Gravity wave meridional wind perturbations (m·s⁻¹) at 50 km (a), 100 km (b), 200 km (c), and 300 km (d) altitudes at 19.416 UT on 20 October in SD-WACCM-X. Black and red arrows denote the propagation directions of GWs emitted from cold and warm fronts, respectively. GWs in the yellow rectangle in (c) will be discussed in detail later. See Movie 1 of the GW meridional winds at 16.33–22.33 UT for supporting information.