Streamwise Vorticity Equation

A streamwise vorticity equation is derived in generalized natural coordinates. This equation reveals thatthe total change and local change of the streamwise vorticity are mainly determined by the curvature ofstreamline, unsteady feature of streamline and magnitude of velocity. This equation enables the study ofmesoscale or small-scale systems since the term associated with pressure gradient force in the originalvorticity equation is replaced by terms associated with streamlines and wind speed. With this modificationthe wind field rather than the pressure field is used in the calculation considering that 1) the pressure field isto adapt wind field. 2) Smoother and more consecutive streamline pattern is easier to obtain either by dataanalysis or by the numerical simulation. From this sense, this present study suggests the application of thisequation to studying the evolution of severe storm system as well as other simplified cases.