Abstract

Lidar measurements of the thickness of the entrainment zone were derived from six case studies which included a wide range of atmospheric conditions. The entrainment zone is the outermost portion of the mixed layer confined between the maximum heights reached by only a few vigorous convective cells and by the height where the mixed layer air occupies 90-95% of the total area. The thickness of the entrainment zone was measured from pictures of RHI-scans generated by means of a color enhanced video display system. Observations were made during the day when the mixed layer depth was increasing: layer depths between 150 and 1600 meters were observed. The entrainment zone was usually 100 to 200 meters thick, with occasional values as large as 700 meters which occurred during periods of rapid mixed layer growth. Measured values of the entrainment zone thickness were compared to the predictions of parcel theory and to the values measured by Deardorff et al. (1980) in tank experiments.