Intercomparison of SCIAMACHY and OMI tropospheric NO₂ columns: Observing the diurnal evolution of chemistry and emissions from space

Abstract

[1] Concurrent (August 2006) measurements of tropospheric NO 2 columns from OMI aboard Aura (1330 local overpass time) and SCIAMACHY aboard Envisat (1000 local overpass time) offer an opportunity to examine the consistency between the two instruments under tropospheric background conditions and the effect of different observing times. For scenes with tropospheric NO 2 columns <5.0 Â 10 15 molecules cm À2 , SCIAMACHY and OMI agree within 1.0-2.0 Â 10 15 molecules cm À2 , consistent with the detection limits of both instruments. We find evidence for a low bias of 0.2 Â 10 15 molecules cm À2 in OMI observations over remote oceans. Over the fossil fuel source regions at northern midlatitudes, we find that SCIAMACHY observes up to 40% higher NO 2 at 1000 local time (LT) than OMI at 1330 LT. Over biomass burning regions in the tropics, SCIAMACHY observes up to 40% lower NO 2 columns than OMI. These differences are present in the spectral fitting of the data (slant column) and are augmented in the fossil fuel regions and dampened in the tropical biomass burning regions by the expected increase in air mass factor as the mixing depth rises from 1000 to 1330 LT. Using a global 3-D chemical transport model (GEOS-Chem), we show that the 1000-1330 LT decrease in tropospheric NO 2 column over fossil fuel source regions can be explained by photochemical loss, dampened by the diurnal cycle of anthropogenic emissions that has a broad daytime maximum. The observed 1000-1330 LT NO 2 column increase over tropical biomass burning regions points to a sharp midday peak in emissions and is consistent with a diurnal cycle of emissions derived from geostationary satellite fire counts.

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

“…The GEOS-Chem simulation of NO x has been evaluated extensively with in situ and satellite observations and generally agrees to within 30 % of measured NO x Hudman et al, 2007;Boersma et al, 2008b). We conducted a simulation for the year 2005 and sample the model output between 13:00 and 15:00 local time for analysis of the OMI data.…”

Ground‐level nitrogen dioxide concentrations inferred from the satellite‐borne Ozone Monitoring Instrument

“…[13] Several previous studies have used GEOS-Chem to interpret in situ measurements of reactive nitrogen Wang et al, 2004;Hudman et al, 2004Hudman et al, , 2007Martin et al, 2006] as well as observations of tropospheric NO 2 columns from satellite instruments [Martin et al, 2003a[Martin et al, , 2004bJaeglé et al, 2005;Guerova et al, 2006;Sauvage et al, 2007;Wang et al, 2007bWang et al, , 2007aBoersma et al, 2008aBoersma et al, , 2008bBucsela et al, 2008]. GEOS-Chem simulations generally agree to within 30% of measured NO x , HNO 3 , and PAN over eastern North America Hudman et al, 2007;Singh et al, 2007] [15] Figure 1 shows seasonal mean tropospheric NO 2 columns from OMI and GEOS-Chem.…”

“…Retrievals of tropospheric NO 2 columns from GOME and SCIAMACHY have been used to demonstrate the close relationship between land surface NO x emissions and tropospheric NO 2 columns [Leue et al, 2001;Martin et al, 2003aMartin et al, , 2006Jaeglé et al, 2005;Zhang et al, 2007]. Observations of a weekly pattern in GOME tropospheric NO 2 columns with significant reductions on weekends [Beirle et al, 2003], diurnal variation in NO 2 columns driven by emissions and photochemistry [Boersma et al, 2008a], and a large increase in tropospheric NO 2 columns over eastern China inferred from GOME and SCIAMACHY [Richter et al, 2005;van der A et al, 2006] demonstrate the capability of observing air pollution from space. Petritoli et al [2004] and Ordóñez et al [2006] found a significant correlation between in situ NO 2 measurements and GOME tropospheric NO 2 columns.…”

Global Potential for Wind-Generated Electricity

“…GEOS data (including GEOS-5 and previous versions) have been used extensively in a variety of atmospheric chemistry investigations and have proved valuable not only in the interpretation of a wide range of atmospheric chemical measurements (6)(7)(8) but also in use of these measurements in an inverse mode to obtain improved estimates for emissions of important atmospheric species (9-11). The GEOS-5 simulation is employed here in a detailed study of the potential for globally distributed wind-generated electricity in 2006.…”