Cross-Validation of Thermospheric Vertical Wind Observations from SDI and FPI Instruments across Scandinavia.

Vertical winds are a critical component of the dynamical motion in Earth’s thermosphere because of the roles they play in wave propagation and potentially in transporting air parcels across isosurfaces of composition. However, this component of the wind is generally considered more difficult to derive than horizontal wind measurements because velocities in the vertical direction are relatively small, and common remote sensing techniques can only unambiguously resolve vertical winds at one location, i.e., immediately above the observatory.
To address these and other limitations, a new project named TITAN-3D (Tristatic Ionosphere-Thermosphere Aeronomy Network) has established three long term observatories in Abisko (Sweden), and Aakenus & Kevo (Finland). Each observatory in the network includes a Scanning Doppler Imager (SDI) operated by University of Alaska Fairbanks and a Fabry-Perot Interferometer (FPI) operated by University of Michigan. Additionally, project participants from Nagoya University operate an FPI at Skibotn in Norway. Each of these instruments has a unique design and each is operated entirely independently of the others.
In this poster, we present a detailed comparison of vertical wind measurements across multiple instruments and observatories. The data show strong agreement between the measurements, despite the differences in instrument design and operation, which provides strong validation of the geophysical accuracy of these observations. We highlight a particular event on January 2, 2025 which contained strong vertical wind velocities early in the night that were seen to be consistent by each of the instruments and across multiple locations. These passive instruments operate routinely each night, and so it is anticipated that TITAN-3D will produce a large volume of similarly validated vertical wind measurements. This data set will be applied in statistical studies of the morphology of thermospheric vertical winds to determine their relation to space weather drivers.