Intercomparison of daytime stratospheric NO<sub>2</sub> satellite retrievals and model simulations

Abstract

Abstract. This paper evaluates the agreement between stratospheric NO 2 retrievals from infrared limb sounders (Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and High Resolution Dynamics Limb Sounder (HIRDLS)) and solar UV/VIS backscatter sensors (Ozone Monitoring Instrument (OMI), Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIA-MACHY) limb and nadir) over the [2005][2006][2007] period and across the seasons. The observational agreement is contrasted with the representation of NO 2 profiles in 3-D chemical transport models such as the Whole Atmosphere Community Climate Model (WACCM) and TM4. A conclusion central to this work is that the definition of a reference for stratospheric NO 2 columns formed by consistent agreement among SCIAMACHY, MIPAS and HIRDLS limb records (all of which agree to within 0.25 × 10 15 molecules cm −2 or better than 10 %) allows us to draw attention to relative errors in other data sets, e.g., (1) WACCM overestimates NO 2 densities in the extratropical lower stratosphere, particularly in the springtime and over northern latitudes by up to 35 % relative to limb observations, and (2) there are remarkable discrepancies between stratospheric NO 2 column estimates from limb and nadir techniques, with a characteristic seasonally and latitudinally dependent pattern. We find that SCIAMACHY nadir and OMI stratospheric columns show overall biases of −0.5 × 10 15 molecules cm −2 (−20 %) and +0.6 × 10 15 molecules cm −2 (+20 %) relative to limb observations, respectively. It is argued that additive biases in nadir stratospheric columns are not expected to affect tropospheric retrievals significantly, and that they can be attributed to errors in the total slant column density, related either to algorithmic or instrumental effects. In order to obtain accurate and long-term time series of stratospheric NO 2 , an effort towards the harmonization of currently used differential optical absorption spectroscopy (DOAS) approaches to nadir retrievals becomes essential, as well as their agreement to limb and ground-based observations, particularly now that limb techniques are giving way to nadir observations as the next generation of climate and air quality monitoring instruments pushes forth.

The version 3 OMI NO<sub>2</sub> standard product

“…The previous NASA algorithm (version SPv2) used the same NO 2 SCDs as DOMINO v2 , employing different approaches to the stratosphere-troposphere separation (STS) and AMF calculation (Bucsela et al, 2013). Both products were in general agreement and produced similar regional trends in tropospheric VCDs , but comparison of OMI stratospheric NO 2 VCDs (SPv2 and DOMINO v2) with other independent measurements revealed that they were overestimated by as much as 40 % over unpolluted regions (Belmonte Rivas et al, 2014). The overestimation was traced to the common DOAS retrieval step ( Van Geffen et al, 2015;Marchenko et al, 2015).…”

“…As expected, the known overestimation in V strat is reduced by a constant offset ∼ 0.6 × 10 15 molec. cm −2 in the new retrievals, bringing them into closer agreement with independent satellite Belmonte Rivas et al, 2014;Marchenko et al, 2015) and ground-based FTIR measurements (Sect. 5).…”

“…Satellite NO 2 data have been used as a proxy for (1) NO x emissions (van der A et al, 2017;Beirle et al, 2011;Boersma et al, 2015;Castellanos and Boersma, 2012;Curier et al, 2014;Ding et al, 2015;Duncan et al, 2014, de Foy et al, 2014Ghude et al, 2013;Jaeglé et al, 2004;Konovalov et al, 2006Konovalov et al, , 2010Lamsal et al, 2011;Liu et al, 2016;Lu et al, 2015;Lu and Streets, 2012;Martin et al, 2006;McLinden et al, 2016;Mijling and Van Der A, 2012;Richter et al, 2004Richter et al, , 2005Russell et al, 2012;Stavrakou et al, 2008;Streets et al, 2013;Vinken et al, 2014;Zhang et al, 2007;Zhou et al, 2012); (2) groundlevel NO 2 (Lamsal et al, 2008) and NO 2 deposition (Nowlan et al, 2014); and (3) emissions of co-emitted gases, including other pollutants, like particulate matter, and greenhouse gases, such as CO 2 (Berezin et al, 2013;Konovalov et al, 2016;Reuter et al, 2014).…”

OMI tropospheric NO<sub>2</sub> profiles from cloud slicing: constraints on surface emissions, convective transport and lightning NO<sub><i>x</i></sub>

“…The effect of errors in the stratospheric column is expected to be small, since stratospheric columns only show a small additive bias (Belmonte Rivas et al, 2014) that is bound to cancel via the pressure difference. One could also include temporal representativity errors from mismatched collocations between model and OMI clouds in this category, which Boersma et al (2015) estimate to lie around 10 %.…”

“…The stratospheric slant column arises from TM4 model stratospheric profiles assimilated to OMI observations over unpolluted areas (Belmonte Rivas et al, 2014). The belowcloud leaked component is defined as…”