FTIR Team: Carlos Aquino Bauer 2, Thomas Blumenstock 3, Martine De Mazière 1, Michel Grutter 4, James Hannigan 5, Nicholas Jones 6, Rigel Kivi 7, Emmanuel Mahieu 8, Maria Makarova 9, Isamu Morino 10, Isao Murata 11, Tomoo Nagahama 12, Justus Notholt 13, Ivan Ortega 5, Mathias Palm 13, Markus Rettinger 14, Amelie Röhling 3, Dan Smale 15, Wolfgang Stremme 4, Kim Strong 16, Youwen Sun 17, Ralf Sussmann 14, Yao Té 18, Pucai Wang 19, Tyler Wizenberg 16
1 Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium; 2 Instituto Federal de Educaçao, Ciência e Tecnologia de Rondônia (IFRO), Porto Velho, Brazil; 3 Karlsruhe Institute of Technology (KIT), IMK-ASF, Karlsruhe, Germany; 4 Universidad Nacional Autónoma de México (UNAM), 04510 Mexico City, México; 5 National Center for Atmospheric Research (NCAR), Boulder, CO, USA; 6 Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, Australia; 7 Finnish Meteorological Institute (FMI), Sodankylä, Finland; 8 Institute of Astrophysics and Geophysics, Université De Liège, Liège, Belgium; 9 Saint Petersburg State University, Atmospheric Physics Department, St Petersburg, Russia; 10 National Institute for Environmental Studies (NIES), Tsukuba, Japan; 11 Graduate School of Environment Studies, Tohoku University, Japan; 12 Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Nagoya, Japan; 13 Institute of Environmental Physics, University of Bremen, Bremen, Germany; 14 Karlsruhe Institute of Technology (KIT), IMK-IFU, Garmisch-Partenkirchen, Germany; 15 National Institute of Water and Atmospheric Research Ltd (NIWA), Lauder, New Zealand; 16 Department of Physics, University of Toronto, Toronto, Canada; 17 Hefei Institute of Physical Sciences, Chinese Academy of_Sciences (CAS), Hefei, China; 18 LERMA-IPSL, Sorbonne Université, CNRS, PSL Research University, 75005 Paris, France; 19 Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), Beijing, China
Within the NIDFORVal project (S5P NItrogen Dioxide and FORmaldehyde VALidation using NDACC and complementary FTIR and UV-Vis DOAS ground-based remote sensing data), we have successfully obtained a harmonized HCHO data set from the FTIR network (Vigouroux et al., 2018). This has led to a comprehensive validation of the S5P HCHO product (Vigouroux et al., 2021), showing the strength of using more than 20 sites covering clean and polluted conditions. Within this NIDFORVAL project, the total, tropospheric, and stratospheric NO2 S5P products have been validated, against Direct-Sun, MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy), and zenith-sky DOAS measurements, respectively (Verhoelst et al., 2021).
Fourier Transform Infrared (FTIR) instruments have the capability to measure NO2, with a sensitivity mainly located in the stratosphere (e.g., Hendrick et al., 2012, Bognar et al., 2019). However, only a few FTIR sites exploited this until now, using different retrieval settings. For the present work, we have optimized the NO2 retrieval settings and applied them consistently to the whole FTIR network (mostly from NDACC, Network for the Detection of Atmospheric Composition Change, but also including additional NDACC candidate sites and TCCON sites operated in NDACC mode). We have obtained a unique harmonized NO2 data set covering 25 FTIR sites, ensuring consistency of the results if used as reference data for validation. This stratospheric NO2 data set can complement the zenith-sky DOAS data. Indeed, the zenith-sky DOAS observations are made during sunset and sunrise which imposes the use of a photochemical box model to adjust the observations to the time of the TROPOMI overpasses, while the FTIR measurements are made during the whole day, allowing direct comparison between measurements that are collocated in time.
In this presentation, we will show the validation results of more than three years of S5P stratospheric NO2 data, allowing robust statistics on the comparisons, and the seasonal cycles to be compared at 25 FTIR sites globally distributed. Diurnal cycles comparisons can also be obtained at high latitude sites. Conclusions about the accuracy and the precision of the S5P stratospheric NO2 products will be drawn and compared to the ones obtained using Zenith-sky DOAS data (Verhoelst et al., 2021).
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Hendrick et al.: Analysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations, Atmos. Chem. Phys., 12, 8851–8864, https://doi.org/10.5194/acp-12-8851-2012, 2012.
Verhoelst et al.: Ground-based validation of the Copernicus Sentinel-5P TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks, Atmos. Meas. Tech., 14, 481–510, https://doi.org/10.5194/amt-14-481-2021, 2021.
Vigouroux et al.: NDACC harmonized formaldehyde time series from 21 FTIR stations covering a wide range of column abundances, Atmos. Meas. Tech., 11, 5049–5073, https://doi.org/10.5194/amt-11-5049-2018, 2018.
Vigouroux et al.: TROPOMI–Sentinel-5 Precursor formaldehyde validation using an extensive network of ground-based Fourier-transform infrared stations, Atmos. Meas. Tech., 13, 3751–3767, https://doi.org/10.5194/amt-13-3751-2020, 2020.