An analysis is presented for both ground- and satellite-based retrievals of total column ozone and nitrogen dioxide levels from the Washington, D.C., and Baltimore, Maryland, metropolitan area during the NASA-sponsored July 2011 campaign of Deriving Information on Surface COnditions from Column and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ). Satellite retrievals of total column ozone and nitrogen dioxide from the Ozone Monitoring Instrument (OMI) on the Aura satellite are used, while Pandora spectrometers provide total column ozone and nitrogen dioxide A. J. Reed (*) : A. M. Thompson : D. E. Kollonige : D. K. Martins Department of Meteorology, The Pennsylvania State University, University Park, PA, USA e-mail: axr5145@psu.edu M. A. Tzortziou Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA M. A. Tzortziou : J. R. Herman : N. K. Abuhassan : A. Cede NASA Goddard Space Flight Center, Greenbelt, MD, USA J. R. Herman Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD, USA T. A. Berkoff Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, MD, USA N. K. Abuhassan LuftBlick, Kreith, Austria A. Cede School of Engineering, Morgan State University, Baltimore, MD, USA