A modification was made to the variation of Rayleigh scattering with
atmospheric pressure, to account for the change with solar geometry.
The refinement will be fully described in Wang, M., "A refinement for the
Rayleigh radiance computation with variation of the atmospheric pressure," Int.
J. Rem. Sens., in press. The effect of this change is negligible at low
solar zenith angles, but large pressure deviations at higher solar angles
can result in spectrally-dependent changes of order 5% in nLw.