README for Optics files
Colarco, March 2007
optics_XX.hdf are constructed from GADS dataset of refractive indices

Exception of
optics_DU.v2.hdf
Basis here is to reduce the dust absorption.  At all wavelengths, dust imaginary index of
refraction is set to be GADS refi / 3.  At wavelengths shorter than 2.5 um -- where
real refractive index is relatively constant -- I force refr = 1.45, else use GADS refr.
At AERONET wavelength range I use refractive index (imaginary) from inversions at Capo
Verde, average of July monthly means and use OMI model #3 for shortwave from Omar.