Summary
In several branches of climatology, and in related disciplines, estimates of shortwave and/or longwave diffuse irradiance are required. In this study, these irradiances are obtained by numerical integration of the fundamental radiance and source-receptor geometry equations for a variety of receptor slopes, receptor orientations, skyline patterns and sky radiance distributions. The angular increment used in the numerical integration over zenith and azimuth angle is varied to determine the optimal value in the trade-off between computing expense and accuracy. It is recommended that an angle ofπ/36 radians (5°) or smaller is required to evaluate the diffuse irradiance to 5 percent; for 10 percent error, the angle should not exceedπ/18 radians (10°).
Zusammenfassung
In etlichen Zweiggebieten der Klimatologie und verwandter Disziplinen ist es oft notwendig, Abschätzungen der kurzwelligen und langwelligen diffusen Einstrahlung zu liefern. In der vorliegenden Studie werden diese Einstrahlungswerte durch numerische Integration der fundamentalen Gleichungen für Strahlung und für die Geometrie der Auffangfläche für eine Vielzahl von Neigungs- und Orientationsverhältnissen, von Horizontabschirmung und von Verteilungen der Himmelsstrahlung bestimmt. Die in der numerischen Integration verwendenten Winkelelemente der Zenith- und Azimutwinkel wurden dahingehend verändert, um die Optimalwerte im Zusammenhang mit Rechenzeitaufwand und Rechengenauigkeit zu ermitteln. Es wird empfohlen, daß ein Winkel vonπ/36 rad (5°) oder kleiner nötig ist, um die diffuse Einstrahlung mit 5 Prozent Genauigkeit zu bestimmen. Für einen 10%igen Fehler soll der Winkelπ/18 rad (10°) nicht übersteigen.
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Arnfield, A.J. Estimation of diffuse irradiance on sloping, obstructed surfaces: An error analysis. Arch. Met. Geoph. Biocl., Ser. B 30, 303–320 (1982). https://doi.org/10.1007/BF02324672
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DOI: https://doi.org/10.1007/BF02324672