The Evolution of Finite Vorticity Strips using a Non-Divergent Barotropic Model

The evolution of finite-length vorticity strips is examined with a non-divergent, barotropic model using the pseudo-spectral method in Mathworks MATLAB. Since vorticity is a conserved quantity in this framework, evolution of vorticity is analogous to the evolution of Ertel's PV for adiabatic flow in the full physics framework. Similar FORTRAN-based models have been used extensively to study barotropic instability and the evolution of vorticity annuli, representing hurricane eyewall structures. Likewise, simple shallow-water models have been used extensively to study the evolution of vorticity strips, representing the ITCZ. MATLAB was chosen for this study to exploit the efficient matrix operations and simple coding of fast Fourier transform functions. The model is initialized with finite vorticity strips of various length-to-width ratios to determine the ratio at which the strips break down into a multiple vortices rather than form a single vortex. Inferences are made to the breakdown of the ITCZ during tropical cyclone genesis. Time integration testing is also performed to compare model performance and output between a third-order Adams-Bashforth scheme and a fourth-order Runge-Kutta scheme. The well-documented model will be used for student education and be made available to the scientific community