Articles | Volume 7, issue 5
Geosci. Model Dev., 7, 2477–2484, 2014
Geosci. Model Dev., 7, 2477–2484, 2014

Model description paper 24 Oct 2014

Model description paper | 24 Oct 2014

Development of a semi-parametric PAR (Photosynthetically Active Radiation) partitioning model for the United States, version 1.0

J. C. Kathilankal1, T. L. O'Halloran2, A. Schmidt3, C. V. Hanson3, and B. E. Law3 J. C. Kathilankal et al.
  • 1LI-COR Inc. 4647 Superior Street, Lincoln, NE 68504, USA
  • 2Sweet Briar College, Department of Environmental Sciences, Sweet Briar, VA 24595, USA
  • 3Department of Forest Ecosystems and Society College of Forestry, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331, USA

Abstract. A semi-parametric PAR diffuse radiation model was developed using commonly measured climatic variables from 108 site-years of data from 17 AmeriFlux sites. The model has a logistic form and improves upon previous efforts using a larger data set and physically viable climate variables as predictors, including relative humidity, clearness index, surface albedo and solar elevation angle. Model performance was evaluated by comparison with a simple cubic polynomial model developed for the PAR spectral range. The logistic model outperformed the polynomial model with an improved coefficient of determination and slope relative to measured data (logistic: R2 = 0.76; slope = 0.76; cubic: R2 = 0.73; slope = 0.72), making this the most robust PAR-partitioning model for the United States currently available.