Comparison and evaluation of Medium Resolution Imaging Spectrometer leaf area index products across a range of land use

Abstract Leaf area index (LAI) is a commonly required parameter when modelling land surface fluxes. Satellite based imagers, such as the 300 m full resolution (FR) Medium Spectral Resolution Imaging Spectrometer (MERIS), offer the potential for timely LAI mapping. The availability of multiple MERIS LAI algorithms prompts the need for an evaluation of their performance, especially over a range of land use conditions. Four current methods for deriving LAI from MERIS FR data were compared to estimates from in-situ measurements over a 3 km × 3 km region near Ottawa, Canada. The LAI of deciduous dominant forest stands and corn, soybean and pasture fields was measured in-situ using digital hemispherical photography and processed using the CANEYE software. MERIS LAI estimates were derived using the MERIS Top of Atmosphere (TOA) algorithm, MERIS Top of Canopy (TOC) algorithm, the Canada Centre for Remote Sensing (CCRS) Empirical algorithm and the University of Toronto (UofT) GLOBCARBON algorithm. Results show that TOA and TOC LAI estimates were nearly identical ( R 2  > 0.98) with underestimation of LAI when it is larger than 4 and overestimation when smaller than 2 over the study region. The UofT and CCRS LAI estimates had root mean square errors over 1.4 units with large (∼ 25%) relative residuals over forests and consistent underestimates over corn fields. Both algorithms were correlated ( R 2  > 0.8) possibly due to their use of the same spectral bands derived vegetation index for retrieving LAI. LAI time series from TOA, TOC and CCRS algorithms showed smooth growth trajectories however similar errors were found when the values were compared with the in-situ LAI. In summary, none of the MERIS LAI algorithms currently meet performance requirements from the Global Climate Observing System.

[1]  E. Vermote,et al.  Operational remote sensing of tropospheric aerosol over land from EOS moderate resolution imaging spectroradiometer , 1997 .

[2]  Steven W. Running,et al.  Comparisons of land cover and LAI estimates derived from ETM+ and MODIS for four sites in North America: a quality assessment of 2000/2001 provisional MODIS products , 2003 .

[3]  Richard Fernandes,et al.  Evaluating image-based estimates of leaf area index in boreal conifer stands over a range of scales using high-resolution CASI imagery , 2004 .

[4]  F. Baret,et al.  Review of methods for in situ leaf area index (LAI) determination: Part II. Estimation of LAI, errors and sampling , 2004 .

[5]  G. Dedieu,et al.  SMAC: a simplified method for the atmospheric correction of satellite measurements in the solar spectrum , 1994 .

[6]  A. Skidmore,et al.  Narrow band vegetation indices overcome the saturation problem in biomass estimation , 2004 .

[7]  Jan G. P. W. Clevers,et al.  A framework for monitoring crop growth by combining directional and spectral remote sensing information. , 1994 .

[8]  R. Lacaze,et al.  Canada-wide foliage clumping index mapping from multiangular POLDER measurements , 2005 .

[9]  M. Schaepman,et al.  Spatial unmixing of MERIS data for monitoring vegetation dynamics , 2007 .

[10]  J. Chen,et al.  Global mapping of foliage clumping index using multi-angular satellite data , 2005 .

[11]  T. Nilson.  A theoretical analysis of the frequency of gaps in plant stands , 1971 .

[12]  John R. Miller,et al.  Hyperspectral vegetation indices and novel algorithms for predicting green LAI of crop canopies: Modeling and validation in the context of precision agriculture , 2004 .

[13]  Jan Pisek,et al.  Algorithm for global leaf area index retrieval using satellite imagery , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[14]  W. Wilhelm,et al.  Comparison of three leaf area index meters in a corn canopy , 2000 .

[15]  V. N. Sridhar,et al.  Estimation and validation of LAI using physical and semi‐empirical BRDF models , 2008 .

[16]  F. Baret,et al.  PROSPECT: A model of leaf optical properties spectra , 1990 .

[17]  F. Baret,et al.  LAI and fAPAR CYCLOPES global products derived from VEGETATION. Part 2: validation and comparison with MODIS collection 4 products , 2007 .

[18]  R. Congalton,et al.  Validation of an Integrated Estimation of Loblolly Pine (Pinus taeda L.) Leaf Area Index (LAI) Using Two Indirect Optical Methods in the Southeastern United States , 2008 .

[19]  Elizabeth Pattey,et al.  Detecting effects of nitrogen rate and weather on corn growth using micrometeorological and hyperspectral reflectance measurements , 2001 .

[20]  Frédéric Baret,et al.  Validation of global moderate-resolution LAI products: a framework proposed within the CEOS land product validation subgroup , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[21]  J. Chen,et al.  Retrieving forest background reflectance in a boreal region from Multi-angle Imaging SpectroRadiometer (MISR) data , 2007 .

[22]  Dennis L. Helder,et al.  Landsat-5 TM and Landsat-7 ETM+ absolute radiometric calibration using the reflectance-based method , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[23]  Y. Knyazikhin,et al.  Validation and intercomparison of global Leaf Area Index products derived from remote sensing data , 2008 .

[24]  F. Baret,et al.  Optimal geometric configuration and algorithms for LAI indirect estimates under row canopies: The case of vineyards , 2009 .

[25]  Sylvain G. Leblanc,et al.  Methodology comparison for canopy structure parameters extraction from digital hemispherical photography in boreal forests , 2005 .

[26]  Frédéric Baret,et al.  Evaluation of the representativeness of networks of sites for the global validation and intercomparison of land biophysical products: proposition of the CEOS-BELMANIP , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[27]  Joseph G. Lauer,et al.  Soybean Growth and Development in Various Management Systems and Planting Dates , 2004 .

[28]  J. Moreno,et al.  Retrieval of chlorophyll content and LAI of crops using hyperspectral techniques: application to PROBA/CHRIS data , 2008 .

[29]  R. Jackson,et al.  Multisite Analyses of Spectral-Biophysical Data for Wheat , 1992 .

[30]  J. Welles,et al.  Canopy structure measurement by gap fraction analysis using commercial instrumentation , 1996 .

[31]  R. Houborg,et al.  Combining vegetation index and model inversion methods for the extraction of key vegetation biophysical parameters using Terra and Aqua MODIS reflectance data , 2007 .

[32]  A. Lang.  Estimation of leaf area index from transmission of direct sunlight in discontinuous canopies , 1986 .

[33]  F. Baret,et al.  Neural network estimation of LAI, fAPAR, fCover and LAI×Cab, from top of canopy MERIS reflectance data : Principles and validation , 2006 .

[34]  R. Fernandes,et al.  A NARROW BAND NDVI FOR ROBUST LAI RETRIEVAL INDEPENDENT OF CANOPY CHLORPHYLL CONCENTRATION – TEST WITH MERIS , 2008 .

[35]  W. Verhoef.  Light scattering by leaf layers with application to canopy reflectance modeling: The Scattering by Arbitrarily Inclined Leaves (SAIL) model , 1984 .

[36]  S. Leblanc,et al.  A Shortwave Infrared Modification to the Simple Ratio for LAI Retrieval in Boreal Forests: An Image and Model Analysis , 2000 .

[37]  Oliver Sonnentag,et al.  Leaf area index measurements at Fluxnet-Canada forest sites , 2006 .

[38]  R. Fernandes,et al.  Landsat-5 TM and Landsat-7 ETM+ based accuracy assessment of leaf area index products for Canada derived from SPOT-4 VEGETATION data , 2003 .

[39]  Rasmus Fensholt,et al.  MODIS leaf area index products: from validation to algorithm improvement , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[40]  Sylvain G. Leblanc,et al.  Evaluation of national and global LAI products derived from optical remote sensing instruments over Canada , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[41]  W. Verhoef.  Light scattering by leaf layers with application to canopy reflectance modelling: The SAIL model , 1984 .

[42]  J. Chen,et al.  Defining leaf area index for non‐flat leaves , 1992 .

[43]  R. Myneni,et al.  Intercomparison and sensitivity analysis of Leaf Area Index retrievals from LAI-2000, AccuPAR, and digital hemispherical photography over croplands , 2008 .

[44]  Sylvain G. Leblanc,et al.  Multiple-scattering scheme useful for geometric optical modeling , 2001, IEEE Trans. Geosci. Remote. Sens..

[45]  Gérard Dedieu,et al.  Estimation of leaf area and clumping indexes of crops with hemispherical photographs , 2008 .

[46]  Richard Fernandes,et al.  A consistency analysis of surface reflectance and leaf area index retrieval from overlapping clear-sky Landsat ETM+ imagery , 2004 .