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Global Formaldehyde Products from the Ozone Mapping and Profiler Suite (OMPS) Nadir Mappers on Suomi NPP and NOAA-20
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  • Caroline R. Nowlan,
  • Gonzalo González Abad,
  • Hyeong-Ahn Kwon,
  • Zolal Ayazpour,
  • Christopher Chan Miller,
  • Kelly Chance,
  • Heesung Chong,
  • Xiong Liu,
  • Ewan O'Sullivan,
  • Huiqun Wang,
  • Lei Zhu,
  • Isabelle De Smedt,
  • Glen Jaross,
  • Colin Seftor,
  • Kang Sun
Caroline R. Nowlan
Center for Astrophysics | Harvard & Smithsonian

Corresponding Author:[email protected]

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Gonzalo González Abad
Center for Astrophysics | Harvard & Smithsonian
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Hyeong-Ahn Kwon
University of Suwon
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Zolal Ayazpour
University at Buffalo
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Christopher Chan Miller
Harvard University
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Kelly Chance
Center for Astrophysics | Harvard & Smithsonian
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Heesung Chong
Center for Astrophysics | Harvard & Smithsonian
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Xiong Liu
Center for Astrophysics | Harvard & Smithsonian
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Ewan O'Sullivan
Center for Astrophysics | Harvard & Smithsonian
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Huiqun Wang
Center for Astrophysics | Harvard & Smithsonian
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Lei Zhu
Southern University of Science and Technology
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Isabelle De Smedt
Belgian Institute for Space Aeronomy (BIRA-IASB)
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Glen Jaross
NASA Goddard Space Flight Center
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Colin Seftor
Science Systems and Applications, Inc.
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Kang Sun
University at Buffalo
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Abstract

We describe new publicly-available, multi-year formaldehyde (HCHO) data records from the Ozone Mapping and Profiler Suite (OMPS) nadir mapper (NM) instruments on the Suomi NPP and NOAA-20 satellites. The OMPS-NM instruments measure backscattered UV light over the globe once per day, with spatial resolutions close to nadir of 50 × 50 km² (OMPS/Suomi-NPP) and 17 × 17 km² or 12 × 17 km² (OMPS/NOAA-20). After a preliminary instrument line shape and wavelength calibration using on-orbit observations, we use the backscatter measurements in a direct spectral fit of radiances, in combination with a nadir reference spectrum collected over a clean area, to determine slant columns of HCHO. The slant columns are converted to vertical columns using air mass factors derived through scene-by-scene radiative transfer calculations. Finally, a correction is applied to account for background HCHO in the reference spectrum, as well as any remaining high-latitude biases. We investigate the consistency of the OMPS products from Suomi NPP and NOAA-20 using long-term monthly means over 12 geographic regions, and also compare the products with publicly-available TROPOMI HCHO observations. OMPS/Suomi-NPP and OMPS/NOAA-20 monthly mean HCHO vertical columns are highly consistent (r = 0.98), with low proportional (2 %) and offset (2×10¹⁴ molecules cm⁻²) biases. OMPS HCHO monthly means are also well-correlated with those from TROPOMI (r = 0.92), although they are consistently 10±16 % larger in polluted regions (columns >8×10¹⁵ molecules cm⁻²). These differences result primarily from differences in air mass factors.