Atmospheric Chemistry Experiment (ACE) Winds

Abstract. The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) uses limb geometry to measure transmittance spectra of Earth's atmosphere by solar occultation. Line-of-sight wind speeds can be derived via Doppler shifts of molecular lines in infrared spectra. The wind look direction angles relative to geodetic North are derived from geometry. We validate the new ACE version 5.3 (v.5.3) line-of-sight winds with MIGHTI and meteor radar vector wind observations and find a ±15 m/s sunrise/sunset shift above 80 km. We also compare line-of-sight winds from ACE-FTS v.5.2 and v.5.3 with vector winds from the MERRA-2, HWM14, and WACCM-X models. A ±15 m/s sunrise-sunset bias persists in v.5.3 winds above 80 km but decreases to less than ±5 m/s below 50 km. The v.5.3 wind speed profiles have improved relative to v.5.2 at all altitudes. Over 20 years of ACE wind speeds can be used to test atmospheric models.