Period: 2000 – present
Sensor: MODIS Terra+Aqua
Frequency: 4 and 8 days
Resolutions: 500m (1km older versions)
Data can be accessed here.
Algorithm description: The algorithm consists of a Look-up-Table (LUT) based procedure that exploits the spectral information content of the MODIS red (648 nm) and near-infrared (NIR, 858 nm) surface reflectances. The LUT was generated using 3D radiative transfer equation. In case of algorithm failure, a back-up empirical method based on relationships between NDVI and canopy LAI is used. Compared to the version 5, biomes classification used in v6 has been improved by addition of two more biomes.
The radiative transfer model is based on photon transfer theory and takes into account clumping at plant and canopy level (but not shoot clumping for pines). This makes the retrieved values more comparable to ‘true LAI’ rather than ‘effective LAI’.
Compositing is done by selecting retrieved value corresponding to maximum LAI over the compositing period.
Accuracy: The consistency of V6 products has been compared with that of v5 products. Global and seasonal comparison between v5 and v6 indicates good continuity and consistency for all biome types.
Comparison with ground measurements (BELMANIP sites) showed that v6 performs better than v5: RMSE=0.66 vs RMSE=0.8 and R2=0.77 vs R2=0.70, respectively. Considering all biome types RMSE of retrieval ranges between 0.36 and 0.56.
- Errors in biome classification can propagate into LAI product and lead to incorrect LAI values.
- LAI represents the true LAI (clumping taken into account) and not the apparent LAI
- More biome specific validation is necessary as the scatter plots for some biomes are worse than the others.
Knyazikhin, Y., J. Glassy, J.L. Privette, Y. Tian, A. Lotsch, Y. Zhang, Y. Wang, J.T. Morisette, P. Votava, and R.B. Myneni. “MODIS Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation Absorbed by Vegetation (FPAR) Product (MOD15) Algorithm Theoretical Basis Document.” USA: NASA Goddard Space Flight Center, 1999.
Knyazikhin, Y., J. V. Martonchik, R. B. Myneni, D. J. Diner, and S. W. Running. “Synergistic Algorithm for Estimating Vegetation Canopy Leaf Area Index and Fraction of Absorbed Photosynthetically Active Radiation from MODIS and MISR Data.” Journal of Geophysical Research: Atmospheres 103, no. D24 (December 27, 1998): 32257–75.
Yan, Kai, Taejin Park, Guangjian Yan, Chi Chen, Bin Yang, Zhao Liu, Ramakrishna R. Nemani, Yuri Knyazikhin, and Ranga B. Myneni. “Evaluation of MODIS LAI/FPAR Product Collection 6. Part 1: Consistency and Improvements.” Remote Sensing 8, no. 5 (April 26, 2016): 359.
Yan, Kai, Taejin Park, Guangjian Yan, Zhao Liu, Bin Yang, Chi Chen, Ramakrishna R. Nemani, Yuri Knyazikhin, and Ranga B. Myneni. “Evaluation of MODIS LAI/FPAR Product Collection 6. Part 2: Validation and Intercomparison.” Remote Sensing 8, no. 6 (May 30, 2016): 460