HR: 15:30h
AN: A53B-07    [Abstracts]
TI: A Computationally-Efficient Kinetic Approach for Gas/Particle Mass Transfer Treatments: Development, Testing, and 3-D Application
AU: * Hu, X
EM: xhu@ncsu.edu
AF: North Carolina State University, Room 5151, Jordan Hall, 2800 Faucette Drive, Raleigh, NC 27606, United States
AU: Zhang, Y
EM: yang_zhang@ncsu.edu
AF: North Carolina State University, Room 5151, Jordan Hall, 2800 Faucette Drive, Raleigh, NC 27606, United States
AB: The Weather Research and Forecast/Chemistry Model (WRF/Chem) that simulates chemistry simultaneously with meteorology has recently been developed for real-time forecasting by the U.S. National Center for Atmospheric Research (NCAR) and National Oceanic & Atmospheric Administration (NOAA). As one of the six air quality models, WRF/Chem with a modal aerosol module has been applied for ozone and PM_2.5 ensemble forecasts over eastern North America as part of the 2004 New England Air Quality Study (NEAQS) program (NEAQS-2004). Significant differences exist in the partitioning of volatile species (e.g., ammonium and nitrate) simulated by the six models. Model biases are partially attributed to the equilibrium assumption used in the gas/particles mass transfer approach in some models. Development of a more accurate, yet computationally- efficient gas/particle mass transfer approach for three-dimensional (3-D) applications, in particular, real-time forecasting, is therefore warranted. Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID) has been implemented into WRF/Chem (referred to as WRF/Chem-MADRID). WRF/Chem-MADRID offers three gas/particle partitioning treatments: equilibrium, kinetic, and hybrid approaches. The equilibrium approach is computationally-efficient and commonly used in 3-D air quality models but less accurate under certain conditions (e.g., in the presence of coarse, reactive particles such as PM containing sea-salts in the coastal areas). The kinetic approach is accurate but computationally-expensive, limiting its 3-D applications. The hybrid approach attempts to provide a compromise between merits and drawbacks of the two approaches by treating fine PM (typically < ~ 1 μm) with the equilibrium approach and coarse PM with the kinetic approach. A computationally-efficient kinetic gas/particle mass transfer approach in MADRID has recently been developed for 3-D applications based on an Analytical Predictor of Condensation (referred to as kinetic/APC). In this study, WRF/Chem-MADRID with the kinetic/APC approach will be further evaluated along with the equilibrium and hybrid approaches using a 19-day NEAQS-2004 episode (July 3-21 2004) over eastern North America. The NEAQS- 2004 episode provides an excellent testbed for WRF/Chem-MADRID with different gas/particle mass transfer treatments for several reasons. First, this region typically suffers a poor air quality with high ozone PM_2.5 episodes and large nitrogen deposition. Second, this region is characterized with complex topography (e.g., land vs. sea), meteorology (e.g., large-scale regional transport vs. local-scale sea-breeze), emissions (e.g., urban vs. natural), and co-existence of major PM species (e.g., sulfate/nitarte vs. sea-salt). Third, extensive gas and aerosol measurements are available from International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) field study. The model outputs will be evaluated using observations from ICARTT and other routine monitoring networks such as Aerometric Information Retrieval Now (AIRNow) and Speciation Trends Network (STN). The effect of different gas/particle mass transfer approaches on simulated gas and aerosol concentrations will be examined along with a comparison of their computational costs. The gas/particle mass transfer approach that provides the best compromise between numerical accuracy and computational efficiency will be recommended for 3-D research-grade and real-time forecasting applications.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly