Lagrangian Analysis of Ozone Production in the Baltimore–Washington Metropolitan Area Based on Air Parcel Trajectories and In Situ Airborne Measurements from the 2011 DISCOVER-AQ Campaign

Tropospheric ozone is a reactive trace gas with a short atmospheric lifetime that absorbs infrared energy and thus acts directly as a greenhouse gas that contributes strong radiative forcing on regional scales. It is also the dominant component of summertime photochemical smog, and at high levels, has deleterious effects on human health, ecosystems, and materials. The University of Maryland (UMD) Regional Atmospheric Measurement Modeling and Prediction Program (RAMMPP) strives to improve air quality in the Mid-Atlantic States and to elucidate contributions of such pollutants from regional transport versus local sources. The National Aeronautics and Space Administration (NASA) Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) project investigates the connection between column measurements and surface conditions to explore the efficacy of remote sensing observations in quantifying atmospheric composition and diagnosing air quality at ground level. During the 2011 DISCOVER-AQ field campaign, in situ measurements were performed along the Baltimore-Washington corridor from the NASA P3B aircraft. To provide regional context, measurements were also performed from the RAMMPP Cessna 402B aircraft over nearby airports. This work presents an analysis of ozone measurements made by the Ultraviolet (UV) Photometric Ambient Ozone Analyzer on the Cessna 402B and by the National Center for Atmospheric Research (NCAR) 4-Channel Chemiluminescence instrument on the P3B. Spatial and temporal patterns of ozone data are examined within the context of forward and backward air parcel trajectories calculated from 12-km North American Mesoscale (NAM) meteorological data using the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model and from a high resolution Weather Research and Forecasting (WRF) model simulation in order to empirically calculate localized ozone production rates and distinguish ozone resulting from regional transport versus ozone generated from local photochemistry. Preliminary examination of measurements from overlapping flight days and corresponding trajectories identifies 38 cases suitable for Lagrangian analysis, resulting in ozone production rates ranging up to 14 ppbv per hour and 4 ppbv per hour on average.