Drake Antarctic Agile Meteor Radar first results: Configuration and comparison of mean and tidal wind and gravity wave momentum flux measurements with Southern Argentina Agile Meteor Radar

Abstract

A new generation meteor radar was installed at the Brazilian Antarctic Comandante Ferraz Base (62.1°S) in March 2010. This paper describes the motivations for the radar location, its measurement capabilities, and comparisons of measured mean winds, tides, and gravity wave momentum fluxes from April to June of 2010 and 2011 with those by a similar radar on Tierra del Fuego (53.8°S). Motivations for the radars include the “hotspot” of small‐scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere (MLT) centered over the Drake Passage, the maximum of the semidiurnal tide at these latitudes, and the lack of other MLT wind measurements in this latitude band. Mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations. The semidiurnal tide contributes most to the large‐scale winds over both radars, with maximum tidal amplitudes during May and maxima at the highest altitudes varying from ∼20 to >70 ms−1. In contrast, the diurnal tide and various planetary waves achieve maximum winds of ∼10 to 20 ms−1. Monthly mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes, with relatively small zonal fluxes over both radars, but with significant, and opposite, meridional momentum fluxes below ∼85 km. These suggest gravity waves propagating away from the Drake Passage at both sites, and may indicate an important source region accounting in part for this “hotspot.”

Multi-year observations of gravity wave momentum fluxes at low and middle latitudes inferred by all-sky meteor radar

“…In recent years the results of a number of studies have been published using the Hocking technique, e.g., Antonita et al (2008), Fritts et al (2010Fritts et al ( , 2012a, Placke et al (2011a, b), Andrioli et al (2013a, b) and de Wit et al (2014a, b). Andrioli et al (2013a) described a method for using the technique in composite days with the purpose of maximizing the number of available meteor echoes and thus allowing the investigation of momentum fluxes using simple meteor radars with improved accuracy and with no contamination by tides and planetary waves.…”

Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

“…A contrary argument was put forward by Fritts et al (2012a). They independently assessed the meteor technique, and argued that the large-amplitude monochromatic gravity waves often observed in the MLT/I region would result in stronger correlations between component velocity fluctuations (i.e.…”

“…Fritts et al (2012a), who employed the same tests as Fritts et al (2010a) on a new meteor radar on King George Island (62.1 • S, 58.7 • W), and three more conventional meteor radars. 4.…”

“…the "effective receive beams" of the radar) distributions peak at large offzenith angles (typically 40-50 • ) and are often asymmetric in azimuth for integration times less than a few hours. An example of an approach to alleviate the former effect can be found in the design of the SAAMER and DrAAMER systems (Fritts et al, 2010b(Fritts et al, , 2012b, in which a larger transmitting aperture was used to increase the signal-to-noise (SNR) of returns (and hence number of detections) at small zenith angles. While reducing the total number of detections, such an approach also has the advantage of increasing the relative contribution of the perturbation component of the vertical wind to the radial velocity, as well as reducing errors in meteor height estimates.…”

“…Some authors (e.g. Fritts et al, 2010bFritts et al, , 2012a have opted to remove the temporal shear imposed by tides and planetary waves by fitting these components to the Cartesian winds, and then subtracting their radial projection from the radial velocities prior to momentum flux estimation. Andrioli et al (2013aAndrioli et al ( , b, 2015 also attempted to remove the same shears by fitting them, directly evaluating the contribution of the fitted components to the momentum fluxes, and then subtracting these from those estimated previously.…”