Aircraft Measurements of Turbulence Spectra in the Marine Stratocumulus-topped Boundary Layer

Abstract

Mixed-layer scaling was successfully applied to the velocity, temperature, and moisture spectra of the marine stratocumulus-topped mixed layers observed during the First ISCCP Regional Experiment (FIRE). These turbulence spectra provide considerable insight into the physical phenomena that affect this kind of boundary layer. At least four of these phenomena contribute to the turbulence spectra: eddies that result directly from shear and buoyant production of turbulent kinetic energy (the microscale energy production subrange); smaller eddies that result from the inertial cascade of energy (the inertial subrange); quasi-two-dimensional mesoscale variations; and gravity waves. The velocity, temperature, and moisture spectra are affected differently by each of these phenomena. The turbulence spectra highlight the differences between the cold-current marine stratocumulus-topped boundary layer and the overland convective boundary layer.