How Can the Latent Heat Entrainment Flux in the Convective Boundary Layer be Characterized?

A proposed theoretical description of the latent heat entrainment flux at the top of a convective boundary layer (CBL) was tested. It is related to the vertical velocity scale times the ratio of the water vapor mixing ratio (WVMR) gradient to the Brunt‐Väisälä frequency. This relation was tested with different LiDAR and radiosonde measurements. Utilized were observations from several months between 2017 and 2019 from the Atmospheric Radiation Measurement Program's Southern Great Plains site. Water vapor mixing ratio and vertical wind data were retrieved from turbulence‐resolving LiDAR systems, while temperature data were obtained by interpolating radiosonde profiles onto a height grid normalized by the boundary layer height. The available data were screened for CBL situations, resulting in 81 selected profiles that were used for the conducted analysis. The analysis, conducted at the lower boundary of the interfacial layer, agreed with the proposed formulation only in parts. In the search for potential driving variables of the flux at this height level, this study confirmed a high correlation with the square root of the variances of vertical wind and WVMR. This study reveals that the flux can be described by the initially tested relationship when the vertical velocity scale is swapped out against the vertical wind variance. A linear fit between the latent heat entrainment flux observations and the found relationship led to a slope of and a correlation of , confirming recent results achieved over Europe.