Southern Argentina Agile Meteor Radar: System design and initial measurements of large‐scale winds and tides

Abstract

[1] The Southern Argentina Agile Meteor Radar (SAAMER) was installed at Rio Grande on Tierra del Fuego (53.8°S, 67.8°W) in May 2008 and has been operational for ∼24 months. This paper describes the motivations for the radar design and its placement at the southern tip of South America, its operating modes and capabilities, and observations of the mean winds, planetary waves, and tides during its first ∼20 months of operation. SAAMER was specifically designed to provide very high resolution of large-scale motions and hopefully enable direct measurements of the vertical momentum flux by gravity waves, which have only been possible previously with dual-or multiple-beam radars and lidars or in situ measurements. SAAMER was placed on Tierra del Fuego because it was a region devoid of similar measurements, the latitude was anticipated to provide high sensitivity to an expected large semidiurnal tide, and the region is now recognized to be a "hot spot" of small-scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere, perhaps the most dynamically active location on Earth. SAAMER was also intended to permit simultaneous enhanced meteor studies, including "head echo" and "nonspecular" measurements, which were previously possible only with high-power largeaperture radars. Initial measurements have defined the mean circulation and structure, exhibited planetary waves at various periods, and revealed large semidiurnal tide amplitudes and variability, with maximum amplitudes at higher altitudes often exceeding 60 m s −1 and amplitude modulations at periods from a few to ∼30 days.

Winds and tides in the mid-latitude Southern Hemisphere upper mesosphere recorded with the Falkland Islands SuperDARN radar

“…Figs. 9 and 11 in Fritts et al, 2010), the individual hourly mean fitted horizontal wind components can be averaged together by hour and month to generate a superposed epoch of the monthly mean day. Figure 6 shows the monthly mean zonal and meridional winds recorded between 18 February 2010 and 28 February 2011 as a function of hour of day and month of year.…”

“…Luo et al, 2001Luo et al, , 2002Manson et al, 2004Manson et al, , 2005Igarashi et al, 2002;Jacobi et al, 2007Jacobi et al, , 2009Middleton et al, 2002;Mitchell et al, 1999;Pancheva, 2000;Lysenko et al, 1994;Merzlyakov et al, 2001;Chshyolkova et al, 2005). In contrast, relatively little ground-based data has been reported from equivalent latitudes in the Southern Hemisphere (Brown et al, 1995;Fritts et al, 2010) with the majority of Southern Hemisphere observations coming from lower latitude tropical and extratropical sites (e.g. Pancheva, 2006;Buriti et al, 2008;Andrioli et al, 2009;Guo and Lehmacher, 2009;Lima et al, 2005Lima et al, , 2006Malinga and Poole, 2002;Kovalam and Vincent, 2003) and high latitude Antarctic stations (e.g.…”

Investigation of gravity waves using horizontally resolved radial velocity measurements

“…There are several in situ (e.g., Eckermann and Vincent, 1989;Theuerkauf et al, 2011) and ground-based observation techniques like, e.g., meteor radars (e.g., Hocking, 2005;Fritts et al, 2010b, a;Placke et al, 2011), MF radars (e.g., Hoffmann et al, 2010Hoffmann et al, , 2011Placke et al, 2013), lidars (e.g., Rauthe et al, 2006;Gerding et al, 2008), airglow imagers (e.g., Nakamura et al, 1999;Pautet and Moreels, 2002;Suzuki et al, 2004Suzuki et al, , 2010 or CCD images of noctilucent clouds (NLC) (e.g., Pautet et al, 2011) as well as satelliteborne observations (e.g., Preusse et al, 2000;Ern et al, 2004Ern et al, , 2011 to quantify the properties of gravity waves and their effect on the background flow. Here we investigate short-period gravity waves using horizontally resolved radar observations.…”

Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

“…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.…”