Interdecadal variability of the tropospheric biennial oscillation in the western North Pacific

The observed tropospheric biennial oscillation (TBO) in the western North Pacific (WNP) monsoon region has an interdecadal variability with a period of 40--50 yr. That suggests a weaker effect of the TBO on the East Asia followed by a stronger one. A simple analytic model was designed to investigate the mechanism of the interdecadal variability of the TBO. The results indicated that a local TBO air--sea system not only supports the TBO variability in the WNP monsoon region but also produces an interdecadal variability of the TBO.