Turbulent and boundary layer characteristics during VOCALS-REx

Abstract. Boundary layer and turbulent characteristics (surface fluxes, kinetic energy – TKE, dissipation rate ϵ), along with synoptic-scale changes in these properties over time, are examined using data collected from 18 research flights made the CIRPAS Twin Otter Aircraft. Data were during Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) at Point Alpha (20∘ S, 72∘ W) October November 2008 off coast South America. The average boundary depth is found to be 1148 m, 28 % profiles analyzed displaying decoupling. Analysis correlation coefficients indicates that as atmospheric pressure decreases, height (zi) increases. As has been shown previously, increase zi accompanied by a decrease turbulence within layer. increases, cooling near cloud top cannot sustain mixing entire layer, resulting less latent heat flux (LHF) sensible (SHF) increase, thickness decreasing increasing LHF. This suggests an enhanced LHF results entrainment, which acts thin while deepening A maximum TKE on 1 (both overall largest single value measured) due sub-cloud precipitation acting destabilize stabilize (through evaporation occurring away surface, primarily confined between normalized height, z/zi, 0.40 0.60). Enhanced moisture above passing synoptic system also reduce cloud-top cooling, reducing potential for observed both vertical ϵ, it distributions in-cloud completely offset one another (i.e., range values measured have slight or no overlap regions), maximizing analysis period, below period. Measures velocity variance, buoyancy averaged all display middle (between Z*, 0.25 0.75). total 10 two peaks base top, signifying evaporative radiational heating base. Decoupled layers tend only peak