Kipp&Zonen UVS-E-T UV Radiometers - Manual (Page 12)

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4 CALIBRATION AND UVIATOR SOFTWARE
From late 2007 the specially developed Kipp & Zonen
UVIATOR Software is included with all new UVS
radiometers. The use of the UVIATOR is explained in
the UVIATOR manual. In this chapter the benefits and
the principles are explained.
Why use UVIATOR software
To improve the quality and relevance of measured UV
irradiance data from UVS radiometers by taking into
account the spectral properties of the radiometer and
of the atmosphere at the time and location of the
measurement.
Theoretical Background
Atmospheric ultraviolet radiation measurements are
difficult to perform due to the drastic decrease of UV-B
irradiance towards shorter wavelengths, caused by the
strong stratospheric Ozone absorption. Besides the
extinction of UV radiation due to Ozone, Rayleigh
scattering also affects the radiation, especially in the
UV-B spectral region.
As UV radiation represents only a small portion of the
solar spectrum, broad-band UV radiometers contain
filters and use signal amplifiers to measure the UV
irradiance in the appropriate spectral region. Filters are
used to measure the UV irradiance in the UV-A or UV-
B spectral region, or to match as closely as possible a
specific theoretical weighting function, such as UV-E.
As the actual radiometer spectral response functions
do not correspond exactly to the theoretical weighting
functions, even for the radiometers measuring only UV-
A or UV-B irradiances, the measurements are affected
by a systematic error caused by spectral mismatch.