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Monsoon gyres have been identified as one of the important large-scale circulation patterns that are associated with tropical cyclone formation in the western North Pacific.In part I of this study,observational analysis indicate that most tropical cyclones form near the center of monsoon gyres or the northeast end of the enhanced low-level southwesterly flows on the southeast-east periphery of the monsoon gyres.In this part,idealized numerical experiments are conducted to examine the role of the Rossby wave energy dispersion with an initial idealized monsoon gyre.Numerical simulations show that the development of the low-level enhanced southwesterly flows on the southeast-east periphery of monsoon gyres can be induced by the Rossby wave energy dispersion.In the control experiment,mesoscale convective systems emerge from the northeast end of the enhanced southwesterly flows with mid-level maximum relative vorticity and the first simulated tropical cyclone forms at 82 h near the center of the monsoon gyre.Sudden northward track changes occur when the tropical cyclone moves close to the center of the monsoon gyre.The formation of the second tropical cyclone is associated with mesoscale convective systems with low-level maximum relative vorticity in the northwest quadrant of the monsoon gyre at 159 h,and takes a general westward track.The numerical experiment with a relatively small size of the initial monsoon gyre shows that only one tropical cyclone forms in association with the enhanced southwesterly flows.This study suggests that Rossby wave energy dispersion can play an important role in tropical cyclone formation in the presence of monsoon gyres.