For the neph correction you would so a linear interpolation using the appropriate angstrom exponent.

The Angstrom exponents of the spectral optical depths ranged from 0.5 to 2.0, and some of the variability was apparently related to distinct aerosol regimes.

Back trajectories and aerosol properties such as size (indicated by the Angstrom exponent) and blackness (indicated by aerosol single scattering albedo) can be used to separate airmasses into categories such as 'clean','polluted', 'smoke-influenced', and 'dust-influenced'.