The Localized 12-hour Wave Over Alaska: Leveraging Meridional Wind Measurements From the Sodium Lidar

Abstract

The 12-h wave in meridional winds in the mesosphere and lower thermosphere (MLT) during the solar minimum 2018-2019 Arctic winter is investigated using sodium lidar observations at Poker Flat Research Range (PFRR), Chatanika, Alaska (64N,147W). Nightly 12-h wave amplitudes increased significantly during December-January, with amplitudes exceeding 130 m/s above 97 km on several days. This was more than double the 12-h wave amplitudes observed outside this time period. Meteor radar winds over Chatanika also showed significant increase in meridional wind 12-h wave amplitudes at altitudes between 82 and 97 km during this time period with lower amplitudes than lidar measurements. The strong variation in 12-h wave amplitudes was not correlated with SME index, though the largest amplitudes coincided with the sudden stratospheric warming (SSW) in early January. Measurements were compared to a seasonal WACCM-X model run and four days of HIAMCM. For the four dates of available HIAMCM data, 12-h wave amplitudes over Chatanika were found to be similar between both HIAMCM and WACCM-X and the lidar below 97 km, with amplitudes measured by lidar exceeding the models at altitudes between 97-105 km. All measurements followed a similar seasonal trend with increasing amplitudes at the end of December/early January. Fits of SW2 from WACCM-X show the SW2 tidal amplitude following similar seasonal trends to 12-h wave measurements. These high-resolution lidar measurements indicate that localized 12-h wave amplitudes are larger than previously reported by studies using meteor radar measurements.