An Optimized North America MODIS Leaf Area Index (LAI) Dataset for Air Quality Modeling

Air Quality Research Division, Environment and Climate Change Canada,

4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada

Email: [e-mail]

Leaf Area Index (LAI) is used in air quality models for land surface processes and for calculating biogenic emissions. MODIS LAI product provided by NASA (https://modis.gsfc.nasa.gov/data/dataprod/mod15.php) has been widely used in the air quality modeling community for such purposes. However, limitations of MODIS LAI product have been seen for some geographic areas, particularly unreasonably low LAI over the evergreen needleleaf boreal forests in the northern hemisphere during wintertime due to snow cover and low sun angle. Missing retrievals over urban areas and areas with persistent cloud cover are also seen. Considerable efforts have been made to improve the MODIS LAI product.  However, some issues are still persistent, such as the very low LAI over boreal forests during wintertime. In order to solve these issues for supporting regional air quality modelling, the 8-day MODIS Collection 6 (C6) LAI product at 500m resolution (MCD15A2H) was examined for North America. Statistics were calculated by month and by land cover type defined in the “Land Cover Type 1” science data set (SDS) of the Collection 6 MODIS Land Cover (MCD12Q1) product. Comparisons with LAI calculated from the EPA’s Biogenic Emissions Landuse Database, version 4 (BELD4, https://www.epa.gov/air-emissions-modeling/biogenic-emission-sources) were also done (Zhang et al., 2020).  Based on the analysis, an updated monthly LAI dataset was calculated based on 1) 17-year (2003-2019) average of MODIS summer-time peak LAI, 2) fraction of evergreen and deciduous for each pixel from BELD4, and 3) monthly profiles of LAI for evergreen and deciduous vegetation species from MODIS LAI (Zhang et al., 2021).  This is the final LAI dataset for North America compiled using the 17 years of MODIS LAI product complemented by information from BELD4.

REFERENCES:

Zhang, J., M. D. Moran, P. A. Makar, and S. Kharol, 2020.  Examination of MODIS Leaf Area Index (LAI) Product for Air Quality Modelling.  19th CMAS Conference, 26-30 Oct., Virtual  [see https://www.cmascenter.org/conference/2020/slides/ZhangJ_MODIS_LAI_CMAS_2020.pdf].

Zhang, J., P. A. Makar, S. Kharol, M. D. Moran, and C. McLinden, 2021.  Examination and Processing of MODIS Leaf Area Index (LAI) Product for Air Quality Modelling.  2021 Meteorology and Climate - Modeling for Air Quality Conference, Sep 14-17, 2021, Virtual