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Application and Evaluation of MODIS LAI, fPAR, and Albedo Products in the WRFCMAQ System
Citation:
Pleim, Jon, R. Gilliam, C. Hogrefe, L. Ran, F. Binkowski, AND L. Band. Application and Evaluation of MODIS LAI, fPAR, and Albedo Products in the WRFCMAQ System. International Technical Meeting (ITM), Montpellier, FRANCE, May 06, 2015.
Impact/Purpose:
The National Exposure Research Laboratory’s Atmospheric Modeling Division (AMAD) conducts research in support of EPA’s mission to protect human health and the environment. AMAD’s research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation’s air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
Leaf area index (LAI), vegetation fraction (VF), and surface albedo are important parameters in the land surface model (LSM) for meteorology and air quality modeling systems such as WRF/CMAQ. LAI and VF control not only leaf to canopy level evapotranspiration flux scaling but also deposition of various atmospheric gases and particles. Albedo affects the surface energy budget and fluxes and photolysis rates in the air quality model. These parameters in WRF/CMAQ are specified in the land surface model (LSM) look-up tables by land use category and plant phenological dynamics are modeled using simple time and temperature dependent functions. Commonly used LSMs such as Noah and PX LSMs within WRF/CMAQ have simple canopy treatment with big-leaf empirical stomatal conductance functions as well as simple hydrology and snow processes. For year-long retrospective WRF/CMAQ simulations, these LSMs using simple canopy treatment with table prescribed surface representations, clearly show limitations in capturing seasonal landscape changes (e.g. phenology and albedo) and disturbances (e.g. fires, storm damages). The goal of this research is to improve land surface modeling in WRF/CMAQ by incorporating MODIS temporal LAI, fraction of absorbed Photosynthetically Active Radiation (fPAR, surrogate for VF) and albedo products for faithful surface representation. WRF is modified to incorporate MODIS LAI, fPAR, and albedo in the PX LSM for 2006 meteorology and CMAQ air quality simulations over the CONUS 12km domain. The simulated meteorology and air quality results will be analyzed with measurement data to demonstrate benefits and issues in using satellite LAI, fPAR and albedo data in the air quality modeling system.
