Knowledge Center

In this glossary Kipp & Zonen sums up commonly used terms and definitions in our field of work. Focused on terms related to solar radiation and atmospheric science. Terms we use throughout our website. If you are looking for a specific term, use the index below to easily find it.  

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 


Process during which incoming energy is absorbed by an object.

Ratio of the actual solar radiation path through the atmosphere to the direct vertical path.

The proportion of incident radiation being reflected by an object or surface.

Sensor for measuring incoming and reflected radiation such that the Albedo can be calculated.

Sensor for measuring wind speed.

All the air surrounding the earth.

General term for sensors measuring the atmospheric air pressure.

Temperature scale named after the Swedisch scientist Anders Celsius. 0 ºC represents the freezing point of water, 100 ºC represents its boiling point; both under standard conditions.

Statistical characteristics of the weather during a certain time period in a certain region.

The changeover from the gaseous state to liquid state.

The coloured ring around the sun or moon caused by the refraction of light through watervapour in the atmosphere.

Dew Point
The temperature point to which air has to cool down to saturate with water vapour.

Change in direction of light waves at the edge of objects or through small apertures.

Diffuse Radiation
Scattered and reflected solar radiation falling onto a horizontal surface, with the direct radiation excluded.

Direct Radiation
Solar radiation falling directly onto a surface normal to the sun, with the diffuse radiation excluded.

Dobson Unit
Unit of measurement for the total amount of ozone between the measuring instrument and the sun. 100 DU = 1m column of ozone at ground level under standard atmospheric conditions. The typical yearly mean value in Europe is 330 to 360 DU.

Slow temporal change of the measuring value of a sensor.

The date when day and night have the same length.

Far Infrared Radiation (FIR)
Long-wave radiation in the range of 3 to 50 µm.

Global Radiation
Total of direct and diffuse solar radiation from the hemisphere falling onto a horizontal surface.

The presence of water vapour in the air, usually measured by hygrometers.

Temporal integral of illuminance (Wh/m²).

Instantaneous value of radiation (W/m²).

Infrared Radiation
Long-wave radiation in the range of 0.7 to 50 µm.

When the air temperature rises in relation to the height above ground level instead of falling.

On meteorological maps, a line connecting locations of equal barometric pressure.

On meteorological maps, a line connecting locations with the same sunshine duration values.

On meteorological maps, a line connecting locations with the same solar irradiance.

On meteorological maps, a line connecting locations with the same air temperature.

Temperature scale named after scientist Lord Kelvin. Zero Kelvin equals - 273.15 º Celsius. One degree on the Kelvin scale equals one degree on the Celsius scale.

ght Detection And Ranging uses laser pulses to determine the concentration and spatial distribution of features in the atmosphere, such as aerosols and gasses.

Electromagnetic radiation visible to the human eye, wavelengths between 400 nm and 700 nm.

Visible electrical discharge in the atmosphere.

Measuring Error
Deviation of a measuring value from the real value.

Measuring Range
Range of values in which measuring errors do not exceed certain specified limits.

Measuring Instrument
A sensor for measuring a physical parameter.

Measuring Chain
Series of components to measure a physical parameter and to transform the measuring signal into the desired output format.

Measuring Principle
Physical basis of the measurements.

Measuring Signal
Output value of a sensor or measuring device which is directly related to the physical parameter being measured.

Measuring Procedure
Application of a measuring principle and a measuring method.

Measuring Value
A numerical value in specified units derived from the measuring signal of a sensor.

Minimum Erythemal Dose. MED/hr is a measure of skin exposure to UV radiation.

A layer of the upper atmosphere located between the stratosphere and the ionosphere.

The science that deals with atmospheric phenomena and processes, particularly with respect to weather conditions and forecasting.

Method of Measurement
Special modus operandi of measuring independent from the measuring principle.

The science of determining measuring values of physical parameters.

Net Radiation
Difference between incoming and outgoing radiation of the same spectral range.

Measuring signal coming out of a sensor.

Gas naturally occurring in the atmosphere. In higher concentrations it is toxic and corrosive. Its molecules consist of three oxygen atoms and the chemical formula is O3.

Ozone Hole
Term for a decrease of the atmospheric ozone content by more than 50 % from normal in a defined geographical area.

Ozone Layer
The ozone layer is the area in the atmosphere at a height from  20 to 40 km which absorbs a considerable part of the UV radiation coming from the sun.

Any form of water falling to earth from the atmosphere including rain, snow, sleet and hail.

Sensor for the measurement of global solar radiation in a spectral range from 300 to 3000 nm.

Sensorfor the measurement of global solar and atmospheric radiation in a spectral range from 5 to 50 µm.

Sensor for the measurement of direct solar radiation in a spectral range from 300 to 3000 nm.  

Sensor for remote measurement of temperature.

RAdio Detection And Ranging uses radio signals to determine the position of features in the atmosphere. In meteorology this is usually Weather Radar for mapping clouds and precipitation.

Transport of energy by electromagnetic waves. The spectrum extends from very short wavelength cosmic radiation through to X-rays, ultraviolet, visible light, infrared and on to radio waves and very long wavelength microwaves.

Radiation Balance
Difference between upward and downward radiation at both short and long wavelengths.

Smallest difference between two measuring values that can be detected by the sensor or subsequent parts of the measuring chain.

Response Time
Time taken for the output value to reach a defined percentage of the input value after a step-change in the input value.

Condition where the concentration of water vapour in the air has reached its theoretical maximum. This maximum depends on the ambient temperature and pressure.

Change of the output value in relation to the input value.

The hemispherical part of the atmosphere that is directed to the sun, it causes diffuse radiation. In space there is only direct solar radiation.

Solar Constant
Long-term mean solar irradiance (1.368 kW/m²) outside the earth's atmosphere falling onto a 1 m² surface which is oriented normal to the sun's rays whilst the distance between earth and sun is medial.

Sensing instrument for the measurement of radiation over a range of wavelengths.

The stratosphere is a layer in the atmosphere at a height from 10 - 15 km up to 50 km. It is above the troposphere and below the mesosphere. It is nearly cloudless and contains the ozone layer.

An input value above or below which there is a specific change of the output value.

Lowest layer of the atmosphere. Here is where the weather occurs. The troposhere reaches up to a height of 10 - 15 km. Between the troposphere and the stratosphere is the tropopause.

Junction layer of troposphere and stratosphere, the height varies from 10 to 15 km depending on location and conditions.

Ultraviolet Radiation
Invisible radiation in the spectral range from 100 to 400 nm.

UV Index
Global UV Index of UN / WMO / WHO for the evaluation of values of erythemally weighted UV radiation that is harmful to skin.

Condition of the atmosphere at a certain time and location. The weather is mainly influenced by solar radiation, air temperature, air humidity, precipitation, air pressure and air movement.

Movements of masses of air in the atmosphere. Traditionally regarded as horizontal but nowadays often measured in 3 axes.

The highest point of the sky, vertically above the observer.