ENERGY DISPERSION EFFECTS ON EXPLOSIVE DEVELOPMENT OF MARINE CYCLONES

A dominant role played by energy dispersion in the explosive development of extratropicalmarine cyclones over the Northwest Pacific has been revealed based on both the eddy energyequations and the energy flux vectors of nonlinear wave packet.At the initial and explosive time.the eddy energy from neighboring upstream systems beyond the radius of Rossby deformation isdispersed into the eddy energy center associated with the cyclone via ageostrophic geopotentialfluxes,and results in the rapid increase of eddy kinetic energy and the occurrence of explosivecyclogenesis.When the cyclone begins to decay,its corresponding eddy energy is exporteddownstream and hence triggers the growth of new perturbation downstream.Through generalizingthe energy flux vectors of quasigeostrophic wave packets to the nonlinear forms and making use ofthe relationship between the energy flux vectors and the total eddy energy,the approximationexpressions of the total group velocity and relative group velocity are derived,and then they areused to compute an explosive case.The normalized ageostrophic geopotential fluxes by dividing thevolume integral of ageostrophic geopotential fluxes by the integral of the total eddy energydetermine the relative group velocity at which the eddy energy is spreading out,and they can beused to evaluate the position of next new disturbance.The nonlinear advective fluxes influenceprimarily the phase speed and translation of the cyclones.The results in this paper facilitate toexpanding the mechanism research on explosive cyclones and have great significance for predictingthe explosive intensification and downstream disturbance growth.