Radiation measurements are a fundamental, integral part of meteorological observation and climate monitoring. Research has been carried out into solar radiation at the Physical Meteorological Observatory in Davos (PMOD) since 1907. In 1971, the World Meteorological Organization (WMO) gave the PMOD the additional mandate of serving as the World Radiation Centre (WRC). With their reference instruments, the World Calibration Centres operated from the PMOD/WRC play a crucial role in maintaining quality standards in the global monitoring programmes.

Entrance side of the three-storey PMOD/WRC building in Davos.
The PMOD/WRC building in Davos ©PMOD/WRC

The sun is the most important influencing factor in the earth's climate. In order to research the effects of fluctuations in solar radiation on climate variability, the measurements taken have to be of the utmost precision. Founded in 1907, the PMOD/WRC has a long tradition and wealth of experience in this field. In addition, it has also served as the World Calibration Centre since 1971. The PMOD/WRC provides reference measurements for solar radiation, infrared radiation, atmospheric optical depth and, since the beginning of 2013, ultraviolet radiation.

Radiometers for satellites

Metal plate on the top of which dozens of metal cylinders with small openings are mounted.
Radiometers directed at the sun at PMOD/WRC (image: PMOD/WRC)

The improvement and new development of high-precision instruments for radiometry is one of the important activities of the PMOD/WRC. A new reference instrument was recently developed that measures atmospheric heat radiation. Radiometers produced in Davos are installed on satellites. The strength of solar radiation outside the earth's atmosphere has been measured at 1361±0.4 W/m². This value is consistent with the most accurate measurements to date.

The PMOD/WRC is co-funded by the Swiss government, the Canton of Graubünden and the municipality of Davos. The PMOD/WRC is a department of the Swiss Research Institutes for High Altitude Climate and Medicine in Davos (SFI) MeteoSwiss presides over the PMOD/WRC Supervisory Commission and is a member of the SFI Foundation Board.

Radiation Measurements and their worldwide compatibility: WMO International Pyrheliometer Comparison (IPC) 2015 in Davos, Switzerland

The International Pyrheliometer Comparison (IPC) is an WMO event that takes place every five years at the Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC) in Davos, Switzerland.

The IPC helps ensure the quality of solar radiation measurements worldwide through comparison of reference instruments to the World Standard Group (WSG) , a group of six instruments located at PMOD/WRC Davos and representing the World Radiometric Reference (WRR) - the world standard for solar radiation. Representatives from WMO Regional and National Radiation Centers and from National Metrology Institutes participate with their reference instruments, which are then used to calibrate field pyranometers and other radiation instruments in the countries they represent.

This ensures traceability of local solar measurements to the world standard (WRR) and thus worldwide comparability.  Measuring solar radiation is important because the measurements are used for meteorology and climatology, detecting climate change, physics applications and  solar energy measurements for use in solar power applications.

Parallel to the IPC the PMOD/WRC is holding two other comparisons: The International Pyrgeometer Comparison (IPgC) for instruments measuring the infrared radiation and the Filter Radiometer Comparison (FRC) for instruments measuring aerosols in the atmosphere. Science seminars were held besides the instrument comparisons where radiation experts from all over the world shared their knowledge to build capacity and to define common standards on measuring radiation throughout the world.

Further information