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

Abstract

Abstract. This paper assesses the ability of a recently installed 55 MHz multistatic meteor radar to measure gravity-wave-driven momentum fluxes around the mesopause and applies it in a case study of measuring gravity wave forcing on the diurnal tide during a period following the autumnal equinox of 2018. The radar considered is in the vicinity of Adelaide, South Australia (34.9∘ S, 138.6∘ E), and consists of a monostatic radar and bistatic receiver separated by approximately 55 km. The assessment shows that the inclusion of the bistatic receiver reduces the relative uncertainty of the momentum flux estimate from about 75 % to 65 % (for a flux magnitude of ∼20 m2 s−2, 1 d's worth of integration, and for a gravity wave field synthesized from a realistic spectral model). This increase in precision appears to be entirely attributable to the increased number of meteor detections associated with the combined monostatic and bistatic receivers rather than changes in the meteors' spatial distribution. The case study reveals large modulations in the diurnal tidal amplitudes, with a maximum tidal amplitude of ∼50 m s−1 and an associated maximum zonal wind velocity of around 140 m s−1. While the observed gravity wave forcing exhibits a complex relationship with the tidal winds during this period, the components of the forcing are seen to be approximately out of phase with the tidal winds above 88 km. No clear phase relationship has been observed below 88 km.

Low Earth Orbit Object Observations Using the Buckland Park VHF Radar

“…The maximum duty cycle is 10%. The radar employs GPS locking, allowing its transmissions to be received using an interferometric Yagi antenna array at Mylor (55 km South East of Buckland Park) for bistatic meteor observations (Spargo et al, ). The radar does not allow continuous operation, typically dwelling on a particular beam direction for 1–2 min, with 5 s “dead” time to allow for data transfer to the data acquisition and analysis PC.…”

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

“…Note that (x, y, z) has been calculated from the meteor location information. The horizontal velocity amplitude V h was obtained by normalizing A(m, ω) using a normalizing factor, c. This 'c' was selected based on Spargo et al (2019), where they used this normalization factor to get the mean values of momentum flux close to 20 m 2 s −2 , which are approximate values of uw and vw in the MLT region (Fritts et al, 2012).…”

Seasonal Variations of High-Frequency Gravity Wave Momentum Fluxes and Their Forcing toward Zonal Winds in the Mesosphere and Lower Thermosphere over Langfang, China (39.4° N, 116.7° E)

“…The perturbed radial velocity was then acquired by subtracting the corresponding projected mean radial velocity from the measured radial velocity of each detected meteor. Assuming the perturbed radial velocity obeyed a Gaussian distribution, the 5-standard-deviations criterion was used to remove outliers that were large enough to substantially bias the resulting momentum flux estimates [29].…”

“…This approach avoids contamination due to vertical wind shear, as described by Placke et al [13]. Furthermore, as mentioned by Spargo et al, measures were taken to remove outliers that biased momentum flux results; in the first step, meteors with radial velocities of more than 200 m/s were discarded, and, in the second step, a 5-standard-deviations criterion was used to remove outliers [29].…”