Microphysical and turbulent structure of nocturnal stratocumulus as observed during ASTEX

Abstract

Measurements of the microphysical and turbulence structure of stratocumulus made during the Atlantic Stratocumulus Transition Experiment are presented. The measurements made from a C-130 aircraft, belonging to the Meteorological Research Flight, on the night of 12-13 June 1992 show that the convection in the boundary layer is driven both by longwave radiative cooling at cloud top and by the surface buoyancy flux. The turbulence kinetic energy budget, velocity and temperature variance, and vertical fluxes are calculated to discover how the turbulence structure varies with height. The vertical velocity variance profile is found to resemble that of a clear convective boundary layer. The results show that the entrainment is very efficient in the case studied. -from Authors