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Diagnostic Evaluation: Indicator Metrics and Instrumented CMAQ investigations for Inorganic Fine Particle System
Research Programs
The indicator metric development and analysis is currently oriented towards the inorganic fine particle system because a key nonlinear response of interest to the client is the degree to which nitrate will replace sulfate as SO2 emissions are reduced. The inorganic fine-particle system is presently better understood and amenable to indicator development. The Gas Ratio of free ammonia to total nitrate is being tested as a indicator for diagnostic analysis of the state of the inorganic system through model sensitivity analyses. This will provide information about whether reductions in SO2 and NH3 will lead to decreases in total fine particles or if it may lead to nitrate replacement of sulfate aerosols. It can also be used to quantify how errors in fine particle inorganic state can translate into errors in the nonlinear response of nitrate replacing sulfate. This work will directly support the need to evaluate CMAQ's ability to predict responses to emission reductions, a key issue for regulatory applications of CMAQ. The diagnostic metric testing will be done with special data sets that include relevant, multiple species measured with high temporal resolution. Currently, data from the EPA Supersite Program, the SEARCH program and the ICARTT 2004 field study have potential to support diagnostic analyses.
Model Evaluation
Diagnostic Evaluation:
Indicator Metrics & Instrumented CMAQ Investiguations for Inorganic Fine Particle System
The instrumented model investigations will first work with the sulfate tracking version of CMAQ that is newly available from the development team and then work with the DDM-3D version of CMAQ that is being brought in-house from the Georgia Institute of Technology. Using these instrumented models will identify processes and inputs that directly contribute to the endpoint concentrations of interest under current and changing emission conditions.
To investigate the sensitivity of the inorganic aerosol predictions to the equilibrium model used, differences will be evaluated between ISORROPIA and AIM, the gold standard reference inorganic equilibrium model, through stand-alone model analyses. Differences will be examined in various portions of the response space (partitioning under current conditions) and examine differences noted regarding the nitrate replacement of sulfate (relative reduction factor nonlinear control strategy response).