Interannual variability of the 10–25‐ and 30–60‐day variation over the South China Sea during boreal summer

The interannual variability (IAV) of the intraseasonal variation (ISV) over the South China Sea (SCS) was investigated, focusing on the relationship between the 10–25‐ and 30–60‐day variation. Both ISV activities over the SCS had larger IAV than those of the Bay of Bengal and Arabian Sea. The 10–25‐ (30–60‐) day variation was relatively active when the 30–60‐ (10–25‐) day variation was suppressed in June, July and September. The IAV of the ISV during early summer (June–July) was related to the IAV of the SCS monsoon onset. A late (early) onset was accompanied by active 10–25‐ (30–60‐) day variation. The IAV of the ISV could be divided into early and late summer (September), because there was little persistence between these two periods. Moreover, large‐scale circulation anomalies associated with the IAV had different spatial structures in these two periods.