Computing differential air mass factor lookup tables using DISORT radiative transfer model

NOAA/NESDIS is implementing its own data processing for MetOP-A/GOME-2 observation. The retrieval method used for Nitrogen dioxide (NO₂) and Bromine monoxide (BrO) is the heritage EOS/OMI differential optical absorption spectroscopic (DOAS) method. To covert the slant column density (SCD) to the vertical column density (VCD) a differential air mass factor (dAmf) lookup table (LUT) is necessary. For the practical need, a NOAA version dAmf lookup table has been generated using a discrete ordinates radiative transfer model (DISORT). A thorough study of the algorithm, which computes air mass factor, has been conducted. It will be discussed in detail in this presentation. In this work, we first set up a DISORT model to simulate a real measurement, and then compute a six-dimensional table of dAmf for DOAS method. The computed LUT has been investigated and compared to that used in the OMINO2B algorithm.