Concentric gravity waves in the mesosphere generated by deep convective plumes in the lower atmosphere near Fort Collins, Colorado

We measured the horizontal wavelengths and periods of these gravity waves as functions of both radius and time. These results agreed reasonably well with the internal Boussinesq gravity wave dispersion relation with an assumed zero background wind. Similarly, for the other 8 cases, strong convective plumes occurred prior to the CGW observations near the apparent center of each of the arcs or rings.

For the 7 out of the 9 cases, radiosonde data were available up to z = 30 - 35 km. These data showed that the wind speeds from the tropopause to ∼30–35 km were smaller than ∼20 - 30 m/s. Because 8 of the 9 cases occurred when the total horizontal mean winds were weak and because the horizontal winds below ∼87 km were less than ∼20 m/s on 11 May 2004 (according to radiosonde and TIME-GCM model data), we postulate that weak background horizontal winds are likely a necessary condition for gravity waves excited from convective overshooting to be observed as concentric arcs or rings in the OH layer.