Investigating thermospheric winds over Tenerife: Fabry-Perot observations and retrieval method comparisons.

Abstract

Thermospheric winds play a crucial role in the transport of momentum and energy in the upper atmosphere which affects the composition and the dynamics of the thermosphere and ionosphere. Understanding thermospheric winds is key for improving satellite operations and global communication systems. An important tool for measuring the thermospheric winds is the Fabry Pérot Interferometer (FPI). The FPI is a remote sensing instrument whose measurement principle relies on an etalon, consisting of two parallel, partially reflective surfaces, producing constructive interference under specific conditions. FPIs are used to image naturally occurring airglow emission lines with well-known spectral characteristics. The resulting images are analyzed to infer temperature and line-of-sight wind. The key mechanism for the retrieval of these physical parameters is the use of the Doppler-broadening and Doppler shift of airglow emission, respectively. In March 2024, DLR installed a new, own construction of a 630 nm FPI on Tenerife (SOFPIT) at geographical coordinates 28.29° N, 16.63° W and geomagnetical coordinates 32.79° N, 60.75° E. SOFPIT delivered almost a full year of thermosphere wind observations during night conditions. Methods for deriving winds and temperatures have been developed based on instrument specifics. Comparisons with the horizontal wind model (HWM) confirm that initial SOFPIT wind observations are in the correct order of magnitude. Using data from SOFPIT, a comparison between retrieval methods is performed. Assessments of the underlying assumptions on the dynamics of the atmosphere (zero-wind reference, constant vertical wind and uniform horizontal wind over a period of time) are made.