Derivation of cloud index from geostationary satellites and application to the production of solar irradiance and daylight illuminance data (PDF 240Ko) (1999) Ineichen P. and Perez R., Theoretical and Applied Climatology, February 1999. We investigate in the present paper, the relationship between satellite count, global irradiance and other solar and illumination and resource components, bringing a particular attention to low solar elevation situations (below 20°) which are very important in northern latitudes. Our investigation is based on data from two geostationary satellites: Meteosat and GOES, backed by ground measurements in Switzerland and the northeastern USA. The study of different clear sky normalizations lead to the conclusion that a linear correlation between the global clearness index and the irradiance (like the heliosat method) would be inaccurate for low solar elevations, and therefore for high latitude regions. We developed a model that directly relates an elevation dependent clearness index to the cloud index. This methodology presents a definite advantage because it can be generalized to address the clearness index of other solar radiation components, besides global irradiance, such as direct irradiance, diffuse illuminance, etc. The correlations described in this paper were developed on the data from Geneva (in the frame of the project Satellight) and evaluated on two other independent data sets (Albany, USA and Lausanne, Switzerland). Their precisions on a hourly basis, are respectively 30%, 40% and 60% for the global, diffuse and beam components (90, 55 and 95 W/m2). The use of independent data for the derivation and the validation of the models show that those can be used in a wide range of locations even if the applicability has to be assessed for very different climates. Remaining problems in the calculation of the ground albedo from Meteosat images. (1998) Hammer A., Heinemann D., Westerhellweg A., Department of Physics, Carl Von Ossietzky Universität Oldenburg, Germany. Report for the sixth SATELLIGHT meeting in Freiburg, Germany, September 1998. Derivation of Daylight and Solar Irradiance Data from Satellite Observations (PDF 188Ko) (1998) Hammer A., Heinemann D., Westerhellweg A. et al., Proceedings 9th Conference on Satellite Meteorology and Oceanography, Paris May 1998, pp 747-750. We present improvements and additions to an existing method for the derivation of the global irradiance. This includes new correction schemes for the influence of atmospheric extinction processes. These have been partly developed by simulating the satellite signal for a cloudless atmosphere using the radiative transfer code MODTRAN. In addition, the derivation of the diffuse irradiance is briefly outlined. Importance of Spatial and Temporal Determination of Meteosat Counts (PDF 156Ko) (1998) Ineichen P., Group of Applied Physics, University of Geneva. Report for the sixth SATELLIGHT meeting in Freiburg, Germany. The advantage of satellite derived ground radiation or illuminance data is their continuity in time and their spatial coverage that cannot be achieved by ground networks. In the first step of the conversion, the precision of the derived radiation from the satellite counts depends on the space and time accuracy of the satellite images. It is then dependent on the clear sky normalization and finally on the model used to convert the satellite counts. This working paper attempts to quantify the influence of the spatial and temporal determination of the satellite counts. Normalization of Meteosat counts - an investigation based on ocean pixels. (1997) Hammer A., Heinemann D., Westerhellweg A., Department of Physics, Carl Von Ossietzky Universität Oldenburg, Germany. Report for the fifth SATELLIGHT meeting in Sophia Antipolis, France, November 1997. Modifications of the Heliosat method - cloud index improvements, detection of snow cover and results of radiative transfer calculations. (1997) Hammer A., Degner T., Heinemann D., Westerhellweg A., Department of Physics, Carl Von Ossietzky Universität Oldenburg, Germany. Report for the fourth SATELLIGHT meeting in Oldenburg, Germany. Description and use of Modtran 5.0 to simulate a satellite signal. (1997) Heinemann D., Department of Physics, Carl Von Ossietzky Universität Oldenburg, Germany. Notes for the third SATELLIGHT meeting in Les Marécottes, Switzerland. Final report of ARMINES/ENSMP to the University of Oldenburg for the Satellight programme. (1997) Iehlé A., Bauer O. and Wald L., Groupe télédétection et modélisation, ENSMP, Sophia-Antipolis, France. Cloud index models: illumination and radiation evaluation. (1997) Ineichen P., Group of Applied Physics, University of Geneva. Report for the fourth SATELLIGHT meeting in Oldenburg, Germany. The strengths of satellite based solar resource measurements. (1997) Perez R., Seals R, Zelenka A. and Renné D., ASES Conference 1997. Modifications of the Heliosat procedure for irradiance estimates from satellite data. (1996) Beyer H. G., Costanzo C., Heinemann D., Solar Energy, 56, pp 207-212. Images taken by geostationary satellites may be used to estimate solar irradiance fluxes at the earth's surface. The Heliosat method is a widely applied procedure for this task. It is based on the empirical correlation between a satellite derived cloud index and the irradiance at the ground. Modifications to this procedure that may reduce the temporal variability of the correlation are presented. The modified method may open the way to the use of a generic relation of cloud index and global irradiance. Gewinnung zeitaufgeloester Solarstrahlungsdaten aus METEOSAT-Aufnahmen zur Analyse von solaren Energiesystemen. (1994) Beyer H.G., Costanzo C., Hammer A., Heinemann D., Reise Ch., Tagungsbericht 9. Int. Sonnenforum, Stuttgart. Satellite-Derived Surface Irradiance Data for the Analysis of Solar Energy Systems. (1994) Beyer H.G, Costanzo C., Hammer A., Heinemann D., Reise Ch., Proc. 10th Meteosat Scientific Users' Conference, Cascais. Statistical characterization of solar irradiance fields an analysis based on satellite images. (1993) Beyer H.G., Costanzo C., Heinemann D., Luther J., Reise Ch., Proc. ISES Solar World Congress, Budapest. Utilization of satellite data for the assessment of large scale PV grid integration. (1992) Beyer H.G., Reise Ch., Wald L., Proc. 11th CEC PV Solar Energy Conference, Montreux. Spatial degradation of satellite data. (1989) Justice J. O., Markham B. L., Townshend J. R. G., and Kennard R. L., International Journal of Remote Sensing, 10, pp 1539-1561. A method for the determination of the global solar radiation from meteorological satellite data. 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