Analyzing the Transition of Ozone Production from the VOC-Limited to the NOx-Limited Regime in the Maryland/DC/Northern Virginia Region

The nonlinear relationship between ozone production and NOx has major policy implications as cities continue to reduce emissions of NOx, CO, and other important ozone precursors. Observations between 1970 and 2015 demonstrate large improvements in air quality in Maryland/DC/Northern Virginia as a result of dramatic, policy-led reductions in NOx and CO. We use over four decades of ground-based data to verify that this area has transitioned from the VOC-limited to the NOx-limited regime of ozone production. The response of modeled ozone production to the reduction of ozone precursors, NOx and CO, is evaluated using the Framework for 0-D Atmospheric Modeling (F0AMv3) constrained to local ground-based measurements using multiple gas-phase chemical mechanisms. We also evaluate proposed definitions of the transition region of the ozone production regimes using NASA satellite data and model output.