Data from GUV radiometers installed on different Belgian sites.
Time period: 2011-2015

I - Technical description and specifications
II - Data available from the Belgian network (2011-2015 - 6 stations)

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%	I - Technical description and specifications
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GUV instruments are manufactured by BIOSPHERICAL Inc (https://www.biospherical.com/).
A GUV is an above-water multi-channel filter radiometer that measures global irradiance from Sun and sky at several wavelengths in the UV and visible. 

Model GUV-2511 (designed in 2003)
Temperature stabilized instrument designed for the measurement of the downwelling global solar irradiance at the following wavelengths:
305 nm, 313 nm, 320 nm, 340 nm, 380 nm and 395 nm, as well as Photosynthetically Active Radiation (PAR - 400-700 nm).
Typical bandwidth for UV channels: ~10 nm FWHM.

Technical specifications:
- Environmentally sealed and temperature-stabilized for long-term operation in harsh environment - Photodiode Array Temperature: 40 °C ±0.5 °C
- Cosine Collector: Teflon-covered quartz
- Collector Area: 2.1 cm diameter

Raw data are converted into solar global spectral irradiance (µW/(cm^2.nm)) for UVA and UVB channels using a factory calibration certificate.
PAR measurements are in the units of microEinsteins per square centimeters per second (µE/(cm^2sec)).
More information: 
https://www.biospherical.com/support/understanding-guv-calibrations/

(Note: 1 einstein = 1 mol × NA × h × f = 1 mol × 6.02214076×1023 mol−1 × 6.62607015×10−34 J x s × f = 3.9903127128934321×10−10 J x s × f
where NA is the Avogadro constant, h is the Planck constant, and f is the frequency) 

Side product: 
1) Calculation of UV index
	--> Measurement of the strength of the sunburn-producing ultraviolet (UV) radiation
	    Weighting of solar global spectral irradiance by a curve known as the CIE-standard McKinlay–Diffey erythemal action spectrum

The UV index can be estimated from GUV measurements using a linear combination of the spectral irradiance measured by the channels 305 nm, 313 nm, 320 nm and 340 nm
Equation: UVi = a1*E(305) + a2*E(313) + a3*E(320) + a4*E(395)
where 'E(nnn)' is the global spectral irradiance in µW/(cm^2.nm) at wavelength 'nnn'.
Coefficients:
a1 = 0.8058
a2 = 0.0887
a3 = 0.0324
a4 = 0.0131

More information: 
https://www.biospherical.com/support/how-do-i-calculate-uv-index-from-guv-data/
and section 6.1 of document 'guv_calibrations_006464ka_an2015-0001_rev1.pdf' (BIOSPHERICAL)

2) Calculation of UVA and UVB global wavelength-integrated solar irradiance 
More information: 
https://www.biospherical.com/support/how-do-i-calculate-uv-b-and-uv-a-from-guv-data/

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%	II - Data available from the Belgian network (2011-2015 - 6 stations)
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Stations of the Belgian network:
Time period: 2011-2015

Longitude and Latitude in (deg.dec hemi)

1) MOL --> Long. 5.1166 E, Lat. 51.1919 N, Altitude 27 m

2) MONT-RIGI --> Long. 6.0742 E, Lat. 50.5113 N, Altitude 680 m

3) OOSTENDE --> Long. 2.9119 E, Lat. 51.2234 N, Altitude 7 m

4) REDU --> Long. 5.2191 E, Lat. 50.0086 N, Altitude 443 m 

5) UCCLE --> Long. 4.3570 E, Lat. 50.7968 N, Altitude 100 m

6) VIRTON --> Long. 5.5315 E, Lat. 49.5668 N, Altitude 237 m

All measurements are performed in UT (Universal Time).

Filenames: 'yyyymmddhhmmss.csv'
Note: daily file! --> '...hhmmss' indicates the creation time of the file. Generally: '000000' for a daily file (beginning of the day 'yyymmdd')

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%  Structures of a .csv data file: 
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- Header: 8 rows, followed by the data rows. One raw per minute
- Row 3 of the header describes the position of global spectral irradiance data in the data rows
		--> after date and time (format --> mm/dd/yyyy hh:mm:ss), there is one data on the electronics (voltage Ed0Gnd) 
		    followed by global spectral irradiance values for wavelengths 305 nm, 313 nm, 320 nm, 380 nm, 395 nm and PAR
					Ed0305,Ed0313,Ed0320,Ed0340,Ed0380,Ed0395,Ed0PAR 
		                  
		    Unit (see also row 6 of the header): µW/(cm^2nm) for UV channels, µE/(cm^2sec) for PAR. Separator: comma