Differences in Annual Cycle and 30-60-day Oscillations between the Summers of Strong and Weak Convection over the Tropical Western North Pacific

摘要

When the JJA mean convection is stronger in this region, anomalously strong convection does not appear uniformly throughout the whole summer, but coincides with the three times of the climatological convection enhancements that appear in mid June, late July, and mid August, respectively. It is also found that strong (weak) JJA mean convection corresponds to enhanced (suppressed) convection of the annual cycle from the beginning to the end of the year, and that these differences in the annual cycle between the strong and weak cases are most significant from May to August. The phases of 30-60-day oscillations tend to be consistent (inconsistent) among the strong (weak) cases, and thus the amplitudes of composite 30-60-day oscillations for the strong cases are greater than those for the weak cases. Both the annual cycle and 30-60-day oscillations contribute much to the interannual variation of the seasonal evolution. The annual cycle is responsible for the eastward extension of the enhanced convection in time in the composite differences between the strong and weak cases, and the 30-60-day component is responsible for weak differences in mid July.