Grantee Research Project Results
2000 Progress Report: Development and Application of an Air Quality Modeling System with Integrated Meteorology, Chemistry, and Emissions
EPA Grant Number: R825388Title: Development and Application of an Air Quality Modeling System with Integrated Meteorology, Chemistry, and Emissions
Investigators: Xiu, Aijun , Hanna, Adel , Coats, Carlie J. , Mathur, Rohit
Current Investigators: Xiu, Aijun , Mathur, Rohit , Hanna, Adel , Coats, Carlie J.
Institution: MCNC / North Carolina Supercomputing Center
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1996 through September 30, 1999
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $372,830
RFA: Exploratory Research - Air Engineering (1996) RFA Text | Recipients Lists
Research Category: Land and Waste Management , Air , Safer Chemicals
Objective:
The overall goal of this project is to develop a computationally efficient, fully-integrated, and physically and numerically consistent atmospheric dynamics and chemistry modeling system, that can be used to study the distribution, production, and accumulation of atmospheric pollutants on regional scales. The specific objectives of this research are to: (1) incorporate atmospheric pollutant transport/transformation/deposition calculations into a state-of-the-science meteorological model; (2) reduce uncertainty, redundancy, and inconsistency arising from separation of the three main interrelated components (meteorology, emissions, chemistry); (3) maintain flexibility and modularity to facilitate incorporation of alternate/improved process and numerical representations; (4) apply the integrated air quality modeling system to several field studies and compare and evaluate model performance with measurements made during the field programs, and conduct detailed analysis of model results; and (5) use the integrated model as a platform to assess feedbacks between meteorology and chemistry through incorporating a methodology for the radiative feedback of atmospheric sulfate aerosols and evaluating the effect of this feedback on meteorology and air quality.Progress Summary:
In this project we have developed, tested, and applied a modular, physically and numerically consistent, fully integrated regional-scale atmospheric dynamics and chemistry modeling system. The modeling system is based on further development and refinement of three existing models: the MM5 meteorological model, the Multiscale Air Quality Simulation Platform (MAQSIP) atmospheric chemistry/transport model, and the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system. In developing the integrated model, we have included directly into the MM5, modules to represent transport, chemistry, and deposition of various chemical species (gas and aerosol), such that the dynamics and chemistry related model calculations are fully synchronized. The integration of the dynamics and chemistry calculations in a consistent modeling framework also enables the investigation of the potential effects and feedbacks of radiatively important trace species. A variety of test cases involving both tracer transport and detailed treatment of tropospheric chemical pathways have been conducted. We also compared the differences in the online and offline mode of the chemistry calculations. The integrated model has been applied over the eastern United States.
To facilitate the coupling of meteorological and chemical tracer transport and chemistry calculations in the integrated model, a Meteorology CouPLing module (MCPL) that fits directly into MM5 has been developed (Coats et al., 1998). MCPL is designed for extremely easy insertion into the MM5 source code and is callable at a variety of times scales from the MM5 advection-step frequency on up (Coats, et al., 1998, http://envpro.ncsc.org/EDSS/ppar/ mcpl.html). MCPL is principally controlled by environmental variables and by ASCII tables and can be configured to write data either to buffered files (for online integrated chemistry calculations) or to files on disk (for offline chemistry calculations).
To assess the radiative feedback of aerosols, we have used the CCM2 radiation
scheme in MM5 (Grell, et al., 1994) for radiation calculations. In the CCM2
radiation scheme, the solar spectrum is divided into 18 discrete spectral
intervals and the ?Eddington
approximation is used to calculate solar absorption. The
-Eddington approximation allows for gaseous
absorption by O3, CO2, O2, and H2O and scattering and absorption of
cloud water droplet. The optical properties of the cloud droplets are
represented in terms of liquid water path, effective radius, and fractional
cloud coverage. We included into MM5 the radiative forcing of aerosols simulated
by MAQSIP by applying the Mie approximation to calculate aerosol scattering and
extinction efficiencies using effective radius and refractive index. Optical
properties of aerosols (single scattering albedo, asymmetry parameter, and
optical depth) are calculated using extinction, scattering and absorption cross
sections, and effective radius and number concentration. Then the optical
properties of aerosols are included in the
-Eddington approximation for shortwave radiation calculation.
We applied the integrated model to a domain over the eastern United States with 36 km resolution grid in horizontal and 21 layers between surface and 100 mb in vertical. The episode covers a 10 days period in the summer of 1995, which is July 10-15, 1995. The MM5 was run in a one-way nested mode wherein a coarse domain with horizontal resolution of 108 km was used for providing hourly boundary conditions for the nested fine domain with horizontal resolution of 36 km. The integrated model domain is located within the 36 km MM5 domain; this set-up is essential for specifying meteorological variables at the boundary of the integrated model. Chemistry/transport calculations are coupled with the dynamical calculation at every MM5 time step (i.e., 100 seconds for this case). The CCM2 radiation scheme with or without aerosol feedback is called every hour but can be called more frequently. The analysis focuses on the results from the last seven days of simulation which have less influence of the initial conditions. In our current testing and simulations with the integrated model, we use input emissions computed in an offline mode.
Refractive index of aerosols is the particle optical property relative to the atmosphere and is used in the Mie scattering calculations for the radiative properties of aerosols. The refractive index is defined as a complex variable, in which the real part (Rr) and the imaginary part (Ri) of the refractive index represents the scattering and absorbing components respectively. In the sensitivity tests of the refractive index in the integrated modeling system, we ran the model in four different ways with: (1) no radiative feedback of aerosols; (2) radiative feedback of aerosols and Rr = 1.5 and Ri = 0; (3) radiative feedback of aerosols and the real part of the refractive index has the effect of aerosol water fraction (WFRAC) Rr = 1.5 0.27 WFRAC and Ri = 0; and (4) radiative feedback of aerosols and both the real part and the imaginary part of the refractive index has the effect of aerosol water fraction Rr = 1.5 0.27 WFRAC and Ri = 0.01 0.01 WFRAC.
The comparison of the model results with observations suggest the model reasonably well captures spatial gradients in concentrations. The case study and sensitivity tests show that the direct radiative effects of aerosols tend to cool the earth/atmosphere system due to the scattering of shortwave radiation, as shown by previous studies (refer to Figure 2). The use of the integrated meteorology-chemistry model simulates the effect of the aerosol feedback on the planetary boundary layer (PBL) height which is generally reduced due to less surface heat fluxes and the aerosol size parameters seem to play an important role in forming the regional feedback pattern.
References:
Coats CJ, Jr., McHenry JN, Lario-Gibbs A, Peters-Lidard CD. MCPL(): A drop-in MM5-V2 module suitable for coupling MM5 to parallel environmental models; with lessons learned for the design of the weather research and forecasting (WRF) model. In: Preprints of the Eighth PSU/NCAR Mesoscale Model Users' Workshop, Mesoscale and Microscale Meteorology Division, National Center for Atmospheric Research, Boulder, CO, 1998, pp. 117-20.
Grell GA, Dudhia J, Stauffer DR. A description of the fifth-generation Penn State/NCAR mesoscale model (MM5). NCAR Technical Note NCAR/TN-398+STR, 1994.
Future Activities:
We will incorporate the latest version of the MM5 modeling system (e.g., MM5 Version 3) into the integrated modeling system. We will link the ozone concentration simulated by CCM with the MM5's CCM2 radiation calculation rather than using the prescribed value. We will introduce the aerosol effects on the actinic fluxes and consequently the photolysis rate of various chemical species and further apply the integrated model for regional climate research.Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
meteorology, radiative feedback, chemistry, coupled model, tropospheric, aerosol, ozone., RFA, Scientific Discipline, Air, particulate matter, air toxics, Environmental Chemistry, Environmental Monitoring, tropospheric ozone, Engineering, meteorology, air quality models, ambient air, emission-based modeling, ozone, chemical composition, air pollution models, air quality data, atmospheric aerosols, atmospheric aerosol particles, atmospheric chemistry, engineering modelsRelevant Websites:
http://www.envpro.ncsc.org/projects/integrated/index.html![Exit EPA icon](https://www.epa.gov/ncer/images/exit.gif)
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.