Austral High-Latitude Atmospheric Dynamics

University Of Washington, Seattle WA

Investigators

Abstract

The study and determination of the latitudinal extent of the high-latitude zonal wavenumber one character mesospheric waves recently discovered (by the PI and others) near the South Pole are the most compelling and contemporary investigations in the polar aeronomy. These mesospheric waves have not been observed elsewhere, because at lower latitudes the spectrum is much richer in larger zonal wavenumbers of mesospheric waves that are seldom directly measured. As one approaches the very high latitudes near the rotational poles, the higher wavenumber oscillations observed at lower latitudes must either transform into the observed higher latitude wavenumber one oscillations, or else lose their energy to the mean flow and as heat dissipation. A unique opportunity to determine where and how this oscillation wavenumber mode transition region occurs is offered by the combined and simultaneous observation from the combined and presently-existing ground-based sites at South Pole and Arrival Heights, in conjunction with the TIMED satellite. This is a unique opportunity for investigating this problem, which is unlikely to happen again in the next ten to fifteen years. These investigations can only be carried out in Antarctica because the defining observations must be made from the rotational pole. Another special problem at high geomagnetic latitudes is the existence of persistent and predictable thermospheric vertical neutral winds, first reported by the PI from the South Pole observations. The existence of these vertical winds, likely to be caused by the divergence of the horizontal wind motions due to ion drag, has profound effects on the energetics of this region of the atmosphere. With the present solar activity maximum, a more complete characterization and investigation of these vertical winds becomes possible, because they are geomagnetic activity dependent. These investigations from South Pole, simultaneously with Arrival Heights and the observations of our Austral Alliance colleagues at Mawson and Davis stations, as well as those with the TIMED satellite will enlarge the geographic and geomagnetic coverage of this neutral vertical wind study. These investigations are possible because of the existing highly versatile ground-based Fabry-Perot spectrometers present at South Pole and Arrival Heights. These devices are able to simultaneously and independently address both of these investigations in the mesosphere and thermosphere. The instruments are capable of resolving the zonal wavenumber structure at mesospheric heights while, at the same time, gathering thermospheric neutral wind observations. In addition to the wind motion, the neutral atmosphere kinetic temperatures can simultaneously be observed. These latter measurements provide another powerful tool to understand the behavior and properties of the upper atmosphere at the very high latitudes. The polar aeronomy has become one of the four initiatives in the CEDAR atmospheric community addressing the Global Climate Change effects and their implications.