Mechanism of poleward propagating, intraseasonal convective anomalies in a model with explicit convection

During boreal summer, the phenomenon accounting for the largest fraction of tropical intraseasonal variance consists of an envelope of convection that propagates both poleward and eastward in Asian longitudes. Over the past thirty years, a number of different mechanisms for the poleward propagating component of this phenomenon have been proposed based on results from zonally symmetric models with diverse and highly idealized parameterizations of moist convection. Here we test some of these hypothesized mechanisms using results from a nonhydrostatic, zonally symmetric model that explicitly simulates moist convection. With an oceanic lower boundary having time-invariant surface temperature, this model produces poleward propagating convective anomalies on intraseasonal time scales. We compare the structure of these anomalies with observations, and illustrate the underlying mechanism using both diagnostics of the momentum budget and results from model integrations with modified physics.