Solar differential rotation profile used in this study. (a) Differential rotation Ω(r, θ) in a meridional plane, deduced from the global helioseismology (Larson & Schou 2018). (b) Latitudinal profiles of differential rotation at different depths. Horizontal dashed lines indicate the theoretically-expected phase speed of the sectoral (l = m) classical Rossby modes for selected azimuthal orders m = 2, 3, 4, 8, 16. The observing frame is chosen to be the Carrington frame rotating at Ω₀/2π = 456.0 nHz.