Hyperspectral radiometer for automated measurement of global and diffuse sky irradiance

- An automated spectroradiometer for global and diffuse irradiance has been designed.
- The spectrometer has been thoroughly characterized.
- Agreement of simultaneous measurements with a BSRN station is good.
- Measured spectra were used for inversion of atmospheric radiative transfer model 6S.
- Column water vapor, ozone, and aerosol optical depth can be retrieved from inversion.

An automated hyperspectral radiometer for the measurement of global and diffuse sky irradiance, SkySpec, has been designed for providing the SMEAR-Estonia research station with spectrally-resolved solar radiation data. The spectroradiometer has been carefully studied in the optical radiometry laboratory of Tartu Observatory, Estonia. Recorded signals are corrected for spectral stray light as well as for changes in dark signal and spectroradiometer spectral responsivity due to temperature effects. Comparisons with measurements of shortwave radiation fluxes made at the Baseline Surface Radiation Network (BSRN) station at Tõravere, Estonia, and with fluxes simulated using the atmospheric radiative transfer model 6S and Aerosol Robotic Network (AERONET) data showed that the spectroradiometer is a reliable instrument that provides accurate estimates of integrated fluxes and of their spectral distribution. The recorded spectra can be used to estimate the amount of atmospheric constituents such as aerosol and column water vapor, which are needed for the atmospheric correction of spectral satellite images.