NOTE ON COMPUTING SCREEN TEMPERATURES, HUMIDITIES AND ANEMOMETER-HEIGHT WINDS IN LARGE-SCALE MODELS

The predictor-corrector method of computing screen temperatures, humid ities and anemometer-height winds proposed by Hess et al. (1995) has b een reconsidered in the light of a range of different methods of deter mining the fluxes and stresses in models of the land surface. We propo se methods of computing effective roughness lengths and mean 'surface' values of temperature and moisture that are compatible with the compu ted stresses and fluxes at the scale of the grid box. These mean surfa ce values can be used to generate appropriate grid-box values for scre en temperatures, humidities and winds. Our method applies to the subgr id 'tiles' of individual surface types within a grid box (we include t he possibility that a tile can be on bare or vegetated land, over the ocean or on sea-ice).