CMAQv5.1 Biogenic Emissions (BEIS) Update
BEIS version 3.6.1
Biogenic volatile organic compounds (BVOC) participate in reactions that can lead to secondarily formed ozone and particulate matter (PM) impacting air quality and climate. BVOC emissions are important inputs to chemical transport models applied on local to global scales but considerable uncertainty remains in the representation of canopy parameterizations and emission algorithms from different vegetation species. The Biogenic Emission Inventory System (BEIS) has been used to support both scientific and regulatory model assessments for ozone and PM. This new version of BEIS v3.6.1 which includes updated input vegetation data and canopy model formulation for estimating leaf temperature and vegetation data on estimated BVOC. The Biogenic Emission Landuse Database (BELD) was revised to incorporate land use data from the Moderate Resolution Imaging Spectroradiometer (MODIS) land product and 2006 National Land Cover Database (NLCD) land coverage. Vegetation species data is based on the US Forest Service (USFS) Forest Inventory and Analysis (FIA) version 5.1 for years from 2002 to 2013 and US Department of Agriculture (USDA) 2007 census of agriculture data.
Revisions to Biogenic Volatile Carbon Emissions and Vegetation data in CMAQ v5.1
- Two layer vegetation canopy model
- Dynamic sunlight and shaded layers following the PAR attenuation of Weiss and Norman (1985)
- Integrated the photosynthetic active radiation response function in the canopy model following Niinemets et al. (2010) for both canopy layers.
- New leaf temperature algorithms
- The temperature functions for BVOC emissions used in BEIS and MEGAN were developed from leaf temperature observations taken at the same time as the BVOC flux measurements. WRF does not explicitly estimate leaf temperature observations and the two meter temperature has been used in BEIS while MEGAN uses a multi-layer canopy model with an estimation of the leaf temperature by iteratively solving for the leaf temperature using a leaf energy balance model. The MEGAN model is not compatible with the WRF or MM5 energy balance because the latent and sensible heat fluxes are taken as free variables and adjusted until a balance in incoming and outgoing energy is achieved. A simple two big leaf (a sun and shade leaf) following the BEIS radiation model was developed to solve for the leaf temperature for sun and shade leaves respectively adapting the energy balance in the Pennman-Montieth approximation from Campbell and Norman (1998) to solve for leaf temperature given the WRF estimated latent heat flux (Bash et al. 2015).
Development of Updated Vegetation Landuse Data
Updates were made to the Biogenic Emission Landuse Data (BELD v4) and emission factors for herbaceous wetlands to address overestimates of BVOCs at coastal sites and updated land use and vegetation species data originally dating from the 1990s with higher resolution (by aproximately factor of 1000) satellite data and survey observations from 2002-2012. The datasets contributing to BELD v4 are listed below.
- Using 2002, 2006, and 2011 National Land Cover Database (NLCD) plant functional types (CONUS) and year specific MODIS plant functional types (global)
- 2001 and 2005 USDA Census of Agriculture data
- USFS Forest Inventory Analysis (FIA) v5.1 data from 2002-2013
- NLCD data was further refined by spatially kriging FIA tree species to the respective NLCD plant functional type constrained by the NLCD canopy coverage (Bash et al. 2015).
Significance and Impact
This update in BEIS 3.6.1 and BELD v4 results in generally higher midday BVOC emissions compared with the previous version of BEIS and subsequently higher secondary organic aerosol concentrations. Baseline and updated BEIS 3.6.1 and BELD 4 emissions estimates were applied in Community Multiscale Air Quality Model (CMAQ) simulations with 4 km grid resolution and evaluated with measurements of isoprene and monoterpenes taken during multiple field campaigns in northern California. The updated canopy model coupled with improved land use and vegetation representation resulted in better agreement between CMAQ isoprene and monoterpene estimates compared with these observations.
Bash, J.O., Baker, K.R., Beaver, M.R., 2015, Evaluation of improved land use and canopy representation in BEIS v3.61 with biogenic VOC measurements in California, Geosci. Model Dev. Discuss. 8, 8117-8154, doi:10.5194/gmdd-8-8117-2015
Campbell, G. S. and Norman, J. M.: An introduction to environmental biophysics, Springer, 5 1998
Niinemets, Ü., Arneth, A., Kuhn, U., Monson, R. K., Peñuelas, J., and Staudt, M.: The emission factor of volatile isoprenoids: stress, acclimation, and developmental responses, Biogeosciences, 7, 2203–2223, doi:10.5194/bg-7-2203-2010, 2010.
Weiss, A. and Norman, J.: Partitioning solar radiation into direct and diffuse, visible and nearinfrared components, Agr. Forest Meteorol., 34, 205–213, 1985.
Jesse Bash, National Exposure Research Laboratory, U.S. EPA, George Pouliot, National Exposure Research Laboratory, U.S. EPA