Larry Mahrt
Oregon State University
ABSTRACT
"Mixing in very stable conditions; problems and new concepts"
| New emerging conceptual frameworks for the stable nocturnal boundary layer will be surveyed. Transport by extremely weak turbulence occurring on nights with clear skies and weak winds will be examined from seven tower levels of eddy-correlation data taken from each of two field programs. The very small flux is systematic, provided that the perturbations are computed from a record-dependent averaging length. For extremely weak turbulence, the fluxes decrease systematically with height and often indicate very shallow boundary-layer depths on the order of 10 m. However, in one field program, the turbulence slowly increases with height above the surface flux-based boundary layer apparently due to horizontal advection of stronger turbulence driven by modest surface heterogeneity. For very weak turbulence, the eddy diffusivity for momentum is systematically greater than that for heat. Major unsolved problems will be outlined. |