The 30-60-day Intraseasonal Oscillations over the Subtropical Western North Pacific during the Summer of 1998

The features of 30-60-day convection oscillations over the subtropical western North Pacific (WNP) were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP during summer 1998. It was found that 30-60-day oscillations were extremely strong in that summer over both the subtropical and tropicalWNP, providing a unique opportunity to study the behavior of subtropical oscillations and their relationship to tropical oscillations. Further analyses indicated that 30-60-day oscillations propagate westwards over the subtropical WNP and reach eastern China. In addition, 30-60-day oscillations in the subtropics are affected by those over the South China Sea (SCS) and tropical WNP through two mechanisms: (1) direct propagation from the tropics into the subtropics; and (2) a seesaw pattern between the tropics and subtropics, with the latter being predominant.