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# New mathematical method enhances hydrology simulations

Date:
April 15, 2015
Source:
Department of Energy, Office of Science
Summary:
A team applied sophisticated mathematical solutions to fine tune water and energy exchange parameters, numerical stand-ins for complex processes, to more accurately simulate water and energy fluxes in an important model under different conditions.
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FULL STORY

Just as a racecar's engine needs the right fuel to get the best performance, so climate models need finely tuned parameters to accurately simulate the impacts of different technologies and policies. Led by researchers at Pacific Northwest National Laboratory, a team applied sophisticated mathematical solutions to fine tune the water and energy exchange parameters, numerical stand-ins for complex processes, to more accurately simulate water and energy fluxes in the Community Land Model under different climate and environmental conditions.

The Impact

Calibrating the water and energy exchange parameters significantly improved simulations compared to results using the default Community Land Model parameter values.

Summary

The exchange of water and energy between the atmosphere and land is among the most uncertain aspects of climate modeling. For example, when rain falls on land, the amount of water that evaporates back into the atmosphere or gets carried by groundwater to rivers and the ocean is unclear. The answer to this and similar questions could be estimated using climate models, but these models have numerous variables or "parameters" that must be adjusted based on observations of different regions of Earth. One way to adjust these parameters is to run the model repeatedly, each time changing the parameters individually until a solution that matches observations is found. However, it is possible that a different set of solutions would also match observations. Researchers evaluated inversion methodologies at select field sites based on global sensitivity analyses. They found significant improvements in the model simulations that better match the observed heat flux and runoff by using the estimated parameters compared to using the default parameters.Improvements in heat flux were found especially in areas with strong energy and water constraints.

Story Source:

Materials provided by Department of Energy, Office of Science. Note: Content may be edited for style and length.

Journal Reference:

1. Y. Sun, Z. Hou, M. Huang, F. Tian, L. Ruby Leung. Inverse modeling of hydrologic parameters using surface flux and runoff observations in the Community Land Model. Hydrology and Earth System Sciences, 2013; 17 (12): 4995 DOI: 10.5194/hess-17-4995-2013