OBSERVATIONS OF PLANVIEW FLUX PATTERNS WITHIN CONVECTIVE STRUCTURES OF THE MARINE ATMOSPHERIC SURFACE-LAYER

Air/sea flux variability on horizontal scales from 50 m to several km results, in part, from the presence of coherent convective structures within the atmospheric boundary layer. The horizontal distribution of fluxes within these convective updrafts and downdrafts is, therefore, central to studies of air/sea interaction and remote sensing of sea su rface wind and wave fields. This study derives these flux patterns fro m observations of the Marine Atmospheric Surface Layer (MASL). Researc h aircraft flights through the MASL provide an optimal means for sampl ing large numbers of the above-mentioned coherent structures. The NCAR Electra flew numerous legs through the MASL at a height of 50 m durin g the 1987 stratocumulus phase of Project FIRE (First ISSCP (Internati onal Satellite Cloud Climatology Program) Regional Experiment). In sit u measurements from these legs serve as the dataset for this paper. Th e data are processed in such a way as to retain only the turbulence fl uctuations. Conditional sampling, based on the vertical velocity field , results in the isolation of convective updrafts and downdrafts. Comp ositing of the data for these two classes of convective drafts results in horizontal planviews of the vertical fluxes of buoyancy, absolute humidity, along-mean-wind component of momentum, and vertical velocity . To ensure dynamical similarity, these horizontal planviews are orien ted in a coordinate system aligned with the mean wind.