Modification de la formule de Dalton à partir d'une nouvelle formulation du flux chaleur sensible en conditions suradiabatiques

Abstract

Using a simplified formula previously derived by B. Itier and Ch. Riou for turbulent fluxes under unstable conditions, the authors give a modified version of Dalton's formula for evaporation or sensible heat flux. In the classical version of Dalton's formula the “bulk transfer coefficient” is written as A + BU where A and B are regression coefficients. The authors show that A is a function of the ratio of the difference in temperature between the air and the surface to the wind velocity. Values of A found in the literature are discussed. The increase of its value when adjusting a Dalton formula to over barren soil instead of over water is presented here in terms of instability effects rather than roughness effects. The results obtained by means of the new modified Dalton's formula are compared to independently measured values of sensible heat flux deduced from the energy balance, using a net radiometer ( R n) and soil temperature profiles ( G) on a dry sand in southern Tunisia.