Estimation of the Entrainment Zone Depth in a Shallow Convective Boundary Layer from Sodar Data

Abstract

This paper describes several methods for estimating the depth of the entrainment zone (?h) at the top of the daytime convective boundary layer (CBL) from sodar data. Both averaged profiles of sound backscatter intensity and high-resolution time series of instantaneous CBL height values derived from the single-pulse intensity profiles are considered. Those methods that are based on the analysis of detrended time series of single-pulse sodar data give ?h values that are well correlated and quite consistent with each other. The frequency distribution of instantaneous CBL height variations around the mean value is shown to be nearly Gaussian. The estimated values of the normalized entrainment zone depth are plotted versus an entrainment Richardson number, resulting in a good ordering of the data and agreement with the parameterization proposed in a study by Gryning and Batchvarova. The analysis also suggests some dependence of this relationship on the stage of the CBL evolution;that is, there appears to exist different entrainment regimes and hysteresis effects in the daytime evolution of the entrainment zone.