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GOS > IMOP > Radiation Centres
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World, Regional and National Radiation Centres were established under the auspices of CIMO. The World Standard Reference for solar radiation measurements is maintained by the World Radiation Centre (Davos, Switzerland). The Regional Standard Instruments are made available at the 22 Regional Radiation Centres established within the WMO Regions.
Please refer to the CIMO Guide: WMO-No. 8 (6th ed.), Chapter I,7 "Radiation Measurements".
A short film on the twelth International Pyrheliometer Comparison held in 2015 Davos, Switzerland is available here:
Film on IPC-XII 
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World Radiation Centres were designated by the thirtieth session of the Executive Committee in 1978 through its Resolution 11 (EC-XXX) to serve as centres for international calibration of meteorological radiation standards within the global network and to maintain the standard instruments for this purpose.
World Radiation Centres shall fulfil the following requirements. It shall either:
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Possess and maintain a group of at least three stable absolute pyrheliometers, with a traceable 95% uncertainty of less than 1 Wm-2 to the World Radiometric Reference, and in stable clear sun conditions with direct irradiances above 700 Wm-2, 95% of any single measurements of direct solar irradiance will be expected to be within 4 Wm-2 of the irradiance. The World Radiation Centre Davos is requested to maintain the World Standard Group for the realization of the World Radiometric Reference;
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It shall undertake training of specialists in radiation;
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The staff of the centre should provide for continuity and should include qualified scientists with wide experience in radiation;
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It shall take all steps necessary to ensure at all times the highest possible quality of its standards and testing equipment;
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It shall serve as a centre for the transfer of the World Radiometric Reference to the regional centres;
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It shall have the necessary laboratory and outdoor facilities for the simultaneous comparison of large numbers of instruments and for the reduction of the data;
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It shall follow closely or initiate developments leading to improved standards and/or methods in meteorological radiometry;
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It shall be assessed by an International agency or CIMO experts, at least every 5 years to verify traceability of the direct solar radiation measurements.
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Provide and maintain an archive for solar radiation data from all the Member States of WMO;
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The staff of the centre should provide for continuity and should include qualified scientists with wide experience in radiation;
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It shall take all steps necessary to ensure at all times the highest possible quality of and access to its database;
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It shall be assessed by an International agency or CIMO experts, at least every 5 years.
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Region I (Africa)
- Cairo (Egypt)
- Khartoum (Sudan)
- Kinshasa (Dem. Rep. of the Congo)
- Lagos (Nigeria)
- Tamanrasset (Algeria)
- Tunis (Tunisia)
Region II (Asia)
- Pune (India)
- Tokyo (Japan)
Region III (South America)
- Buenos Aires (Argentina)
- Lima (Peru)
- Santiago (Chile)
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Region IV (North and Central America)
- Toronto (Canada)
- Boulder (United States)
- Mexico City (Mexico)
Region V (South-West Pacific)
- Melbourne (Australia)
Region VI (Europe)
- Budapest (Hungary)
- Davos (Switzerland)
- St. Petersburg (Russian Federation)
- Norrköping (Sweden)
- Trappes/Carpentras (France)
- Uccle (Belgium)
- Lindenberg (Germany)
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A Regional Radiation Centre is a centre designated by a Regional Association to serve as a centre for interregional comparisons of radiation instruments within the Region and to maintain the standard instruments necessary for this purpose.
Regional Radiation Centres shall satisfy the following conditions before it is designated as such and shall continue to fulfil them after being designated:
- It shall possess and maintain a standard group of at least three stable pyrheliometers, with a traceable 95% uncertainty of less than 1 Wm-2 to the World Standard Group, and in stable clear sun conditions with direct irradiances above 700 Wm-2, 95% of any single measurements of direct solar irradiance will be expected to be within 6 Wm-2 of the irradiance;
- One of the radiometers shall be compared through a WMO/CIMO sanctioned comparison, or calibrated, at least once every five years against the World Standard Group;
- The standard radiometers shall be intercompared at least once a year to check the stability of the individual instruments. If the mean ratio, based on at least 100 measurements, and having an 95% uncertainty less than 0.1%, has changed by more than 0.2% and if the erroneous instrument cannot be identified, then a recalibration at one of the World Radiation Centres must be performed prior to further use as standard;
- It shall have, or have access to, the necessary facilities and laboratory equipment for checking and maintaining the accuracy of the auxiliary measuring equipment;
- It shall provide the necessary outdoor facilities for simultaneous comparison of national standard radiometers from the Region;
- The staff of the centre should provide for continuity and should include a qualified scientist with wide experience in radiation;
- It shall be assessed by a National or International agency or CIMO experts, at least every 5 years to verify traceability of the direct solar radiation measurements.
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A National Radiation Centre is a centre designated at the national level to serve as a centre for the calibration, standardization, and checking of the instruments used in the national network of radiation stations and for maintaining the national standard instrument necessary for this purpose.
A National Radiation Centre shall satisfy the following requirements:
- It shall possess and maintain at least two pyrheliometers for use as a national reference for the calibration or radiation instruments in the national network of radiation stations with a traceable 95% uncertainty of less than 4 Wm-2 to the regional representation of the World Radiometric Reference, and in stable clear sun conditions with direct irradiances above 700 Wm-2, 95% of any single measurements of direct solar irradiance will be expected to be within 20 Wm-2 of the irradiance;
- One of the national standard radiometers shall be compared with a regional standard at least once every five years;
- The national standard radiometers shall be intercompared at least once a year to check the stability of the individual instruments. If the mean ratio, based on at least 100 measurements, and having an 95% uncertainty less than 0.2%, has changed by more than 0.6% and if the erroneous instrument cannot be identified then a recalibration at one of the Regional Radiation Centres must be performed prior to further use as standard;
- It shall have, or have access to, the necessary facilities and equipment for checking the performance of the instruments used in the national network;
- The staff of the centre should provide for continuity and should include a qualified scientist with experience in radiation.
National Radiation Centres shall be responsible for preparing and keeping up to date all necessary technical information for the operation and maintenance of the national network of radiation stations.
Arrangements should be made for the collection of the results of all radiation measurements made in the national network of radiation stations and for the regular scrutiny of these results with a view to ensuring their accuracy and reliability. If this work is done by some other body, the National Radiation Centre shall maintain close liaison with that body.
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