GABLS3-LES Intercomparison Study

Recently, a large-eddy simulation (LES) intercomparison study was organized under the auspices of the GEWEX Atmospheric Boundary Layer Study (GABLS). Eleven LES modelling groups around the world participated in this study to model a baroclinic, mid-latitude nighttime stable boundary layer utilizing several LES subgrid-scale (SGS) models. Some of the findings from this intercomparison study are unexpected, which make it quite unique. First of all, the LES-ensemble not only captures the statistics, but also the dynamical evolution of the observed variables remarkably well. Second, the diversity among the members of the ensemble is found to be surprisingly low. In other words, the simulated results (especially the first-order statistics) are not very sensitive to the LES-SGS parameterizations. Last, a relatively coarse spatial resolution of 6.25 m is shown to be adequate for representing the basic characteristics of a moderately/strongly stratified (the ratio of the boundary layer height and the Obukhov length is on the order of 5) boundary layer. In this conference paper, we discuss a subset of these findings.