NIMFR

The normal incidence multifilter radiometer (NIMFR) is a ground-based instrument that provides a time series of the shortwave spectral direct normal irradiance. Additionally, a broadband silicon detector can crudely measure the direct normal broadband irradiance.

These irradiance measurements can be used to infer clear-sky aerosol optical depth and columnar abundances of ozone and water vapor. The NIMFR is one of a class of instruments known as sun photometers.