SIMULATIONS OF NOCTURNAL DRAINAGE FLOWS BY A q2l TURBULENCE CLOSURE MODEL.

Noctural drainage flows observed over a nearly two-dimensional ridge called Rattlesnake Hills near Richland, Washington, are simulated by using a simplified turbulence closure model in which only turbulence kinetic energy and turbulence length scale equations are solved prognostically. The present model is slightly simpler than a level 2. 5 model which has been extensively used in previous simulations of various atmospheric boundary layer phenomena. Wind and temperature profiles computed by the present model are generally in excellent agreement with observations made by towers erected on the slope of Rattlesnake Hills. Strong coupling between the mean and turbulence variables is also demonstrated.