Abstract: In this paper, the effects of stratification on turbulent exchange in. the surface layer of the atmosphere are studied from the viewpoint of similarity theory and dimensional analysis. Using data recently published, the size of the experiment coefficient D in the universal function of the turbulent exchange are calculated. A scheme of transition from forced to free convection, which shows a rather smooth character. Based on a characteristic length LRi, the author set up a model of. turbulent exchange in diabatic surface layer.