Kippzonen UVS-E-T UV Radiometers Manual de usuario descargar pdf (Pagina 16)

4.1.2 CALIBRATION STEP B:

DETERMINATION OF THE CONVERSION

FACTOR TABLE

Without any measurement correction, a broad-band UV

radiometer can provide results that deviate by a factor

of 2 or more from the true values. The magnitude of the

deviation depends mainly on the extent of the spectral

mismatch and the measurement conditions.

The measurement conditions for which correction

factors are calculated are obtained by varying the solar

zenith angle, Θ

, and the total Ozone column density,

] in the radiative transfer model TUV [Ref. 3]. Other

atmospheric parameters affecting UV irradiances, such

as extinction due to aerosols, are not explicitly included

as they are assumed to be comparatively small.

The modelled UV spectra are used to determine the

conversion factors

, γ (Θ

), which are defined as:

γ =T

UVS

UVX

where T

UVS

and T

UVX

denote the normalized spectral

response function-weighted irradiance and the ‘true’

irradiance, respectively:

where e

TUV

(

Θ

) denotes the TUV modelled

irradiance as a function of the variable input

parameters Θ

and O

. Note, that the ‘true’ irradiance,

UVX

, represents the modelled irradiance weighted with

a theoretical spectral response function, s

UVX

(

). Such

a theoretical spectral response function could be the

Erythemal weighting function CIE-1987 [Ref. 4]. The

conversion factors calculated with the Erythemal

weighting function provide the corrections for the UVS-

E-T and UVS-AE-T radiometers.

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