“…From (1), when = 0 , we formally recover the inviscid Boussinesq equations, which are often used for the determination of the coupled flow and temperature field in natural convection (see, e.g., [22]). These equations are also used, for instance, as a mathematical scheme to describe Newtonian fluids whenever salinity concentration or density stratification -according to the meaning of -play a significant role (see, e.g., [3][4][5]7] for some recent papers on this subject). Moreover, they are extensively employed in studying oceanographic and atmospheric phenomena (see [26,27,30]).…”