Leaf Area Index (LAI) is used to quantify the amount of foliage in a landscape. MEGAN uses a value, referred to as LAIv), that is representative of the m2 of one sided leaf area per m2 of canopy area (vegetation covered area).
If the time period and region you need is not available below then you can generate your own LAIv data using satellite databases of LAI and vegetation cover fraction (VCF) from sources such as as NASA or ESA. Note that these LAI data must first be converted to LAIv (LAI divided by the vegetation cover fraction) before used in MEGAN2.1 (MEGAN3.2 will accept either LAI or LAIv).
For example, if the LAI for a specific location is 2 m2/m2 and the vegetation cover fraction (VCF) is 0.4 then the LAIv = LAI/VCF = 2/0.4 = 5. Note that the unit used for input to MEGAN2.1 and MEGAN3.2 pre-processor is m2 leaf area per 10 m2 surface area so if you generate LAIv in m2/m2 then multiply this by 10 to get m2 leaf area per 10 m2.
The following LAIv datasets have been used previously to drive MEGAN.
Global, monthly ~1-km LAIv for year 2003 (access here: doi.org/10.5281/zenodo.10521585). These files were created in 2005 for use in MEGAN 2.0 (Guenther et al. 2006). There are 12 netcdf format files (one for each month of 2003). The file naming convention is laiv2003MM where MM is month of the year. The values range from 0 to 60 and the units are m2 leaf area per 10 m2 surface area (which is the unit expected for the MEGANv2.1 preprocessor). These files were created in 2005 for use in MEGANv2 as described by Guenther et al. 2006 (doi.org/10.5194/acp-6-3181-2006). They are based on MODIS (MOderate Resolution Imaging Spectroradiometer) satellite LAI estimates described by Zhang et al JGR (2004) doi:10.1029/2004JD004720 and the vegetation cover fraction of Hansen et al. Earth Interactions 7: 1-15 (2003). Urban and wetland areas and other regions with missing LAI data in this MODIS database were assigned an LAIv based on the average for the surrounding region.
MEGAN LAIv inputs: 8-day, LAIv for US and North America for 2003 to 2013 (access here: doi.org/10.5281/zenodo.10525008)
There are 3 files
1-km LAIv for North America for year 2011 (filename: laiv2011.rar). These files were created in 2011 for use in MEGAN 2.1 for a project supported by the Western Governors' Association - Western Regional Air Partnership (WGA-WRAP). The 46 netcdf format files (one for each 8-day period) are combined into a single file (760MB zipped) and are based on MODIS (MOderate Resolution Imaging Spectroradiometer) satellite version 5 LAI product (MCD15A2.005) and the MEGAN2.1 total PFT cover fraction. They have a file naming convention of lainaYYYYDDD.nc where YYYY is year and DDD is day of year at the start of the 8 day period (goes from 001 to 361). The values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area which is the expected input for MEGAN2.1 data pre-processor.
1-km LAIv for North America for year 2013 (filename: laina2013.zip). These files were created in 2015 for use in MEGAN2.1 for a project supported by the Texas Air Quality Research Program (AQRP) . The 46 netcdf format files are combined in a single file ( 20MB zipped) and are based on MODIS (MOderate Resolution Imaging Spectroradiometer) satellite version 5 product (MCD15A2.005) and applied maximum green vegetation fraction from USGS which is also based on MODIS. They have a file naming convention of laina2008DDD.nc where DDD is day of year at the start of the 8 day period (goes from 001 to 361). The file is labeled 2008, even though it is 2013 data, so that it can directly be used in the MEGAN2.1 or MEGAN3.0 LAI preprocessor which has the year 2008 as the default LAI file name. The values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area which is the expected input for MEGAN2.1 data pre-processor.
5-km LAIv for USA for individual years from 2003 to 2013 (filename: laiv5kmUS2003to2013.zip). These files were created in 2015 for use in MEGAN2.1 for a project supported by the Texas Air Quality Research Program (AQRP) . The 506 netcdf format files are grouped into 11 zipped files (one for each year) each with 46 files (one for each 8-day period). Each 1-year dataset is 31MB zipped and are based on MODIS (MOderate Resolution Imaging Spectroradiometer) satellite version 5 product (MCD15A2.005) and maximum green vegetation fraction from USGS, which is also based on MODIS. They have a file naming convention of LAIv_YYYYDDD_WGS_5km.nc where YYYY is year and DDD is day of year at the start of the 8 day period (goes from 001 to 361). The LAI name needs to be changed from the default in the MEGAN preprocessor. The values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area which is the expected input for MEGAN2.1 data pre-processor.