Airborne MAX‐DOAS measurements over California: Testing the NASA OMI tropospheric NO₂ product

Abstract

[1] Airborne Multi-AXis Differential Optical Absorption Spectroscopy (AMAX-DOAS) measurements of NO 2 tropospheric vertical columns were performed over California for two months in summer 2010. The observations are compared to the NASA Ozone Monitoring Instrument (OMI) tropospheric vertical columns (data product v2.1) in two ways: (1) Median data were compared for the whole time period for selected boxes, and the agreement was found to be fair (R = 0.97, slope = 1.4 ± 0.1, N = 10). (2) A comparison was performed on the mean of coincident AMAX-DOAS measurements within the area of the corresponding OMI pixels with the tropospheric NASA OMI NO 2 assigned to that pixel. The effects of different data filters were assessed. Excellent agreement and a strong correlation (R = 0.85, slope = 1.05 ± 0.09, N = 56) was found for (2) when the data were filtered to eliminate large pixels near the edge of the OMI orbit, the cloud radiance fraction was <50%, the OMI overpass occurred within 2 h of the AMAX-DOAS measurements, the flight altitude was >2 km, and a representative sample of the footprint was taken by the AMAX-DOAS instrument. The AMAX-DOAS and OMI data sets both show a reduction of NO 2 tropospheric columns on weekends by 38 ± 24% and 33 ± 11%, respectively. The assumptions in the tropospheric satellite air mass factor simulations were tested using independent measurements of surface albedo, aerosol extinction, and NO 2 profiles for Los Angeles for July 2010 indicating an uncertainty of 12%.

Chemical feedback effects on the spatial patterns of the NO&lt;sub&gt;x&lt;/sub&gt; weekend effect: a sensitivity analysis

“…We simulate the average 1 p.m. NO 2 column for 1-14 June 2008 with NEI2005 anthropogenic emissions (weekday) and the same model with an emission rate of 0.625 × E NO x −NEI2005 (weekend), well within the range of values determined previously (∼30-45 % reduction, Harley et al, 2005;Pollack et al, 2012;Oetjen et al, 2013). The first two days are used as spin-up.…”

Space-based retrieval of NO&lt;sub&gt;2&lt;/sub&gt; over biomass burning regions: quantifying and reducing uncertainties

“…This is consistent with the changes in retrieved NO 2 columns over polluted areas found in Russell et al (2011) when using highresolution NO 2 profiles. A study using in situ data from previous aircraft campaigns (e.g., INTEX-A, INTEX-B, PAVE) (see also more recently Oetjen et al, 2013) as well as from ground-based measurements of NO 2 columns (Ma et al, 2013;Rivera et al, 2013;Irie et al, 2012) would allow for a proper evaluation of the robustness of the above formula for different retrieval conditions (biomass burning, urban or remote areas) as well as to better characterize errors.…”

Evaluation of OMI operational standard NO&lt;sub&gt;2&lt;/sub&gt; column retrievals using in situ and surface-based NO&lt;sub&gt;2&lt;/sub&gt; observations

“…Tropospheric NO 2 column retrievals from satellites have been evaluated with in situ NO 2 profile measurements from aircraft (Heland et al, 2002;Martin et al, 2006;Boersma et al, 2008a;Bucsela et al, 2008Bucsela et al, , 2013Celarier et al, 2008;Hains et al, 2010), NO 2 column measurements from groundbased and airborne instruments Celarier et al, 2008;Brinksma et al, 2008;Kramer et al, 2008;Irie et al, 2008Irie et al, , 2012Wenig et al, 2008;Oetjen et al, 2013), in situ surface measurements (Schaub et al, 2006;Blond et al, 2007;Boersma et al, 2009;Lamsal et al, 2008Lamsal et al, , 2010, and a bottom-up NO x emission inventory (Lamsal et al, 2010). Aircraft offer precise in situ measurements within vertical spirals covering a spatial domain over a satellite field of view, but these are generally campaign-based experiments spanning only a few days to weeks and are limited by the need to extrapolate below the lowest measurement altitude (e.g.…”