Surface Stress with Non-stationary Weak Winds and Stable Stratification
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The behaviour of turbulent transport in the weak-wind, stably-stratified, boundary layer over land is examined in terms of the non-stationarity of the wind field using measurements from three field programs. These field programs include towers ranging from 12 to 20 m in height and an extensive horizontal network of sonic anemometers. The relationship of the friction velocity to the stratification and non-stationary submeso motions is investigated from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected partly due to enhancement of the turbulence by submeso motions. Cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases in the downward transport of momentum.
KeywordsNocturnal boundary layer Non-stationarity Stable boundary layer Stratified turbulence Submeso
This project received support from Grants AGS-1115011 and AGS 0955444 from the National Science Foundation. The measurements for the SCP and FLOSSII field programs were provided by the Integrated Surface Flux System of the Earth Observing Laboratory of the National Center for Atmospheric Research.
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