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Broad band features are filtered out by subtracting a low order
polynomial. From the differential structures the slant column
amount will be determined by least-squares fitting the measured
optical depth to a linear combination of reference absorption
cross-section spectra. To derive the desired vertical trace
gas column, the slant column has to be divided by an appropriate
dimensionless air mass factor (AMF) describing the enhancement
of the absorption due to the slant path viewing geometry and the
solar elevation. This factor is obtained by radiative transfer
model (RTM) simulations. For GOME the DOAS works successfully
for O3, NO2, BrO, OClO, SO2 and HCHO.
The FURM algorithm consists of two parts, a forward model, based
on a radiation transfer model (RTM) GOMETRAN (Rozanov,
1997), which calculates for the relevant geometry the radiance
for a given state of the atmosphere and an inversion scheme
which matches in iterative steps the calculated radiance to the
measured radiance by modifying model atmospheric parameters such
as the vertical distribution of ozone using appropriate weighting
functions as provided by the RTM.
© 1997-2000, page created by
Stefan Noël,
latest change 2000/11/16.
Measurement Modes
Level 2 Products
SCIAMACHY Main Page