World Radiation Center
The World Radiation Center (WRC) has the following terms of reference (Fröhlich
Guarantee world-wide homogeneity of meteorological radiation measurements
by maintaining the World Standard Group (WSG) which is used to establish the World
Radiometric Reference (WRR, Fröhlich, 1978).
of meteorological radiation instruments.
Research and development in radiometry and methods of observation of atmospheric
Training of radiation specialists.
The Swiss government offered the World Meteorological Organization
(WMO, Geneva) to operate the WRC as a contribution
to the World Weather Watch program ( WWW).
Every five years, an International Pyrheliometer
Comparison (IPC) is held at PMOD/WRC to transfer the WRR to the participating
pyrheliometers in order to ensure world-wide homogeneity of solar radiation
measurements. It is chiefly intended for the calibration of absolute radiometers
from the Regional Radiation Centers of the six WMO regions. The next IPC(X)
will be held in 2010.
The World Radiometric Reference
The World Radiometric Reference is the measurement standard representing the SI
unit of irradiance. It was introduced in order to ensure world-wide homogeneity
of solar radiation measurements and is in use since 1980.
The WRR was determined from the weighted mean of the measurements of a group of
15 absolute cavity radiometers which have been fully characterized. It has an estimated
accuracy of 0.3%. The WMO introduced its mandatory use in its statutes in 1979.
Definition of the WRR using the results of 15 absolute cavity radiometers. The
shaded area represents the ± 0.2% deviation from the WRR (Fröhlich,
The World Standard Group (WSG)
||The WRR is determined by a group of absolute cavity radiometers
named the World Standard Group (WSG). At the moment, the WSG is composed
of 6 instruments: PMO-2, PMO-5, CROM-2L, PACRAD-3, TMI-67814 and HF-18748.
Fröhlich, C., 1977, 'World Radiometric Reference', in: WMO/CIMO Final
, WMO No. 490, 97-110. (PMOD/WRC intern: 545a)
Fröhlich, C., 1991, History of solar radiometry and the World Radiation Reference,
, 111-115. (PMOD/WRC intern: 650)
Fröhlich, C., Philipona, R., Romero, J., and Wehrli, C., 1995, Radiometry
at PMOD/WRC in Davos, Optical Engineering 34, No. 9, p. 2757-2766. (PMOD/WRC intern: 674)