Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 2917-2932, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
10 Dec 2014
Coupling the high-complexity land surface model ACASA to the mesoscale model WRF
L. Xu1, R. D. Pyles2, K. T. Paw U2, S. H. Chen2, and E. Monier1 1Joint Program on the Science and Policy of Global Change, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
2Department of Land, Air, and Water Resources, University of California Davis, Davis, California, USA
Abstract. In this study, the Weather Research and Forecasting (WRF) model is coupled with the Advanced Canopy–Atmosphere–Soil Algorithm (ACASA), a high-complexity land surface model. Although WRF is a state-of-the-art regional atmospheric model with high spatial and temporal resolutions, the land surface schemes available in WRF, such as the popular NOAH model, are simple and lack the capability of representing the canopy structure. In contrast, ACASA is a complex multilayer land surface model with interactive canopy physiology and high-order turbulence closure that allows for an accurate representation of heat, momentum, water, and carbon dioxide fluxes between the land surface and the atmosphere. It allows for microenvironmental variables such as surface air temperature, wind speed, humidity, and carbon dioxide concentration to vary vertically within and above the canopy.

Surface meteorological conditions, including air temperature, dew point temperature, and relative humidity, simulated by WRF-ACASA and WRF-NOAH are compared and evaluated with observations from over 700 meteorological stations in California. Results show that the increase in complexity in the WRF-ACASA model not only maintains model accuracy but also properly accounts for the dominant biological and physical processes describing ecosystem–atmosphere interactions that are scientifically valuable. The different complexities of physical and physiological processes in the WRF-ACASA and WRF-NOAH models also highlight the impact of different land surface models on atmospheric and surface conditions.

Citation: Xu, L., Pyles, R. D., Paw U, K. T., Chen, S. H., and Monier, E.: Coupling the high-complexity land surface model ACASA to the mesoscale model WRF, Geosci. Model Dev., 7, 2917-2932,, 2014.
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