Modeling Solar Radiation at the Earth’s Surface
Uncertainty and Characterization of Solar Radiometers
Every measurement only approximates the quantity being measured, and is incomplete without a quantitative uncertainty. ISO defines uncertainty as:
A parameter, associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand [the measured quantity].
Every element of a measurement system contributes elements of uncertainty. The Guide to Measurement Uncertainty (GUM) of the International Bureau of Weights and Measures is presently the accepted guide for measurement uncertainty (BIPM 1995). The GUM defines Type-A uncertainty as derived from statistical methods, and Type-B sources as evaluated by “other means”, such as scientific judgment, experience, specifications, comparisons, or calibration data. These components of uncertainty are identified and combined in a rigorous manner to produce a standard, and eventually an expanded uncertainty reflecting the best estimate of uncertainty in a measurement parameter.
Various sources of uncertainty are reviewed in the next subsections. These indepth developments largely result from recent investigations.
