Figure 2.3.3 shows a typical terrestrial solar spectrum and the spectral response of a siliconsolar cell. If the spectral distribution of incident radiation was fixed, a calibration couldbe established that would remain constant; however, there are some variations in spectraldistribution2 with clouds and atmospheric water vapor. LI-COR estimates that the errorintroduced because of spectral response is±5% maximum under most conditions of naturaldaylight and is ±3% under typical conditions.