||Research Triangle Park, NC 27711
The Computational Exposure Division is developing the next generation air quality modeling system. The AQ modeling system will include both meteorology models and atmospheric chemistry components and be capable of both global domains with seamless mesh refinement and more traditional limited area domains with uniform resolution structured grids. The design is for an AQ component that can flexibly couple to different meteorology models where 3-D advection of chemical species is modeled in the meteorology component and all other AQ related processes are modeled by the AQ component. Progress to date has focused on a prototype global AQ model where the Community Multiscale Air Quality (CMAQ) model is coupled to the Model for Prediction Across Scales (MPAS).
The objective of this research opportunity is to advance air quality modeling in any of several areas of meteorological, chemical, and physical process modeling, or in advancing numerical and computational modeling techniques for the next generation system. This research opportunity could contribute to one of the following areas of investigation:
(1) Cloud modeling: One important area of research is in the modeling of cloud processes related to both meteorology and chemistry. Currently, there are separate convective cloud models in the meteorology model (WRF or MPAS) and the chemical/AQ model (CMAQ). Thus, there is a research opportunity for the development of an integrated convective cloud model that includes the thermodynamics, convective dynamics, and microphysical processes of cloud and precipitation, as well as aqueous chemistry, gas and aerosol scavenging, and cloud-aerosol interactions. There has already been preliminary model development in this area with prototype implementation in the EPA's WRF-CMAQ coupled model. Further development and application in the NextGen system including the MPAS model is needed.
(2) Atmosphere-biosphere interactions: Another area of focus is improved atmosphere-biosphere connections, through explicit treatment of CO2 exchange. Currently, the WRF-CMAQ system considers CO2 concentration to be constant in space and time for the limited area and time periods involved in typical air quality simulations. However, while its chemical lifetime is extremely long, CO2 can have significant spatial and temporal variations resulting from source distributions that impact local radiation balance and ecosystem processes. Both radiation and ecosystem influences can directly and indirectly affect air quality concentrations and deposition. Additionally, technology- and emission-driven changes are likely to alter local CO2 gradients that can potentially modulate both local radiative budgets and CO2 uptake, which in turn can modulate local air quality. Representing such connections and interactions between the atmosphere and the biosphere will also require detailed representation of both the anthropogenic sources and ecosystem sources and sinks of CO2. Such a framework could then be used to model the feedbacks of CO2 controls on regional air quality (ozone and fine particulate matter), assess impacts of CO controls on local/regional CO2 concentrations, and model the atmosphere-biosphere linkages to assess feedbacks of CO2 on deposition of air pollution to vegetation.
(3) Atmospheric chemistry: Another area of possible research could relate to improving the representation of atmospheric chemistry in 3-D Air Quality Models. The next generation atmospheric modeling system can be expected to simultaneously address increasingly complex multi-pollutant issues which would require more detailed chemical mechanisms than those traditionally used. Methods are needed to efficiently translate and condense in a consistent manner explicit mechanisms such as the Master Chemical Mechanism (MCM) to condensed versions that can enable practical model applications. Such mechanisms would be expected to simultaneously represent atmospheric chemistry across multiple spatial and temporal scales as well as multiple phases (gas, aqueous, aerosol). It is likely that different condensations would be required for different applications. Research is thus needed to investigate and develop methods for updating, expanding and evaluating the types of chemical reactions that are available in research and regulatory models, allowing chemical interactions between gas, aqueous and aerosol phases, and deriving condensation rules that enable consistent condensations from explicit mechanisms to computationally efficient representations. This research could also include efficient incorporation of atmospheric chemistry and its numerical representation in the next generation atmospheric modeling system.
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Air quality modeling; Cloud processes; Atmosphere-biosphere interactions; Atmospheric chemistry; CMAQ; MPAS;