Tropical and mid-latitude 45-day perturbations over the Western Pacific during the northern summer

摘要: The tropical Madden-Julian oscillation (MJO), which is of convective origin, systematically propagates northward in the Western North Pacific summer monsoon region (5°-20°N, 110°-160°E). propagating MJO, statistically significant, displays strong horizontally and vertically asymmetric circulation. low-level cyclonic response pronounced due to presence convergent, cyclonically sheared mean flow, while upper-level anticyclonic counterpart weak influence divergent, anticyclonically flow. upper tropospheric MJO largely associated with divergent winds, as manifested by equatorward outflows that export vorticity into troposphere Southern Hemisphere. flow responsible for reinforcing vertical asymmetry circulation induced heating, generating a barotropic component baroclinic through flow-MJO interaction. mid-latitude intraseasonal (ISO) wave train structure along great circle traversing Pacific, exhibits largest variability westerly jet exit (40°-50°N, 180°-150°W). This phenomenon attributed combination two different dynamic processes. While northward, generated interaction produces significant tropical-extratropical on time scale. Namely, when 45-day activity becomes strongest near Philippines, acts an origin Rossby dispersion emanating out forcing, eventually contributing development extratropical ISO. enstrophy budget analysis shows, other hand, contribution ISO situ flow-ISO around exit.