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Book ; Online: Global, regional and seasonal analysis of total ozone trends derived from the 1995–2020 GTO-ECV climate data record

Coldewey-Egbers, Melanie / Loyola, Diego G. / Lerot, Christophe / Roozendael, Michel

eISSN: 1680-7324

2022

Abstract: In this study we present an updated perspective on near-global total ozone trends for the period 1995–2020. We use the GOME-type Total Ozone Essential Climate Variable (GTO-ECV) satellite data record which has been extended and generated as part of the ... ...

Abstract	In this study we present an updated perspective on near-global total ozone trends for the period 1995–2020. We use the GOME-type Total Ozone Essential Climate Variable (GTO-ECV) satellite data record which has been extended and generated as part of the European Space Agency’s Climate Change Initiative (ESA-CCI) and European Union Copernicus Climate Change Service (EU-C3S) ozone projects. The focus of our work is the analysis of regional patterns in the ozone trend as well as the investigation of its seasonal dependence. In the Southern Hemisphere we found regions that indicate statistically significant positive trends increasing from 0.6 ± 0.5 % decade −1 in the subtropics to 1.0 ± 0.9 % decade −1 in the middle latitudes and 2.8 ± 2.6 % decade −1 in the latitude band 60°–70° S. In the middle latitudes of the Northern Hemisphere the trend exhibits distinct regional patterns, i.e. latitudinal and longitudinal structures. Significant positive trends (∼1.5 ± 1.0 % decade −1 ) over the North Atlantic region as well as negative trends (−1.0 ± 1.0 % decade −1 ) over Eastern Europe were found. Moreover, these trends indicate a correlation with long-term changes in tropopause pressure. Total ozone trends in the tropics are not significant. Regarding the seasonal dependence of the trends we found only very small variations over the course of the year. However, we identified different behavior depending on latitude. In the latitude band 40°–70° N the positive trend maximizes in boreal winter from December to February. In the middle latitudes of the Southern Hemisphere (35°–50° S) the trend is maximum from March to May. Further south toward the high latitudes (55°–70° S) the trend denotes a relatively strong seasonal cycle which varies from 2 % decade −1 in December and January to 3.8 % decade −1 in June and July.
Subject code	333 ; 550
Language	English
Publishing date	2022-01-17
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Troposphere – stratosphere integrated BrO profile retrieval over the central Pacific Ocean

Koenig, Theodore K. / Hendrick, Francois / Kinnison, Douglas / Lee, Christopher F. / Roozendael, Michel / Volkamer, Rainer

eISSN:

2023

Abstract: Bromine is a reactive trace element in the atmosphere, that destroys ozone, oxidizes mercury, modifies oxidative capacity and affects the lifetime of climate-active gases (e.g., methane). About 75 % of tropospheric ozone and methane is destroyed in the ... ...

Abstract	Bromine is a reactive trace element in the atmosphere, that destroys ozone, oxidizes mercury, modifies oxidative capacity and affects the lifetime of climate-active gases (e.g., methane). About 75 % of tropospheric ozone and methane is destroyed in the tropics, primarily in the lower free troposphere, where bromine monoxide (BrO) radical measurements are generally scarce. The few available aircraft observations find BrO is variable, and measurements in different compartments of the atmosphere are not easily reconciled. While zenith-sky DOAS measurements provide long-term records of the stratospheric O 3 and NO 2 abundances, autonomous MAX-DOAS placed at remote mountaintop observatories (MT-DOAS) provides cost effective and maximally sensitive access to probe the lower free troposphere, a climate-relevant yet understudied region of the atmosphere. Here we describe and evaluate an innovative full-atmosphere BrO and formaldehyde (HCHO) profile retrieval algorithm using MT-DOAS measurements at Mauna Loa Observatory (19.536° N; 155.577° W; 3401 m asl) during two case study days, characterized by the absence (26 Apr 2017, base case) and presence of a Rossby Wave breaking double tropopause (29 Apr 2017, RW-DT case) above Big Island, Hawaii. The full atmosphere retrieval is based on time-dependent optimal estimation, and simultaneously inverts 190+ individual BrO (and formaldehyde, HCHO) SCDs (slant column densities, SCD = dSCD + SCD Ref ) from solar stray light spectra measured in the zenith and off-axis geometries at high and low solar zenith angle (92º > SZA > 30º) to derive BrO concentration profiles with 7.5 degrees of freedom (DoF) from 1.9 to 35 km altitude. Stratospheric BrO vertical columns are near identical on both days (VCD = (1.5 ± 0.2) ×10 13 molec cm -2 ), and the stratospheric BrO profile peaks at a lower altitude during the Rossby wave breaking event (1.6 – 2.0 DoFs). Tropospheric BrO VCDs increase from (0.70 ± 0.14) ×10 13 molec cm -2 (base case) to (1.00 ± 0.14) ×10 13 molec cm -2 (RW-DT), owing ...
Subject code	333
Language	English
Publishing date	2023-11-07
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Constraining industrial ammonia emissions using hyperspectral infrared imaging

Noppen, Lara / Clarisse, Lieven / Tack, Frederik / Ruhtz, Thomas / Merlaud, Alexis / Van Damme, Martin / Van Roozendael, Michel / Schuettemeyer, Dirk / Coheur, Pierre

Remote Sensing of Environment. 2023 June, v. 291 p.113559-

2023

Abstract: Atmospheric emissions of reactive nitrogen in the form of nitrogen dioxide (NO2) and ammonia (NH3) worsen air quality and upon deposition, dramatically affect the environment. Recent infrared satellite measurements have revealed that NH3 emitted by ... ...

Abstract	Atmospheric emissions of reactive nitrogen in the form of nitrogen dioxide (NO2) and ammonia (NH3) worsen air quality and upon deposition, dramatically affect the environment. Recent infrared satellite measurements have revealed that NH3 emitted by industries are an important and underestimated emission source. Yet, to assess these emissions, current satellite sounders are severely limited by their spatial resolution. In this paper, we analyse measurement data recorded in a series of imaging surveys that were conducted over industries in the Greater Berlin area (Germany). On board the aircraft were the Telops Hyper-Cam LW, targeting NH3 measurements in the longwave infrared at a resolution of 4 m and the SWING+ spectrometer targeting NO2 measurements in the UV–Vis at a resolution of 180 m. Two flights were carried out over German’s largest production facility of synthetic NH3, urea and other fertilizers. In both cases, a large NH3 plume was observed originating from the factory. Using a Gaussian plume model to take into account plume rise and dispersion, coupled with well-established radiative transfer and inverse methods, we retrieve vertical column densities. From these, we calculate NH3 emission fluxes using the integrated mass enhancement and cross-sectional flux methods, yielding consistent emissions of the order of 2200 t yr⁻¹ for both flights, assuming constant fluxes across the year. These estimates are about five times larger than those reported in the European Pollutant Release and Transfer Register (E-PRTR) for this plant. In the second campaign, a co-emitted NO2 plume was measured, likely related to the production of nitric acid at the plant. A third flight was carried out over an area comprising the cities of Staßfurt and Bernburg. Several small NH3 plumes were seen, one over a production facility of mineral wool insulation, one over a sugar factory and two over the soda ash plants in Staßfurt and Bernburg. A fifth and much larger plume was seen to originate from the sedimentation basins associated with the soda ash plant in Staßfurt, indicating rapid volatilization of ammonium rich effluents. We use the different measurement campaigns to simulate measurements of Nitrosat, a potential future satellite sounder dedicated to the sounding of reactive nitrogen at a resolution of 500 m. We demonstrate that such measurements would allow accurately constraining emissions in a single overpass, overcoming a number of important drawbacks of current satellite sounders.
Keywords	air quality ; aircraft ; ammonia ; ammonium ; environment ; flight ; insulating materials ; models ; nitric acid ; nitrogen ; nitrogen dioxide ; pollutants ; radiative transfer ; satellites ; spectrometers ; sugar industry ; synthetic fibers ; urea ; volatilization ; Germany ; Hyperspectral infrared ; Aircraft measurements ; Emission fluxes ; Fertilizer production ; Soda ash ; Nitrosat
Language	English
Dates of publication	2023-06
Publishing place	Elsevier Inc.
Document type	Article ; Online
ZDB-ID	431483-9
ISSN	0034-4257
ISSN	0034-4257
DOI	10.1016/j.rse.2023.113559
Database	NAL-Catalogue (AGRICOLA)

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Article: The effect of considering polar vortex dynamics in the validation of satellite total ozone observations

Paschou, Peristera / Balis, Dimitrios / Koukouli, Maria-Elissavet / Lerot, Christophe / Van Roozendael, Michel

Atmospheric research. 2020 July 01, v. 238

2020

Abstract: The main aim of this paper is to demonstrate the magnitude in which validation results of space-based total ozone column, TOC, measurements are affected by the location of the polar vortex. Potential Vorticity is used as an indicator to determine the ... ...

Abstract	The main aim of this paper is to demonstrate the magnitude in which validation results of space-based total ozone column, TOC, measurements are affected by the location of the polar vortex. Potential Vorticity is used as an indicator to determine the polar vortex's boundary and surface area, provided by ERA-Interim reanalysis datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF). The total ozone measurements that were examined fall within the hemispherical winter-spring period, focusing on middle and high latitudes on both hemispheres. The space-based total ozone data produced by the GODFIT (GOME-type Direct FITting) v4 algorithm as applied to the OMI/Aura, GOME-2/Metop-A and Metop-B observations, part of the European Space Agency's Ozone Climate Change Initiative project, are compared to TOC measurements from Brewer and Dobson spectrophotometers archived at the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) repository. The satellite-to-ground collocations were classified depending on whether both satellite and ground-based measurements are inside or outside the polar vortex (matched) or one measurement is inside whereas the other one is outside the polar vortex (mismatched). It is shown that the matched cases present an improved agreement between satellite and ground TOC measurements compared to the mismatched cases. Considering all examined stations for GOME2-A, GOME2-B, and OMI, the mean bias for the mismatched cases was found to be 2.22 ± 0.4%, 1.84 ± 0.57%, and 1.93 ± 0.39% respectively, while for the matched cases was found to be 1.46 ± 0.17%, 1.69 ± 0.22%, 1.7 ± 0.19% respectively. For the three satellite sensors, the mismatched cases do not exceed 3.3% of the total available collocations per station during the winter-spring period between years 2007 and 2017, where applicable. Hence, on a global scale, the exclusion of mismatched collocated measurements does not cause significant changes and the resulting impact on the validation of the satellite TOCs is small. However, when considering single stations consistently affected by the polar vortex, we conclude that mismatched cases should be excluded from the comparisons.
Keywords	algorithms ; climate change ; data collection ; latitude ; ozone ; satellites ; spectrophotometers ; surface area ; ultraviolet radiation ; weather forecasting
Language	English
Dates of publication	2020-0701
Publishing place	Elsevier B.V.
Document type	Article
ISSN	0169-8095
DOI	10.1016/j.atmosres.2020.104870
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Assessment of NO

Roșu, Adrian / Constantin, Daniel-Eduard / Voiculescu, Mirela / Arseni, Maxim / Roșu, Bogdan / Merlaud, Alexis / Van Roozendael, Michel / Georgescu, Puiu Lucian

International journal of environmental research and public health

2021 Volume 18, Issue 2

Abstract: This study investigates changes in pollution associated with the lockdown period caused by the COVID-19 pandemic in Galati (45.43° N, 28.03° E), a Romanian city located in the southeast of Romania. The study is focused on nitrogen dioxide ( ... ...

Abstract	This study investigates changes in pollution associated with the lockdown period caused by the COVID-19 pandemic in Galati (45.43° N, 28.03° E), a Romanian city located in the southeast of Romania. The study is focused on nitrogen dioxide (NO
MeSH term(s)	Air Pollutants/analysis ; Air Pollution/analysis ; COVID-19/epidemiology ; Cities ; Environmental Monitoring ; Humans ; Nitrogen Dioxide/analysis ; Pandemics ; Romania
Chemical Substances	Air Pollutants ; Nitrogen Dioxide (S7G510RUBH)
Language	English
Publishing date	2021-01-11
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2175195-X
ISSN	1660-4601 ; 1661-7827
ISSN (online)	1660-4601
ISSN	1661-7827
DOI	10.3390/ijerph18020544
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: Investigation of Aerosol Peak Height Effect on PBL and Volcanic Air Mass Factors for SO2 Column Retrieval from Space-Borne Hyperspectral UV Sensors

Choi, Wonei / Yang, Jiwon / Lee, Hanlim / Roozendael, Michel Van / Koo, Ja-Ho / Park, Junsung / Kim, Daewon

Remote Sensing. 2020 May 04, v. 12, no. 9

2020

Abstract: We investigate the effects of aerosol peak height (APH) and various parameters on the air mass factor (AMF) for SO₂ retrieval. Increasing aerosol optical depth (AOD) leads to multiple scattering within the planetary boundary layer (PBL) and an increase ... ...

Abstract	We investigate the effects of aerosol peak height (APH) and various parameters on the air mass factor (AMF) for SO₂ retrieval. Increasing aerosol optical depth (AOD) leads to multiple scattering within the planetary boundary layer (PBL) and an increase in PBL SO₂ AMF. However, under high AOD conditions, aerosol shielding effects dominate, which causes the PBL SO₂ AMF to decrease with increasing AOD. The height of the SO₂ layer and the APH are found to significantly influence the PBL SO₂ AMF under high AOD conditions. When the SO₂ and aerosol layers are of the same height, aerosol multiple scattering occurs dominantly within the PBL, which leads to an increase in the PBL SO₂ AMF. When the APH is greater than the SO₂ layer height, aerosol shielding effects dominate, which decreases the PBL SO₂ AMF. When the SO₂ and aerosol layers are of the same height under low AOD and solar zenith angle (SZA) conditions, increased surface reflectance is found to significantly increase the PBL SO₂ AMF. However, high AOD dominates the surface reflectance contribution to PBL SO₂ AMF. Under high SZA conditions, Rayleigh scattering contributes to a reduction in the light path length and PBL SO₂ AMF. For volcanic SO₂ AMF, high SZA enhances the light path length within the volcanic SO₂ layer, as well as the volcanic SO₂ AMF, because of the negligible photon loss by Rayleigh scattering at high altitudes. High aerosol loading and an APH that is greater than the SO₂ peak height lead to aerosol shielding effects, which reduce the volcanic SO₂ AMF. The SO₂ AMF errors are also quantified as a function of uncertainty in the input data of AOD, APH, and surface reflectance. The SO₂ AMF sensitivities and error analysis provided here can be used to develop effective error reduction strategies for satellite-based SO₂ retrievals.
Keywords	aerosols ; air ; altitude ; photons ; reflectance ; remote sensing ; satellites ; sulfur dioxide ; troposphere ; uncertainty
Language	English
Dates of publication	2020-0504
Publishing place	Multidisciplinary Digital Publishing Institute
Document type	Article
ZDB-ID	2513863-7
ISSN	2072-4292
ISSN	2072-4292
DOI	10.3390/rs12091459
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Evolution of SO

Constantin, Daniel-Eduard / Bocăneala, Corina / Voiculescu, Mirela / Roşu, Adrian / Merlaud, Alexis / Roozendael, Michel Van / Georgescu, Puiu Lucian

International journal of environmental research and public health

2020 Volume 17, Issue 10

Abstract: The aim of this paper is to investigate the evolution of ... ...

Abstract	The aim of this paper is to investigate the evolution of SO
MeSH term(s)	Air Pollutants/analysis ; Air Pollution ; Environmental Monitoring ; Europe ; Nitric Oxide/analysis ; Power Plants ; Sulfur Dioxide/analysis
Chemical Substances	Air Pollutants ; Sulfur Dioxide (0UZA3422Q4) ; Nitric Oxide (31C4KY9ESH)
Language	English
Publishing date	2020-05-21
Publishing country	Switzerland
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	1660-4601
ISSN (online)	1660-4601
DOI	10.3390/ijerph17103630
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: Updated merged SAGE-CCI-OMPS+ dataset for the evaluation of ozone trends in the stratosphere

Sofieva, Viktoria F. / Szelag, Monika / Tamminen, Johanna / Arosio, Carlo / Rozanov, Alexei / Weber, Mark / Degenstein, Doug / Bourassa, Adam / Zawada, Daniel / Kiefer, Michael / Laeng, Alexandra / Walker, Kaley A. / Sheese, Patrick / Hubert, Daan / Roozendael, Michel / Retscher, Christian / Damadeo, Robert / Lumpe, Jerry D.

eISSN: 1867-8548

2023

Abstract: In this paper, we present the updated SAGE-CCI-OMPS + climate data record of monthly zonal mean ozone profiles. This dataset covers the stratosphere and combines measurements by nine limb and occultation satellite instruments – SAGE II (Stratospheric ... ...

Abstract	In this paper, we present the updated SAGE-CCI-OMPS + climate data record of monthly zonal mean ozone profiles. This dataset covers the stratosphere and combines measurements by nine limb and occultation satellite instruments – SAGE II (Stratospheric Aerosol and Gases Experiment II), OSIRIS (Optical Spectrograph and InfraRed Imaging System), MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), SCIAMACHY (SCanning Imaging Spectrometer for Atmospheric CHartographY), GOMOS (Global Ozone Monitoring by Occultation of Stars), ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer), OMPS-LP (Ozone Monitor Profiling Suite Limb Profiler), POAM (Polar Ozone and Aerosol Measurement) III, and SAGE III/ISS (Stratospheric Aerosol and Gases Experiment III on the International Space Station). Compared to the original version of the SAGE-CCI-OMPS dataset (Sofieva et al., 2017b), the update includes new versions of MIPAS, ACE-FTS, and OSIRIS datasets and introduces data from additional sensors (POAM III and SAGE III/ISS) and retrieval processors (OMPS-LP). In this paper, we show detailed intercomparisons of ozone profiles from different instruments and data versions, with a focus on the detection of possible drifts in the datasets. The SAGE-CCI-OMPS + dataset has a better coverage of polar regions and of the upper troposphere and the lower stratosphere (UTLS) than the previous dataset. We also studied the influence of including new datasets on ozone trends, which are estimated using multiple linear regression. The changes in the merged dataset do not change the overall morphology of post-1997 ozone trends; statistically significant trends are observed in the upper stratosphere. The largest changes in ozone trends are observed in polar regions, especially in the Southern Hemisphere. The updated SAGE-CCI-OMPS + dataset contains profiles of deseasonalized anomalies and ozone concentrations from 1984 to 2021, in 10 ∘ latitude bins from 90 ∘ S to 90 ∘ N and in the altitude range from 10 to 50 km. The ...
Subject code	333
Language	English
Publishing date	2023-04-12
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Horizontal distribution of tropospheric NO2 and aerosols derived by dual-scan multi-wavelength multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements in Uccle, Belgium

Dimitropoulou, Ermioni / Hendrick, François / Friedrich, Martina Michaela / Tack, Frederik / Pinardi, Gaia / Merlaud, Alexis / Fayt, Caroline / Hermans, Christian / Fierens, Frans / Roozendael, Michel

eISSN: 1867-8548

2022

Abstract: Dual-scan ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO 2 ) and aerosols were carried out in Uccle (50.8 ∘ N, 4.35 ∘ E; Brussels region, Belgium) for 2 years from March ... ...

Abstract	Dual-scan ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO 2 ) and aerosols were carried out in Uccle (50.8 ∘ N, 4.35 ∘ E; Brussels region, Belgium) for 2 years from March 2018 to February 2020. The MAX-DOAS instrument operated in both UV and visible wavelength ranges in a dual-scan configuration consisting of two submodes: (1) an elevation scan in a fixed viewing azimuthal direction and (2) an azimuthal scan in a fixed low elevation angle (2 ∘ ). By analyzing the O 4 and NO 2 differential slant column density (dSCD) at six different wavelength intervals along every azimuthal direction and by applying a new optimal-estimation-based inversion approach (the so-called mapping MAX-DOAS technique), the horizontal distribution of the NO 2 near-surface concentrations and vertical column densities (VCDs) as well as the aerosol near-surface extinction coefficients are retrieved along 10 azimuthal directions. The retrieved horizontal NO 2 concentration profiles allow the identification of the main NO 2 hotspots in the Brussels area. Correlative comparisons of the retrieved horizontal NO 2 distribution were conducted with airborne, mobile, air quality model, and satellite datasets, and overall good agreement is found. The comparison with TROPOMI observations from operational and scientific data products reveals that the characterization of the horizontal distribution of tropospheric NO 2 VCDs by ground-based measurements and an adequate a priori NO 2 profile shape in TROPOMI retrievals lead to better consistency between satellite and ground-based datasets.
Subject code	511 ; 333
Language	English
Publishing date	2022-08-09
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Assessment of the TROPOMI tropospheric NO2 product based on airborne APEX observations

Tack, Frederik / Merlaud, Alexis / Iordache, Marian-Daniel / Pinardi, Gaia / Dimitropoulou, Ermioni / Eskes, Henk / Bomans, Bart / Veefkind, Pepijn / Roozendael, Michel

eISSN: 1867-8548

2020

Abstract: Sentinel-5 Precursor (S-5P), launched in October 2017, carrying the TROPOspheric Monitoring Instrument (TROPOMI) nadir-viewing spectrometer, is the first mission of the Copernicus Programme dedicated to the monitoring of air quality, climate, and ozone. ... ...

Abstract	Sentinel-5 Precursor (S-5P), launched in October 2017, carrying the TROPOspheric Monitoring Instrument (TROPOMI) nadir-viewing spectrometer, is the first mission of the Copernicus Programme dedicated to the monitoring of air quality, climate, and ozone. In the presented study, the TROPOMI tropospheric nitrogen dioxide (NO 2 ) L2 product (OFFL v1.03.01; 3.5 km × 7 km at nadir observations) has been validated over strongly polluted urban regions by comparison with coincident high-resolution Airborne Prism EXperiment (APEX) remote sensing observations (~75 m × 120 m). Satellite products can be optimally assessed based on (APEX) airborne remote sensing observations as a large amount of satellite pixels can be fully mapped at high accuracy and in a relatively short time interval, reducing the impact of spatio-temporal mismatches. In the framework of the S5PVAL-BE campaign, the APEX imaging spectrometer has been deployed during four mapping flights (26–29 June 2019) over the two largest urban regions in Belgium, i.e. Brussels and Antwerp, in order to map the horizontal distribution of tropospheric NO 2 . For each flight, 10 to 20 TROPOMI pixels were fully covered by approximately 2800 to 4000 APEX measurements within each TROPOMI pixel. The TROPOMI and APEX NO 2 vertical column density (VCD) retrieval schemes are similar in concept. Overall for the ensemble of the four flights, the standard TROPOMI NO 2 VCD product is well correlated (R = 0.92) but biased negatively by −1.2 ± 1.2 × 10 15 molec cm −2 or −14 % ± 12 %, on average, with respect to coincident APEX NO 2 retrievals. When replacing the coarse 1° × 1° TM5-MP a priori NO 2 profiles by NO 2 profile shapes from the CAMS regional CTM ensemble at 0.1° × 0.1°, the slope increases by 11 % to 0.93, and the bias is reduced to −0.1 ± 1.0 × 10 15 molec cm −2 or −1.0 % ± 12 %. When the absolute value of the difference is taken, the bias is 1.3 × 10 15 molec cm −2 or 16 %, and 0.7 × 10 15 molec cm −2 or 9 % on average, when comparing APEX NO 2 VCDs with TM5-MP-based and CAMS-based NO 2 VCDs, respectively. Both sets of retrievals are well within the accuracy requirement of a maximum bias of 25–50 % for the TROPOMI tropospheric NO 2 product for all individual compared pixels. Additionally, the APEX data set allows the study of TROPOMI subpixel variability and impact of signal smoothing due to its finite satellite pixel size, typically coarser than fine-scale gradients in the urban NO 2 field. The amount of underestimation of peak plume values and overestimation of urban background values in the TROPOMI data is in the order of 1–2 × 10 15 molec cm −2 on average, or 10 %–20 %, in case of an urban scene.
Subject code	333 ; 290
Language	English
Publishing date	2020-06-29
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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