Empirical orthogonal function analysis was applied to outgoing longwave radiation (OLR) data over three limited regions during the three winters of 1974–75, 1975–76 and 1976–77. Regional composite maps were constructed by truncating the eigenvector series of 4–6 day OLR anomalies for each winter at 70% representation. Based on these composite charts, an attempt was made to investigate the phase relationships between changes in truncated 4–6 day filtered OLR data at a selected reference point, and those in other areas within the same region. Over region 1(25°N‐O°, 95–160°E), the winters of 1974–75 and 1976–77 have similar features in 4–6 day OLR disturbances, with systematic westward phase propagation in equatorial latitudes over the western North Pacific (∼8 m s−1) and the South China Sea (∼5 m s−1). In contrast, the 1975–76 winter is of a different character with eastward (westward) phase propagation to the west (cast) of about 130°E at equatorial latitudes. These large year-to-year changes in p... Abstract Empirical orthogonal function analysis was applied to outgoing longwave radiation (OLR) data over three limited regions during the three winters of 1974–75, 1975–76 and 1976–77. Regional composite maps were constructed by truncating the eigenvector series of 4–6 day OLR anomalies for each winter at 70% representation. Based on these composite charts, an attempt was made to investigate the phase relationships between changes in truncated 4–6 day filtered OLR data at a selected reference point, and those in other areas within the same region. Over region 1(25°N‐O°, 95–160°E), the winters of 1974–75 and 1976–77 have similar features in 4–6 day OLR disturbances, with systematic westward phase propagation in equatorial latitudes over the western North Pacific (∼8 m s−1) and the South China Sea (∼5 m s−1). In contrast, the 1975–76 winter is of a different character with eastward (westward) phase propagation to the west (cast) of about 130°E at equatorial latitudes. These large year-to-year changes in p...