Numerical Simulation And Dynamic Characterics On The Development And Evolution Of Super Typhoon SANBA

Super Typhoon SANBA(2012)was studied by numerical experiments with the mesoscale model WRF.Comparative analysis of effects on the track and intensity of simulated Typhoon SANBA by different planetary boundary layer(PBL)parameterization schemes as well as initial wind parameterization model.And then dynamical diagnostic analyses were conducted on the development and evolution process of Super Typhoon SANBA.The main results as following:(1)Different PBL parameterizations have significant effect on the simulated intensity and path of SANBA during its initial phase.The simulated results by the QNSE and ACM2 PBL parameterization schemes are closest to its best track data in numerical experiments without the Bogus method.Trajectories of the simulated typhoon were improved significantly when the Bogus method was used.Among them,the QNSE and ACM2 schemes can represent the initial PBL process satisfactorily,especially for the formation and development of disturbed low vortexes at PBL.(2)The simulated intensity and track of SANBA differed due to differences in the initial wind field generated by the four parametric representations of the primary tropical cyclone wind field.Compared with the best track data and TRMM data the Holland scheme had the most accurate intensity,track and location.Vertical structure has better symmetry.(3)Comparative analyses of energy and helicity during the evolution of Typhoon SANBA indicate that the temporal variation of the primary circulation(p)and the horizontal helicity is consistent.The vertical helicity increased rapidly when the Typhoon developed from the STY to the SuperTY stage which means vertical helicity can be used to represent rapid intensification of the typhoon.(4)Analyses on characters of circulation during the development and evolution process of SANBA show that the radial velocity had a strong outflow in the upper troposphere as well as strong inflow at lower troposphere and which gradually increased with the development of the typhoon.The maximum of tangential wind appeared in the lower troposphere.The average circulation intensity in the central area of the typhoon is enhanced with the typhoon intensification and developed from 900 hPa height to upper levels.Wherein the variations of EED / EET item in the circulation equations may represent the major characterics of the divergence term typhoon and tilt term in early development stage.(5)Analyses the development and evolution of vertical vorticity and circulation by using the method of scale separation during super typhoon SANBA suddenly increase process show that the intensity of vorcity in typhoon internal region is enhanced when Tropical storm develop into a strong tropical storm(the 30 th hour of the simulation),,the enhancement of vorticity tendency is closely related the divergence /convergence and the nonuniform distribution of vertical velocity and when SANBA developed into super typhoon(the 50 th hour of the simulation),the low-level radial inflow enhancement play the major role for the development of typhoon.(6)Comparative analyses on the deformation field show that the radius of maximum wind is increase at first,then constriction,and increase again at last with the typhoon intensification.The term of rotation and divergence are the major process in the typhoon inner core and the transformation is more important at the external part of typhoon.