A Numerical Simulation Study About The Rapid Intensification Of Tropical Cyclone Haiyan(2013)

In this study,Tropical Cyclone Haiyan(2013) was selected to investigate its rapid intensification (RI) process based on Mesoscale numerical model WRF.The sensitivity of the simulated track,intensity and structure to the cumulus parameterization scheme and cloud microphysic parameterization scheme was analyzed.Then with the use of well-performed high-resolution output fields,the main characteristics and evolution features was explored from different perspectives.Finally,the vorticity equation was applied to diagnosed the budget of the inner-cord vorticity during the RI process.Results show that:The simulated track is more sensitive to the cumulus parameterization scheme.The effect of the KF scheme after the break of RI is outstanding,while before the onset the results of different cumulus schemes are similar.The intense of TC depends highly on the choice of cloud microphysic schemes due to the significant influence of microphysics on TC intense.The impact of microphysic schemes on TC inner structure is more substantial.With the comparison bwtween simulated brightness temperature calculated by UPP and TBB satellite data from FY2E,the superiority of MO scheme is confirmed due to its reproduction of TC eye,spiral rainband and other features.The investigation of the main characteristics and evolution features from the perspectives of environmental factors,inner core structure and convective bursts shows that:The warmer sea surface temperature,higher humidity,weak vertical wind shear and other favorable environmental conditions are significant in the genesis and intensification of TC.During the RI process,the circulation of TC intensifies with the contraction of eyewall,the decrease of the difference of equivalent potential temperature between the eyewall and eye,and the increase of radar reflectivity in the eyewall.The CBs has a sharp upward trend before the break of RI and decreases until the next intensification of TC.Convective(Stratiform) precipitation is dominant in the inner(outer) core of TC.The vertical velocities falling between 0-2ms-1 have the maximum contribution to the mass flux.The distribution of mass flux shows striking variance in different levels(lower,middle and upper levels)or precipitation modes.During the RI process,the increase of mass flux in convective(stratiform) precipitation area occurs in lower(upper) level.By the analysis of the evolution of each term of the vorticity equation and its axisymmetric characteristics,we obtain the following conclusions:The stretching term(stre) has positive(negative) contribution to the vorticity at lower(upper) level and intensifies mainly in lower level after the onset of RI.The tilting term(tilt) promotes the increase of vorticity in each level and its effect also enhanced in lower level in company with the alternation of positive effect and negative effect at middle level.The distribution of the horizontal-advection term(advh) doesn’t apply to all TCs,which is alternated with positive and negative values in horizon.The vertical-advection term(advv) contributes(suppresses) the vorticity genesis at lower (upper) level.Then from the axisymmetric perspective,there is a well relation between the distribution and the inner core stracture.