Calculation of Sensitivity Coefficients for Individual Airport Emissions in the Continental U.S. using CMAQ-DDM/PM

Abstract

Fine particulate matter (PM2.5) is a federally-regulated air pollutant with well-known impacts on human health. The FAA's Destination 2025 program seeks to decrease aviation-related health impacts across the U.S. by 50% by the year 2018. Atmospheric models, such as the Community Multiscale Air Quality model (CMAQ), are used to estimate the atmospheric concentration of pollutants such as PM2.5. Sensitivity analysis of these models has long been limited to finite difference and regression-based methods, both of which require many computationally intensive model simulations to link changes in output with perturbations in input. Further, they are unable to offer detailed or ad hoc analysis for changes within a domain, such as changes in emissions on an airport-by-airport basis. In order to calculate the sensitivity of PM2.5 concentrations to emissions from individual airports, we utilize the Decoupled Direct Method in three dimensions (DDM-3D), an advanced sensitivity analysis tool recently implemented in CMAQ. DDM-3D allows calculation of sensitivity coefficients within a single simulation, eliminating the need for multiple model runs. However, while the output provides results for a variety of input perturbations in a single simulation, the processing time for each run is dramatically increased compared to simulations conducted without the DDM-3D module. Use of the XSEDE Stampede computing cluster allows us to calculate sensitivity coefficients for a large number of input parameters. This allows for a much wider variety of ad hoc aviation policy scenarios to be generated and evaluated than would be possible using other sensitivity analysis methods or smaller-scaled computing systems. We present a design of experiments to compute individual sensitivity coefficients for 139 major airports in the US, due to six different precursor emissions that form PM2.5 in the atmosphere. Simulations based on this design are currently in progress, with full results to be published at a later date.