An improved tropospheric NO<sub>2</sub> column retrieval algorithm for the Ozone Monitoring Instrument

Abstract

Abstract. We present an improved tropospheric nitrogen dioxide column retrieval algorithm (DOMINO v2.0) for OMI based on better air mass factors (AMFs) and a correction for across-track stripes resulting from calibration errors in the OMI backscattered reflectances. Since October 2004, NO 2 retrievals from the Ozone Monitoring Instrument (OMI), a UV/Vis nadir spectrometer onboard NASA's EOSAura satellite, have been used with success in several scientific studies focusing on air quality monitoring, detection of trends, and NO x emission estimates. Dedicated evaluations of previous DOMINO tropospheric NO 2 retrievals indicated their good quality, but also suggested that the tropospheric columns were susceptible to high biases (by 0-40 %), probably because of errors in the air mass factor calculations. Here we update the DOMINO air mass factor approach. We calculate a new look-up table (LUT) for altitude-dependent AMFs based on more realistic atmospheric profile parameters, and include more surface albedo and surface pressure reference points than before. We improve the sampling of the TM4 model, resulting in a priori NO 2 profiles that are better mixed throughout the boundary layer. We evaluate the NO 2 profiles simulated with the improved TM4 sampling as used in the AMF calculations and show that they are highly consistent with in situ NO 2 measurements from aircraft during the INTEX-A and INTEX-B campaigns in 2004 and 2006. Our air mass factor calculations are furCorrespondence to: Folkert Boersma (boersma@knmi.nl) ther updated by the implementation of a high-resolution terrain height and a high-resolution surface albedo climatology based on OMI measurements. Together with a correction for across-track stripes, the overall impact of the improved terrain height and albedo descriptions is modest (<5 %) on average over large polluted areas, but still causes significant changes locally. The main changes in the DOMINO v2.0 algorithm follow from the new LUT and the improved TM4 sampling that results in more NO 2 simulated aloft, where sensitivity to NO 2 is higher, and amount to reductions in tropospheric NO 2 columns of up to 20 % in winter, and 10 % in summer over extended polluted areas. We investigate the impact of aerosols on the NO 2 retrieval, and based on a comparison of concurrent retrievals of clouds from OMI and aerosols from MODIS Aqua, we find empirical evidence that OMI cloud retrievals are sensitive to the presence of scattering aerosols. It follows that an implicit correction for the effects of aerosols occurs through the aerosol-induced cloud parameters in DOMINO, and we show that such an empirical correction amounts to a 20 % AMF reduction in summer and ±10 % changes in winter over the eastern United States.

Quantitative bias estimates for tropospheric NO&lt;sub&gt;2&lt;/sub&gt; columns retrieved from SCIAMACHY, OMI, and GOME-2 using a common standard for East Asia

“…4), supporting the conclusion that differences among biases for all sensors are small, as found from the China case. Thus, our study confirms the hypothesized consistent quality KNMI products retrieved with the new method of Boersma et al (2011).…”

Accounting for the effects of surface BRDF on satellite cloud and trace-gas retrievals: a new approach based on geometry-dependent Lambertian equivalent reflectivity applied to OMI algorithms

“…Comparisons of the retrieved OCPs with those from the operational KNMI OMI O 2 -O 2 algorithm, OMCLDO2, have shown good agreement with a correlation coefficient of ∼ 0.99 for ECF > 0.2 when identical surface climatological LERs are used. The OMI NO 2 spectral fitting algorithm (OMNO2A) currently uses differential optical absorption spectroscopy (DOAS) to fit OMI-measured spectra in the wavelength range of 405-465 nm to estimate total (stratospheric and tropospheric) NO 2 SCDs (Boersma et al, 2011). The SCDs are then converted to NO 2 stratospheric and tropospheric VCDs using pre-calculated AMFs: VCD = SCD/AMF (Bucsela et al, 2013;Lamsal et al, 2014).…”

“…Many satellite UV-vis algorithms are based on the socalled mixed Lambert equivalent reflectivity (MLER) model, first introduced by Seftor et al (1994). For example, the MLER concept is currently used in most trace-gas (Boersma et al, 2011;Bucsela et al, 2013) and cloud (Acarreta et al, 2004; retrieval algorithms for the Ozone Monitoring Instrument (OMI), a Dutch-Finnish UVvis sensor (Levelt et al, 2006) onboard the NASA Aura satellite. The MLER model treats cloud and ground as horizontally homogeneous Lambertian surfaces and mixes them using the independent pixel approximation (IPA).…”

Comparison and evaluation of anthropogenic emissions of SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;x over China

“…But the top-down evaluations are subject to uncertainties from both satellite retrievals and model simulations. The uncertainties of retrieved individual NO 2 column of DOMINO v2.0 product are estimated at 1.0 × 10 15 molecules cm 2 , +25% mainly arising from the AMF calculation (Boersma et al, 2007(Boersma et al, , 2011. Because of the high 5 aerosol loadings in eastern China, the aerosol scattering and absorption have positive or negative effects on NO 2 retrieval, with a mean effect of 14% (Lin et al, 2014).…”

“…We use the tropospheric slant NO 2 columns data of DOMINO v2 (Dutch OMI NO 2 version 2) product accessed from the TEMIS website (Tropospheric Emission Monitoring Internet Service, http://www.temis.nl/) (Boersma et al, 2011). Slant columns are converted to vertical columns using the air mass factor (AMF), which is sensitive to the NO 2 vertical profile 20 (Palmer et al, 2001;Lamsal et al, 2010).…”