Solar Irradiance  (or  Solar radiation Energy Flow) through a horizontal surface with an area of  1 m2, is measured in  W/m2  [ or equivalently in (J/s) / m2 ], as it is recorded separately in the  UV-A  and the UV-B  bands.


UV-A and UV-B irradiance values are provided by the Kipp & Zonen UV-S-AB-T radiometer[†]


[†] Spectral Range : 315 ~ 400 nm for the UV-A  and  280 ~ 315 nm for the  UV-B .