UV spectra and atmospheric parameters measured with ultraviolet solar radiation instruments in EURAMET BIOSPHERE campaigns

The European Partnership on Metrology (EPM) joint research project BIOSPHERE investigates how the increasing ionization of the atmosphere, caused by extraterrestrial radiation fields (cosmic rays and solar UV radiation) and amplified by anthropogenic emissions, affects the human and ecological health of our planet. One main aspect is how these extraterrestrial radiation fields impact the stratospheric ozone (enforced depletion), resulting in an increase of Ultraviolet (UV) radiation on the ground.

To assess the influence of extraterrestrial radiation fields on atmospheric parameters and on solar UV radiation on the Earth surface, BIOSPHERE organizes four measurement campaigns with colocated SCR (Secondary Cosmic Rays) measurements (revealing the cosmic rays events) and solar UV radiation measurements, in GHI (global horizontal irradiance) and DNI (direct-sun normalized irradiance) geometries of observation. From the DNI UV radiation measurements we extract some atmospheric parameters: the total ozone column (TOC) in dobson units (DU) and the aerosol optical depth (AOD) for the UV wavelength range (290 nm - 400 nm).

The measurement campaigns took place at Athens (near urban site) in summer, in Brussels (urban site) in winter, in Milesovka (Czech Republic, rural mountain site) in spring/summer and will take place in Lindenberg (North-East Germany, rural flatland site) in autumn.

In addition to the correlation study confronting SCR measurements to TOC, AOD and UV measurements, we focus here on the quality of the UV radiation and atmospheric parameters’ measurements during the first campaigns: UV radiation (GHI) and especially the UV index from spectroradiometers (array spectrometers: Gigahertz-Optik BTS2048-UV-S-WP, Bentham DTMc300 double monochromators) are compared to measurements from UVB pyranometers and  a multi-channel filters radiometer (GUV-511 from BIOSPHERICAL Inc.) on the same site. TOC and AOD measurements done with UV DNI spectral measurements with an array spectrometer (Gigahertz-Optik BTS-Solar based on BTS2048-UV-S-WP) are compared to Brewer and photometer measurements done on geographically close sites. This survey analyzes the measurement differences, considering the instrumentation itself, the measurement retrieval procedures, and the spatial heterogeneity of the atmospheric parameters when the measurements that are compared to each other are not done at the same site.