“…Based on this work, there has been a plenty of researches about the exact azimuthal equatorial flows with continuous stratification, such as [15,18] in the cylindrical coordinates, [16,17] in the spherical coordinates, and [26] in the β-plane approximation. Moreover, we introduce some excellent studies related to the exact solutions to the geophysical fluid dynamics equations in the β-plane, see [14,21,24,25,28]. For exact azimuthal solutions for equatorial flows with discontinuous stratification, see [22] for the case of a discontinuous density that varies with depth, and [23] for a discontinuous density that varies with both depth and latitude.…”