14-16 Solar Radiation Measurement Standard
Author: Source: Datetime: 2016-12-26 09:49:08
In 1905, at the International Conference on Meteorology in Innsbruck, Austria, the Angstrom compensatory direct solar radiation table (in Table A) was used as a standard instrument for measuring solar radiation. This is the origin of the Angstrom scale (AS-1905). It is based on a group of instruments, including the A70 (the Institute of Physics, Uppsala University, Sweden), and the A158 and A153, which are sub-benchmarks (the Swedish Institute of Hydrometeorology, as an absolute standard) However, before 1956, all measuring instruments were based on the AS1905, which was not revised, and AS1905 was widely accepted in Europe.
In 1913, Abbot of the Smithsonian Institute in the United States designed a water-flow direct solar radiation meter to form the Smithson scale (SS-1913), which was later refined and perfected to make the SS-1913 more accurate. -1913 system is 2.5% higher. This correction value is used to correct the solar constant measurement results, but never used to calibrate the station of the sun radiation instrument .This correction value in 1934, 1947 and 1952, Since the instrument is too cumbersome and cumbersome to operate, Abbot later devised a silver disk radiation meter, the SS-1913, which is popular in the Americas.
For these two kinds of radiation scale, in the course of several decades of coexistence has been the sun for the light source were compared. The main difficulty in coordinating these alignment results is that the aperture angles of the two instruments are not uniform. The difference between the two instruments can not be a constant, but between 3% and 6%, due to the variation of the sky brightness during the different solar height conditions. According to the results of the measurements at that time, SS-1913 was 3,5% higher than the average of AS-1905 measurements. In the laboratory with the artificial light source to compare the results of the difference of 2.8%. In order to facilitate the data reference and comparison, in order to facilitate the international geophysical years of scientific research activities carried out in 1956 September in Davos, Switzerland, the International Association of Meteorology and Atmospheric Physics Radiation Committee adopted the American scholar AJ Drummond's comments: Implementing a new international direct solar surveying scale as the only universal solar standard in the world. The new scale is actually a compromise between the first two rulers, denoted by IPS-1956. This recommendation was endorsed by the Second Session of the Commission on Instruments and Methods of Observation (CIMO) and scheduled for implementation on 1 January 1957. IPS-1956 was achieved by an increase of 1.5% in AS-19905 or 2.0% in the original SS-1913. The relationship between the various radiation # scale scales as shown in Figure 1-14
After the founding of new China, China is the reference standard for the measurement of radioactivity is IPS-1956.
To ensure the coherence of radiometric data, WMO has established a system of radiation centers, including the world's regional and national secondary radiation centers (see Figure 1-14), and regularly organizes international direct comparison tables (IPC) for standard direct sunlight tables.
The first international direct comparison of standard direct sunlight tables - IPC-I was held in Davos in 1956. IPS-1956 is defined and passed during this comparison. It is based on the original standard equipment A158 Stockholm, Sweden as a benchmark, and its own instrumental constant increased by 1.5%. Then, as the standard, through the actual comparison again to determine the other instrument calibration constant. IPC-II was held in 1964. From 1959 to 1964, the variation of the instrument constant was less than 0.4%. but,
A comparison of the standard direct solar radiometer in the VI area of Calpenta in 1969 revealed that the results of the A158 measurements were different from those of other instruments that had participated in IPC-I and IPC-II , To be higher than 1.2%.
During IPC-III (1970), a further 1.2% difference was found between A158 and the standard instrument A210 stored in Davos. Upon verification, these differences from the A158 supporting the use of the meter tolerance. A158 itself is not a problem. However, in order to avoid the recurrence of a similar situation, IPC-III, decided to use seven instruments, namely A140 (former Democratic Germany), A212 (former Soviet Union), A525 [Switzerland], A542 (South Africa) A561 (Sudan) A576 [Nigeria ) And A2273
On the other hand, after 1956 and a series of AS-1905 and SS-1913 between the alignment activities. The results show that the difference between the two is more than 3.5%, but between 4.4% to 5.0%. Thus, IPS-1956 itself is not very accurate, the reason is the original standard instrument itself, there are some problems.
Since the 1960s, with the rapid development of space science, it is required to continuously improve the accuracy of solar radiation measurement. For this purpose, an absolute radiometric reference consistent with the full irradiance of the International System of Units is required. IPS's experience shows that such a benchmark can not be established at the time of the standard direct solar table.
The late 1960s, the cavity as a receiver, and has a self-test function of the absolute emergence table have emerged. PACRDA, ECR and other models of absolute radiation in 970 to participate in the IPC-III. The results of the comparison show that there is a difference of about 2% between "IPS-1956" and Absolute Radiation Table, and the difference between "IPS-1956" and "Absolute Radiation Table" is low, but at the time, 1956, and the establishment of a new scale, the Radiation Board also made similar observations at the Grenoble Conference in 1975. It is not surprising that this is not the case.
It was only after several years of effort, that a new radiation standard, the World Radiometric Reference (expressed in WRR), was adopted at the seventh session of the WNO CIMO at its seventh session, in 1977, with effect from 1 January 1981 "IPS-1956".
China Meteorological Administration has decided to accept the above proposal, and in January 1, 1981 in the national implementation.
World Radiometric Reference (WRR)
Between 1970 and 1976, there were 10 types of altogether 15 absolute radiographs in Davos. A total of more than 25,000 determinations were made during this period, most of which were carried out during IPC-IV from August to October 1975. Due to historical reasons, PACRDA was used as the standard for comparison. By comparison, it can be seen that the ratio of "IPS-1956" to PACRDA 205 simultaneously measured at IPC-III in October 1970 was 0.9812. In October 1975, the ratio of 226 simultaneous determinations during IPC-IV was 0.9803. The difference between the two less than 0.1%. This means that PACRDA and the representative "IPS-1956" instruments are highly stable.
In addition, the absolute values of the 15 absolute radiographs for the comparison were within the range of 0.8% above the PACRDA 0.2%, half of which were within a narrow range of 0.15% . This indicates that the true value of the full irradiance of the International System of Units is within this range. As the absolute radiation table and PACRDA ratio of 1.0019, so there
WRR provides a full irradiance physical unit with an accuracy of better than 0.3%. It was recognized by the 1979 WMO Executive Committee and was included in the 1979 edition of the technical specifications.
To ensure the long-term stability of the new benchmark, the Absolute Radiation Table of four different designs (excluding the same type of instrument) is specified as the World Benchmark Group (WSG). In the composition of the WSG, the group of each instrument must meet the following requirements: ① long-term stability is better than ± 0.2%; ② instrument accuracy and precision within the WRR uncertainty limits (± 0.3%) ③ instrument The design is different from other instruments in the group.
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