Contributions of barotropic energy conversion to northwest pacific tropical cyclone activity during ENSO

摘要

The contribution of barotropic energy conversion to tropical cyclone (TC) activity over the western North Pacific (WNP) during warm and cold phases of El Ni?o-Southern Oscillation (ENSO) is investigated by separating TC vortices from reanalysis data and using a linearized eddy kinetic energy tendency equation. By comparing the characteristics of TC disturbances with synoptic-scale disturbances, it is found that the modulation of ENSO on theWNPTC intensity is presented more objectively by using TC kinetic energy (EKE_(TC)) than eddy kinetic energy (EKE). Barotropic energy conversion (KmKe) into TC disturbances (KmKe_(TC)) is an effective indicator in detecting the barotropic energy source of low-level cyclone genesis and maintenance during the ENSO cycle. However, its dynamical processes play different roles. Shear in large-scale zonal wind and convergence in large-scale meridional wind provide direct barotropic energy source for TC genesis, but make effects in different regions of the WNP. In contrast, convergence in large-scale zonal and shear in largescale meridional wind exert little influence on TC genesis during ENSO.