A climatology of the nighttime thermospheric winds over Sutherland, South Africa

Taiwo T. Ojo, Zama T. Katamzi-Joseph, Kristina T. Chu, Matthew A. Grawe, Jonathan J. Makela

Research output: Contribution to journalArticlepeer-review

Abstract

We present a climatology of nighttime thermospheric neutral winds between February 2018 and January 2019 measured by a Fabry-Perot interferometer (FPI) located in Sutherland, South Africa (32.2°S, 20.48°E; geomagnetic latitude: 40.7°S). This FPI measures the nighttime oxygen airglow emission at 630.0 nm, which has a peak intensity at an altitude of roughly 250 km. The annual meridional and zonal winds at this location vary between −100 and 120 m/s and show typical midlatitude nocturnal and seasonal variations. During local summer months (December-February), the meridional wind is predominantly equatorward from dusk to predawn. However, during the winter months, the meridional wind is poleward from dusk, turns equatorward around midnight, and either remains in this direction for the rest of the night (June) or turns poleward again just before dawn (July and August). The zonal wind velocity is generally eastward during the evening until just before midnight, changing westward post-midnight. The zonal wind peaks at higher velocities during the winter months compared to the summer months. The eastward-to-westward transition occurs later during the winter months compared to the summer months. We compare results from HWM14 with the FPI measurements and find a better agreement between FPI measured winds and HWM14 modeled winds for the meridional component compared to the zonal component. In addition, the HWM14 zonal wind consistently peaked several hours (∼3 h) prior to the measured wind. Furthermore, the HWM14-modeled eastward-to-westward transitions times were a couple of hours (∼2 h) earlier during the months of November to January creating what looks like a phase shift compared to the measured wind. This phase shift was apparent in all months and we suggest this can be attributed to a phase shift of the terdiurnal tide between the model and measurements.

Original languageEnglish (US)
Pages (from-to)209-219
Number of pages11
JournalAdvances in Space Research
Volume69
Issue number1
DOIs
StatePublished - Jan 2022
Externally publishedYes

Keywords

  • FabryPerot interferometer (FPI)
  • Horizontal wind model (HWM14)
  • Nighttime thermospheric winds

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • General Earth and Planetary Sciences

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