National Solar Radiation Measurement Standards and Quality Control

In order to ensure the accuracy of national solar radiation measurements and the world radiometric reference (WRR) transfer, quality control is carried out on the solar radiation measurement standards. There is a full set of sound management system and quality guarantee measure over many years' improvement, including the measurement standard of value transfer and traceability, the selection and validation of calibration method, calibration process and data quality control, staffed and personnel skill requirements and so on. It also passes the measurement standard reexamination organized by General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ).The radiation value is directly traceable to the WRR every five years through attending the World Meteorological Organization (WMO) International Pyrheliometer Comparisons (IPC), and then the metrological verification or calibration method is adopted for the standard radiation instrument value transfer, to ensure the accuracy of WRR in China and neighboring countries. China national solar radiation measuring standard is directly compared with the WRR for 3 times in 15 years, and comparison results of the uncertainty is 0.17%, surpassing requirements of WMO.In order to ensure measurement standards between the international cycle comparison interval, and keep them in good confidence calibration status, the repeatability and stability of solar radiation measurement standards should be checked every year to determine standards in original state. In fact, there should be more times of checking if conditions allow to reduce the uncertainty introduced by the repeatability of measurement error. Mean value control chart is used to judge whether the measurement process is affected by uncontrolled system bias, and graphics memory way is used to achieve continuous and long-term statistical quality control. Period verification shows the solar radiation measurement repeatability and years of stability is no more than 0.1% and less than 0.25%, within the control limits and taking a random distribution state. That ensures the measuring process in a stable controlled status, meeting the standard requirements.Above all, the WRR international comparison itself cannot ensure the national solar radiation measurement standards fully meet the quality assurance requirements, a lot of collaborative international comparison and period verification should be carried out to ensure that the measurement uncertainty is controlled within the allowable range of 0.25%.