A coordinated study of 1-h gravity wave propagating from Logan to Boulder using two Na Doppler lidars and a temperature mapper
Wednesday, 17 December 2014
Vertical winds in the mesosphere and lower thermosphere can be obtained with good accuracy and precision with the STAR sodium (Na) lidar system at Boulder (40.1°N, 105.2°W), CO, after its receiving efficiency has been substantially improved by an order of magnitude. A remarkable gravity wave signature with a period of ∼1h is the most prominent feature shown in the vertical wind on Nov 27, 2013 at Boulder. Similar wave signatures are also present in the temperature and Na density variations. From the USU lidar and the temperature mapper, the gravity wave oscillation with a period of ∼1h is also observed in the temperature and horizontal winds at Logan (41.7°N, 111.8°W), Utah. By combining the observations from these two stations, we determine the vertical wavelength is about 25 km and horizontal wavelength is about 327 km. This wave is propagating from Logan to Boulder with an elevation angle of 4.4° and an azimuth angle of 133°. The wave amplitudes in vertical wind, horizontal winds and temperature are provided and their ratios are in good agreement with the gravity wave polarization relation. This coordinated study has uniquely provided 3-D information and magnitude of the 1-h gravity wave, which has a great potential to be the seed of TIDs, affecting the ionospheric variabilities. Using the ray-tracing model, we find that the wave source is above 10 km. It is likely generated by the geostrophic adjustment of the jet stream, whose orientation is consistent with the horizontal propagation direction of the wave.