GREGARIOUS TROPICAL CONVECTION

A heat source with a vertical profile like that of observed tropical m esoscale convective systems (MCSs) is shown to cause, through inviscid gravity wave dynamics, upward displacement at low levels in a mesosca le region surrounding the heating. Typical values are approximately 10 %-30% area contraction at the surface everywhere within 270 km of the heating 6 h after it starts. As a result, conditions near an existing MCS (but beyond the area of MCS outflow) become more favorable for the development of additional convection. This theory predicts that cloud clusters should be gregarious. Infrared satellite imagery confirms th at almost half of the cold cloudiness observed in a month over the oce anic warm pool region was contributed by just 14 objectively defined m ultiday ''superclusters.''