Abstract In the study of Liang et al. (2005) shown that the two neglected Coriolis force terms ew, the Coriolis force in the x-momentum equation due to vertical motion and we, the Coriolis force in the vertical equation of motion due to the zonal wind should be taken into account in the motion and structure of tropical cyclone. In this study, effects of these terms on the structure and motion of a TC are investigated through numerical simulations using the Pennsylvania State University/National Center for Atmospheric Research mesoscale model MM5 and its tangential linear model.
The we term induces the upward motion in the westerly wind and downward motion in the easterly wind. Around the TC center, anomaly upward (downward) motion is produced to the south (north). The upward (downward) motion leads to the anomaly low (high) in the lower vertical levels and the high (low) in the upper levels. Finally, anticyclone (cyclone) is established related to the high (low).
Combination of term ew and we creates anomaly low (high) to the southwest (northeast) of TC center in the lower levels and high (low) to the southwest (northeast) in the upper levels. As results, the effects of the ew and we term induce a cyclonic (anticyclonic) flow with low (high) to the southwest (northeast) to the TC center in the lower and middle levels which are as same as the demonstrated gamma-gyres in Liang et al. (2005).
The gamma-gyres are rotated as the same mechanical of vortex Rossby wave. Because of the rotation of the gamma-gyres, the mean flow cross the TC center is also rotated. The rotation of the mean flow and anomaly rainfall make the track of the TC in a rotation way.