The structure of the unstable marine boundary layer viewed by lidar and aircraft observations

Abstract The combination of vertical lidar and in situ meteorological observations from two aircraft provide an unprecedented view of the marine atmospheric boundary layer (MABL) during a cold air outbreak. To a first approximation, the lidar reflectivity is associated with the concentration of sea salt aerosols. Across the capping inversion, the lidar reflectivity contours approximate isentropes and streamlines thereby defining the inversion. Within the mixed layer, high reflectivity cores are associated with updrafts carrying aerosol-rich air upward and conversely. These effects are enhanced by increasing humidity in updraft and decreasing humidity in downdrafts that operate to increase and decrease aerosol sizes. Narrow high reflectivity columns extend upward from the ocean indicating that organized flow exists all the way to the surface. Entrainment across the inversion is manifested by small scale perturbations (∼200–500 m) superimposed upon the large scale (&sim 1–2 km) undulations of the inversion....