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. Author manuscript; available in PMC: 2018 Apr 2.
Published in final edited form as: Atmos Chem Phys. 2016 Nov 1;16(21):13561–13577. doi: 10.5194/acp-16-13561-2016

Figure 6.

Figure 6

Vertical distribution of NO2 over the Southeast US during SEAC4RS (August-September 2013) and contributions to tropospheric NO2 columns measured from space by OMI. The top left panel shows median vertical profiles of NO2 number density measured from the SEAC4RS aircraft by the NOAA and UC Berkeley instruments and simulated by GEOS-Chem. The top right panel shows the fractional contribution of NO2 below a given altitude to the total tropospheric NO2 slant column measured by OMI, accounting for increasing sensitivity with altitude as determined from the retrieval scattering weights. The bottom left panel shows the median vertical profiles of the daytime [NO]/[NO2] molar concentration ratio in the aircraft observations (NOAA for NO and UC Berkeley for NO2) and in GEOS-Chem. Also shown is the ratio computed from NO-NO2-O3 photochemical steady state (PSS) as given by reactions (5)+(7) (blue) and including reaction (6) with doubled HO2 and RO2 concentrations above 8km (purple). The bottom right panel shows the median H2O2 profile from the model and from the SEAC4RS flights over the Southeast US. H2O2 was measured by the Caltech CIMS (see Figure 2).