Effect of temperature on biological
dose rates derived
from spectral solar UV irradiance measurements.
- Trond Morten Thorseth*, Berit Kjeldstad and
University of Science and Technology, Department of Physics, N-7034 Trondheim, Norway.
* To whom correspondence should be addressed. (email:
spectral solar irradiance measurements depend upon a good calibration. If the
spectroradiometer operates at a different temperature than the calibration temperature,
sensitivity and wavelength setting of the instrument will change. This is the case for
most spectroradiometers, but the magnitude of this effect will vary for different types of
instruments. In this study a widely used spectroradiometer, Optronic OL752, from
Optronic Laboratories Inc. has been investigated. Both the effect of temperature on
sensitivity and wavelength shift has been quantified. The sensitivity of the Optronic
OL752 in the ultraviolet region, 290-400 nm, decreased approximately 0.8 %/K when the
instrument was heated above the calibration temperature. Wavelength shift coefficients
were derived for several wavelength regions with two independent methods. One of the
methods used was direct observation of how the measured spectral lines from a Hg lamp,
shifted with temperature. The other method, calculated the relative shift in the spectral
global irradiance measurements by comparing the Fraunhofer structure in the measured
spectra to the structure in an extraterrestrial spectrum. OL752 had a systematic
wavelength shift, varying from 0.10 nm/K at 254 nm to 0.06 nm/K at 633 nm.
CIE-weighted irradiance derived from modeled data, was used to estimate errors due to temperature effects. If the
spectroradiometer temperature is not controlled, a change of 5 K may lead to an error in
the derived CIE-weighted irradiance from 10% to 15% dependent upon solar zenith angle and