Modeling Solar Radiation at the Earth’s Surface
Large Networks and Primary Data Sources
Member countries of WMO contribute measured data to the World Radiation Data Center (WRDC), located at the Main Geophysical Observatory in St. Petersburg, Russia. The WRDC serves as a central depository for solar radiation data collected at over 1000 measurement sites throughout the world. The WRDC was established in accordance with a resolution of WMO in 1964. This data set is highly summarized, and difficult to keep up to date, as massive contributions are made on a monthly basis, and intensive quality control measures are implemented before the data becomes available. The majority of data available from 1964 to 1993 is accessible at http://wrdc-mgo. nrel. gov, and data from 1994 to present is available at http://wrdc. mgo. rssi. ru. (Unfortunately, these sites present data in dissimilar formats.) The WRDC archive contains mainly global solar radiation and sunshine duration data. Rarely, other data such as direct solar radiation or net total radiation are recorded. Not all observations are made at all sites. Data are usually available in the form of daily sums of global radiation. Monthly-mean sunshine data are also available at many sites. The map in Fig. 1.8 shows those stations from which at least some solar radiation data has been collected and reported. Similar data, but limited to monthly-average global irradiation, are also available from the International Solar Irradiation Database (http://energy. caeds. eng. uml. edu).
Other WMO-supported networks include BSRN (see Sect. 6.1) and the Global Atmospheric Watch (GAW; http://www. wmo. ch/web/arep/gaw/ gaw_home. html). A map showing the current and projected BSRN sites appears in Fig. 1.9. As mentioned earlier, BSRN has been a leader in developing high-quality radiation data. It adds its own stringent quality-control process to that from the member organizations collecting the data. Some publications detailing these quality-control procedures and other experimental issues are available from http://bsrn. ethz. ch.
The International Daylight Measurement Programme (IDMP; http://idmp. entpe. fr) consists of a specialized international network that is worth mentioning because it combines photometers to measure illuminance and radiometers for irradiance, with a unified quality-control procedure. Measuring stations are scattered around 22 countries, but many are not operational anymore.
The U. S. National Oceanic and Atmospheric Administration (NOAA) Surface Radiation, or SURFRAD (http://www. srrb. noaa. gov/surfrad/ sitepage. html) and U. S. Department of Energy Atmospheric Radiation Measurement (ARM) program (http:// www. arm. gov) have also established national research networks, whose sites are
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Fig. 1.8 Map of stations contributing at least some data to the WRDC database |
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Fig. 1.9 Stations of the BSRN network |
shown in Fig. 1.10. (Note that most of these sites are also part of BSRN.) Other important U. S. sources of quality data are grouped into the CONFRRM network http:// rredc. nrel. gov/solar/newdata/confrrm. Older data are accessible from http:// rredc. nrel. gov/solar/#archived.
Other nations with large solar radiation measurement networks include Brazil (Fig. 1.11), India, and Australia. More national networks do exist, but their datasets are sometimes difficult (or expensive) to obtain, and/or difficult to quality assess. Many times, the full complement of solar components (direct beam, total
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Fig. 1.10 United States SURFRAD National Oceanic and Atmospheric Administration and Department of Energy ARM Southern Great Plains (SGP) measurement networks |
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Fig. 1.11 Brazilian solar radiation measurement network |
horizontal and diffuse horizontal) are not measured so quality checks on the balance of the three components are not available. In addition, calibration and measurement schedules may be irregular and intermittent.
