Exploring Monin-Obukhov similarity in the surface layer over complex terrain during T-REX

In atmospheric boundary layer studies, information about the turbulent surface momentum and heat fluxes is often needed. Measuring these fluxes directly is difficult and expensive. It is much easier and cheaper to measure mean wind speed and temperatures profiles and use Monin-Obukhov similarity functions to relate these profiles to the turbulent fluxes. There are many empirical estimates of these functions that have been determined from data collected over flat terrain and are commonly used in surface layer parameterization schemes in numerical atmospheric models.

The goal of this work is to explore and determine similarity functions in the surface layer over complex terrain. We use data from three 30 m towers where mean and turbulent variables were measured at 6 levels during the Terrain-induced Rotor Experiment (T-REX) conducted in Owens Valley, California in March and April 2006. We use data from the entire two month period providing estimates of the similarity functions for a wide range of stability parameter z/L, ranging from a value of -50 (very unstable) to a value of 20 (very stable). We compare these functions with the existing functions and discuss the potential impact of the differences on simulations of flows in complex terrain.