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6 d-radiation-from sun2earth

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It contains the description of the Solar radiation relation with the astronomical movements of both Earth and sun. Used in the class of Hydrology at the University of Trento

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6 d-radiation-from sun2earth

  1. 1. Riccardo Rigon IlSole,F.Lelong,2008,ValdiSella Solar Radiation From Sun to Earth
  2. 2. R. Rigon The energy irradiated by the Sun passes through an imaginary disc with diameter the same as the Earth’s. The energy flow is maximum at that point on the Earth where the radiation is perpendicular. From Sun to Earth 18 2 From Sun To Earth
  3. 3. R. Rigon T h e S u n i r r a d i a t e s approximately at the solar constant rate, which is, on the average, on the top of the atmosphere, Solar radiation http://en.wikipedia.org/wiki/Solar_constant Frolich,1985 19 3 From Sun To Earth
  4. 4. R. Rigon In its orbit around the Sun, the Earth keeps its north-south rotational axis unvaried, causing a different angle between the Sun’s rays and the surface of the Earth. Astronomical variability of radiation 4 Copying with Earth surface
  5. 5. R. Rigon Seasons The Earth is 5 million kilometers closer to the Sun during the northern winter: a clear indication that temperature is controlled more by orientation than by distance. Figure 3.1 5 From Sun To Earth
  6. 6. R. Rigon The Earth’s orbit around the Sun is an ellipse. The shape of the ellipse is determined by its eccentricity, which varies in time, changing the distances of the aphelion and perihelion Corrections to the solar constant http://www.ascensionrecta.com/ 20 6 From Sun To Earth
  7. 7. R. Rigon Precession of the polar axis The axis of rotation moves with a slow period, executing a complete precession every 26,000 years. Polar stars behave like this for only a very short period 7 From Sun To Earth
  8. 8. R. Rigon Astronomical influences Orbit angle Orbit change Orbit shape 8 From Sun To Earth
  9. 9. R. Rigon Therefore the solar contant must be corrected (e.g. Corripio, 2002): Solar radiation in hydrological models 9 S From Sun To Earth
  10. 10. R. Rigon N is the day of the year (in 1, ..., 365) where: Solar radiation in hydrological models 10 Therefore the solar contant must be corrected (e.g. Corripio, 2002):S From Sun To Earth

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