AMAZON COASTAL SQUALL LINES .2. HEAT AND MOISTURE TRANSPORTS

The column response to propagating deep convection over the central Am azon Basin is investigate with rawinsonde data from the Amazon Boundar y Layer Experiment (ABLE 2B). Heat and moisture budgets are calculated from a relatively small surface network (1000 km2) to determine the d istribution of heating within the convective and stratiform regions of three Amazon coastal squall lines (ACSL) in varying degrees of maturi ty. Portable Automated Mesonet instrumentation, satellite imagery, and radar data are used to partition the large-scale system into distinct cloud and rainfall components. The dimensions of the surface network enable an evaluation of the collective effects of an ensemble of conve ctive elements that are considered to be representative of the synopti c-scale system. Calculations of Q1 and Q2 from the ABLE 2B network fol low the methods used by Johnson and Young and Gallus and Johnson. The computations are performed over intervals of 3-6 h using composite sou ndings derived from a network average. The distribution of heating and drying for the 1 May 1987 ACSL and its variation in time are shown to be similar to the results of other studies, particularly those of Wes t African squall lines. Peak heating occurs between 500 and 550 mb, an d peak drying is concentrated between 450 and 650 mb. A lack of separa tion between the peaks in the convective Q, and Q2 profiles indicates a coupling of Q1 and Q2 and suggests the presence of significant strat iform processes in the absence of pronounced eddy transports. The vert ical eddy flux of total heat (F) is calculated by assuming the horizon tal eddy flux term is small relative to the net vertical transports. E ven though the horizontal transfer of heat and moisture may not be neg ligible in this study, the area encompassed by the surface network is large relative to the area occupied by active portions of convective c louds. From a network perspective, these cloud-scale fluxes are consid ered small relative to the vertical eddy flux of total heat. The distr ibution of vertical eddy flux compares favorably with a mesoscale calc ulation performed by Gallus and Johnson for a midlatitude squall line suggesting the assumptions regarding the net contribution of the horiz ontal fluxes may be reasonable. Convective transports of heat are equa lled by transports occurring within the stratiform region of the syste m. The heat transported by a single ACSL when extrapolated to the ACSL as a whole represents a significant contribution to the global heat b alance.