A method for the determination of the global solar radiation from meteorological satellites data

International audienceA statistical method is presented for the determination of the global solar radiation at ground level. It makes use of data from the meteorological satellites, which provide extensive coverage as well as adequate ground resolution. In the first step, a reference map of ground albedo is deduced from the time-sequence of satellite images. Then, by comparing the satellite data with the computed albedo map, a cloud coverage index is determined for each ground point of 5 km x 5 km. This index is linearly correlated to the atmospheric transmission factor. The regression parameters are estimated using a training set provided by ground pyranometers. Tests for two different time periods show a good agreement between the actual and model-derived hourly global radiation

Mise en œuvre et validation d'une méthode opérationnelle et automatique pour l'évaluation d'atlas solaires en Europe à l'aide de mesures satellitaires Meteosat (années 1983, 1984 et 1985)

We have set up the existing method of Cano (1982) to assess the global solar radiation using images acquired by the Meteosat satellite. The method is validated against approximately 1800 ground measurements taken during 11 months in 1983, 11 months in 1984 and 7 months in 1985. The major points of this method are 1) the construction of a map of planetary albedo in clear skies, 2) the estimation of a cloud index, n, denoting the percentage of cloud coverage within a pixel relatively to the albedo reference map, 3) the assessment of the relationship between the hourly atmospheric transmittance (K), defined as the ratio between the gloabl radiation and the radiation at the top of the atmosphere (G0h), and the cloud index n. The relationship has a form : K = -a n + b or Gh / G0h = -a n + b, where a and b > 0. Coefficients a and b are computed using measurements performed in the Meteo-France network (Gh) and images acquired in the visible channel of Meteosat (n). We conclude that the method is satisfactory. Existing atlases may be refined or completed (oceans) and unknown or poorly known micro-climates (accuracy 5 km) are evidenced. Accuracy in assessing the monthly means of hourly irradiation is 0,1 kWh/m2. The method is simple enough to be used in several applications relating to solar energy.Nous avons mis en oeuvre une méthode statistique déjà existante (Cano, 1982) d'évaluation du rayonnement global à 1' aide des mesures du satellite Météosat. Cette méthode a été testée sur environ 1800 données : 11 mois de l'année 1983, 11 mois de l'année 1984 et 7 mois de l'année 1985. Les grands points de cette méthode statistique sont les suivants : 1) la construction d'une carte d'albédo planétaire par ciel clair d'après une série temporelle d'images sous conditions ciel clair, 2) l'évaluation d'un indice d'ennuagement, n, représentant le pourcentage du pixel recouvert par les nuages, par comparaison avec la carte d'albédo planétaire (albédo référence), 3) l'évaluation de la relation statistique entre la transmittance atmosphérique horaire (K), définie comme le rapport entre le rayonnement global et le rayonnement hors atmosphère (G0h), et n (l'indice d'ennuagement). Cette relation est du type : K = -a n + b ou Gh / G0h = -a n + b, où a et b > 0. Les coefficients de régression de cette relation ont été établis à partir des données du réseau de la Météorologie Nationale (Gh) et des données quotidiennes du canal visible de Météosat (n). En conclusion, nous pouvons dire que cette méthode est satisfaisante, elle permet 1) d'affiner ou de compléter (océans) les atlas du rayonnement déjà existants, en mettant en évidence des micro-climats (précision à 5 km près) peu connus ou inconnus, 2) l'évaluation du rayonnement global horaire moyen mensuel avec une précision de l'ordre de 0,1 kWh/m2, 3) un grand nombre d'application dites solaires (précision de rentabilité, méthode de conception architecturale assistée par micro-ordinateur, dimensionnement ...)

Mise en oeuvre et validation d'une methode operationnelle et automatique pour l'evaluation d'atlas solaires en Europe a l'aide de mesures satellitaires Meteosat (1983-1984-1985)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Mapping the ground albedo of Western Africa and its time evolution during 1984 using Meteosat visible data

International audienceThis paper deals with the use of Meteosat visible data for the production of maps of the ground albedo. Meteosat visible data were routinely received at Ecole des Mines using a receiving station connected to a microcomputer during 1984 and the ground albedo was weekly mapped for Western Africa (4S to 16N, 18E to 4W). The main patterns as well as the variations in time of the albedo are depicted with respect to the vegetation types. The great spatial variability of the vegetation growth rate is confirmed and correlated to the variability of the rainfall

Estimating incident solar radiation at the surface from images of the Earth transmitted by geostationary satellites: the Heliosat Project

International audienceThe goals of the Heliosat project of Ecole Nationale Supérieure des Mines de Paris are: (i) to design a system for the estimation of incident solar radiation at ground level from images of the Earth acquired by geostationnary satellites, (ii) to produce detailed maps of the spatial distribution of the global radiation, and (iii) to improve the system depending upon the results and progress in science. Among the numerous methods already developed, one of them has been selected for its accuracy as well as its simplicity. It has been tested during 30 consecutive months starting from January 1983. Operations were performed in a completely automatic, unmanned fashion and trades-off between routine and accuracy have been adopted. Areas under concern were Europe and Central-Western Africa (1984 only). This paper presents the results of the tests conducted during 1983. Measurements of sixteen pyranometers were compared three times a day to the estimates of the selected method. Different comparisons are presented. The errors in the reconstruction of both the instantaneous hourly global radiation Gh and the monthly average of Gh is less than 0.06 kWh/m2. When compared to other methods, Heliosat ranks as one of the most accurate

Exploitation opérationnelle de la station Héliosat

Résultat d'exploitation pour l'année 1984 de la station Héliosat de réception et de traitement d'images Météosat. Obtention des cartes mensuelles de la fréquence d'ennuagement des 12 mois de 1984 pour l'Europe. Extension de la méthode à l'Afriqu