Mystery of Polar Inertia-gravity Waves: An Observational Study Combining Lidar, Radar and Airglow Imager at McMurdo/Scott Base (77.8°S, 166.7°E)

Abstract:

Since the start of the McMurdo Fe lidar campaign, large-amplitude (~±30 K), long-period (4 to 9 h) perturbations with upward propagating Inertia Gravity Wave (IGW) signatures are frequently observed in the MLT temperature data. Despite its frequent appearance, such type of wave was neither widely observed, nor well understood in the past, primarily due to a paucity of measurements in Polar Regions. At McMurdo, the simultaneous observations of such waves using lidar, radar and airglow imager can provide their unique 3-D intrinsic wave-propagation properties, which are greatly needed for understanding their sources and potential impacts. This study presents the first coincident observation of IGWs by lidar, radar and airglow imager in the Antarctic mesopause region. On 11 June 2013, coherent wave structures with observed period of ~ 5 h and vertical wavelength of ~20 km were observed in both the Fe lidar temperature and MF radar winds. Derived from hodograph analysis, the wave has a horizontal wavelength of ~1200 km and propagates southward at ~60 m/s. The phase relationship between the temperature and winds is in good agreement with the gravity wave polarization relationship. Similar wave structures were also observed in the airglow keograms. The results of the horizontal propagation information obtained from appropriate filtering and applying a non-linear least-square fit of the keograms are similar to those estimated from the combined lidar-radar hodograph analysis. A Monte Carlo sampling method is used to perform all the non-linear fits of the observations to the linear gravity wave models.