Ozone profiles in the Baltimore-Washington region (2006-2011): satellite comparisons and DISCOVER-AQ observations

Anne M Thompson; Ryan M Stauffer; Sonya K Miller; Douglas K Martins; Everette Joseph; Andrew J Weinheimer; Glenn S Diskin

doi:10.1007/s10874-014-9283-z

Ozone profiles in the Baltimore-Washington region (2006-2011): satellite comparisons and DISCOVER-AQ observations

J Atmos Chem. 2015;72(3-4):393-422. doi: 10.1007/s10874-014-9283-z. Epub 2014 May 14.

Authors

Anne M Thompson¹, Ryan M Stauffer², Sonya K Miller², Douglas K Martins², Everette Joseph³, Andrew J Weinheimer⁴, Glenn S Diskin⁵

Affiliations

¹ Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802-5013 USA ; NASA/Goddard Space Flight Center, Code 614, Greenbelt, MD 20771 USA.
² Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, PA 16802-5013 USA.
³ Department of Physics and Astronomy, Howard University, 2355 Sixth Street NW, Washington, DC 20059 USA.
⁴ Atmospheric Chemistry Division, NCAR, Boulder, CO 80307 USA.
⁵ NASA Langley Research Center, MS 401B, Hampton, VA 23681 USA.

Abstract

Much progress has been made in creating satellite products for tracking the pollutants ozone and NO₂ in the troposphere. Yet, in mid-latitude regions where meteorological interactions with pollutants are complex, accuracy can be difficult to achieve, largely due to persistent layering of some constituents. We characterize the layering of ozone soundings and related species measured from aircraft over two ground sites in suburban Washington, DC (Beltsville, MD, 39.05 N; 76.9 W) and Baltimore (Edgewood, MD, 39.4 N; 76.3 W) during the July 2011 DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) experiment. First, we compare column-ozone amounts from the Beltsville and Edgewood sondes with data from overpassing satellites. Second, processes influencing ozone profile structure are analyzed using Laminar Identification and tracers: sonde water vapor, aircraft CO and NO_y. Third, Beltsville ozone profiles and meteorological influences in July 2011 are compared to those from the summers of 2006-2010. Sonde-satellite offsets in total ozone during July 2011 at Edgewood and Beltsville, compared to the Ozone Monitoring Instrument (OMI), were 3 % mean absolute error, not statistically significant. The disagreement between an OMI/Microwave Limb Sounder-based tropospheric ozone column and the sonde averaged 10 % at both sites, with the sonde usually greater than the satellite. Laminar Identification (LID), that distinguishes ozone segments influenced by convective and advective transport, reveals that on days when both stations launched ozonesondes, vertical mixing was stronger at Edgewood. Approximately half the lower free troposphere sonde profiles have very dry laminae, with coincident aircraft spirals displaying low CO (80-110 ppbv), suggesting stratospheric influence. Ozone budgets at Beltsville in July 2011, determined with LID, as well as standard meteorological indicators, resemble those of 4 of the previous 5 summers. The penetration of stratospheric air throughout the troposphere appears to be typical for summer conditions in the Baltimore-Washington region.

Keywords: Air quality; Aircraft chemical measurements; Baltimore pollution; Carbon monoxide; DISCOVER-AQ; Ozonesondes; Satellite validation; Stratosphere-troposphere exchange; Tropospheric ozone; Washington DC pollution.