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A. Henderson-Sellers, A. J. Pitman, P. K. Love, P. Irannejad, and T. H. Chen

The World Climate Research Programme Project for Intercomparison of Land Surface Parameterization Schemes (PILPS) is moving into its second and third phases that will exploit observational data and consider the performance of land surface schemes when coupled to their host climate models. The first stage of phase 2 will focus on an attempt to understand the large differences found during phase 1. The first site from which observations will be drawn for phase 2 intercomparisons is Cabauw, the Netherlands (51 °58′N, 4°56′E), selected specifically to try to reduce one of the causes of the divergence among the phase 1 results: the initialization of the deep soil moisture. Cabauw's deep soil is saturated throughout the year. It also offers a quality controlled set of meteorological forcing and 160 days of flux measurements. PILPS phase 2 follows the form of the phase 1 intercomparisons: simple off-line integrations and comparisons, but in phase 2 participating schemes' results will be compared against observed fluxes. Preliminary results indicate that between model variability persists (i) in better specified experiments and (ii) in comparison with data. Although median values are consistent with observations, there is a large range among models. Phase 3, in which the intercomparison of PILPS schemes as a component of global atmospheric circulation models, is being conducted jointly with the Atmospheric Model lntercomparison Project (AMIP) as diagnostic subproject number 12. Preliminary results suggest that results differ by about the same range as in the off-line experiments in phases 1 and 2. Incomplete diagnostics suggest that bucket and canopy models differ and that variability among models can be tracked to the soil moisture parameterization. This paper offers a review of the PILPS project to date and an invitation to participate in PILPS' current and future activities.

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Reinder A. Feddes, Holger Hoff, Michael Bruen, Todd Dawson, Patricia de Rosnay, Paul Dirmeyer, Robert B. Jackson, Pavel Kabat, Axel Kleidon, Allan Lilly, and Andrew J. Pitman

From 30 September to 2 October 1999 a workshop was held in Gif-sur-Yvette, France, with the central objective to develop a research strategy for the next 3–5 years, aiming at a systematic description of root functioning, rooting depth, and root distribution for modeling root water uptake from local and regional to global scales. The goal was to link more closely the weather prediction and climate and hydrological models with ecological and plant physiological information in order to improve the understanding of the impact that root functioning has on the hydrological cycle at various scales. The major outcome of the workshop was a number of recommendations, detailed at the end of this paper, on root water uptake parameterization and modeling and on collection of root and soil hydraulic data.

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