Large-eddy simulation of a shear-driven planetary boundary layer flow: Comparison with the CASES'99 experiment observations

A recent study suggests that the neutral atmospheric surface layer (SL) can be divided into 2 sublayers (Drobinski et al. 2004): (i) the eddy surface layer (ESL) which is the lower sublayer where the longitudinal velocity fluctuation spectrum E11 displays an intermediate spectral range with a -1 power law; (ii) the shear surface layer (SSL) which is the upper sublayer, where E11 and E33 (vertical velocity spectrum) have the same spectral shape with a -1 subrange.

Several authors suggest that the -1 power law range measured in E11 is related to near-surface organized eddies. It was suggested that large eddies impinge onto the ground (top-down mechanism for eddy motion at high Reynolds number) where they generate internal boundary layers due to blocking in which smaller eddies develop (Hunt and Carlotti 2001). Following the same argument, Drobinski et al. (2004) suggested that the ESL is the sublayer where blocking of impinging eddies is the dominating mechanism and where small-scale eddies are created, and that the SSL is the upper sublayer, where shear affects the isotropy of turbulence and where large-scale eddies also called streaks are created.

One of the goals of this study is to investigate the capability of large-eddy simulations to retrieve the ESL and SSL dynamics.