Numerical Studies of the Beta-Effect in Tropical Cyclone Motion Using a Semi-Lagrangian Model
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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It has been found that the beta effect can have an important effect on tropical cyclones. To conduct an experimental study of tropical cyclone movement on a beta plane a numerical model was developed. This model is based on the barotropic vorticity equation and used a semi-Lagrangian technique for the advective terms. The basic model is studied for accuracy and efficiency. It is seen that the accuracy of the semi-Lagrangian scheme is very good at moderate grid intervals, 20 km to 40 km, producing a much smoother vorticity field than that produced by the finite difference model. The efficiency of the semi- Lagrangian scheme as the time interval was increased was not fully achieved due to the shear effect in this regional model. When the beta effect was added, the model predicted vortex tracks and beta gyres compared well with those obtained from the finite difference model with a 20 km grid size. However, the semi- Lagrangian forecast with a grid size of 10 km gave somewhat different track, which could not be explained.