Grachev A. A., E. L. Andreas, C. W. Fairall, P. S. Guest and P. O. G. Persson (November 2007): On the turbulent Prandtl number in the stable atmospheric boundary layer. Boundary-Layer Meteorol., 125 (2), 329-341. doi:10.1007/s10546-007-9192-7

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Abstract

This study focuses on the behaviour of the turbulent Prandtl number, Pr t , in the stable atmospheric boundary layer (SBL) based on measurements made during the Surface Heat Budget of the Arctic Ocean experiment (SHEBA). It is found that Pr t increases with increasing stability if Pr t is plotted vs. gradient Richardson number, Ri; but at the same time, Pr t decreases with increasing stability if Pr t is plotted vs. flux Richardson number, Rf, or vs. ζ = z/L. This paradoxical behaviour of the turbulent Prandtl number in the SBL derives from the fact that plots of Pr t vs. Ri (as well as vs. Rf and ζ) for individual 1-h observations and conventional bin-averaged values of the individual quantities have built-in correlation (or self-correlation) because of the shared variables. For independent estimates of how Pr t behaves in very stable stratification, Pr t is plotted against the bulk Richardson number; such plots have no built-in correlation. These plots based on the SHEBA data show that, on the average, Pr t decreases with increasing stability and Pr t < 1 in the very stable case. For specific heights and stabilities, though, the turbulent Prandtl number has more complicated behaviour in the SBL.

Item Type: Article
Subjects: PSD Publications
Divisions: Physical Sciences Division
DOI: 10.1007/s10546-007-9192-7
URI: http://www.esrl.noaa.gov/psd/pubs/id/eprint/321