The development and movement of the tropical intraseasonal system (TIS) exhibit remarkable annual variations. It was hypothesized that spatial and temporal variation in sea surface temperature (SST) is one of the primary climatic factors that are responsible for the annual variation of TISs. This paper examines possible influences of SST on the TIS through numerical experiments with a 2.5-layer atmospheric model on an equatorial β plane, in which SST affects atmospheric heating via control of the horizontal distribution of moist static energy and the degree of convective instability. The gradient of the antisymmetric (with respect to the equator) component of SST causes a southward propagation of the model TIS toward northern Australia in boreal winter and a northward propagation over the Indian and western Pacific Oceans in boreal summer. The phase speed of the meridional propagation increases with the magnitude, of antisymmetric SST gradients. The poleward propagation of the equatorial disturba... Abstract The development and movement of the tropical intraseasonal system (TIS) exhibit remarkable annual variations. It was hypothesized that spatial and temporal variation in sea surface temperature (SST) is one of the primary climatic factors that are responsible for the annual variation of TISs. This paper examines possible influences of SST on the TIS through numerical experiments with a 2.5-layer atmospheric model on an equatorial β plane, in which SST affects atmospheric heating via control of the horizontal distribution of moist static energy and the degree of convective instability. The gradient of the antisymmetric (with respect to the equator) component of SST causes a southward propagation of the model TIS toward northern Australia in boreal winter and a northward propagation over the Indian and western Pacific Oceans in boreal summer. The phase speed of the meridional propagation increases with the magnitude, of antisymmetric SST gradients. The poleward propagation of the equatorial disturba...