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Has anyone derived MODIS rayleigh corrected reflectance using Seadas. It was suggested I use MODIS values of Lt - Lr to obtain a rayleigh corrected radiance, and then convert that to reflectance. Does that sound feasible?
Any advice gratefully received.
regards
Will
By @sean
Date 2007-10-31 19:01
Use rhos.
MSl12 has an output product, rhos_nnn (where nnn is wavelength - e.g. rhos_412)
This product is TOA reflectance minus Rayleigh reflectance.
Sean
Hi Sean, thanks for that. I did get some seadas feedback previously about rhos_nnn ..........."There is no product that is simply Rayleigh-corrected reflectance.
The rhos product is quasi-surface reflectance (surface + aerosol)."
So I wasn't sure if it was atmospherically corrected or not. That was why I was initially deriving Lt-Lr.
Can you clarify, thanks
regards
Will
By @sean
Date 2007-11-01 15:36
Will,
What do you mean by 'atmospherically corrected'?
Removing Rayleigh is a partial atmospheric correction, so in that
sense Lt-Lr is 'partially' atmospherically corrected.
As for rhos, it does not remove aerosol reflectance, but does make
adjustments for various atmospheric transmittances, hence the
seadas group's remark that it is a quasi-surface reflectance.
Here's what it is :
rhos = PI / F0 / mu0 * (Lt / tg_sol / tg_sen - Lr) / t_sol / t_sen / t_o2 / t_h2o
(the t's are the various transmittances, mu0 is cosine solar zenith, F0 is extraterrestiral irradiance)
If you want a product that is simply total reflectance minus rayleigh reflectance, you'll need to
make your own ala:
rhot-r = PI / F0 / mu0 * (Lt - Lr)
Sean