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Intercomparison of clumping index estimates from POLDER, MODIS, and MISR satellite data over reference sites
journal contribution
posted on 2023-05-19, 06:34 authored by Pisek, J, Govind, A, Arndt, SK, Hocking, D, Timothy WardlawTimothy Wardlaw, Fang, H, Matteucci, G, Longdoz, BClumping index is the measure of foliage grouping relative to a random distribution of leaves in space. It is a key structural parameter of plant canopies that influences canopy radiation regimes and controls canopy photosynthesis and other land-atmosphere interactions. The Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at 6 km resolution and the Bidirectional Reflectance Distribution Function (BRDF) product from Moderate Resolution Imaging Spectroradiometer (MODIS) at 500 m resolution. Most recently the algorithm was also applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this study for the first time we characterized and compared the three products over a set of sites representing diverse biomes and different canopy structures. The products were also directly validated with both in-situ vertical profiles and available seasonal trajectories of clumping index over several sites. We demonstrated that the vertical distribution of foliage and especially the effect of understory need to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements responded to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can propagate into the foliage clumping maps. Our results indicate that MODIS data and MISR data, with 275 m in particular, can provide good quality clumping index estimates at spatial scales pertinent for modeling local carbon and energy fluxes.
History
Publication title
ISPRS Journal of Photogrammetry and Remote SensingVolume
101Pagination
47-56ISSN
0924-2716Department/School
School of Natural SciencesPublisher
Elsevier Science BvPlace of publication
Po Box 211, Amsterdam, NetherlandsRights statement
?Copyright 2014 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.Repository Status
- Restricted