Barotropic Interactions Between Summertime Tropical Cyclones/Sub-Monthly Wave Patterns and Intraseasonal Oscillations over the Western North Pacific


This study used the barotropic kinetic energy conversion to record the active eddy-mean flow interaction between the TC/sub-monthly wave pattern (TSM) and the intraseasonal oscillation (ISO) in the western North Pacific (WNP). Overall, the TSM extracted (lost) kinetic energy from (to) the cyclonic (anticyclonic) circulation of the ISO, which is located in the South China Sea and the Philippine Sea, during the ISO westerly (easterly) phase. The phase change in barotropic energy conversion was due to the opposite background flow set up by the ISO. When the climatological-mean southwesterly was retained as part of the background flow in both ISO westerly and easterly phases as in previous studies, the ISO along with the low-frequency background flow always provided kinetic energy to the TSM regardless of the phase. The stronger (weaker) southwesterly in the ISO westerly (easterly) phase, the stronger (weaker) energy conversion to the TSM. Climatological mean flow exclusion showed an upscale feedback in the TSM to the ISO during the easterly phase. However, this feedback was weaker than the downscale conversion from the ISO to the TSM during the westerly phase.

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