Recorded presentation6.1
Common nonstationary heterogenous stable boundary layers
Larry Mahrt, Oregon State University, Corvallis, OR
Existing models of turbulent transport are poor approximations for weak-wind conditions, partly due to nonstationarity of the wind field. Common shifting of the wind direction leads to enhanced horizontal dispersion while nonstationarity of the wind field leads to more complex behavior of the turbulence. The problem is particularly difficult for weak-wind stable conditions where the distinction between turbulence and larger scales is sometimes blurry and previous methods for separating the two regimes fail. In this study, the behavior of the flux is examined for different time scales ranging from predominately turbulence to transitions scales and larger scale nonturbulent motions. In addition, with weak-winds and stable stratification, even common weak heterogeneity significantly modifies the turbulence fluxes. Some initial attempts to formulate area-averaged fluxes for heterogeneous surfaces are examined. While universal solutions are unlikely, improvement upon existing understanding is expanded through analysis of networks of fast response data.
Session 6, Stable Boundary Layers I
Thursday, 5 August 2010, 9:00 AM-10:00 AM, Torrey's Peak I&II
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