\noindent the basic problem faced in geophysical fluid dynamics is that a mathematical description based only on fundamental physical principles, the so-called the ``primitive equations'', is often prohibitively expensive computationally, and hard to study analytically. in this talk i will survey the main obstacles in proving the global regularity for the three-dimensional navier-stokes equations and their geophysical counterparts. even though the primitive equations look as if they are more difficult to study analytically than the three-dimensional navier-stokes equations i will show in this talk that they have a unique global (in time) regular solution for all initial data. \vskip .2in \noindent inspired by this work i will also provide a new global regularity criterion for the three-dimensional navier-stokes equations involving the pressure. \vskip .2in \noindent this is a joint work with chongsheng cao.