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Term
Explanation
Albedo
The portion of incoming radiation which is reflected by a surface
Azimuth angle
Angle in horizontal direction (0 to 360°) normally referred to North
Angle of incidence
Incident angle from zenith (0° is vertical, 90° is horizontal)
Cosine response
Radiometer directional response according to the cosine law
Diffuse horizontal irradiance
Solar radiation, scattered by water vapour, dust and other particles as it passes through
the atmosphere falling on a horizontal surface (DHI)
Direct normal irradiance
Radiation that has travelled in a straight path from the sun falling on a surface normal to
the beam (DNI)
Global horizontal irradiance
Total irradiance falling on a horizontal surface (GHI)
Global = Diffuse + (Direct x cos
α
);
α
is the solar zenith angle
Irradiance
Radiant flux density (W/m²)
Long-wave radiation
Radiation with wavelengths from 4 µm to more than 40 µm
Pyranometer
Radiometer for measuring short-wave global radiation
Pyrgeometer
Radiometer for measuring long-wave radiation
Pyrheliometer
Radiometer for measuring direct short-wave radiation
Net radiation
Long-wave downward radiation minus outgoing radiation
Short-wave radiation
Radiation with wavelengths from approximately 300 nm to 4000 nm (4 µm)
Thermopile
Thermal detector made up of many thermocouple junctions
WMO
World Meteorological Organisation, Geneva, Switzerland
WRC
World Radiation Centre, Davos, Switzerland
WRR
World Radiometric Reference (standard radiation scale) at WRC
WSG
World Standard Group of radiometer at WRC
Zenith angle
Angle from zenith (0° is vertical)
11. Keyword index
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