Field Measurements of the Percentage of Mixed Layer Air vs Height in the Entrainment Zone

摘要

In situ observations by an instrumented aircraft of continental daytime convective boundary layers are made to study the humidity structure of the entrainment zone (EZ). The entrainment zone is the interfacial layer between the convective boundary layer (CBL) and the stable air aloft. The frequency distributions of specific humidity obtained during horizontal flight legs are used in a statistical approach to estimate the amounts of three types of air in the EZ: (1) unmixed free atmosphere (FA); (2) unmixed surface layer (SL); and (3) a mixture of the first two. The amount of SL air reaching various heights in the EZ is significant because it governs the coverage of fair air weather cumulus. Deardorff et al., (1980) simulated the atmospheric CBL in a water-filled laboratory tank experiment to study the amount of SL fluid at various heights in the EZ. However, in situ measurements in the atmosphere have not been reported before.