Non-stationary Generation of Weak Turbulence for Very Stable and Weak-Wind Conditions
Turbulence measurements for very stable conditions near the surface are contrasted among three sites: a high altitude basin during winter with grass or snow-covered grass, a broad valley with complex agricultural land use, and a more narrow valley that is influenced by a valley cold pool and cold air drainage. In contrast to previous studies, this investigation emphasizes the very weak turbulence with large bulk Richardson number occurring during extensive periods between brief mixing events. The relationship of the turbulence to the non-stationary wind and stratification is examined along with the impact of short-term flow accelerations, directional shear and downward diffusion of turbulence from higher levels. The failure of the turbulence for strong stratification to decrease with further increase of stratification is explored. Additional analyses are applied to weak-wind cases for the entire range of stratification, including weak stratification associated with cloudy conditions.
KeywordsIntermittent turbulence Nocturnal boundary layer Stable boundary layer Submeso Weak winds
- Basu S, Porté-Agel F, Foufoula-Georgiou E, Vinuesa JF, Pahlow M (2006) Revisiting the local scaling hypothesis in stably stratified atmospheric boundary-layer turbulence: an integration of field and laboratory measurements with large-eddy simulations. Boundary-Layer Meteorol 119: 473–500CrossRefGoogle Scholar
- Grachev A, Andreas E, Fairall C, Guest P, Persson P (2012a) The critical Richardson number and limits of applicability of local similarity theory in the stable boundary layer. Boundary-Layer Meteorol. doi:10.1007/s10546-012-9771-0
- Mahrt L, Richardson S, Seaman N, Stauffer D (2010) Nonstationary drainage flows and motions in the cold pool. Tellus 62: 698–705Google Scholar
- Pardyjak E, Monti P, Fernando H (2002) Flux Richardson number measurements in stable atmospheric shear flows. J Fluid Mech 449: 307–316Google Scholar
- Sorbjan Z (2010) Gradient-based scales and similarity laws in the stable boundary layer. Q J R Meteorol Soc 136: 1243–1254Google Scholar
- Sukorianski S, Galperin B (2012) An analytical theory of the buoyancy—Kolmogorov subrange transition in turbulent flows with stable stratification. Philos Trans R Soc Lond A. doi:10.1098/rsta.2012.0212
- Tennekes H, Lumley J (1972) A first course in turbulence. The MIT Press, Cambridge, 300 ppGoogle Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.