A substantial fraction of precipitation is associated with mesoscale convective systems (MCSs), which are currently poorly represented in climate models. Convective parameterizations are highly sensitive to the assumptions of an entraining plume model, in which high equivalent potential temperature air from the boundary layer is modified via turbulent entrainment. Here we show, using multiinstrument evidence from the Green Ocean Amazon field campaign (2014-2015; GoAmazon2014/5), that an empirically constrained weighting for inflow of environmental air based on radar wind profiler estimates of vertical velocity and mass flux yields a strong relationship between resulting buoyancy measures and precipitation statistics. This deep-inflow weighting has no free parameter for entrainment in the conventional sense, but to a leading approximation is simply a statement of the geometry of the inflow. The structure further suggests the weighting could consistently apply even for coherent inflow structures noted in field campaign studies for MCSs over tropical oceans. For radar precipitation retrievals averaged over climate model grid scales at the GoAmazon2014/5 site, the use of deep-inflow mixing yields a sharp increase in the probability and magnitude of precipitation with increasing buoyancy. Furthermore, this applies for both mesoscale and smaller-scale convection. Results from reanalysis and satellite data show that this holds more generally: Deep-inflow mixing yields a strong precipitation-buoyancy relation across the tropics. Deep-inflow mixing may thus circumvent inadequacies of current parameterizations while helping to bridge the gap toward representing mesoscale convection in climate models.

We reexamine the well known empirical relationship between area‐averaged surface precipitation (P) and the column moisture content (r) using ground radar and satellite observations, with an emphasis on the convective and stratiform rainfall classifications. The rapid rise in P above critical r (rc) or the “pickup” is more pronounced for stratiform rainfall on hourly and less time scales while convective rainfall, displays only a weak pickup above rc. After partitioning the area‐averaged rainfall into conditional rain rates and rain area, we find that the nonlinearity in the P‐r curve can be almost entirely explained by the nonlinear increase in rain area, especially in stratiform regions. These findings have implications for the representation of organized convective cloud systems in global circulation models.

A westward‐propagating Rossby‐like wave signal is found to explain a large fraction of the intraseasonal variance in cloud brightness over the Western Hemisphere. A series of diagnostic criteria suggest that this wave is a moisture mode: its moisture anomalies dominate the distribution of moist static energy (MSE) and are in phase with the precipitation anomalies; and the thermodynamic equation obeys the weak temperature gradient approximation. The wave propagates westward due to zonal moisture advection by the mean flow and is maintained by radiative heating and meridional moisture advection. These properties compare favorably with the westward propagating Rossby mode in an equatorial beta‐plane model with prognostic moisture, mean meridional moisture gradient, and mean zonal wind. These results underscore the importance of water vapor in the dynamics of slowly evolving tropical systems, and the limitations of dry shallow water theory that rely on a “reduced equivalent depth” to represent moist dynamics.

In this study, we show that the well‐documented exponential increase in the precipitation‐water vapor (P‐r) curve over tropical oceans also applies to tropical land but that the land curve starts its exponential increase at smaller values of column moisture than over ocean. We demonstrate that daytime surface heating contributes to this characteristic shape of the land P‐r curves. There is also significant geographical variation in the shape of the P‐r curve within land and ocean regions, with the Amazon, the Maritime Continent, and the eastern edges of oceans as distinct outliers. We further show that convective and stratiform rain intensities exhibit a pickup that is separate from the corresponding rain areas in the tropical P‐r curve while shallow convective rain has a yet another pickup. These variations of the P‐r curve characteristics likely represent geographical variations of environmental controls on storm life cycle.