The Project for the Intercomparison of Land-surface Parameterization Schemes (PILPS) aims to improve understanding and modeling of land-surface processes. PILPS Phase 2(d) uses a set of meteorological and hydrological data spanning 18 years (1966-1983) from a grassland catchment at the Valdai water-balance research site in Russia. A suite of standalone simulations is performed by 21 land-surface schemes (LSSs) to explore sensitivity to downward longwave radiative forcing, time scales of simulated hydrologic variability, and baises resulting from single-year simulations that use recursive spin-up. These simulations are the first in PILPS to investigate the performance of LSSs at a site with a well-defined seasonal snow cover and frozen soil. Considerable model scatter for the control simulations exists. However, nearly all of the LSS scatter in simulated root-zone soil moistureis contained within the spatial variabiity observed inside the catchment. In addition, all models show a considerable sensitvity to longwave forcing for the simulation of the snow pack which during the spring melt affects runoff, melt-water infiltration, and subsequent evapotranpiration. A greater sensitivity of the ablation, compared to the accumulation, of the winter snow pack to the choice of snow parameterization is found. Sensitivity simulations starting at prescribed conditions with no spin-up demonstrate that the treatment of frozen soil (moisture) processes can affect the long-term variability of the models. The single-year recursive runs show large biases, compared to the corresponding year of the control, run that can persist through the entire year and further emphasize the importance of performing multi-year simulations.
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Center for Ocean-Land-Atmosphere Studies
last update: 5 January 1998
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