A new meteor radar with unprecedented sensitivity is established at Usuahia, Argentina, the southernmost municipality in the world. This location is beneath the most dynamic tidal and gravity wave activity field in the middle atmosphere, according to models, but present observation capability does not exist. Placement of the meteor radar at Usuahia thereby provides a key link in chain of middle-atmosphere monitoring stations extending from the Arctic to the Antarctic, through the Americas. Inter-hemispheric field-aligned dynamic studies are also made possible because conjugate magnetic mapping occurs between Usuahia and instrumented sites at Juliusruh, Germany, Obninsk, Russia, and Saskatoon, Canada. The meteor radar system transmitting nominally at 33 MHz will achieve at least 48 kW peak power and may achieve 96 kW peak power.
This research grant supported the purchase, installation, and operation of a new-generation meteor radar designed specifically for advanced atmospheric dynamics and meteoroid studies. The Southern Argentina Agile MEteor Radar (SAAMER) was installed on Tierra del Fuego, Argentina in May 2008 and has operated nearly continuously since that time. SAAMER employs high power and a transmitting antenna that directs the majority of radar energy near zenith, allowing atmospheric dynamics studies (via wind measurements from meteor trail backscatter) and meteoroid studies that were previously possible only with much larger and more expensive radars. An example of the meteor distribution seen by SAAMER on 20 May 2008 which enables these various studies is shown in the accompanying figure. The central antenna beams extend to ~50 degrees off zenith and largely account for the enhanced dynamics and meteoroid measurement capabilities with SAAMER. SAAMER was located on Tierra del Fuego because the region encompassing the southern Andes, the Drake Passage, and the Antarctic Peninsula (i.e., the Drake Passage "hotspot") is the most dynamically active region of Earth's atmosphere extending from the surface to over 100 km altitude. This region hosts a variety of atmospheric motions, including solar tides and planetary waves occurring on global scales as well as smaller-scale (~10 to 1000 km) gravity waves, all of which play key roles in defining the structure and variability of the atmosphere spanning these altitudes. These wave motions have large impacts on weather and climate and their predictability, and the Drake Passage "hotspot" is essentially a natural laboratory for studies that are advancing our understanding and predictive capabilities having major societal benefits. SAAMER capabilities for advanced meteor trail, source region, and ablation dynamics studies are likewise addressing topics of high scientific interest with implications for atmospheric composition and the dynamics and sources of near-Earth objects. Science highlights of our research under this grant include the following: 1. measurements of large and variable semidiurnal tides at the latitude of the expected maximum in the southern hemisphere which have not been measured previously, 2. measurements of mean winds and planetary waves that exhibit significant differences from their counterparts at conjugate northern latitudes, 3. measurements of momentum transports by gravity waves that are significantly larger than at any other site, presumably because of strong local sources in the Drake Passage "hotspot", and 4. measurements of meteor radiants (apparent source regions) and nonspecular echoes that have proven difficult or impossible with other radars in routine operation. The research performed under this grant was managed by Co-PIs Drs. Dave Fritts and Diego Janches, with contributions and participation by many collaborators in Argentina, the U.S., Canada, Australia, and the U.K. Also playing significant roles, particularly in SAAMER installation and testing, were a number of U.S. graduate and undergraduate students supported with separate NSF Office of International Science and Engineering funds specifically to facilitate such international collaborations.
