Marine Stratocumulus Layers. Part II: Turbulence Budgets

Abstract

This paper discusses the turbulence profiles and budgets for two days of radiation, dynamical and thermodynamical observations by the NCAR Electra in shallow marine stratocumulus off the California coast in June 1976. The boundary layer is characterized by relatively high wind speeds (12–20 m s−1) and low liquid water contents (0.1 g kg−1); the clouds are not very convective and seem to have little influence on the turbulence budgets. In cloud, drizzle has a significant impact on the liquid water budget and occasionally even on the total water budget even though no drizzle is observed at the surface. The stresses, velocity variances, and their budgets behave as in a neutral boundary layer, sometimes with an additional peak in the cross-wind variance at the inversion due to shear production. There is scant evidence of direct production of vertical velocity variance at cloud top due to radiative cooling or latent heat release; it is maintained principally by the pressure-scrambling terms through re... Abstract This paper discusses the turbulence profiles and budgets for two days of radiation, dynamical and thermodynamical observations by the NCAR Electra in shallow marine stratocumulus off the California coast in June 1976. The boundary layer is characterized by relatively high wind speeds (12–20 m s−1) and low liquid water contents (0.1 g kg−1); the clouds are not very convective and seem to have little influence on the turbulence budgets. In cloud, drizzle has a significant impact on the liquid water budget and occasionally even on the total water budget even though no drizzle is observed at the surface. The stresses, velocity variances, and their budgets behave as in a neutral boundary layer, sometimes with an additional peak in the cross-wind variance at the inversion due to shear production. There is scant evidence of direct production of vertical velocity variance at cloud top due to radiative cooling or latent heat release; it is maintained principally by the pressure-scrambling terms through re...