## How to derive Lw from Rrs product

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guorz
Posts: 18
Joined: Wed Apr 19, 2017 1:22 pm America/New_York

### How to derive Lw from Rrs product

I wanna derive Lw from Rrs product, found this formula on Rrs algorithm description page:
Rrs(λ)=(Lw(λ)/(F0fscos(θs)tds)fb(λ)fλ
F0 = extraterrestrial solar irradiance (Thuillier et al. 2003)

fs= adjustment of F0 for variation in Earth-Sun distance

fb = bidirectional reflectance correction

fλ = correction for out-of-band response

but I have no idea how to get fb and fλ, any idea?

Thanks!
RG

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OB General Science - guoqingw
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### Re: How to derive Lw from Rrs product

Hi RG,

Do you mind sharing a little detail about why you want to get Lw? If you meant to obtain the nLw (normalized water-leaving radiance, some products use it as standard L2 data), there is a simple equation: nLw = Rrs*F0, and you can find F0 here: https://oceancolor.gsfc.nasa.gov/docs/rsr/rsr_tables/

Please let us know.
Guoqing

guorz
Posts: 18
Joined: Wed Apr 19, 2017 1:22 pm America/New_York

### Re: How to derive Lw from Rrs product

Hi Guoqing,

Thanks for your anwser!

The reason why I want to get Lw is I'm trying to calculate Lt(the formula below), and will calculate Lr,La,Lg,Lwc through corresponding model and look-up table, but unable to get in-situ Lw data for my study area, so I'm thinking about derive it from Rrs, seems that I should use Lw here,right?

L_t (λ)=L_r (λ)+L_a (λ)+T(λ) L_g (λ)+t(λ) L_wc (λ)+t(λ)L_w (λ)

Thanks，
RG

OB General Science - guoqingw
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### Re: How to derive Lw from Rrs product

The easy way to get Lw is using the l2gen of SeaDAS. Other parameters including brdf can also be obtained from l2gen.
Guoqing

guorz
Posts: 18
Joined: Wed Apr 19, 2017 1:22 pm America/New_York