Spectral Measurements of Solar Irradiance and Radiance in Clear and Cloudy Atmospheres - Short-Wave Solar Radiation in the Earth's Atmosphere - page 84

Tab l e 3 . 1 . Evaluation of the uncertainty (standard deviation) of airborne measurements of
the radiative characteristics

Uncertainty source Uncertainty

type

Observations, which
the uncertainty
influences

Uncertainty estimation

Displacement of the Systematic All observations 1 nm

wavelength scale Random All observations 1 nm

Deviation from the
cosine dependence

Systematic The irradiance

observations

Look at Fig. 3.1

Calibration Systematic All observations 15% within UV, 10%

within VD and NIR

K-3 spectrometer Random All observations 5%withinUV, 1%within

VD and NIR

Aircraft pitch Systematic Observations of the

downwelling irradi-
ance in the clear
atmosphere

5% within UV, 10%
within VD and NIR for
the azimuths 0 and 180 ◦

Aircraft bumps Random Observations of the

downwelling irradi-
ance in the clear
atmosphere below
the bumps level

5% within UV, 10%
within VD and NIR for
the azimuths 90 and 270 ◦

Illumination
heterogeneity

Random Observations below

the inhomogeneous
clouds

10%

Surface heterogeneity Random Observations of the

upwelling radiance
and irradiance
below the bumps
level

10%

area in the field of view of the instrument is smoothing the surface hetero-
geneity. It is especially distinct during the upwelling irradiance observations:
the corresponding estimations indicated that the surface heterogeneity could
be neglected if the flight altitude was higher than the bumps level. Table 3.1
concludes the reasons and estimations of the uncertainties of the airborne
observations with the information-measuring system based on the K-3 instru-
ment.