A New Diagnostic Turbulence Parameterization Scheme for Representing Diurnal Variations of the Boundary Layer Wind Speed PDF and Clouds in CANAM4 SCM
A new diagnostic turbulence parameterization scheme is developed to improve atmospheric boundary layer wind, temperature, humidity simulations used in climate models. The scheme is compared with observations and the default scheme in the CCCma fourth generation atmospheric general circulation model (CANAM4) using single-column modeling cases studies and using both operational and high vertical resolution in the boundary layer. Diurnal variations of near surface wind speed PDF was much better simulated using the new scheme and higher vertical resolution in both nocturnal stable PBLs and convective PBLs over Cabauw, Netherlands. The TKE budget and boudary layer clouds are reasonably simulated for both the DYCOMS marine stratus and stratocumulus cases and for the Cabauw boundary layer over land. The impacts of intermittent turbulence and precipitations on near surface wind speed probability distribution and boundary layer clouds are also addressed in this study.