A Parameterization of Third-order Moments for the Dry Convective Boundary Layer

Authors: Tomas, Séverine; Masson, Valéry

Source: Boundary-Layer Meteorology, Volume 120, Number 3, September 2006 , pp. 437-454(18)

Publisher: Springer

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Abstract:

We describe one-dimensional (1D) simulations of the countergradient zone of mean potential temperature <EquationSource Format="TEX"><![CDATA[$$overline{theta}$$]]></EquationSource> observed in the convective boundary layer (CBL). The method takes into account the third-order moments (TOMs) in a turbulent scheme of relatively low order, using the turbulent kinetic energy equation but without prognostic equations for other second-order moments. The countergradient term is formally linked to the third-order moments <EquationSource Format="TEX"><![CDATA[$$overline{w^{prime 2}theta'}$$]]></EquationSource> and <EquationSource Format="TEX"><![CDATA[$$overline{w'theta^{prime 2}}$$]]></EquationSource> , and a simple parameterization of these TOMs is proposed. It is validated for several cases of a dry CBL, using large-eddy simulations that have been realized from the MESO-NH model. The analysis of the simulations shows that TOMs are responsible for the inversion of the sign of <EquationSource Format="TEX"><![CDATA[$$partial overline{theta},/,partial z$$]]></EquationSource> in the higher part of the CBL, and budget analysis shows that the main terms responsible for turbulent fluxes and variances are now well reproduced.

Keywords: Convective boundary layer; Countergradient term; Heat flux; Parameterization; Third-order moments; Turbulence

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10546-006-9071-7

Affiliations: 1: Email: Severine.tomas@meteo.fr

Publication date: 2006-09-01