MODIS leaf area indices
This page describes the leaf area index product derived from the MODIS satellite instrument. This product is used in GEOS-Chem with the MEGAN v2.1 biogenic emissions.
For an overview of how the MODIS leaf area index product is used in GEOS-Chem, please visit our Leaf area indices in GEOS-Chem wiki page.
Mike Barkley has written a document entitled Description of the MODIS Leaf Area Index used in GEOS-Chem which provides a full description of the MODIS-derived leaf area index product used by GEOS-Chem. Please see this document for full details.
The MODIS leaf area index product that we currently use in GEOS-Chem is version 5. This may be updated in the future.
--Bob Y. 11:41, 13 April 2012 (EDT)
- For validation of the original implementation of MODIS LAI in GEOS-Chem, see Barkley 
- For validation of the updated LAI algorithm in GEOS-Chem (i.e. now reading data from netCDF files and regridding to GEOS-Chem resolution in a more consistent manner), please see this wiki post.
--Bob Y. 12:02, 13 April 2012 (EDT)
Source code and data
Obtaining the raw data
To obtain the "raw" MODIS leaf area index product, you must contact the head of the Boston University Climate and Vegetation Research Group.
LAI data files in netCDF format
NOTE: GEOS-Chem v9-01-03 (and higher versions) exclusively use the MODIS LAI data in netCDF format. Support for the ASCII data format has been removed.
Bob Yantosca has code to the existing MODIS LAI files in binary punch format into netCDF format. This is for use with the updated LAI routines in GEOS-Chem.
If you are using the Olson 1992 land map (which is at 0.5° x 0.5° resolution), then you must also read MODIS LAI data from netCDF files at 0.5° x 0.5° resolution. These files are stored in the data directory:
If, on the other hand, you are using the Olson 2001 land map (which is at 0.25° x 0.25° resolution), then you must also read MODIS LAI data from netCDF files at 0.25° x 0.25° resolution. These files are stored in the data directory:
GEOS-Chem module modis_lai_mod.F90 contains routines and variables for the updated LAI scheme. The existing GEOS-Chem modules and routines are now obsolete and have been removed from GEOS-Chem v9-01-03 (and higher versions):
- Boston University Climate and Vegetation Research Group.
- Barkley, M., Description of the MODIS Leaf Area Index used in GEOS-Chem, 2010. PDF
- Guenther, A., T. Karl, P. Harley, C. Wiedinmyer, P. I. Palmer, and C. Geron, Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6(11), 3181-3210, 2006.
- Mueller, J.-F., et al., Global isoprene emissions estimated using MEGAN, ECMWF analyses and a detailed canopy environment model, Atmos. Chem. Phys., 8, 1329-1341, 2008.
- Justice, C. O., et al., The Moderate Resolution Imaging Spectroradiometer (MODIS): Land remote sensing for global change research, IEEE Trans. GeoSci. Remote Sens., 36(4), 1228-1249, 1998.
- Myneni, R. B., et al, Global products of vegetation leaf area and fraction absorbed PAR from year one of MODIS data, Remote Sensing of Environment, 83, 214231, 2002.
- Myneni, R. B., et al., Large seasonal swings in leaf area of Amazon rainforests, Proceedings of the National Academy of Sciences, 104(12), 4820-4823, doi:10.1073/pnas.0611338104, 2007.
- Yang, W. et al., MODIS Leaf Area Index Products: From Validation to Algorithm Improvement, u>Transactions on GeoScience and Remote Sensing</u>, 44(7), 2006.
--Bob Y. 10:03, 3 March 2010 (EST)
0.25x0.25 MODIS LAI data
These updates are slated for inclusion in v11-02
Jenny Fisher discovered an issue in the MODIS LAI files in CHEM_INPUTS/MODIS_LAI_201204/For_Olson_2001/ that resulted in LAI being 0 in places where it shouldn’t be. For a complete description of the issue see this post on our MEGAN v2.1 plus Guenther 2012 biogenic emissions wiki page.
MODIS LAI vs AVHRR LAI
NOTE: This point is moot, as support from the AVHRR LAI fields have been removed from GEOS-Chem v9-01-03 and higher versions.
Long story short: The AVHRR-derived leaf area indices are biased high w/r/t the MODIS-derived leaf area indices and should not be used with MEGAN v2.1 biogenic emissions. Please see the full discussion on the MEGAN wiki page.
--Bob Y. 15:09, 17 December 2012 (EST)