Monthly Climatologies of Zonal-Mean and Tidal Winds in the Thermosphere as Observed by ICON/MIGHTI During April 2020-March 2022

Version 5 (v05) of the thermospheric wind data from the Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument on the Ionospheric Connection Explorer (ICON) mission has been recently released, which largely avoids local-time dependent artificial baseline drifts that are found in previous versions of the ICON/MIGHTI wind data. This paper describes monthly climatologies of zonal-mean winds and tides based on the v05 ICON/MIGHTI data under geomagnetically quiet conditions (Hp30 < 3o) during April 2020-March 2022. Green-line winds in the lower thermosphere (90-110 km) and red-line winds in the middle thermosphere (200-300 km) are analyzed, as these data cover both daytime and nighttime. The latitude and height structures of zonal-mean winds and tides are presented for each month, and the results are compared with the widely used empirical model, Horizontal Wind Model 2014 (HWM14). The ICON/MIGHTI and HWM14 results are in general agreement, providing a validation of the v05 ICON/MIGHTI data. The agreement is especially good for the zonal-mean winds. Amplitudes of lower thermospheric tides from ICON/MIGHTI tend to be larger than those from HWM14 as well as from an empirical model, Climatological Tidal Model of the Thermosphere (CTMT). This could be due to the influence of interannual variability of the tides. The amplitude structure of lower thermospheric tides in HWM14 does not match those from ICON/MIGHTI and CTMT in some months. Also, HWM14 underestimates the meridional-wind amplitude of the migrating diurnal tide in the middle thermosphere. These results highlight the need for improved tidal representation in HWM14.

Automated summary

This paper presents the monthly climatology of zonal-mean winds and tides based on the v05 ICON/MIGHTI data and compares it with the HWM14 model. The results show good agreement between ICON/MIGHTI and HWM14, but larger amplitudes of lower thermospheric tides are observed in ICON/MIGHTI, suggesting the need for improvements in the tidal representation of HWM14.