Interdecadal Variability of Rossby Wave Breaking Frequency near Japan in August

抄録

Rossby waves propagating along the Asian jet frequently cause the breaking near the jet exit region. This study examines characteristics of oceanographic condition and atmospheric circulation associated with interdecadal variability of Rossby wave breaking frequency near Japan in August. Sea surface temperature during a period of the higher Rossby wave breaking frequency is cooler over the central part of the tropical North Pacific, compared with that during a period of the lower frequency. Convective activities are suppressed over the region consistent with the cooler sea surface temperature, contributing to an enhanced and southwestward extended mid-Pacific trough. Deceleration and diffluence of the Asian jet are stronger during the period of the higher frequency than that during the period of the lower one. The enhanced deceleration and diffluence of the jet are associated with the enhanced and southwestward extended mid-Pacific trough. The abovementioned dynamical influence is also shown by a numerical simulation using an atmospheric linear baroclinic model. These results indicate that the interdecadal variability of sea surface temperature over the central part of the tropical North Pacific has an impact on that of the Rossby wave breaking frequency near Japan, through the modulated convective activities and mid-Pacific trough.