LAIv

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 MODIS or PROBA-A. This may require considerable effort if your domain covers a large region, in which case you may want to check to see if it has already been processed and available in a database such as the GLASS Leaf Area Index (LAI) product. Note that these LAI data must first be converted to LAIv (LAI divided by the vegetation cover fraction) before used in MEGAN.

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 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 datasets have been used previously to drive MEGAN. Any of the following files can be used with any version of MEGAN2 or 3.

  • Global, monthly ~1-km LAIv for year 2003 (MEGANLAIv05). These files were created in 2005 for use in MEGAN 2.0 (Guenther et al. 2006). There are 12 ARCGIS GRID format files that are grouped into 3 zipped groups (a: JAN to APR, b: MAY to AUG, c: SEP to DEC) of 4 files (each are ~900MB zipped). They are based on MODIS (MOderate Resolution Imaging Spectroradiometer) satellite data using the LAI estimates of Zhang et al JGR (2004) doi:10.1029/2004JD004720 and the vegetation cover fraction of Hansen et al. Earth Interactions 7: 1-15 (2003). They have a file naming convention of laiv2003MM where MM is month of the year. 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.

Note the values range from 0 to 6000 and the units are m2 leaf area per 1000 m2 ground area. These values should be divided by 100 to use with MEGAN2.1 or MEGAN3

  • 8-day, ~1-km LAIv for North America for year 2008 (MEGANLAIv11). 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). Note that urban and wetland areas and other regions with missing LAI data in this MODIS database are assigned an LAIv based on the average for the surrounding region.

Note the values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area.

  • 8-day, ~1-km LAIv for North America for year 2013 (MEGANLAIv15k1). 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 (http://landcover.usgs.gov/green_veg.php), 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 expects year 2008 in the file name (it is recognized that this is confusing and it will be changed in future versions of MEGAN). Note that urban and wetland areas and other regions with missing LAI data in this MODIS database are assigned an LAIv value of zero.

Note the values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area.

  • 8-day, 5-km LAIv for USA for individual years from 2003 to 2013 (MEGANLAIv15k5). 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 (http://landcover.usgs.gov/green_veg.php), 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). You will either need to change the name to "laina2008DDD" for use in the MEGAN LAI preprocessor or change the name that the preprocessor is expecting (it is recognized that this is confusing and it will be changed in future versions of MEGAN). Note that urban and wetland areas and other regions with missing LAI data in this MODIS database are assigned an LAIv value of zero.

Note the values range from 0 to 100 and the units are m2 leaf area per 10 m2 ground area.