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Main Properties of the HelioClim Databases |
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HelioClim is a family of databases which comprises total (total radiation is equivalent to "spectrally integrated") solar irradiance and irradiation values at ground level. The HelioClim databases, HC1 and HC3, are estimated from the Meteosat Second Generation (MSG) images. The method used to estimate the radiation values is named HelioSat-2. The main publication on this method is the one of Rigollier et al. (2004). The database HC2 is not available since summer 2009. An improved method HelioSat-4 is under preparation to process the future Meteosat images (Meteosat Third Generation, approx. 2017); it will create the database HC4.
| HC1 | HC2 | HC3 | HC4 | |
|---|---|---|---|---|
| Availability | available | not available anymore | available | available in 2017 |
| Main Properties | [1985 - 2005] 20 km daily horizontal |
not available anymore | [Feb. 2004 - yesterday] 3 km 15 min all plane orientations |
[2017 - ...] 500 m 10 min all plane orientations |
The HelioClim1 and HelioClim3 databases are referred in the website of the United Nation Environment Program (UNEP)
The Source of the data is the two images in the visible part of the spectra of MSG i.e. 600 nm and 800 nm. These images are acquired every 15 min, and covers Europe, Africa, the Mediterranean Basin, the Atlantic Ocean and part of the Indian Ocean, more precisely from -66° to 66° both in latitude and longitude. The spatial resolution is 3 km at the Nadir, and decreasing away from this point. The spatial coverage and resolution are depicted in this illustration. Principle of HelioSat-2: first, the two images are merged into a synthetic image normalized according to the sensor and the sun elevation. As this image is located in the visible part of the spectra, the idea of the HelioSat2 method is the following: the whiter the pixel, the cloudier. The method calculates the proportion of cloud contained in each MSG pixel compared to the same pixel value in clear sky conditions, in order to deduce the irradiation value at ground level. |
 Click on the image to magnify. |
The MSG satellites and images are the property of 
, Darmstadt. Once acquired on MSG the images are transmitted toward the ground in Darmstadt for geometrical and radiometric rectifications. Then the images are sent back to the satellite, which forward its images to a satellite named Hotbird located in its vicinity, which disseminates the images using a video channel to all the individual dishes of reception. The different steps are described on the following illustration:
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NB: The field of view is restricted to the pixels belonging to the Earth and for which an observer located on these pixels sees the satellite with an elevation angle above horizon larger than 12 degrees.
A pdf document of presentation of the HelioClim database is available here. As well, a lesson in French about the HelioSat-2 method as well as about the HelioClim database is accessible here.
HelioClim partly or fully sees 265 countries in the world 
Last update: 10/5/12 11:48 AM
