Typhoon Interaction With Midlatitude Flow And Structural Change During Extratropical Transition

This study based on FY-2E satellite data,the best path data set up the JMA and the FNL global analysis provided by the NCEP to carry out the numerical simulation(WRF)and the trajectory simulation(LAGRANTO)of the 2010 typhoon Malakas,and use the physical quantity diagnostics as Equivalent Potential Temperature,Potential Vorticity,Vorticity Equation,Vertical Integrated Moistrue Transport,The vector Front Function.The impact of typhoon Malakas on the midlatitude flow and structure change during extratropical transition.The results show that:During extratropical transition,the structural change of Malakas experienced two stages:(1)In the initial stage of Malakas,Malakas maintained a positive pressure structure,the Malakas center sank,both sides rose,and maintained a "warm heart",and the surrounding was accompanmied by the spiral cloud system;(2)the cold air began to invade at the stage of Malakas extratropical transition and the cold air began to invade,forming the vertical distribution of the dry and cold,warm and wet air.The height field is lagging behind the temperature field,and the formation and maintenance of the front structure on the west side causes the original positive pressure structure to be a baroclinie structure,accompanied by low altitude convergence and high divergence.The analysis showed that Malakas had experienced three stages during its extratropical transition:(1)Upper disturbance intensifying,The cyclonic circulation generated by high-level positive Potential vorticity(PV)generates negative temperature advection on the west side of the baroclinic zone in the northern part of the Malakas center,which is manifested as the invasion of cold air;(2)TC-midiatitude flow interaction,the typhoon headed northward and led to the occurrence of the baroclinic zone.The deep convection eruption caused the low-level warm wet air to rised along the baroclinic zone,Latent heat release in rapidly ascending air leaded to a net transport of low-PV air into the upper troposphere to rebuild a ridge in tihe part of north;(3)Extratropical cyclone stage,The merging of the remnants of the TC inner core wint the baroclinic zone,Negative PV advection by the diabatically driven outflow initiates ridge building,accelerates and anchors a midlatitude jet streak,and overall amplifies the upper-level Rossby wave pattern.