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
Received: 22 Jan 2014 – Discussion started: 06 Mar 2014
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.
Revised: 29 Jul 2014 – Accepted: 03 Sep 2014 – Published: 24 Oct 2014
Kathilankal, J. C., O'Halloran, T. L., Schmidt, A., Hanson, C. V., and Law, B. E.: Development of a semi-parametric PAR (Photosynthetically Active Radiation) partitioning model for the United States, version 1.0, Geosci. Model Dev., 7, 2477-2484, doi:10.5194/gmd-7-2477-2014, 2014.