Investigation of vertical eddy fluxes under stable conditions in the surface boundary layer
Dobrovolschi, Dan ; Steeneveld, Gert-Jan ; Paci, Alexandre ; Eiff, Olivier ; Lacaze, Laurent
Understanding and prediction of atmospheric stably stratified boundary layers (SBL) is a longstanding challenge in the field of meteorology (Louis et al., 1981; Holtslag and Nieuwstadt, 1986). In spite of previous SBL studies, either from field experiments (e.g. CASES-99, SHEBA, Cabauw tower, SABLES) or by LES numerical simulations, a need exists for improving the parameterization of turbulent transport of heat, momentum and scalars in the SBL (Cuxart et al., 2006; Steeneveld et al. 2006). This will improve the skill of models for weather forecasting; climate and air quality, in particular for winter and nocturnal conditions. As an alternative laboratory experiments can provide an extensive dataset with very well-controled parameters such as wind and density vertical profile. Despite a few wind-tunnel experiments have been carried out on SBL, none have been performed with a stratified water flume although this equipment is excellent to investigate the SBL. The current work extends these earlier approaches by parameterization development from laboratory experiments at the CNRM-GAME Toulouse stratified water flume, and compares with field studies and LES. This unique facility is indeed very pertinent for such a study, in particular due to its ability to generate density stratified flow at high Reynolds numbers with low confinement effect. Preliminary tests were performed to ensure that a turbulent, well-developed boundary layer close to a statistical equilibrium can be physically simulated. Our main objectives now are to measure vertical turbulent fluxes of momentum and density, under different conditions of stability and mean flow velocity.
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