Abstract
This study presents the Ozone Monitoring Instrument (OMI) Collection 4
formaldehyde (HCHO) retrieval developed with the Smithsonian
Astrophysical Observatory’s (SAO) Making Earth System Data Records for
Use in Research Environments (MEaSUREs) algorithm. The retrieval
algorithm updates and makes improvements to the NASA operational OMI
HCHO (OMI Collection 3 HCHO) algorithm, and has been transitioned to use
OMI Collection 4 Level-1B radiances. This paper describes the updated
retrieval algorithm and compares Collection 3 and Collection 4 data
products. The OMI Collection 4 HCHO exhibits remarkably improved
stability over time in comparison to the OMI Collection 3 HCHO product,
with better precision and the elimination of artificial trends present
in the Collection 3 during the later years of the mission. We validate
the OMI Collection 4 HCHO data product using Fourier-Transform Infrared
(FTIR) ground-based HCHO measurements. The climatological monthly
averaged OMI Collection 4 HCHO vertical column densities (VCDs) agree
well with the FTIR VCDs, with a correlation coefficient of 0.83,
root-mean-square error (RMSE) of 2.98 × 1015 molecules cm-2, regression
slope of 0.79, and intercept of 8.21 × 1014 molecules cm-2.
Additionally, we compare the monthly averaged OMI Collection 4 HCHO VCDs
to OMPS Suomi NPP, OMPS NOAA-20, and TROPOMI HCHO VCDs in overlapping
years for twelve geographic regions. This comparison demonstrates high
correlation coefficients of 0.98 (OMPS Suomi NPP), 0.97 (OMPS NOAA-20),
and 0.90 (TROPOMI).