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I heard that modis atmosphere correction is based on 6s code.i want to know how to build the aerosol and Rayleigh LUT using 6s code? Is there some DOC or introduction for this.Thanks for help
MODIS atmospheric correction is not based on 6S. LUTs are derived using a recent version of the Ahmad-Fraser vector radiative transfer code. See:
Ahmad, Z., B.A. Franz, C.R. McClain, E.J. Kwiatkowska, J. Werdell, E.P. Shettle, and B.N. Holben (2010). New aerosol models for the retrieval of aerosol optical thickness and normalized water-leaving radiances from the SeaWiFS and MODIS sensors over coastal regions and Open Oceans, Appl. Opt., 49(29).
I believe that the MODIS Land discipline group does use a 6S derived code.
Specifically, the land surface reflectance processing. See: http://modis-sr.ltdri.org/
We do processing for the Ocean discipline, and as Bryan pointed out - we do not use 6S.
Thanks for answer my question. you means that both rayleigh and aerosol correction are not based on 6s, and i want to know that Is there some instroduction about the architecture or computation process of the modis LUTS . Recently, i need to build LUTS for a satllite,and i don not have some experience on it
Yes, both Rayleigh and aerosol LUTs were derived using the same code described in Ahmad et al. 2010. We do not use 6S. The LUTs are HDF files, so you can look at them to see what content is required, but running the radiative transfer computations and building the LUTs is not really a job for the inexperienced.
I want to know how to calculate the value of aerosol scattering phase function for a scattering angle.Then i can use it to obtain aerosol optical
thickness form it. The LUTs provide the diffuse transmittance for a given aerosol optical thickness.
I wonder if this LUT has been generated already in SeaDAS, or one has the option of running some source code (those under build/src/) to get the reflected radiance for a specific aerosol model and other input parameters (tau(865), sen_z, sol_z..., etc.)? In other words, if I do not call SeaDAS, can I still produce the LUT using SeaDAS source code? (I guess not as I didn't spot anything like Mie.c in that directory...)
I'm also curious about if there are any recent studies on any non-spherical aerosol impacts on ocean color products.
One last question: has the Ahmad-Fraser algorithm been made open-source or not?
The code to produce the LUTs is not provided with SeaDAS. The Ahmad-Fraser code is not really portable; it would take a lot of work to make it useable without direct access to Ahmad. Non-spherical particles are a topic of interest, of course, but I don't know of any recent work that has been published on application to atmospheric correction for oceans.