Air-sea coupled modes on intraseasonal and interannual time scales over the tropical western Pacific

Dominant phase relationships between sea surface temperature (SST), high cloud cover (HCC), and zonal wind at 850 mbar on intraseasonal and interannual time scales in the warm pool region of the western Pacific are examined. An intraseasonal mode and an interannual mode, are statistically extracted. It is found that in the intraseasonal mode the area of maximum SST anomaly lies to the east of the center of the active large-scale convection area and therefore positive SST anomalies exist at the easterly anomaly area. The interannual mode has a characteristic that the phase relation of 850 mbar zonal wind (u) is different in each region of the tropical western Pacific, whereas the SST is almost in phase with HCC. The predominant growth of the mode defined in the key region (0°-10°N, 130°-160°E) corresponds to the life cycle that occurs when the El Nino/Southern Oscillation (ENSO) begins, develops, and decays. -from Author