Large-scale organization of tropical convection in two-dimensional explicit numerical simulations

The large-scale organization of tropical deep convection is investigated in idealized two-dimensional cloud-resolving simulations. A 20 000 km periodi c computational domain allows interactions among moist convection, mesoscal e organization, and surface exchange on a wide range of scales. A uniform 1 0 m s(-1) easterly wind and a uniform sea surface temperature of 30 C are a ssumed. A prescribed temperature tendency mimicking the mean radiative cool ing of the tropical troposphere is used in this pilot study. The large-scal e organization of convection resembles the observed tropical atmosphere as well as results from some previous numerical studies using parametrized con vection. The simulation highlights mesoscale convective systems with horizo ntal scales of several hundred kilometres moving east to west with speeds s imilar to the mean flow, and an envelope of convection with a horizontal ex tent of a few thousand kilometres and propagating west to east. The propaga tion speed of the large-scale envelope compares well with the phase velocit ites of convectively coupled Kelvin waves observed in the equatorial wavegu ide. Convective momentum transport and the impact of convective systems on temperature and moisture near the surface are key processes responsible for the large-scale organization of convection. These results are discussed in the context of recent observations and numerical studies of convection org anization in the tropics.