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SoDa-Helioclim Data

SoDa: Solar Data portal

The SoDa Service is located at www.soda-pro.com and offers an access to a large set of information relating to solar radiation and its use. It builds links to other services that are located in various countries. To answer a request, the SoDa service invokes several resources to elaborate the appropriate answer and ensures the flow and exchange of information between the services and itself, as well as with the customer.

It provides weather data from different sources, mainly from the Helioclim database, managed by Mines PariTech. The data are computed from meterological geostationary satellite images, and are representative of real years.

SoDa proposes also a climatic data bank in monthly values, with irradiance and temperature, averaged over the years 1990 to 2004. It is provided by Mines ParisTech.

Services available from the SoDa portal

  • HelioClim 3: data for Europe and Africa, from 15 minutes time step to monthly values, for the horizontal global irradiance, the normal beam irradiance, and the global, beam and diffuse on inclined surfaces. These data are available for free for the year 2005. The same components are available for pay from 2004 to the current month, from a 1 minute time step to monthly values. |
  • MARS data: this resource provides time-series of daily irradiation from 1975 onwards for 50km x 50km aeras, computed from spatial interpolation of time-series measured in weather data networks; they are provided by the European Commission (UE). |
  • Nasa SSE: this resource provides time-series of daily irradiation from the 1st of July 1983 to the 31st December 2003 for cells of 1 degree by 1 degree. |
  • Nasa-SSE + HelioClim-1: get the best of the NASA SSE and HelioClim Databases of Solar Radiation over the world. This service provides time-series of daily irradiation from the 1st of July 1983 to the 31st of December 2003. It automatically selects the database offering the best quality for the selected site. |

These data don't provide temperatures, which have to be obtained by other means.

Details of the method

The Helioclim 3 data bank is produced with the Heliosat-2 method that converts observations made by geostationary weather data satellites into estimates of the global irradiation at ground level. This version integrates the knowledge gained by various exploitations of the original Heliosat method and its varieties in a coherent and thorough way.

It is based upon the same physical principles as for Solargis, but the inputs to the method are calibrated radiances, instead of the digital counts output from the sensor. This change opens the possibilities of using known models of the physical processes in atmospheric optics, thus removing the need for empirically defined parameters and of pyranometric measurements to tune them. The ESRA models are used for modeling the clear-sky irradiation. The assessment of the ground albedo and the cloud albedo is based upon explicit formulations of the path radiance and the transmittance of the atmosphere. The turbidity is based on climatic monthly Linke Turbidity coefficients data banks.

The Liu and Jordan (1960) model is used to split the global irradiance into the diffuse and beam components.