| Albedo | The albedo is the measure for the reflected radiation power. It is calculated from the ratio of the radiation, reflected by the ground, to the totally infalling global radiation from the atmosphere. |
| Albedometer | Instrument for the measurement of the short-wave radiation balance and the reflex-radiation of the ground, and the global radiation and the short-wave radiation, reflected by the ground. The albedometer measures the radiation in the range from 300 to 2800 nm. |
| Azimuth Angle | Horizontal angle (0 – 360°) |
| Brightness Intensity | The brightness intensity (E) states the ratio of the striking luminous flux
(F) to the illuminated area (A). Unit lux [lx]: E = F / A F = luminous flux in Lumen A = area |
| Solar radiation which is diffused on its way through the atmosphere by clouds, water- and dust-particles, and reaches the earth’s surface. | |
| Direct Radiation | Direct radiation is the share of the solar radiation which spreads out without striking an obstacle and which reaches the earth’s surface coming from directly from the sun. |
| Elevation Angle | Elevation angle, also called altitude angle, is the angle between the horizontal plane und a high-located arrival point (for ex. sun) over the horizon. |
| Global Radiation | Global radiation is the solar radiation which strikes the earth’s surface on a horizontal area. The global radiation consists of the directly infalling radiation (direct radiation) and the radiation which reaches the earth’s surface, diffused by clouds, water- and dust-particles (diffuse radiation). The spectral range extends in the short-wave range. (approx. 290 nm to 4000 nm) |
| Infrared Radiation | The wave length range extends from 780 nm to 1 mm. Infra red radiation is divided into the short-wave IR-A radiation with a wave length from 780 to 1400 nm, the IR-B radiation (1400 to 3000 nm), and the longwave partition, the IR-C radiation (3000 nm to 1 nm). |
| Short-wave Radiation | Solar radiation in the spectral range 290 – 4000 nm. The radiation source is the sun, the solar radiation is absorbed to some extend in the atmosphere, and partly on the earth’s surface. |
| Long-wave Radiation | Terrestrial radiation in the spectral range 4000 – 100 000 nm. It is irradiated by the atmosphere and the earth’s surface. |
| Net Radiation | Difference from short-wave global radiation, and long-wave atmospheric counter radiation on the one hand, and short-wave reflex-radiation and long-wave temperature radiation of the earth on the other hand |
| Net Radiometer | Instrument for the measurement of the net radiation. The sensor consists of thermopiles. The acquired spectral range is approx. between 200 and 100 000 nm. |
| PAR | Photo-synthetically active radiation in the spectral range 400 - 700 nm. It is an essential factor for plant growth (Forming of chlorophyll). (PAR = Photo-synthetically Active Radiation |
| Pyrradiometer | Instrument for the measurement of the radiation balance in the total spectrum (short- and long-wave range) of the solar radiation 300 - > 60 000 nm. Two separate thermo-elements acquire the infalling and reflected radiation and output them as electric voltage. The reference temperature is measured by a Pt100. |
| Pyranometer | Instrument for the measurement of the short-wave. The sensor consists of thermo-elements. The acquired spectral range is approx. between 300 und 2800 nm. |
| Silicon Pyranometer | The sensor-element of this instrument is a special siliconphotodiode. The acquired spectral range is approx. between 350 und 1000 nm. |
| Silicon Photodiode | Semi-conductor diodes, converting visible light, or IR-, UV as well, into electric power. |
| Visible Radiation | The light perceived by the human eye in the spectral range 360 ... 780 nm |
| Solar Constant | Radiation power of the solar radiation out of atmosphere. Mean value determined by WMO : 1367 W/m² |
| Sunshine Duration | Time period of the direct solar radiation in a certain place. |
| Solar Radiation | The solar radiation is the radiation of the sun. The maximum power of the electro-magnetic radiation is the visible light, however, comprises also other electro-magnetic waves from X-rays and UV- radiation up to radio waves. |
| Radiation Balance | Difference from infalling global radiation and the reflected radiation of the ground. |
| Radiation Balance Meter | Two contra-connected thermopiles form a difference: the global radiation infalling from above, and the radiation of the ground reflected from below. The difference is the radiation balance and is output as electric voltage. |
| Radiation Intensity | Radiation flux density (W/m²) |
| Thermopile | Consisting of blackened area and thermo-elements, which are affiliated with each others. Radiation is converted into heat and is output as thermo-voltage. |
| UV Radiation | Ultra-violet radiation, below the visible radiation. The ultra-violet spectrum comprises wave-lengths from 1 nm to 380 nm |
| UV-A Radiation | Radiation in the spectral range 380-315 nm. It is essential for the strengthening of the human immunity system, and is responsible for the sun tan of the skin. |
| UV-B Radiation | Radiation in the spectral range 280-315 nm It is dangerous for irreversible damages of the human skin (cancer of the skin). |
| WMO | World Meteorological Organization |
| Units | 1 cal cmֿ² minֿ¹ = 697,8 Wmֿ² 1 Wmֿ² = 0,001433 cal cmֿ² minֿ¹ 1 cal cmֿ² dֿ¹ = 0,0116 kWh mֿ² |
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