The Shallow-to-deep Transition in Convective Clouds During the Green Ocean Amazon 2014/5 Campaign

Nearly two years of measurements from the DOE Atmospheric Radiation Measurement's (ARM's) Mobile Facility (AMF) taken during the Green Ocean Amazon (GOAmazon) 2014/5 campaign in Manacapuru, Brazil are analyzed in order to investigate the variability in environmental conditions controlling the transition from shallow to deep convective clouds. The lifecycle of convective clouds, and particularly the transition from shallow to deep convection and the environmental controls of this transition, are poorly understood and not represented well in climate model simulations. The Active Remote Sensing of CLouds (ARSCL) data product, which combines observations from a vertically pointing W-band cloud radar, a micropulse lidar and a ceilometer, is used to objectively define two subsets of convective clouds: 1) Transition cases, where a period of shallow convective clouds is followed by a period of deep convective clouds and 2) Non-transition cases, where shallow convective clouds persist without any subsequent deeper development. For these two subsets, observations of the time varying thermodynamic properties of the atmosphere, including surface heat and radiative fluxes, and profiles of atmospheric state variables, are composited to define averaged properties for each transition state. Initial analysis indicates that the presence of a transition depends strongly on the convective inhibition, low-level humidity and surface temperature with little dependence on the convective available potential temperature and surface heat fluxes.