The Project for Intercomparison of Land-surface Parametrization Schemes (PILPS): 1992 to 1995

Abstract.

The World Climate Research Programme Project for Intercomparison of Land-surface Parametrization Schemes (PILPS) is an on-going international intercomparison of land surface schemes designed for use in climate modelling and weather prediction. The five phases of PILPS are described in this work with an indication of the status of each. Phase 0 documented the status of land surface schemes. Phase 1 performed a series of off-line tests using synthetic atmospheric forcing. Phase 2 exploited observational data in off-line tests. Phase 3 was comprised of coupled tests within the Atmospheric Model Intercomparison Project (AMIP) project and finally Phase 4 will consider the performance of land-surface schemes when coupled to their host climate models in fully coupled evaluations. Results from Phase 1 indicate that there is a wide range among models. Phase 2 indicates that while some models are consistent with observations, there remains a large range among models and that many diverge greatly from observations. PILPS phases 2(a) and 2(b) results suggest that individual land-surface schemes capture specific aspects of the complex system with reasonable accuracy but no one scheme captures the whole system satisfactorily and consistently. In Phase 3 the intercomparison of PILPS schemes as a component of global atmospheric circulation models is being conducted jointly with the AMIP as diagnostic subproject number 12. Preliminary results suggest that results differ by about the same range as in the offline experiments in Phases 1 and 2. Phase 4 will couple selected land-surface schemes to the USA's National Center for Atmospheric Research climate system model and to the Australian Bureau of Meteorology limited area model.