(a) Total electron density content (TEC) perturbations in GNSS at 21.258 UT on 20 October 2020. The perturbations were derived in accordance with Chou et al. (2023), but a Butterworth filter with 10–60-min cutoff period was applied in this paper. The perturbations were averaged over 0.47° × 0.625° bins to align with the grid of the SD-WACCM-X output. (b) The same as (a), but in SAMI3/SD-WACCM-X. The black dashed lines in (a) and (b) denote the crests of concentric waves. (c) Radar reflectivity in NEXRAD. The red box indicates convection in the cold front area; i.e., the high convective activity area.