A Preliminary Study Of The 2015 Typhoon Soudelor:Its Genesis,Intensification,Decay And Relation To MJO

This study applies a new methodology for nonlinear hydrodynamic stability analysis,i.e.multiscale window transform(MWT),and the MWT-based multiscale energy and vorticity analysis(MS-EVA)and canonical transfer theory,to analyze the dynamical processes in the super strong typhoon Soudelor in 2015,and the effect of MJO.The original atmospheric field is reconstructed with MWT onto three subspaces,or scale windows,namely,tropical cyclone window,intraseasonal window and large-scale window.After filtering out the sub-seasonal oscillations,the barotropic component of the flow of the whole troposphere best steers the movement of Soudelor,implying an improved track prediction based on filtered large-scale flow.On tropical cyclone window,Soudelor forms from bottom but decays from top.Through multiscale energetic analysis,the formation and intensification of Soudelor in lower layer is attributed to barotropic instability,and transport and diffusion distribute kinetic energy from lower troposphere to upper part,accounting for its upward genesis.The rapid intensification of Soudelor is indirectly related to the baroclinic instability in higher layer,which is advantage to the establishment of warm core.Soudelor decays downward from the top after landing,due to the barotropic stability in higher layer when its kinetic energy in lower layer decreases without the support of the instable background.The weak westward-moving MJO triggers the genesis of the typhoon by adjusting the divergent background flow rather than transferring kinetic energy to it,but makes little contribution to the rapid intensification and decay of Soudelor.