Published in:
Earth System Science Data, 12 (2020) 4, Seite 2787-2810
Language:
English
DOI:
10.5194/essd-12-2787-2020
ISSN:
1866-3516
Origination:
Footnote:
Description:
<jats:p>Abstract. A Bentham DTMc300 spectroradiometer is deployed at the
station of Aosta–Saint-Christophe, Italy, at the headquarters of the
Regional Environmental Protection Agency (ARPA) and has been performing
continuous high-quality spectral measurements of the solar ultraviolet (UV)
irradiance since 2006. The measuring site is located in the north-western
region of the Alps, on a large valley floor at the altitude of
570 m a.s.l.,
surrounded by mountains. It is very significant to have accurate
measurements in such a sensitive environment, since the complex terrain and
the strongly variable meteo-climatic conditions typical of the Alps induce
large spatial and temporal variability in the surface levels of the solar UV
irradiance. The spectroradiometer is also used as a reference of a regional
UV network, with additional stations located at different altitudes (1640
and 3500 m a.s.l.) and environmental conditions (mountain and glacier). In
the present study we discuss the procedures and the technical aspects which
ensure the high quality of the measurements performed by the reference
instrument and the procedures used to characterize the Bentham. The quality
control and quality assurance (QA–QC) procedures are also discussed. We show
that the good quality of the spectral measurements is further ensured by a
strong traceability chain to the irradiance scale of the
Physikalisch-Technische Bundesanstalt (PTB) and a strict calibration
protocol. Recently, the spectral UV dataset of Aosta–Saint-Christophe has
been re-evaluated and homogenized. The final spectra constitute one of the
most accurate datasets globally. At wavelengths above 310 nm and for solar
zenith angles below 75∘, the expanded (k=2) uncertainty in the
final dataset decreases with time, from 7 % in 2006 to 4 % in the
present. The present study not only serves as the reference document for any
future use of the data, but also provides useful information for experiments
and novel techniques which have been applied for the characterization of the
instrument and the QA–QC of the spectral UV measurements. Furthermore, the
study clearly shows that maintaining a strong traceability chain to a
reference scale of spectral irradiance is critical for the good quality of
the measurements. The studied spectral dataset is freely accessible at
https://doi.org/10.5281/zenodo.4028907
(Fountoulakis et al., 2020b).
</jats:p>