Albedo estimates for land surface models and support for a new paradigm based on foliage nitrogen concentration |
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| Authors: | D Y HOLLINGER S V OLLINGER A D RICHARDSON T P MEYERS D B DAIL M E MARTIN N A SCOTT T J ARKEBAUER D D BALDOCCHI K L CLARK P S CURTIS K J DAVIS A R DESAI D DRAGONI M L GOULDEN L GU G G KATUL S G PALLARDY K T PAW U H P SCHMID P C STOY A E SUYKER S B VERMA |
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| Institution: | 1. Northern Research Station, USDA Forest Service, 271 Mast Rd, Durham, NH 03824, USA;2. Complex Systems Research Center, Institute of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA;3. NOAA/ARL/ATDD, Oak Ridge, TN, USA;4. Department of Plant, Soil, and Environmental Sciences, The University of Maine, Orono, ME, USA;5. Department of Geography, Queen's University, Kingston, ON, Canada;6. Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, USA;7. Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA;8. Northern Research Station, USDA Forest Service, Silas Little, NJ, USA;9. Department of Evolution, Ecology & Organismal Biology, The Ohio State University, Columbus, OH, USA;10. Department of Meteorology, The Pennsylvania State University, University Park, PA, USA;11. Atmospheric & Oceanic Sciences Department, University of Wisconsin ‐ Madison, Madison, WI, USA;12. Department of Geography, Indiana University, Bloomington, IN, USA;13. Department of Earth System Science, University of California – Irvine, Irvine, CA, USA;14. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA;15. Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC, USA;16. School of Natural Resources, University of Missouri, Columbia, MO, USA;17. Department of Land, Air and Water Resources, University of California – Davis, Davis, CA, USA;18. Institute for Meteorology and Climate Research, Atmospheric Environmental Research (FZK/IMK‐IFU), Garmisch‐Partenkirchen, Germany;19. School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, UK;20. School of Natural Resources, University of Nebraska, Lincoln, NE, USA |
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| Abstract: | Vegetation albedo is a critical component of the Earth's climate system, yet efforts to evaluate and improve albedo parameterizations in climate models have lagged relative to other aspects of model development. Here, we calculated growing season albedos for deciduous and evergreen forests, crops, and grasslands based on over 40 site‐years of data from the AmeriFlux network and compared them with estimates presently used in the land surface formulations of a variety of climate models. Generally, the albedo estimates used in land surface models agreed well with this data compilation. However, a variety of models using fixed seasonal estimates of albedo overestimated the growing season albedo of northerly evergreen trees. In contrast, climate models that rely on a common two‐stream albedo submodel provided accurate predictions of boreal needle‐leaf evergreen albedo but overestimated grassland albedos. Inverse analysis showed that parameters of the two‐stream model were highly correlated. Consistent with recent observations based on remotely sensed albedo, the AmeriFlux dataset demonstrated a tight linear relationship between canopy albedo and foliage nitrogen concentration (for forest vegetation: albedo=0.01+0.071%N, r2=0.91; forests, grassland, and maize: albedo=0.02+0.067%N, r2=0.80). However, this relationship saturated at the higher nitrogen concentrations displayed by soybean foliage. We developed similar relationships between a foliar parameter used in the two‐stream albedo model and foliage nitrogen concentration. These nitrogen‐based relationships can serve as the basis for a new approach to land surface albedo modeling that simplifies albedo estimation while providing a link to other important ecosystem processes. |
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| Keywords: | albedo nitrogen vegetation |
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