Kipp&Zonen UVS-E-T UV Radiometers - Manual (Page 41)

The solar zenith angles, Θ₀, are varied between 0° and 85° (using steps of 5°) and the ozone column densities, [O₃] are varied
between 200 DU and 500 DU (using steps of 10 DU), yielding 18•31=558 conversion factors. If UV irradiances under exceptional
conditions have to be measured with broadband UV radiometers, it is recommended to calculate new conversion factors using
model parameters that are representative for the exceptional condition (e.g. snow covered land surface at a location which is
mostly snow free).
12.4 Adjustment Step: UVIATOR correction method
To obtain the most accurate UV irradiances using broadband UV radiometers, the readings (“raw radiometer output”) must be
multiplied with the adjustment factor, χ. The adjustment factor, χ, is a combined correction factor, composed of the radiometric
calibration factor, ρ, and the conversion factor, γ, i.e. χ=1/(ρ•γ).
The UVIATOR program performs the required selection of the appropriate conversion factor automatically and corrects an
instantaneous UV radiometer measurement according to the measurement condition at the time of the UV radiometer reading.
For the selection of the conversion factor, the parameters Θ₀ and O₃ have to be determined according to the measurement
conditions at the time of the UV radiometer reading. The UVIATOR program calculates the solar zenith angle, Θ₀, for each
measurement as a function of the measurement location (latitude and longitude) and the GMT of the UV radiometer reading.
The total ozone column density, O₃, is retrieved from the TOMS data archive(2). Note, that the TOMS retrieved ozone values are
daily mean values only. However, the UVIATOR program offers so-called plug-ins, which allows using other ozone column
observation methods for the correction, such as the Brewer-derived ozone column density measurements. Finally the UVIATOR
program performs the UV measurement using the appropriate solar zenith angles and ozone column densities as obtained
according to the available metadata of the UV radiometer readings (metadata: data about the measurement data).
(2) See on http://toms.gsfc.nasa.gov/eptoms/ep.html
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UVIATOR software manual