Fine-scale turbulence can be visualized in terms of slow diffusion of thin striations in the fog videos.  This seems to occur in cases with very weak winds (< 1 m/s) and clear nights that frequent some of our sites.

thin_sheet_3-oldsite
Early morning natural fog creeps from right to left.  The striated layers seem unperturbed by the road bed indicating very strong stratification.

Striated fog, both natural and machine generated, is casually examined in a striation report. A lattice was used to suppress larger eddies and generate fine-scale turbulence, which is briefly documented in a  lattice report.

Thin layers of fog may originate from layered mixing events. Mixing across a layer of stratified flow decreases the temperature at the top of the layer and increases the temperature at the bottom of the layer. If the flow is near saturation, then even a slight decrease of temperature may lead to condensation at the top of the  thin mixing layer. Observations of the effect of thin mixing layers on temperature structure in the lower atmosphere are reported in Muchinski and Wode (1998) and Balsley et al. (2006, 2009). The dynamics of such mixing layers have been recently examined by Fritts et al. (2009). Once formed, the role of radiative cooling at the top of the fog layer is not known.

We have also observed thin layers of fog to originate higher on a gentle slope and flow downslope over the top of colder air at the bottom of the slope.

Balsley, B. B., R. G. Frehlich, M. L. Jensen, and Y. Meillier (2006) High-resolution in situ profiling through the stable boundary layer: Examination of the SBL top in terms of minimum shear, maximum stratification, and turbulence decrease, J. Atmos. Sci., 63: 1291-1307.

Balsley, B. B., G. Svensson, and M. Tjernström (2009) On the scale-dependence of the gradient Richardson number in the residual Layer, submitted.

Fritts D, Wang L, Werne J (2009) Gravity wave – fine structure interactions: a reservoir of small-scale and large-scale turbulence energy. Submitted to Geophy. Rev. Letters.

Muschinski, A., and C. Wode, 1998: First in situ evidence for coexisting submeter temperature and humidity sheets in the lower free troposphere, J. Atmos. Sci., 55: 2893-2906.

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