Calculation and Evaluation of Neutral Winds in the Lower Thermosphere Based on SYISR Observations.

An algorithm for obtaining ion vector velocities and neutral winds in the lower thermosphere (100–150 km) was applied to the Sanya incoherent scatter radar (SYISR; located at 18.3°N, 109.6°E) for the first time. The observational experiment transmitted alternating code pulses with a code width of 20 μs. The ion vector velocities and neutral winds were derived from multiple‐beam line‐of‐sight ion velocities. To verify the reliability, we first analyzed the variations and errors of the ion vector velocity and the neutral wind at different time scales. Then, we used an empirical model (HWM) and a theoretical model (NCAR‐TIEGCM) for comparison. Both comparisons exhibited good consistency in terms of neutral wind velocity. Furthermore, we compared the SYISR neutral winds with the meteor radar and ICON/MIGHTI winds. The zonal (meridional) wind speeds of the meteor radar and SYISR are 24.95 m/s (13.95 m/s) and 20.68 m/s (16.85 m/s), respectively, at 6:30 LT at 100 km. The amplitudes and phases of the tides derived from the SYISR data are in accordance with those of the meteor radar. The ICON/MIGHTI and SYISR showed consistencies in terms of the wind velocity when ignoring interannual variation. Plain Language Summary: In the lower thermosphere, atmospheric waves propagating from lower altitudes transfer energy and momentum to the ionosphere, playing a critical role in atmosphere/ionosphere coupling. Atmospheric fluctuations are measured mainly through neutral wind measurements. However, measuring neutral winds, especially height profiles in the lower thermosphere, is very challenging and rare. In this paper, using the newly built Sanya incoherent scatter radar (SYISR), we developed a sophisticated algorithm to derive ion vector velocities and neutral winds from multiple‐beam SYISR measurements between 100 and 150 km. Evaluations show that the data are reliable and useful. Key Points: Neutral winds from 100 to 150 km are obtained using 85 days of continuous SYISR alternating code observationsThe neutral winds derived from the SYISR data are in good agreement with those of the HWM and NCAR‐TIEGCMThe neutral winds derived from the SYISR data are further evaluated with meteor radar and ICON/MIGHTI [ABSTRACT FROM AUTHOR]