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Up Topic SeaDAS / SeaDAS - General Questions / Regarding Atmospheric Correction in L2GEN
- By alakes Date 2017-07-12 09:34
In L2GEN , 'Processing Options' tab there is 'aero_opt' option (aer_opt (int) (default=99) = aerosol mode option).
There is various atmospheric correction to choose form in this option.
        0: White aerosol extrapolation.
       -1: Multi-scattering with 2-band model selection
       -2: Multi-scattering with 2-band, RH-based model selection and
           iterative NIR correction
       -3: Multi-scattering with 2-band model selection
           and iterative NIR correction

  etc etc..

Can anyone help me find the details of each schemes used here? I mean, how can distinguish one scheme from another?
Any documentation in this regarding will also be helpful..

Thanks in advance..
- By seanbailey Date 2017-07-13 16:24 Edited 2017-07-14 11:29
While there are over a dozen options for aer_opt, there are really two flavors:

1) those that use the basic Gordon and Wang(1994) approach to aerosol  retrieval
2) those that use an alternate aerosol derivation

Options -1 is the most true to the original GW94 implementation.  It assumes black pixel and makes no attempt to adjust for non-negligible NIR radiance.
Options -2 and -3 implement the Bailey et al., (2010) iterative correction to remove non-negligible NIR radiance from the NIR signal prior to the aerosol determination and are effectively the same (and unless you have the older GW94 12-model set available prior to the implementation of the relative humidity specific models derived by Ahmad they are EXACTLY the same).

Option -9 is similar to these, except that it also employs the SWIR channels (so only works with sensors that have SWIR channels) doing a switch with the NIR based model selection.  It is the Wang and Shi (2007) approach.

Options -4, -5, -6, -7 and -8 do not use the GW94 aerosol determination approach, rather they select the aerosol based on various user defined inputs. Options with positive values are the extreme case for these, in that the user literally selects the aerosol model to use (by its number - not a trivial task to define now that there are 80 of them - in RH order ...a trick I use is to limit the aermodels list to the model I want and set aer_opt=1 that way I don't have to figure out what number in the list is the model I want :wink:)

Option -10 is the MUMM approach (Ruddick et al., 2006)

Options -11 and -12 are special cases, specific to SeaWiFS and can be ignored.

Option 0 just uses the same aerosol reflectance derived from the long-wave NIR band (by simple subtraction of Rayleigh) for all bands (thus a "white" aerosol).

Option -99 (No aerosol subtraction) should be pretty obvious :razz:

- By alakes Date 2017-07-14 06:30
Thank you Sean..:smile:
Up Topic SeaDAS / SeaDAS - General Questions / Regarding Atmospheric Correction in L2GEN

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