UNIDEF   23986
UNIDAD DE INVESTIGACION Y DESARROLLO ESTRATEGICO PARA LA DEFENSA
Unidad Ejecutora - UE
artículos
Título:
An alternative method for calibration of narrow band radiometer using a radiative transfer model
Autor/es:
SALVADOR J., E. WOLFRAM, R. DELIA, F. ZAMORANO, C. CASICCIA , A. ROSALES AND E. QUEL
Revista:
J. Phys.: Conf. Ser
Editorial:
iopscience
Referencias:
Año: 2011 vol. 274 p. 12107 - 12114
ISSN:
1742-6588
Resumen:
The continual monitoring of solar UV radiation is one of the major objectives
proposed by many atmosphere research groups. The purpose of this task is to determine
the status and degree of progress over time of the anthropogenic composition
perturbation of the atmosphere. Such changes affect the intensity of the UV solar
radiation transmitted through the atmosphere that then interacts with living organisms
and all materials, causing serious consequences in terms of human health and durability
of materials that interact with this radiation. One of the many challenges that need to be
faced to perform these measurements correctly is the maintenance of periodic
calibrations of these instruments. Otherwise, damage caused by the UV radiation
received will render any one calibration useless after the passage of some time. This
requirement makes the usage of these instruments unattractive, and the lack of frequent
calibration may lead to the loss of large amounts of acquired data.
Motivated by this need to maintain calibration or, at least, know the degree ofMotivated by this need to maintain calibration or, at least, know the degree of
stability of instrumental behavior, we have developed a calibration methodology that
uses the potential of radiative transfer models to model solar radiation with 5% accuracy
or better relative to actual conditions. Voltage values in each radiometer channel
involved in the calibration process are carefully selected from clear sky data. Thus,
tables are constructed with voltage values corresponding to various atmospheric
conditions for a given solar zenith angle. Then we model with a radiative transfer model
using the same conditions as for the measurements to assemble sets of values for each
zenith angle. The ratio of each group (measured and modeled) allows us to calculate the
calibration coefficient value as a function of zenith angle as well as the cosine response
presented by the radiometer. The calibration results obtained by this method were
compared with those obtained with a Brewer MKIII SN 80 located in the city of Punta
Arenas, Chile using the sun as a source. These results show us that the proposed method
is a viable alternative for developing countries that use instrumentation of this type and
find it difficult to apply calibration programs on a regular basis.