vol.9 (9), p.n/a
• Main Authors: Poblet, Facundo L., Chau, Jorge L., Conte, J. Federico, Avsarkisov, Victor, Vierinen, Juha, Charuvil Asokan, Harikrishnan
• Format: Article
• Language: English
• Subjects: Altitude; correlation function; Decomposition; divergence; General circulation models; Gravity waves; Internal waves; mesoscales; meteor radar; Meteors; MLT; Physics; Radar; Spread spectrum; Stratosphere; Troposphere; Velocity; vorticity; Wavelengths
• ISSN: 2333-5084; 2333-5084
• DOI: 10.1029/2021EA002201

Specular meteor radars (SMRs) have significantly contributed to the understanding of wind dynamics in the mesosphere and lower thermosphere (MLT). We present a method to estimate horizontal correlations of vertical vorticity (Qzz) and horizontal divergence (P) in the MLT, using line‐of‐sight multistatic SMRs velocities, that consists of three steps. First, we estimate 2D, zonal, and meridional correlation functions of wind fluctuations (with periods less than 4 hr and vertical wavelengths smaller than 4 km) using the wind field correlation function inversion (WCFI) technique. Then, the WCFI's statistical estimates are converted into longitudinal and transverse components. The conversion relation is obtained by considering the rotation about the vertical direction of two velocity vectors, from an east‐north‐up system to a meteor‐pair‐dependent cylindrical system. Finally, following a procedure previously applied in the upper troposphere and lower stratosphere to airborne wind measurements, the longitudinal and transverse spatial correlations are fitted, from which Qzz, P, and their spectra are directly estimated. The method is applied to a special Spread spectrum Interferometric Multistatic meteor radar Observing Network data set, obtained over northern Germany for seven days in November 2018. The results show that in a quasi‐axisymmetric scenario, P was more than five times larger than Qzz for the horizontal wavelengths range given by ∼50–400 km, indicating a predominance of internal gravity waves over vortical modes of motion as a possible explanation for the MLT mesoscale dynamics during this campaign. Key Points We investigate the horizontal correlation functions of vertical vorticity and horizontal divergence for mesoscale wind fluctuations in the mesosphere and lower thermosphere 2D zonal and meridional correlation functions and 1D longitudinal and transverse correlation functions as a function of horizontal lags are analyzed The divergence dominated over the vorticity during November 2018 in northern Germany