Higher surface ozone concentrations over the Chesapeake Bay than over the adjacent land: Observations and models from the DISCOVER-AQ and CBODAQ campaigns

Abstract

h i g h l i g h t sObservations of ozone are higher over the Chesapeake Bay than areas upwind on land. Dry deposition rates, boundary layer depth, and photolysis play an integral role. Model resolution plays a role in determining accurate surface ozone concentrations. Observations of total reactive nitrogen are much lower than model simulations. a b s t r a c tAir quality models, such as the Community Multiscale Air Quality (CMAQ) model, indicate decidedly higher ozone near the surface of large interior water bodies, such as the Great Lakes and Chesapeake Bay. In order to test the validity of the model output, we performed surface measurements of ozone (O 3 ) and total reactive nitrogen (NO y ) on the 26-m Delaware II NOAA Small Research Vessel experimental (SRVx), deployed in the Chesapeake Bay for 10 daytime cruises in July 2011 as part of NASA's GEO-CAPE CBODAQ oceanographic field campaign in conjunction with NASA's DISCOVER-AQ air quality field campaign. During this 10-day period, the EPA O 3 regulatory standard of 75 ppbv averaged over an 8-h period was exceeded four times over water while ground stations in the area only exceeded the standard at most twice. This suggests that on days when the Baltimore/Washington region is in compliance with the EPA standard, air quality over the Chesapeake Bay might exceed the EPA standard. Ozone observations over the bay during the afternoon were consistently 10e20% higher than the closest upwind ground sites during the 10-day campaign; this pattern persisted during good and poor air quality days. A lower boundary layer, reduced cloud cover, slower dry deposition rates, and other lesser mechanisms, contribute to the local maximum of ozone over the Chesapeake Bay. Observations from this campaign were compared to a CMAQ simulation at 1.33 km resolution. The model is able to predict the regional maximum of ozone over the Chesapeake Bay accurately, but NO y concentrations are significantly overestimated. Explanations for the overestimation of NO y in the model simulations are also explored.

Measured and modeled CO and NO y in DISCOVER-AQ: An evaluation of emissions and chemistry over the eastern US

“…O 3 concentrations have decreased comparatively little, with multiple sites across the country exceeding NAAQS limits (Cooper et al, 2012;Fiore et al, 1998). This is particularly true in the Baltimore/Washington Region (BWR) which has significant surface O 3 throughout, especially over the Chesapeake Bay (Goldberg et al, 2014).…”

An evaluation of ozone dry deposition simulations in East Asia

“…1, the largest difference of the simulated dry deposition velocity appears on the continents, but the ozone concentrations difference is the greatest over the downwind ocean. We think that this feature is caused by the efficient ozone export from the polluted continent to the downwind oceans, where ozone accumulates (Goldberg et al, 2014). In addition, the ozone differences over the ocean may significantly be attributed to excessively high surface water resistance (low deposition loss) in the M3DRY relative to the Wesely.…”

CAMx ozone source attribution in the eastern United States using guidance from observations during DISCOVER‐AQ Maryland

“…Pennsylvania, Virginia, and Ohio contribute more than 4 ppbv each. Further discussion on the interstate transport of ozone is included in Goldberg et al [2015]. When changing model platforms, Maryland shows a slight rise in attribution (27.9 ppbv to 29.1 ppbv), while other states show small declines in ozone attribution (i.e., Virginia).…”

“…Many studies show an overestimate, by up to a factor of two, of total reactive oxidized nitrogen (NO y ) in regional air quality models compared to observations [Doraiswamy et al, 2009;Castellanos et al, 2011;Yu et al, 2012;Brioude et al, 2013;Anderson et al, 2014;Goldberg et al, 2014]. Some link the calculation of too much NO y to the overestimate of NO x emissions from area sources [Doraiswamy et al, 2009], while others link it to an overestimate of NO x emissions from commercial marine vessels [Brioude et al, 2013].…”

“…Global models can reflect changes in ozone resulting from control measures [e.g., Clifton et al, 2014;Rieder et al, 2015], especially for rural sites representative of regional atmospheric composition, but nonattainment is based on monitors with the highest readings. Urban-scale events, such as seen in Edgewood, MD, discussed below, require urban scale resolution of 12 km or better [e.g., Loughner et al, 2011;Goldberg et al, 2014].…”