Long-lead ENSO control of the boreal summer intraseasonal oscillation in the East Asian-western North Pacific region

The boreal summer 30-60-day intraseasonal oscillation (ISO) in the East Asian-western North Pacific (EAWNP) region strongly influences persistent heavy rainfall in East Asia and tropical cyclone activities in the tropical western Pacific. In this study, we show that there exists a significant interannual south-north shift of the EAWNP-ISO activity between the equatorial eastern Indian Ocean -Maritime continent region and the subtropical South China Sea-western Pacific. This is reflected by the year-to-year changes in the occurrence frequency of individual ISO phases that correspond to different latitudinal locations of the convection anomaly. This interannual shift is largely controlled by the El Nino-Southern Oscillation (ENSO) in the preceding winter and spring. Following an El Nirio event, the ISO convective activity tends to occur in the equatorial eastern Indian Ocean-Maritime continents, whereas after a La Nina, frequent ISO-related precipitation occurs in the region of south China and the subtropical South China Sea-western Pacific. This result implies long-lead predictability for the occurrence of the summertime EAWNP-ISO activity and its associated weather.