Abstract : 2D.4
T-REX EOPs III: Dynamic stability, near surface turbulent exchange and surface energy balance characteristics

Gregory Poulos, Juerg Schmidli, Stephen Mobbs
National Center for Atmospheric Research, EOL-ISF

During the Terrain Induced Rotors Experiment (T-REX), three heavily instrumented 30 m towers were set amongst a vast array of shorter towers and sub-arrays of cross and along valley temperature and soil moisture sensors. As a result the near-surface atmosphere and its heterogeneity of this deep valley were sampled in a heretofore unique way. These instruments operated continuously and were periodically supplemented with soundings and aircraft flights for Enhanced Observing Periods - EOPs - which were focused on nocturnal periods of nearly clear skies and relatively quiescent conditions.

This work describes and intercompares components of the surface energy balance during EOPs and other similar nights. Our analysis includes a summary of evolution of dynamic stability, flux profiles and turbulence during the selected nights. In addition, the flux profiles on the valley side slope (the 'West' tall tower) are specifically compared with those in the valley bottom to assess our ability to discern valuable turbulent exchange information on sloped surfaces. In contrast to much more flat terrain or plains geography, where the strength of synoptic forcing governs windspeed and is thereby related to the magnitude of surface fluxes and flux profiles at night, we find that a complex interaction of intra-valley mesoscale processes govern the general behavior of surface fluxes.