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An improved TROPOMI tropospheric NO2 research product over Europe

Liu, Song and Valks, Pieter and Pinardi, Gaia and Xu, Jian and Chan, Ka Lok and Argyrouli, Athina and Lutz, Ronny and Beirle, Steffen and Khorsandi, Ehsan and Baier, Frank and Huijnen, Vincent and Bais, Alkiviadis and Donner, Sebastian and Dörner, Steffen and Gratsea, M. and Hendrick, Francoise and Karagkiozidis, D. and Lange, Kezia and Piters, Ankie and Remmers, J. and Richter, A. and Van Roozendael, M. and Wagner, T. and Wenig, M. and Loyola, Diego (2021) An improved TROPOMI tropospheric NO2 research product over Europe. Atmospheric Measurement Techniques (AMT), 14 (11), pp. 7297-7327. Copernicus Publications. doi: 10.5194/amt-14-7297-2021. ISSN 1867-1381.

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Official URL: https://amt.copernicus.org/articles/14/7297/2021/amt-14-7297-2021.html


Launched in October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) aboard Sentinel-5 Precursor provides the potential to monitor air quality over point sources across the globe with a spatial resolution as high as 5.5 km × 3.5 km (7 km × 3.5 km before 6 August 2019). The DLR nitrogen dioxide (NO2) retrieval algorithm for the TROPOMI instrument consists of three steps: the spectral fitting of the slant column, the separation of stratospheric and tropospheric contributions, and the conversion of the slant column to a vertical column using an air mass factor (AMF) calculation. In this work, an improved DLR tropospheric NO2 retrieval algorithm from TROPOMI measurements over Europe is presented. The stratospheric estimation is implemented using the STRatospheric Estimation Algorithm from Mainz (STREAM), which was developed as a verification algorithm for TROPOMI and does not require chemistry transport model data as input. A directionally dependent STREAM (DSTREAM) is developed to correct for the dependency of the stratospheric NO2 on the viewing geometry by up to 2×10^14 molec/cm2. Applied to synthetic TROPOMI data, the uncertainty in the stratospheric column is 3.5×10^14 molec/cm2 in the case of significant tropospheric sources. Applied to actual measurements, the smooth variation of stratospheric NO2 at low latitudes is conserved, and stronger stratospheric variation at higher latitudes is captured. For AMF calculation, the climatological surface albedo data are replaced by geometry-dependent effective Lambertian equivalent reflectivity (GE_LER) obtained directly from TROPOMI measurements with a high spatial resolution. Mesoscale-resolution a priori NO2 profiles are obtained from the regional POLYPHEMUS/DLR chemistry transport model with the TNO-MACC emission inventory. Based on the latest TROPOMI operational cloud parameters, a more realistic cloud treatment is provided by a Clouds-As-Layers (CAL) model, which treats the clouds as uniform layers of water droplets, instead of the Clouds-As-Reflecting-Boundaries (CRB) model, in which clouds are simplified as Lambertian reflectors. For the error analysis, the tropospheric AMF uncertainty, which is the largest source of NO2 uncertainty for polluted scenarios, ranges between 20 % and 50 %, leading to a total uncertainty in the tropospheric NO2 column in the 30 %–60 % range. From a validation performed with ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, the new DLR tropospheric NO2 data show good correlations for nine European urban/suburban stations, with an average correlation coefficient of 0.78. The implementation of the algorithm improvements leads to a decrease of the relative difference from −55.3 % to −34.7 % on average in comparison with the DLR reference retrieval. When the satellite averaging kernels are used to remove the contribution of a priori profile shape, the relative difference decreases further to  −20 %.

Item URL in elib:https://elib.dlr.de/146327/
Document Type:Article
Title:An improved TROPOMI tropospheric NO2 research product over Europe
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Liu, Songlius7 (at) sustech.edu.cnUNSPECIFIED
Valks, PieterPieter.Valks (at) dlr.dehttps://orcid.org/0000-0002-2846-7863
Pinardi, Gaiagaia.pinardi (at) aeronomie.beUNSPECIFIED
Xu, Jianjian.xu (at) dlr.dehttps://orcid.org/0000-0003-2348-125X
Chan, Ka LokKa.Chan (at) dlr.deUNSPECIFIED
Argyrouli, Athinaathina.argyrouli (at) dlr.deUNSPECIFIED
Lutz, RonnyRonny.Lutz (at) dlr.deUNSPECIFIED
Beirle, Steffensteffen.beirle (at) mpic.deUNSPECIFIED
Khorsandi, EhsanEhsan.Khorsandi (at) dlr.deUNSPECIFIED
Baier, FrankFrank.Baier (at) dlr.deUNSPECIFIED
Huijnen, VincentRoyal Netherlands Meteorological Institute (KNMI), De Bilt, the NetherlandsUNSPECIFIED
Bais, AlkiviadisLaboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greecehttps://orcid.org/0000-0003-3899-2001
Donner, SebastianMax Planck Institute for Chemistry, Mainz, GermanyUNSPECIFIED
Dörner, SteffenMax Planck Institute for Chemistry, Mainz, GermanyUNSPECIFIED
Gratsea, M.National Observatory of AthensUNSPECIFIED
Hendrick, FrancoiseBelgian Institute for Space Aeronomy, Brussels, BelgiumUNSPECIFIED
Karagkiozidis, D.Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, AUTH, Thessaloniki, GreeceUNSPECIFIED
Lange, KeziaInstitute of Environmental Physics (IUP-UB), University of Bremen, Bremen, GermanyUNSPECIFIED
Piters, AnkieRoyal Netherlands Meteorological Institute (KNMI), De Bilt, the NetherlandsUNSPECIFIED
Remmers, J.Max Planck Institute for Chemistry, Mainz, GermanyUNSPECIFIED
Richter, A.Institute of Environmental Physics, University of Bremen, Bremen, GermanyUNSPECIFIED
Van Roozendael, M.Michel.VanRoozendael (at) aeronomie.beUNSPECIFIED
Wagner, T.thomas.wagner (at) mpic.deUNSPECIFIED
Wenig, M.mark.wenig (at) lmu.deUNSPECIFIED
Loyola, DiegoDiego.Loyola (at) dlr.dehttps://orcid.org/0000-0002-8547-9350
Date:22 November 2021
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
DOI :10.5194/amt-14-7297-2021
Page Range:pp. 7297-7327
Publisher:Copernicus Publications
Keywords:TROPOMI, NO2, Air Quality, troposphere
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Atmospheric and climate research
Location: Oberpfaffenhofen
Institutes and Institutions:Remote Sensing Technology Institute > Atmospheric Processors
Deposited By: Valks, Dr. Pieter
Deposited On:29 Nov 2021 08:15
Last Modified:01 Dec 2021 10:52

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