Idealized Numerical Simulations of Tropical Cyclone Formation Associated with Monsoon Gyres

Monsoon gyres have been identified as one of the important large-scale circulation patterns associated with tropical cyclone (TC) formation in the western North Pacific. A recent observational analysis indicated that most TCs form near the center of monsoon gyres or at the northeast end of the enhanced low-level southwesterly flows on the southeast-east periphery of monsoon gyres. In the present reported study, idealized numerical experiments were conducted to examine the tropical cyclogenesis associated with Rossby wave energy dispersion with an initial idealized monsoon gyre. The numerical simulations showed that the development of the low-level enhanced southwesterly flows on the southeast-east periphery of monsoon gyres can be induced by Rossby wave energy dispersion. Mesoscale convective systems emerged from the northeast end of the enhanced southwesterly flows with mid-level maximum relative vorticity. The simulated TC formed in the northeast of the monsoon gyre and moved westward towards the center of the monsoon gyre. The numerical experiment with a relatively smaller sized initial monsoon gyre showed the TC forming near the center of the initial monsoon gyre. The results of the present study suggest that Rossby wave energy dispersion can play an important role in TC formation in the presence of monsoon gyres.