Identifying gravity waves launched by the Hunga Tonga-Hunga Ha′apai volcanic eruption in mesosphere/lower-Thermosphere winds derived from CONDOR and the Nordic Meteor Radar Cluster

The Hunga Tonga-Hunga Ha′apai volcano eruption was a unique event that caused many atmospheric phenomena around the globe. In this study, we investigate the atmospheric gravity waves in the mesosphere/lower-Thermosphere (MLT) launched by the volcanic explosion in the Pacific, leveraging multistatic meteor radar observations from the Chilean Observation Network De Meteor Radars (CONDOR) and the Nordic Meteor Radar Cluster in Fennoscandia. MLT winds are computed using a recently developed 3DVAR+DIV algorithm. We found eastward-and westward-Traveling gravity waves in the CONDOR zonal and meridional wind measurements, which arrived 12 and 48ĝ€¯h after the eruption, and we found one in the Nordic Meteor Radar Cluster that arrived 27.5ĝ€¯h after the volcanic detonation. We obtained observed phase speeds for the eastward great circle path at both locations of about 250ĝ€¯mĝ€¯s-1, and they were 170-150ĝ€¯mĝ€¯s-1 for the opposite propagation direction. The intrinsic phase speed was estimated to be 200-212ĝ€¯mĝ€¯s-1. Furthermore, we identified a potential lamb wave signature in the MLT winds using 5ĝ€¯min resolved 3DVAR+DIV retrievals

Inferring neutral winds in the ionospheric transition region from atmospheric-gravity-wave traveling-ionospheric-disturbance (AGW-TID) observations with the EISCAT VHF radar and the Nordic Meteor Radar Cluster

Atmospheric gravity waves and traveling ionospheric disturbances can be observed in the neutral atmosphere and the ionosphere at a wide range of spatial and temporal scales. Especially at medium scales, these oscillations are often not resolved in general circulation models and are parameterized. We show that ionospheric disturbances forced by upward-propagating atmospheric gravity waves can be simultaneously observed with the EISCAT very high frequency incoherent scatter radar and the Nordic Meteor Radar Cluster. From combined multi-static measurements, both vertical and horizontal wave parameters can be determined by applying a specially developed Fourier filter analysis method. This method is demonstrated using the example of a strongly pronounced wave mode that occurred during the EISCAT experiment on 7 July 2020. Leveraging the developed technique, we show that the wave characteristics of traveling ionospheric disturbances are notably impacted by the fall transition of the mesosphere and lower thermosphere. We also demonstrate the application of using the determined wave parameters to infer the thermospheric neutral wind velocities. Applying the dissipative anelastic gravity wave dispersion relation, we obtain vertical wind profiles in the lower thermosphere