Earthdata Forum

Hello everyone,
Recently,I confused that how to calculate MODIS/Aqua Rayleigh reflectance using Rayleigh look up tables:
     rayleigh_modisa_412_iqu.hdf
     rayleigh_modisa_443_iqu.hdf
     rayleigh_modisa_469_iqu.hdf
     ...
1. In MODIS/Aqua Rayleigh look up tables,there are three tables in each band of LUTS: Rayleigh Reflectance Coefficients for I-component?Q-component?U-component. There are 3 rows,41 columns for Stokes each component. Does  3 rows denote the Fourier coefficient at order 0?1?2(that is :Ir(0)?Ir(1)?Ir(2)?Qr(0)?Qr(1)?Qr(2)?Ur(0)?Ur(1)?Ur(2)?), and 41 colunms denote number of Sensor Zenith Angles?

2. According to the Rayleigh Reflectance Coefficients for IQU component, how to calculate Rayleigh Reflectance? What's the specific computational rule ?

Thank you so much for your help !

The format of the Rayleigh tables is specific to the code used to read them (i.e. l2gen).  If you are dealing with MODIS data, you could simply use l2gen to output the Lr, L_q and L_u components.
Or, go the hard way and look at the code :grin:

Sean

Dear Sean,
Thank you for your help!
I have another question,if I use 6SV1.0B to calculate Rayleigh reflectance,the results will output like this:

                           Rayleigh     aerosol        total
reflectance I        0.01098      0.01335      0.02182
reflectance Q       0.00118      0.00039      0.00124
reflectance U       -0.00156     0.00000      -0.00176

How should I calculate Rayleigh total reflectance using Stokes components? Just use Rayleigh reflectance I or I should use these three components IQU to express Rayleigh?(Are there any paper to reference?or some specific fomulas?)

If all you need is the intensity, I would suppose you could just use I.  Unless you plan to account for the polarization sensitivity of the instrument, I should be all you need.

Sean,
Thank you for your help!