Showing papers by "David C. Fritts published in 2020"

Coordinated Observations of 8- and 6-hr Tides in the Mesosphere and Lower Thermosphere by Three Meteor Radars Near 60°S Latitude

Abstract: Atmospheric 8‐ and 6‐hr tides are observed for the first time in the zonal and meridional winds at ~82–97 km altitudes simultaneously at Tierra del Fuego (TDF; 53.7°S, 67.7°W), King Edward Point (KEP; 54.3°S, 36.5°W), and Rothera (ROT; 67.5°S, 68.0°W) at Southern Hemisphere (SH) middle‐to‐high latitudes during long time spans, allowing to reveal climatology and migrating nature. The monthly averaged amplitudes vary between ~1 and 8 m/s for the 8‐hr tides while the amplitudes of 6‐hr tides are smaller ~0.5–4 m/s. Both tides exhibit an annual pattern having the amplitude maxima during SH winter and minima in SH summer. The tidal phases are smaller (earlier) in the zonal wind than in the meridional wind by about 90°. The phase differences observed between TDF and KEP, which are located at similar latitudes but different longitudes suggest the propagation of migrating tides. The study finds that 8‐ and 6‐hr tides are correlated. Plain Language Summary Atmospheric oscillations with 8‐ and 6‐hr periods at middle‐to‐high latitudes in the Southern Hemisphere are poorly understood due to the lack of measurements. In this study, we report the climatology of these oscillations in the altitude range from ~82–97 km in the mesosphere 13 and lower thermosphere through the analysis of the coordinated observations by three meteor radars located at Rio Grande, Tierra del Fuego (TDF; 53.7°S, 67.7°W) in Argentina, King Edward Point station (KEP; 54.3°S, 36.5°W) on South Georgia Island, and Rothera station (ROT; 67.5°S, 68.0°W) on Adelaide Island west of the Antarctic Peninsula. The oscillations are observed in both zonal and meridional winds with the zonal component leading the meridional component corresponding to the counterclockwise rotation. The observations from TDF and KEP at similar latitudes suggest that the oscillations are propagating westward in the phase speed of ~360° longitude/day following the apparent motion of the Sun. Approximately 11 years of continuous observations at TDF and ROT show that the long‐term changes between 8‐ and 6‐hr oscillations are correlated with each other. These short‐period tides should have significant impacts on the variability of the thermosphere and the ionosphere.

The PMC Turbo Balloon Mission to Measure Gravity Waves and Turbulence in Polar Mesospheric Clouds: Camera, Telemetry, and Software Performance.

Abstract: The Polar Mesospheric Cloud Turbulence (PMC Turbo) instrument consists of a balloon-borne platform which hosts seven cameras and a Rayleigh lidar. During a 6-day flight in July 2018, the cameras captured images of Polar Mesospheric Clouds (PMCs) with a sensitivity to spatial scales from ~20 m to 100 km at a ~2-s cadence and a full field of view (FOV) of hundreds of kilometers. We developed software optimized for imaging of PMCs, controlling multiple independent cameras, compressing and storing images, and for choosing telemetry communication channels. We give an overview of the PMC Turbo design focusing on the flight software and telemetry functions. We describe the performance of the system during its first flight in July 2018.