Eastward propagating similar to 2- to 15-day equatorial convection and its relation to the tropical intraseasonal oscillation

Anomalies of outgoing longwave radiation (OLR) in 1980-1989 were examined in a narrow latitude band about the equator to elucidate the propagation and interaction of tropical intraseasonal oscillations (TIOs) and synoptic-scale convective activity. Hovmoller diagrams of OLR data reconstructed from two frequency bands (corresponding to periods of similar to 30-60 days and similar to 2-15 days, respectively) revealed a clear distinction between the phase speed of eastward moving TIOs (3-7 m s(-1)) and that of eastward synoptic-scale convection (10-13 m s(-1)). Coherent propagation of TIOs from the Indian to the western Pacific Oceans was often observed with temporary diminution of amplitude over the maritime continent. Propagation of high-frequency anomalies was generally confined to an individual basin. Dominance of eastward propagating synoptic-scale convection in the equatorial zone contrasts sharply with the westward propagation of off-equatorial convergence zones. Interaction between the TIO and high-frequency activity resolved by daily OLR was visible as a modest enhancement of eastward synoptic-scale events (and of high-frequency activity in general) during the convectively active phase of the TIO.