Historical Evaluation of Hydrologic Components of CLM4: Surface Soil Moisture and Surface Runoff

Monday, May 12, 2014 - 07:00
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Climatic trends affect water availability and suitability through soil water storage, groundwater recharge, and surface runoff. The integrated Earth System Model (iESM) offers the dynamic platform for evaluating energy/water/climate/land use feedbacks. The Community Land Model (CLM) is the land component of the Community Earth System Model (CESM) and simulates biogeophysics, biogeochemistry, hydrologic cycle, and ecosystem dynamics of the terrestrial ecosystem. We conduct error quantification and sensitivity studies of iESM/CESM water supply and demand to evaluate the performance of hydrologic components of the model. Surface soil moisture (10 cm) was compared to microwave satellite soil moisture product maintained by European Space Agency (ESA), and runoff field was compared to Global Runoff Data Base (GRDB). CESM was found to perform the best among four CMIP5 archived models (MIROC5, HadCM3, CSIRO). The CESM overestimates soil moisture in the wetland/lake area in high latitude that is likely due to misrepresentation of the open water body as saturated soils. Overall CESM tends to underestimate runoff, especially in Amazon, Japan, south China, and Southeast Asia. Further analyses indicate surface soil moisture is dependent on precipitation during unfrozen seasons, and is inversely correlated to surface temperature. Surface soil moisture is also correlated to evapotranspiration except in monsoon prevailing areas where summer high humidity prevents evapotranspiration even when soils are wet.