RADIATION

One of the most important meteorological radiation parameters is solar radiation. The sun is the energy source behind meteorological processes. The primary meteorological measurements, done in virtually every network, are those of global solar radiation, called pyranometer, and of sunshine duration.

Specialized companies are Hukseflux , Kipp & Zonen, Eplab and EKO.

The choice of instruments for the measurement of solar radiation largely depends on the application. There are three classes of pyranometers: secondary standard (the highest), first class and second class. The pyranometer is standardised according to ISO9060.

When purchasing a radiometer, it is suggested to look at temperature dependence and directional response.

The choice of instruments for sunshine duration is more difficult. This type of instrument is not standardized and the measurement can be done in various ways. Sunshine duration is often monitored only in order not to interrupt historical records (the sunshine duration measurement came well before the global solar radiation measurement and is demanded by WMO) and for tourism. From a physics point of view, the global radiation measurement is more useful. The present tendency is to use the pyranometer measurement combined with some specialized software. The method is promoted by Kipp & Zonen and gets around the necessity to buy additional sensors and facilitates calibration.

In agricultural and surface energy balance studies not only the incoming but also the reflected radiation play a role. Also another spectral region comes into the equation, Far Infra Red radiation. The instruments necessary for this are called net-radiometers (total radiation budget) and pyrgeometers (Far Infra Red only). Manufacturers are again Hukseflux , Kipp & Zonen, Eplab and EKO.

The radiation budget is extremely important for the global climate studies. There is a large number of specialized manufacturers of radiometers for scientific application.

A large variety of radiometers with a large spectral resolution can be offered by ASDI and Hovermere (wavelength meters and Fabry Perot interferometers.)

For the Ultra Violet (damaging to the human skin), there is Solar Light and Scintec making a sensor with an erythemal sensitivity. And Sci-Tec making the Brewer spectrophotometer for spectral measurements.

For oceanographic and under water measurements there is Biospherical Instruments.

For satellite ground truthing the Skye Instruments company offers special sensors that are tuned to satellite channels.

For analysis of aerosols the PREDE and Hovermere companies make special sun photometers and sky radiometers.

WMO also defines LUX measurements (detectors with the sensitivity of the human eye). Supplier Kipp & Zonen and Li-Cor.

In agriculture the measurement of PAR (Photosynthetically Active Radiation, or the part of the solar radiation that can be used by an average plant) is very common. Supplier Li-Cor.