Comparisons of Simulations of Soil Moisture Variations in the Yellow River Basin Driven by Various Atmospheric Forcing Data Sets

Based on station observations, The European Centre for Medium-Range WeatherForecasts reanalysis (ERA40), the National Centers for EnvironmentalPrediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysisand Princeton University's global meteorological forcing data set(Princeton), four atmospheric forcing fields were constructed for use indriving the Community Land Model version 3.5 (CLM3.5). Simulated soilmoisture content throughout the period 1951--2000 in the Yellow River basinwas validated via comparison with corresponding observations in the upper,middle, and lower reaches. The results show that CLM3.5 is capable ofreproducing not only the characteristics of intra-annual and annualvariations of soil moisture, but also long-term variation trends, withdifferent statistical significance in the correlations between theobservations and simulations from different forcing fields in variousreaches. The simulations modeled with station-based atmospheric forcingfields are the most consistent with observed soil moisture, and thesimulations based on the Princeton data set are the second best, on average.The simulations from ERA40 and NCEP/NCAR are close to each other in quality,but comparatively worse to the other sources of forcing information thatwere evaluated. Regionally, simulations are most consistent withobservations in the lower reaches and less so in the upper reaches, with themiddle reaches in between. In addition, the soil moisture simulated byCLM3.5 is systematically greater than the observations in the Yellow Riverbasin. Comparisons between the simulations by CLM3.5 and CLM3.0 indicatethat simulation errors are primarily caused by deficiencies within CLM3.5and are also associated with the quality of atmospheric forcing fieldapplied.