km⁻¹
per kilometer
Wavenumberexact by definition
The reciprocal kilometre is 10⁻³ m⁻¹. It is the unit of atmospheric extinction and attenuation: aerosol extinction coefficients, visibility calculations and lidar returns are all expressed per kilometre, and a coefficient of 0.15 km⁻¹ corresponds to roughly 26 km of meteorological visibility.
| 1 km⁻¹ | 0.001 m⁻¹ |