ESTIMATION OF THE ENTRAINMENT ZONE DEPTH IN A SHALLOW CONVECTIVE BOUNDARY-LAYER FROM SODAR DATA

This paper describes several methods for estimating the depth of the e ntrainment zone (Delta h) at the top of the daytime convective boundar y layer (CBL) from sodar data. Both averaged profiles of sound backsca tter intensity and high-resolution time series of instantaneous CBL he ight values derived from the single-pulse intensity profiles are consi dered. Those methods that are based on the analysis of detrended time series of single-pulse sodar data give Delta h values that are well co rrelated and quite consistent with each other. The frequency distribut ion of instantaneous CBL height variations around the mean value is sh own to be nearly Gaussian. The estimated values of the normalized entr ainment zone depth are plo:ted versus an entrainment Richardson number , resulting in a good ordering of the data and agreement with the para meterization proposed in a study by Gryning and Batchvarova. The analy sis also suggests some dependence of this relationship on the stage of the CBL evolution; that is, there appears to exist different entrainm ent regimes and hysteresis effects in the daytime evolution of the ent rainment zone.