Wet season boundary layer dynamics over a deforested pasture site in Amazonia

The evolution of the convective boundary layer (CBL) over a deforested pasture site in Rondonia, Brazil is examined using tethersonde, radiosonde, and surface flux data obtained during the LBA/TRMM field campaign, conducted during the wet season of January and February, 1999. Tethered balloon and radiosonde profiles were taken every 3 hours while a ten-meter micrometeorology tower and radiation sensors were used to obtain continuous surface measurements. A simple slab model of the convective boundary layer is applied based upon sensible heat flux and average mixed layer potential temperature. Two days, February 5th and 24th, representative of the two wet season meteorological regimes observed, break (intense convection) and non-break (suppressed convection), respectively, were analyzed in detail. Our results suggest a greater height and stronger diurnal evolution of the boundary layer during the break period, as well as a deeper nocturnal boundary layer associated with a stronger thermal inversion. Days during the non-break period are characterized by slower growth of the boundary layer height.