Geosci. Model Dev. Discuss., 4, 2327-2363, 2011
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This discussion paper has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD.
Vegetation height products between 60° S and 60° N from ICESat GLAS data
S. O. Los1, J. A. B. Rosette1,2, N. Kljun1, P. R. J. North1, J. C. Suárez2,3, C. Hopkinson4, R. A. Hill5, L. Chasmer6, E. van Gorsel7, C. Mahoney1, and J. A. J. Berni7
1Department of Geography, Swansea University, Singleton Park, Swansea SA2 8PP, UK
2Biospheric Sciences Branch, code 614.4, NASA/Goddard Space Flight Center, Greenbelt and University of Maryland College Park, Maryland 20771, USA
3Forest Research, Northern Research Station, Roslin, Midlothian, EH25 9SY, UK
4Applied Geomatics Research Group, Centre of Geographic Science, Nova Scotia Community College, Lawrencetown, Nova Scotia, B0S 1P0, Canada
5School of Applied Science, Bournemouth University, Poole, Dorset, BH12 5BB, UK
6Cold Regions Research Centre, Wilfrid Laurer University, Waterloo ON N2L 3C5, Canada
7CSIRO Marine and Atmospheric Research, Pye Laboratory, Canberra ACT 2601, Australia

Abstract. We present a new method to obtain coarse resolution (0.5° × 0.5°) vegetation height and vegetation-cover fraction data sets between 60° S and 60° N for use in climate models and ecological models. The data sets are derived from the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat), which is the only LiDAR instrument that provides close to global coverage when all data collected for 2003–2009 are combined. Filters are applied to the GLAS data to identify and eliminate spurious observations, e.g. data that are affected by clouds, atmosphere and terrain and as such result in erroneous estimates of vegetation height or vegetation cover. GLAS vegetation height estimates are aggregated in histograms from 0 to 70 m in 0.5 m intervals. The GLAS vegetation height product is evaluated in four ways. First, unfiltered and filtered individual GLAS vegetation height measurements are compared with aircraft LiDAR measurements of the same from seven sites in the Americas, Europe, and Australia. Application of filters increases the correlation with aircraft data from r = 0.36 to r = 0.67 and decreases the root-mean-square error by a factor 3. Second, the global aggregated GLAS vegetation height product is tested for sensitivity towards the choice of data quality filters; areas with frequent cloud cover and areas with steep terrain are the most sensitive to the choice of thresholds for the filters. Thirdly, the GLAS global vegetation height product is compared with two other global vegetation height products and is believed to produce more realistic characteristics: dominant vegetation height for tropical forests between 30 and 60 m versus 20 and 40 m in existing products. Finally, the GLAS bare soil cover fraction is compared globally with the MODIS bare soil fraction (r = 0.55) and with the FASIR bare soil cover fraction estimates (r = 0.58); the correlation between GLAS and MODIS tree-cover fraction was (r = 0.76). The evaluation indicates that filters applied to the GLAS data are conservative and eliminate a large proportion of spurious data, while only in a minority of cases at the cost of removing reliable data as well. The present GLAS vegetation height product appears more realistic than previous data sets used for input to climate models and ecological models and hence should significantly improve simulations that involve the land surface.

Citation: Los, S. O., Rosette, J. A. B., Kljun, N., North, P. R. J., Suárez, J. C., Hopkinson, C., Hill, R. A., Chasmer, L., van Gorsel, E., Mahoney, C., and Berni, J. A. J.: Vegetation height products between 60° S and 60° N from ICESat GLAS data, Geosci. Model Dev. Discuss., 4, 2327-2363, doi:10.5194/gmdd-4-2327-2011, 2011.
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