Shortwave irradiance is the energy of direct and diffuse sunlight as measured by pyranometers. Conrtrary, the longwave infrared radiance is the heat radiation of any body not at 0°C, i.e. the earth' surface or the atmosphere (water vapour/clouds), and is measured by pyrgeometers. Both devices are often deployed twice in the same location, once directed upwards and once downwards. This allows to measure individually the four components of the radiation balance: R_net = SW_in - SW_out + LW_in - LW_out. These terms denotate (f.l.t.r.) radiation balance, shortwave radiation from sun/atmosphere, shortwave radiation from surface, longwave radiation from atmosphere, longwave radiation from surface.

All components of the radiation are energy fluxes and are denoted as energy per second [J s^-1] (= [W]) per squaremeter [m^-2]. The albedo is the ratio between incoming shortwave and outgoing shortwave radiation and is a value for sun energy available for the system. The albedo is thus also an indicator for surface, i.e. how much radiation they can absorb. Snow for example is very bright and reflects back large amounts of the incoming radiation, its albedo is typically close to 1 (0.95-0.99, depending on the age of snow). Other surfaces, such as forest oder grassland have a much lower albedo, ranging from 0.15 to 0.3, depending on the specific kind of vegetation. Globaly, the albedo is at approximately 0.3, and is obviously influenced by changes in the surface. Additionally, the albedo, or rather the reflection of the shortwave incoming radiation can be depenent on the angle of incidence. An example for this is the albedo of water, where, when the sun is low over the horizon, a much larger amount is reflected, yielding the image of a mirror instead of a water surface. Certainly, rough water movement inhibits this phenomenon.