This talk will discuss some observational aspects of the organization of equatorialrainfall systems. It is well-known that convective disturbances in the tropics occurover a very broad spectrum of scales, ranging from individual cumulus cells toplanetary scale features such as the Madden-Julian Oscillation (MJO). It is alsoobserved that the larger scale features are composed of smaller scale equatorialwaves, so that for example the "envelope" of the MJO is often comprised ofeastward propagating Kelvin, and westward inertio-gravity waves. The envelopesof these smaller waves are in turn are comprised of a broad spectrum ofmesoscale features, which are predominantly westward propagating. While it iscertainly evident that the larger envelopes must be creating a favorableenvironment for the higher frequency activity within them, the precisemechanisms for this modulation are still a subject of debate, as is the inverse roleof the mesoscale disturbances in the upscale transfer of energy.

For example, a census of a large number of individual MJOs shows that they arecomprised of a wide variety of smaller scale disturbance types from case to case,suggesting that parameterization of their upscale impacts of might be feasible. Apotential aid to the understanding of scale interactions within the tropicalatmosphere, and their simulation in models, is the fact that there is a certaindegree of "self similarity" in observed gross features of the dynamical structuresof organized tropical convection. In general these disturbances display a warmmoist lower troposphere ahead of the wave, with cooling and drying behind, anda warm moist mid-troposphere within the convective region. These dynamicalsignals are consistent with the observation that the waves show a progressionfrom a dominance of shallow to congestus, then deep convection, and finallystratiform precipitation, regardless of their size or propagation direction.