Community Modeling and Analysis System

Research and Development

Ongoing Research and Development | Model Development Guidelines

CMAS is keen on providing updates of current research efforts engaged by members of the community on the development and analysis of air quality modeling systems, including meteorology and emissions processing models. Research is focused on efforts to enhance the capability of air quality modeling systems to adequately address existing and future National Ambient Air Quality Standards (NAAQS). CMAS will provide leadership to bridge the gap between research and application needs by coordinating efforts among members of the community. Eventually, these research topics will lead to new research versions of CMAQ. Upon receiving new modules from the developers, CMAS will review the computational performance of the developed version and compare it to a benchmark case study provided by the developer to ensure accuracy, compilation, and compatibility among various computational platforms. CMAS will also review documentation that is provided by developers of the new material. CMAS will acknowledge the contribution of the developers of various modules.

CMAQ Review Process

Ongoing Research and Development

CMAS wants to hear about your CMAS-related research and/or model development! Please take a moment to provide us with some brief information about your CMAS-related research and/or model development, and we will post that information below. We also want your feedback on developing a vision for the next generation air quality modeling systems. Click on a title below to read more about the research.

  1. Efficient Radiative Transfer Calculations for Photolysis in CMAQ
  2. Extensions to chemically active coarse mode: Incorporation of sea-salt aerosols
  3. Incorporation of the Pleim-Xiu (PX) land surface model into the Weather Research and Forecasting (WRF) model

Extensions to chemically active coarse mode: Incorporation of sea-salt aerosols

In our on-going work, the modal approach used in models such as the CMAQ and the MAQSIP for the aerosol size distribution dynamics has been extended to represent the variability of the aerosol composition in each mode. The current method adapts the existing modal algorithm for the condensational growth of aerosol to the condensation/evaporation process. In our initial work, the bulk equilibrium composition has been determined using the ISOYYOPIA thermodynamic model. Any mass transferred to the aerosol from the gas phase for each aerosol species is partitioned between the modes according to the particle surface area. The interaction of sea salt particles with anthropogenic inorganic species provides a test case to evaluate the algorithm. Comparisons of model simulations with and without sea-salt emissions showed that the model was capable of capturing the displacement of Cl- by NO3- in the coarse mode, though magnitudes were small. Additionally, initial comparisons of model predictions with measurements from the IMPROVE network showed under prediction in fine aerosol Na+. Since Na+ is a primary species, the under predictions can be attributed to underestimation of emissions; analysis of deposition amount showed that the dry deposition sink is negligible as expected. In our initial implementation we used the approach of Monahan et al. (1986) and Gong et al. (1997) to calculate the production rate of sea-salt particles. This approach is appropriate for estimating open ocean aerosol fluxes. However, recent investigations report sea-salt aerosol concentrations in the surf zone to be 1-2 orders of magnitude higher than oceanic background (de Leeuw et al., 2000).

Thus, as a next step we propose to include the surf-zone source term of de Leeuw et al. (2000) in the emissions and then examine the sensitivity of model results to these emission changes.

We will also explore the extension of the model to include species specific diffusion coefficients in the condensation-evaporation algorithm. Currently, a single value is used for all species.

Following these activities, we will implement the hybrid approach for partitioning of the transferred mass among the modes. Following the general approach of Capaldo et al. (2000), we will use a dynamic mass transfer scheme for the coarse mode particles followed by a bulk equilibrium calculation for the mass transferred to the fine modes.

Observational data from the IMPROVE and CASTNet networks will be compared with modeled aerosol concentrations to evaluate these enhancements.

Since our initial approach has already been implemented in MAQSIP, we propose that additional algorithmic enhancements and testing be continued in that model. Once a stable method is in place, it will be ported to the CMAQ. Where possible the CMAQ modifications to incorporate sea-salt aerosol and coarse mode chemistry (e.g., include files, transport, cloud and aqueous chemistry modules) will be performed in parallel with the algorithm development.

Model Development Guidelines

CMAS has compiled a set of guidelines for new code development, based on experience with portability testing of the CMAQ-MADRID code, developed by AER under an EPRI contract. The code has just been released in stand-alone mode (April 2004). Download instructions are available through Software Downloads.

For more information about research opportunities in conjunction with the CMAS Center, please contact Sarav Arunachalam, CMAS Modeling Research Coordinator.