New measure of entrainment zone structure

A wavelet covariance algorithm designed to objectively identify the upper and lower limits of the local transition zone between boundary layer and free troposphere is applied to the output fields from a series of Large Eddy Simulations of the convective atmospheric boundary layer. A new measure of entrainment zone structure is defined - the normalized difference between the standard deviations of the local transition zone limits; this is found to be a function of the convective Richardson number and a predictor of normalized entrainment rate. This provides a robust and objective means for determining the Richardson number from remote sensing observations, and the basis for determining the entrainment rate.