Tributary, Valley and Sidewall Air Flow Interactions in a Deep Valley

Abstract

Field experiments measuring nocturnal tributary flows have shown complex internal structure. Variations in the flow range from short-term (8?16 min) oscillations (related to tributary/valley flow interactions) to long-term flow changes throughout the night (related to upper ridge slope and tributary sidewall cooling rate changes). The mean vertical structure in the tributary flow shows a three layer structure. Outflow winds are observed near the surface and in an elevated jet up to several hundred meters height. A flow minimum or counterflow exists at about the height of the drainage flow maximum in the main valley. Comparisons of flow volumes and variations from a single large tributary show that 5%?15% of the nocturnal flow in the main valley may be contributed through one tributary. This implies that tributaries may dominate main valley sidewall and midvalley subsidence contributions to valley drainage flows.