Note 1 to entry: The International Global UV Index, I_UV, is defined by the formula:

$I_{\text{uv}}=k_{\text{er}}{\displaystyle \underset{250\text{nm}}{\overset{400\text{nm}}{\int }}{E}_{\lambda }(\lambda )s_{\text{er}}(\lambda )\text{d}\lambda }$

where E_λ(λ) is the solar spectral irradiance expressed in W·m⁻²·nm⁻¹ at wavelength λ, s_er(λ) is the erythema spectral weighting function, and k_er is a constant equal to 40 m²·W⁻¹.

Note 2 to entry: The global UV index has unit one.