Due to the existence of thermal offsets,global solar irradiances measured by pyranometers are smaller than actual values,and errors are larger in the daytime.Until now,there is no universally-recognized correction met...Due to the existence of thermal offsets,global solar irradiances measured by pyranometers are smaller than actual values,and errors are larger in the daytime.Until now,there is no universally-recognized correction method for thermal offset errors.Therefore,it is imperative to identify a convenient and effective correction method.Five correction methods were evaluated based on the data measured from a field experiment from 23 January to 15 November,2011.Results have shown:1) Temporal variation characteristics of thermal offsets in the four tested pyranometers are consistent.2) Among the five methods,non-dimensional quantity method is suggested for use to correct thermal offsets,because it is convenient and no modification of instruments is required.If collocated net longwave radiation and wind speed data are available and their uncertainties are small,the historical solar radiation datasets can also be corrected.And correction effects by the method are better.展开更多
Using the temperature compensation and structure optimization design technology,developed the TBQ-2-B type standard pyranometer on the original pyranometer basis,its stability is better than 2%,reached the internation...Using the temperature compensation and structure optimization design technology,developed the TBQ-2-B type standard pyranometer on the original pyranometer basis,its stability is better than 2%,reached the international standard ISO 9060 and the World Meteorological Organization(WMO) instruments and methods of observation Committee(CIMO) on the first level pyranometer request. Over the years,comparing with our national solar radiation standard(absolute cavity radiometer),its performance is very stable. As a working standard pyranometer,it has been used for more than twenty years in the field of metrological calibration of meteorological radiation instruments.展开更多
Directional response is one of the most important parameters of pyranometer,which is crucial to evaluate the performance of the pyranometer by determining the responsivityand the corresponding radiation for solar beam...Directional response is one of the most important parameters of pyranometer,which is crucial to evaluate the performance of the pyranometer by determining the responsivityand the corresponding radiation for solar beam radiation from different directions of the pyranometer. In the paper,the method for testing directional error is present,four pyranometers are tested,after data processing,the directional errors of a secondary standard CM P22 and a first class CM P11 are 4.5 W/m^2 and 8.3 W/m^2 respectively,which are within the nominal specification given by the manufacturer. M eanwhile,the directional error of a first class pyranometerF S-S6 is 11.0 W/m^2,while the value of a second class pyranometer TBQ-2-B is15.2 W/m^2,which both meet the specification for classification. The results showthat these four pyranometers can reach the levels recommended by WM O and ISO,which validates that the method is feasible and the China made pyranometers are reliable.展开更多
Sahel is an African area with high solar potential. However, this potential is not uniform across the region. This paper examines the spatial distribution of the available solar potential by using six stations across ...Sahel is an African area with high solar potential. However, this potential is not uniform across the region. This paper examines the spatial distribution of the available solar potential by using six stations across the Sahel area. This comparative study was based on the analysis of in situ measurements in Dakar in Senegal, Niamey in Niger, Ouagadougou, Gaoua, Dori in Burkina Faso and N’Djamena in Chad. The results showed the presence of a good global solar potential with an average value of about 5.43 kWh/m<sup>2</sup>/day. The maxima of global potential are noted in the northern part in Niamey with a value of 6.24 kWh/m<sup>2</sup>/day while the minima are recorded in the south-eastern part in N’Djamena with an irradiation close to 4.71 kWh/m<sup>2</sup>/day. Then, the monthly evolution of this potential shows similar trends for all stations. Indeed, two maximums are observed during the year in Spring (March) and Autumn (October). However, for most of these stations, the minima of global potential are recorded in Winter (November, February) and during the rainy season (July, October). Moreover, the direct normal potential also shows seasonal trends for the two stations (Dakar, Niamey) where it was measured. The maxima of direct normal irradiation (DNI) are observed between February and May with a value of 5.5 kWh/m<sup>2</sup>/day in Dakar and in Niamey with a value around 5.32 kWh/m<sup>2</sup>/day between February and November.展开更多
Clouds affect the climate by positive and negative feedback. To study these effects at local scale, a radiation station was set up, which used two CM21 Kipp ＆ Zonen pyranometers （one inverted）, and two CG1 Kipp ＆ ...Clouds affect the climate by positive and negative feedback. To study these effects at local scale, a radiation station was set up, which used two CM21 Kipp ＆ Zonen pyranometers （one inverted）, and two CG1 Kipp ＆ Zonen pyrgeometers （one inverted） in Logan, Utah, USA. The pyranometers and pyrgeometers were ventilated using four CV2 Kipp ＆ Zonen ventilation systems. Ventilation of pyranometers and pyrgeometers prevent dew, frost and snow accumulation, which otherwise would disturb the measurement. Knowing that available energy （Rn） as Rn = Rsi - Rso ＋ Rli - Rio where Rsi and Rso are downward and upward solar radiation, respectively, and Rli and Rio as atmospheric and terrestrial, respectively, the effects of cloudiness were evaluated on a daily and annual basis. The results indicate that for the partly cloudy days of 4 and 5 September, 2007, cloudiness caused less available energy （Rn） in the amounts of-1.83 MJ·m^-2·d^-1 and -3.83 MJ·m^-2·d^-1 on these days, respectively. As shown, due to cloudiness at the experimental site, the net radiation loss was 2,804 - 4,055 = -1,251 MJ·m^-2·d^-1, which indicates a negative feedback due to cloudiness.展开更多
Shortwave radiometers such as pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to consensus reference, maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity w...Shortwave radiometers such as pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to consensus reference, maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity with no window that measures the extended broadband spectrum of the terrestrial direct solar beam irradiance, unlike shortwave radiometers that cover a limited range of the spectrum. The difference between the two spectral ranges may lead to calibration bias that can exceed 1%. This article describes a method to reduce the calibration bias resulting from using broadband ACRs to calibrate shortwave radiometers by using an ACR with Schott glass window to measure the reference broadband shortwave irradiance in the terrestrial direct solar beam from 0.3 μm to 3 μm. Reducing the calibration bias will result in lowering the historical solar irradiance by at least 0.9%. The published results in this article might raise the awareness of the calibration discrepancy to the users of such radiometers, and open a discussion within the solar and atmospheric science community to define their expectation from such radiometers to the radiometers’ manufacturers and calibration providers.展开更多
We used parallel sunshine duration datasets obtained with a Jordan sunshine recorder and three automatic sunshine duration sensors to investigate the differences between these instruments.We used measurements obtained...We used parallel sunshine duration datasets obtained with a Jordan sunshine recorder and three automatic sunshine duration sensors to investigate the differences between these instruments.We used measurements obtained at Shangdianzi(SDZ)regional Global Atmosphere Watch(GAW)station with a Jordan sunshine recorder,a DFC2 photoelectric sunshine meter,a CHP1 pyrheliometer,and two CMP11 pyranometers from 1 January to 5 July 2019 and from 3 November 2020 to 28 February 2021.The results showed that the daily sunshine duration measurements obtained from the Jordan sunshine recorder were comparable with those from the DFC2 meter and the CMP11 pyranometers under all-sky conditions,but were considerably different from those observed by the CHP1 pyrheliometer.An analysis of potential influencing factors showed that the solar zenith angle,the spectral range of the automatic sensors,the relative humidity,and the sky conditions were the main factors affecting the measurements of sunshine duration between the Jordan sunshine recorder and three automatic sensors.We proposed a simple linear regression function-the DFC2-equivalent sunshine duration estimation(DFCESD)model—to guarantee the consistency of the long-term sunshine duration series observed by the Jordan sunshine recorder at SDZ and the measurements from the DFC2 meter.Validation of the DFCESD model showed that the mean absolute difference(MAD)between the daily sunshine duration observed by the Jordan sunshine recorder and those from the DFC2 meter improved from-0.7 to-0.2 h day^(-1),the relative deviation(RD)improved from-9.3%to-2.3%,and the root-mean-square deviation(RMSD)decreased from 1.0 to 0.8 h day^(-1).展开更多
基金National Science Foundation of China for Young Scholars(40905071)National Natural Science Foundation of China for General Program(41275114)
文摘Due to the existence of thermal offsets,global solar irradiances measured by pyranometers are smaller than actual values,and errors are larger in the daytime.Until now,there is no universally-recognized correction method for thermal offset errors.Therefore,it is imperative to identify a convenient and effective correction method.Five correction methods were evaluated based on the data measured from a field experiment from 23 January to 15 November,2011.Results have shown:1) Temporal variation characteristics of thermal offsets in the four tested pyranometers are consistent.2) Among the five methods,non-dimensional quantity method is suggested for use to correct thermal offsets,because it is convenient and no modification of instruments is required.If collocated net longwave radiation and wind speed data are available and their uncertainties are small,the historical solar radiation datasets can also be corrected.And correction effects by the method are better.
文摘Using the temperature compensation and structure optimization design technology,developed the TBQ-2-B type standard pyranometer on the original pyranometer basis,its stability is better than 2%,reached the international standard ISO 9060 and the World Meteorological Organization(WMO) instruments and methods of observation Committee(CIMO) on the first level pyranometer request. Over the years,comparing with our national solar radiation standard(absolute cavity radiometer),its performance is very stable. As a working standard pyranometer,it has been used for more than twenty years in the field of metrological calibration of meteorological radiation instruments.
基金supported by public sector(Meteorology)research projects(GYHY201006044)meteorological key technology integration and application projects(CMAGJ2011M68)
文摘Directional response is one of the most important parameters of pyranometer,which is crucial to evaluate the performance of the pyranometer by determining the responsivityand the corresponding radiation for solar beam radiation from different directions of the pyranometer. In the paper,the method for testing directional error is present,four pyranometers are tested,after data processing,the directional errors of a secondary standard CM P22 and a first class CM P11 are 4.5 W/m^2 and 8.3 W/m^2 respectively,which are within the nominal specification given by the manufacturer. M eanwhile,the directional error of a first class pyranometerF S-S6 is 11.0 W/m^2,while the value of a second class pyranometer TBQ-2-B is15.2 W/m^2,which both meet the specification for classification. The results showthat these four pyranometers can reach the levels recommended by WM O and ISO,which validates that the method is feasible and the China made pyranometers are reliable.
文摘Sahel is an African area with high solar potential. However, this potential is not uniform across the region. This paper examines the spatial distribution of the available solar potential by using six stations across the Sahel area. This comparative study was based on the analysis of in situ measurements in Dakar in Senegal, Niamey in Niger, Ouagadougou, Gaoua, Dori in Burkina Faso and N’Djamena in Chad. The results showed the presence of a good global solar potential with an average value of about 5.43 kWh/m<sup>2</sup>/day. The maxima of global potential are noted in the northern part in Niamey with a value of 6.24 kWh/m<sup>2</sup>/day while the minima are recorded in the south-eastern part in N’Djamena with an irradiation close to 4.71 kWh/m<sup>2</sup>/day. Then, the monthly evolution of this potential shows similar trends for all stations. Indeed, two maximums are observed during the year in Spring (March) and Autumn (October). However, for most of these stations, the minima of global potential are recorded in Winter (November, February) and during the rainy season (July, October). Moreover, the direct normal potential also shows seasonal trends for the two stations (Dakar, Niamey) where it was measured. The maxima of direct normal irradiation (DNI) are observed between February and May with a value of 5.5 kWh/m<sup>2</sup>/day in Dakar and in Niamey with a value around 5.32 kWh/m<sup>2</sup>/day between February and November.
文摘Clouds affect the climate by positive and negative feedback. To study these effects at local scale, a radiation station was set up, which used two CM21 Kipp ＆ Zonen pyranometers （one inverted）, and two CG1 Kipp ＆ Zonen pyrgeometers （one inverted） in Logan, Utah, USA. The pyranometers and pyrgeometers were ventilated using four CV2 Kipp ＆ Zonen ventilation systems. Ventilation of pyranometers and pyrgeometers prevent dew, frost and snow accumulation, which otherwise would disturb the measurement. Knowing that available energy （Rn） as Rn = Rsi - Rso ＋ Rli - Rio where Rsi and Rso are downward and upward solar radiation, respectively, and Rli and Rio as atmospheric and terrestrial, respectively, the effects of cloudiness were evaluated on a daily and annual basis. The results indicate that for the partly cloudy days of 4 and 5 September, 2007, cloudiness caused less available energy （Rn） in the amounts of-1.83 MJ·m^-2·d^-1 and -3.83 MJ·m^-2·d^-1 on these days, respectively. As shown, due to cloudiness at the experimental site, the net radiation loss was 2,804 - 4,055 = -1,251 MJ·m^-2·d^-1, which indicates a negative feedback due to cloudiness.
文摘Shortwave radiometers such as pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to consensus reference, maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity with no window that measures the extended broadband spectrum of the terrestrial direct solar beam irradiance, unlike shortwave radiometers that cover a limited range of the spectrum. The difference between the two spectral ranges may lead to calibration bias that can exceed 1%. This article describes a method to reduce the calibration bias resulting from using broadband ACRs to calibrate shortwave radiometers by using an ACR with Schott glass window to measure the reference broadband shortwave irradiance in the terrestrial direct solar beam from 0.3 μm to 3 μm. Reducing the calibration bias will result in lowering the historical solar irradiance by at least 0.9%. The published results in this article might raise the awareness of the calibration discrepancy to the users of such radiometers, and open a discussion within the solar and atmospheric science community to define their expectation from such radiometers to the radiometers’ manufacturers and calibration providers.
基金Supported by the National Key Research and Development Program of China(2017YFB0504002)Special Fund for Basic Scientific Research of Institute of Urban Meteorology(2017)。
文摘We used parallel sunshine duration datasets obtained with a Jordan sunshine recorder and three automatic sunshine duration sensors to investigate the differences between these instruments.We used measurements obtained at Shangdianzi(SDZ)regional Global Atmosphere Watch(GAW)station with a Jordan sunshine recorder,a DFC2 photoelectric sunshine meter,a CHP1 pyrheliometer,and two CMP11 pyranometers from 1 January to 5 July 2019 and from 3 November 2020 to 28 February 2021.The results showed that the daily sunshine duration measurements obtained from the Jordan sunshine recorder were comparable with those from the DFC2 meter and the CMP11 pyranometers under all-sky conditions,but were considerably different from those observed by the CHP1 pyrheliometer.An analysis of potential influencing factors showed that the solar zenith angle,the spectral range of the automatic sensors,the relative humidity,and the sky conditions were the main factors affecting the measurements of sunshine duration between the Jordan sunshine recorder and three automatic sensors.We proposed a simple linear regression function-the DFC2-equivalent sunshine duration estimation(DFCESD)model—to guarantee the consistency of the long-term sunshine duration series observed by the Jordan sunshine recorder at SDZ and the measurements from the DFC2 meter.Validation of the DFCESD model showed that the mean absolute difference(MAD)between the daily sunshine duration observed by the Jordan sunshine recorder and those from the DFC2 meter improved from-0.7 to-0.2 h day^(-1),the relative deviation(RD)improved from-9.3%to-2.3%,and the root-mean-square deviation(RMSD)decreased from 1.0 to 0.8 h day^(-1).
