The effects of gap flows on turbulence structures in the atmospheric surface layer over complex terrain of the Birch Creek Valley, Idaho

The objective of this study is to investigate the turbulence regimes under the effects of gap flows in the atmospheric surface layer over complex terrain. Data were collected in the Birch Creek Valley in eastern Idaho. Gap flows are often induced by an asymmetric flow through a topographical constriction. There is a distinct topographic constriction in the Birch Creek Valley that creates two sub-basins, an upper and lower valley, with dissimilar flow regimes. A field study examining the flow through the valley was conducted during June 13 to September 6, 2013. Here, the data collected from two levels of eddy covariance systems (3.0 and 8.0 m) at a 10-meter flux tower in the upper and lower valley, were classified into one of three groups based on synoptic influence. Gap flows were identified with and without synoptic influences, and characterized by high wind speeds with jet-like vertical profiles in the lower valley. From these classifications, the impact of the gap flows upon the turbulence structures will be examined using the methods of continuous wavelet transforms and empirical ensemble mode decomposition.