;-----------------------------------------------------------------------------------------
; grab the priors from the values stored in the lut
; note, these should be the same for all groups in the lut
; note, Sfc_Idx is assumed to 1 based so in IDL we subtract 1
;-----------------------------------------------------------------------------------------
pro grab_prior_from_lut, lut, Sfc_Idx, Prior_Prob_Clear, Prior_Prob_Water, Prior_Prob_Ice
     Prior_Prob_Water = lut[Sfc_Idx-1].water_fraction
     Prior_Prob_Ice = lut[Sfc_Idx-1].ice_fraction
     Prior_Prob_Cloud = lut[Sfc_Idx-1].cloud_fraction
     if (Prior_Prob_Cloud ge 0.0) then begin
        Prior_Prob_Clear = 1.0 - Prior_Prob_Cloud
     endif
print, 'in grab_prior_from_lut ', Sfc_Idx, Prior_Prob_Water, Prior_Prob_Ice, Prior_Prob_Clear
end