Streamwise vorticity equation

A streamwise vorticity equation is derived in generalized natural coordinat es. This equation reveals that the total change and local change of the str eamwise vorticity are mainly determined by the curvature of streamline, uns teady feature of streamline and magnitude of velocity. This equation enable s the study of mesoscale or small-scale systems since the term associated w ith pressure gradient force in the original vorticity equation is replaced by terms associated with streamlines and wind speed. With this modification the wind field rather than the pressure field is used in the calculation c onsidering that 1) the pressure field is to adapt wind field. 2) Smoother a nd more consecutive streamline pattern is easier to obtain either by data a nalysis or by the numerical simulation. From this sense, this present study suggests the application of this equation to studying the evolution of sev ere storm system as well as other simplified cases.