Gravity Waves induced Wind Shears Derived from SABER Temperature Observations

Abstract

<jats:p>Abstract. Large wind shears around the mesopause region play important roles in atmospheric neutral dynamics and ionospheric electrodynamics. Based on previous observations using sounding rockets, lidars, radars and model simulations, large shears are mainly attributed to gravity waves (GWs) and modulated by tides (Liu, 2017). Based on the dispersion and polarization relations of linear GWs and the SABER temperature data from 2002 to 2019, a method of deriving GW-induced wind shears is proposed. The zonal mean GW-induced shears have peaks (13–17 ms−1 km−1) at around the mesopause region, i.e., at z = 90–100 km at most latitudes and at z = 80–90 km around the cold summer mesopause. This latitude-height pattern is robust over the 18 years and coincides with model simulations. The magnitudes of the GW-induced shears exhibit year-to-year variations and coincide with the lidar and sounding rocket observations on climatology sense but are 60–70 % of the model results in the zonal mean sense. The GW-induced shears are hemispheric asymmetric and have strong annual oscillation (AO) at around 80 km (above 92 km) at the northern (southern) middle and high latitudes. At middle to high latitudes, the peaks of AO shift from winter to summer and then to winter again with increasing height. However, these GW-induced shears may be overestimated because the GW propagation direction cannot be resolved by the method and may be underestimated due to the observational filter, sampling distance and cutoff criterion of the vertical wavelength of GWs. </jats:p>