Estimating energy balance fluxes above a boreal forest from radiometric temperature observations

• Published in: Agricultural and forest meteorology 2009-06, Vol.149 (6), p.1037-1049
• Main Authors: Sánchez, J.M., Caselles, V., Niclòs, R., Coll, C., Kustas, W.P.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; air temperature; Biological and medical sciences; Boreal forest; boreal forests; Canopy temperature; energy balance; Energy balance closure; Energy fluxes; energy transfer; estimation; forest ecosystems; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; heat transfer; mathematical models; meteorological data; model validation; radiometry; simulation models; soil temperature; solar radiation; storage heat transfer; STSEB model; surface temperature; surface-atmosphere energy exchange
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2008.12.009

The great areal extent of boreal forests confers these ecosystems potential to impact on the global surface-atmosphere energy exchange. A modelling approach, based on a simplified two-source energy balance model, was proposed to estimate energy balance fluxes above boreal forests using thermal infrared measurements. Half-hourly data from the Solar-Induced Fluorescence Experiment, carried out in a Finnish boreal forest, was used to evaluate the performance of the model. Energy balance closure, determined by linear regression, found all fluxes to underestimate available energy by 9% ( r 2 = 0.94). Significance in the energy balance of the heat storage in the air and in the soil terms was also analyzed. Canopy temperatures, measured by a CIMEL Electronique CE 312 radiometer, together with ancillary meteorological variables and vegetation characteristics, were used to run the model. Comparison with ground measurements showed errors lower than ±15 W m −2 for the retrieval of net radiation, soil heat flux and storage heat flux, and about ±50 W m −2 for the sensible and latent heat fluxes. A sensitivity analysis of the approach to typical operational uncertainties in the required inputs was conducted showing the necessity of accurate measurements of the target radiometric surface temperature.