(a) Vertical profiles of GW intrinsic horizontal phase speeds. The blue and orange lines indicate the northeastward and southwestward GWs, respectively. The thick green line indicates the upper limit of intrinsic horizontal phase speed. (b) Same as (a) but local vertical wavelengths from equation (1). (c) Brunt–Väisälä frequency. (d) Density scale height. (e) Horizontal winds. These values are averaged over 35–45°N, 90–100°W, and 18.3–20.3 UT on 20 October 2020.