The 14th Conference on Hydrology

5B.1
PILPS PHASE 2(D)- SIMULATIONS OF A BOREAL GRASSLAND HYDROLOGY AT VALDAI, RUSSIA (INVITED)

C. Adam Schlosser, Calverton, MD; and A. Slater, A. Robock, A. J. Pitman, K. Ya Vinnikov, A. Henderson-Sellers, and N. A. Speranskaya

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 the LSSs’ sensitivity to downward longwave radiative forcing, timescales of simulated hydrologic variability, and biases 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. We present a summary of the participating LSSs' control simulations and sensitivity runs. Considerable model scatter for the control simulations exist. However, nearly all of the LSS scatter in simulated root-zone soil moisture is contained within the spatial variability observed inside the catchment. In addition, all models show a considerable sensitivity to longwave forcing for the simulation of the snow pack, which during the spring melt affects runoff, melt-water infiltration, and subsequent evapotranspiration. A greater sensitivity of simulated snow melt, compared to snow accumulation, 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

The 14th Conference on Hydrology