Recent progress and results from the project for the intercomparison of landsurface parameterization schemes

The Project for the Intercomparison of Landsurface Parameterization Schemes (PILPS) is briefly described. The partitioning of available energy between sensible and latent heat on the annual time scale is then described from the first two phases of this international project. In Phase 1, where synthetic atmospheric forcing is used to drive the landsurface models, equilibrium results show that there was considerable scatter in the partitioning of available energy, although this scatter was significantly reduced when the experimental design of Phase 1(a) was improved in Phase l(c). Equilibrium results from Phase 2(a), where observational data were used for the atmospheric forcing, are then presented. These illustrate that about 70% of those landsurface schemes included simulate the latent and sensible heat fluxes to within 5 W m^-2 of the observed value on the annual time scale, but since this 5 W m^-2 is equivalent to 63 mm year^-1 in total evaporation, this represents considerable variation in the partitioning of precipitation between evaporation and run-off. It is noted that the magnitude of the scatter appears to be related to the amount of annual rainfall. PILPS is working on understanding the masons for this scatter more fully.