Raman scattering moves energy from the incoming wavelength to neighbouring wavelengths and thus changes the spectral distribution in the scattered light. Unlike Rayleigh and Mie scattering, which are forms of elastic scattering, Raman scattering is inelastic.

There are two types of Raman scattering, rotational and vibrational scattering.

• Rotational Raman scattering on air molecules is important in the atmosphere.
• Vibrational Raman scattering is significant in water.

Rotational Raman scattering

Raman scattering is

• non polarising;
• isotropic;
• proportional to λ^-4;
• responsible for about 4% of all Rayleigh scattered light:

Vibrational Raman scattering

In water, vibrational Raman scattering has a shift in wavelength (Δλ) of approximately 30..50 nm, and thus has a similar effect on scattered sun light as rotational Raman scattering in air. The effect is asymmetric as the intensity in the UV is decreasing rapidly.

The impact on remote sensing measurements is that over clear water where a significant amount of scattered light can leave the ocean large spectral signatures appear in the measurements

The effect can be used to measure water turbidity and thereby chlorophyll content.