SUMMARYThis paper describes a representation of the distribution of sensible and latent heat from the surface through the atmospheric boundary layer which has been formulated for use in a 10-level primitive equation model atmosphere. The transfer process is represented in two parts : (i) the transfer of energy across the Earth's surface into the lowermost 100 mb layer of the model atmosphere; and (ii) the subsequent redistribution of this energy through two or more such layers by small-scale convection. The fluxes of energy across the surface are calculated using empirical ' bulk aerodynamic ' relationships. In land regions consideration of the energy balance at the surface is also necessary, and diurnal variations of radiation are taken into account. The redistribution of energy by small-scale convection is represented by convective adjustments which ensure that a certain neutral lapse rate of temperature is never exceeded. Some results of the incorporation of these effects into the 10-level model are described. INTRODCCTIONCarlson and Ludlam (1965) have described the important role played by a layer of small-scale convection near the Earth's surface in the general scheme of midlatitude tropospheric motion. It is by means of the distribution of energy from the surface through such a layer that the large-scale flow regains both the energy lost by radiation to space and the water lost in precipitation. A n adequate representation of this process is therefore an essential requirement for any numerical model attempting to simulate the long-term global circulation of the atmosphere.Such a representation is perhaps less important when forecasts of one or two days are envisaged, as is the case with the 70-level primitive equation model of the atmosphere described by Bushby and Timpson (1967), Benwell and Timpson (1968), and Benwell and Bushby (1970). The incorporation of a representation of surface energy transfers into this 10-level model is, nevertheless, desirable for two reasons. Firstly, in some situations, as when cold air blows over a much warmer sea, the surface energy transfers can be so rapid (Craddock 1951, Manabe 1957) that they significantly influence the development of the large-scale flow over periods of one or two days. Eveninothersituations, the accuracy of details in the forecasts computed with the model should be improved if surface exchanges are represented. Secondly, the representation of surface energy transfers is necessary in order that the model may be able to predict the associated distributions of convective rainfall.The representation of surface energy exchanges which has been formulated for use in the 10-level model treats the transfer process in two parts : (i) the transfer of energy across the Earth's surface; and (ii) the distribution of this energy through the atmospheric boundary layer. In the sense that the term is used here, the ' atmospheric boundary layer ' ranges in vertical extent from a few metres to several kilometres, according to the varying vertical extent of motions initiat...

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