<P> Vertical pressure variation is the variation in pressure as a function of elevation . Depending on the fluid in question and the context being referred to, it may also vary significantly in dimensions perpendicular to elevation as well, and these variations have relevance in the context of pressure gradient force and its effects . However, the vertical variation is especially significant, as it results from the pull of gravity on the fluid; namely, for the same given fluid, a decrease in elevation within it corresponds to a taller column of fluid weighing down on that point . </P> <P> A relatively simple version of the vertical fluid pressure variation is simply that the pressure difference between two elevations is the product of elevation change, gravity, and density . The equation is as follows: </P> <Dl> <Dd> d P d h = − ρ g (\ displaystyle (\ frac (dP) (dh)) = - \ rho g), and </Dd> </Dl>

The difference in pressure between the top and bottom of a column of gas is calculated as