The effect of cold air intrusion on the development of tropical cyclone
冷空气入侵对热带气旋发生发展的影响

It is confirmed through the gradient wind equation that the rising of temperature gradient will cause the rising of vorticity.This means that cold air will promote the development of tropical cyclone if the warm-core of the tropical cyclone has not been destroyed.A number of numerical experiments are designed by changing lateral boundary conditions with cold air or warm air.Numerical results show that the major change is the environmental circulation of tropical cyclone when the surges immerge into the outmost of the tropical cyclone.The warm air from the Northern Hemisphere will reduce the north wind of the tropical cyclone.The pulling force away from the center of the tropical cyclone is formed,which weakens the mass convergence.On the contrary,the cold air from the Northern Hemisphere will intensify the north wind of the tropical cyclone.The pushing force to the center of the tropical cyclone is formed,which intensifies the mass convergence.Because of the pushing force,on the one hand,the energy is transported to tropical cyclone,which is generated for the intrusion of the cold air;on the other hand,the temperature gradient is intensified.In the weather system,the cold anticyclone in the north and the Australian cold air activity will intensify the tropical cyclone in the Western Pacific.