Analytical And Numerical Studies On Sensitivity Of Tropical Cyclone Motion To Its Intensity And Structure

Statistical analysis of tropical cyclone translational speed and intensity over the Western Pacific during 2001-2012 shows no obvious differences between median translational speed in each intensity region. But for those reaching tropical storms, the faster they moves, the weaker the maximum intensity they can reach.It’s complicated how tropical cyclone moves. Holland (1983) found that tropical cyclone motion is a combination of environmental interaction and a beta effect in the barotropic model. Both analytical and numerical methods are used to investigate tropical cyclone motion in this article. Besides, barotropic shallow water model with the radiation boundary condition is used. On the premise of not considering the beta effect, tropical cyclone moves with the environmental flow but slower. Analytical results show that the translational speed in the same environmental flow varies with tropical cyclone intensity, the rate of tangential wind decreasing, mean convergence into the cyclone and the radius of maximum winds. Numerical results show that the intenser, the slower the tangential wind decreasing, the more mean convergence into the cyclone, the slower tropical cyclone moves in the same environmental flow, but no significant relationships between the radius of maximum winds and translational speed. Without environmental basic flow on β plane, tropical cyclone moves as a result of the beta effect. Analytical results show that the speed of beta drift varies with tropical cyclone intensity, the rate of tangential wind decreasing, mean convergence into the cyclone and the radius of maximum winds. Numerical results show that the intenser, the slower the tangential wind decreasing, the bigger the radius of maximum winds, the faster tropical cyclone moves due to beta effect, but no significant relationships between mean convergence and the speed of beta drift. To sum up, tropical cyclones have opposite reactions to environmental basic flow and beta effect and they can be offset, so different tropical cyclones have no significant differences in translational speeds on average, as mentioned above about tropical cyclones over the Western Pacific.It’s noticed that tropical cyclones become weaker as translational speeds increases in our numerical models. We suppose that the fast translation is negative to tropical cyclone intensity, which is consistent with the phenomenon that the maximum intensity tropical cyclones can reach decreases with translational speed over the Western Pacific for those reaching tropical storms. But it’s not quite sure as the shallow water model with the radiation boundary condition is a dissipative one.