Abstract. Retrieving aerosol optical depth (AOD) from top-of-atmosphere (TOA)
satellite-measured radiance requires separating the aerosol signal from the
total observed signal. Total TOA radiance includes signal from the underlying
surface and from atmospheric constituents such as aerosols, clouds and gases.
Multispectral retrieval algorithms, such as the dark-target (DT) algorithm
that operates upon the Moderate Resolution Imaging Spectroradiometer (MODIS,
on board Terra and Aqua satellites) and Visible Infrared Imaging Radiometer
Suite (VIIRS, on board Suomi-NPP) sensors, use wavelength bands in “window”
regions. However, while small, the gas absorptions in these bands are
non-negligible and require correction. In this paper, we use the
High-resolution TRANsmission (HITRAN) database and Line-By-Line Radiative
Transfer Model (LBLRTM) to derive consistent gas corrections for both MODIS
and VIIRS wavelength bands. Absorptions from H2O, CO2 and
O3 are considered, as well as other trace gases. Even though MODIS
and VIIRS bands are “similar”, they are different enough that applying
MODIS-specific gas corrections to VIIRS observations results in an
underestimate of global mean AOD (by 0.01), but with much larger regional AOD
biases of up to 0.07. As recent studies have been attempting to create a long-term
data record by joining multiple satellite data sets, including MODIS and
VIIRS, the consistency of gas correction has become even more crucial.
Correcting for trace gas absorption when retrieving aerosol optical
depth from satellite observations of reflected shortwave radiation
