15 research outputs found
Sensitivity study of the instrumental temperature corrections on Brewer total ozone column measurements
The instrumental temperature corrections to be applied to the ozone measurements by the Brewer spectrophotometers are derived from the irradiance measurements of internal halogen lamps in the instruments. These characterizations of the Brewer spectrophotometers can be carried out within a thermal chamber, varying the temperature from -5 to +45ºC, or during field measurements, making use of the natural change in ambient temperature. However, the internal light source used to determine the thermal sensitivity of the instrument could be affected in both methods by the temperature variations as well, which may affect the determination of the temperature coefficients. In order to validate the standard procedures for determining Brewer’s temperature coefficients, two independent experiments using both external light sources and the internal halogen lamps have been performed within the ATMOZ Project. The results clearly show that the traditional methodology based on the internal halogen lamps is not sensitive to the temperature-caused changes in the spectrum of the internal light source. The three methodologies yielded equivalents results, with differences in total ozone column below 0.08% for a mean diurnal temperature variation of 10ºC.This work has been supported by the European Metrology Research Programme (EMRP) within the joint research project ENV59 “Traceability for atmospheric total column ozone” (ATMOZ)
Characterization of Dobsons instruments within EMRP ATMOZ Project
Presentación realizada en: ATMOZ workshop at 11th RBCC-E, celebrado en El Arenosillo, Huelva, el 1 de junio de 2017
Liquid nitrogen cryostat for predictable quantum efficient detectors
We present the design and testing of a cryostat to be used with induced junction photodiodes of the Predictable Quantum Efficient Detector (PQED). Long-term reflectance measurements indicate that possible ice growth on the photodiodes at the temperature of liquid nitrogen (LN) is significantly reduced from earlier PQED cryostat designs.Peer reviewe
Adaption of an array spectroradiometer for total ozone column retrieval using direct solar irradiance measurements in the UV spectral range
A compact array spectroradiometer that enables precise and robust
measurements of solar UV spectral direct irradiance is presented. We
show that this instrument can retrieve total ozone column (TOC)
accurately. The internal stray light, which is often the limiting
factor for measurements in the UV spectral range and increases the
uncertainty for TOC analysis, is physically reduced so that no other
stray-light reduction methods, such as mathematical corrections, are
necessary. The instrument has been extensively characterised at the
Physikalisch-Technische Bundesanstalt (PTB) in Germany. During an
international total ozone measurement intercomparison at the
Izaña Atmospheric Observatory in Tenerife, the high-quality applicability of
the instrument was verified with measurements of the direct solar
irradiance and subsequent TOC evaluations based on the spectral data
measured between 12 and 30 September 2016. The results showed
deviations of the TOC of less than 1.5 % from most other
instruments in most situations and not exceeding 3 %
from established TOC measurement systems such as Dobson or Brewer
Characterization of the instrument temperature dependence of Brewer total ozone column measurements [Discussion paper]
The instrumental temperature correction to be applied to the ozone measurements by the Brewer spectrophotometers is derived from measurements of the irradiance from an internal halogen lamp in the instrument. These characterisations of the
Brewer instruments can be carried out within a thermal chamber, varying the temperature from -5◦C to +45◦C, or during field measurements, making use of the natural change in ambient temperature. However, the internal light source used to determine 5 the thermal sensitivity of the instrument could be affected in both methods by the temperature variations as well, which may affect the determination of the temperature coefficients. In order to validate the standard procedures for determining Brewer’s temperature coefficients, two independent experiments using both external light sources and the internal lamps have been performed within the ATMOZ Project. The results clearly show that the traditional methodology based on the internal lamps is not affected by possible temperature effects on the internal lamps. The three methodologies yielded equivalents results, with differences in total ozone column below 0.08% for a mean diurnal temperature variation of 10◦
10 C
Sensitivity study of the instrumental temperature corrections on Brewer total ozone column measurements
The instrumental temperature corrections to be applied to the ozone measurements by the Brewer spectrophotometers are derived from the irradiance measurements of internal halogen lamps in the instruments. These characterizations of the Brewer spectrophotometers can be carried out within a thermal chamber, varying the temperature from -5 to +45ºC, or during field measurements, making use of the natural change in ambient temperature. However, the internal light source used to determine the thermal sensitivity of the instrument could be affected in both methods by the temperature variations as well, which may affect the determination of the temperature coefficients. In order to validate the standard procedures for determining Brewer’s temperature coefficients, two independent experiments using both external light sources and the internal halogen lamps have been performed within the ATMOZ Project. The results clearly show that the traditional methodology based on the internal halogen lamps is not sensitive to the temperature-caused changes in the spectrum of the internal light source. The three methodologies yielded equivalents results, with differences in total ozone column below 0.08% for a mean diurnal temperature variation of 10ºC.This work has been supported by the European Metrology Research Programme (EMRP) within the joint research project ENV59 “Traceability for atmospheric total column ozone” (ATMOZ)
Sensitivity study of the instrumental temperature corrections on Brewer total ozone column measurements
The instrumental temperature corrections to be applied to the ozone
measurements by the Brewer spectrophotometers are derived from the irradiance
measurements of internal halogen lamps in the instruments. These
characterizations of the Brewer spectrophotometers can be carried out within
a thermal chamber, varying the temperature from −5 to +45 °C, or during field measurements, making use of the natural change in ambient
temperature. However, the internal light source used to determine the thermal
sensitivity of the instrument could be affected in both methods by the
temperature variations as well, which may affect the determination of the
temperature coefficients. In order to validate the standard procedures for
determining Brewer's temperature coefficients, two independent experiments
using both external light sources and the internal halogen lamps have been
performed within the ATMOZ Project. The results clearly show that the
traditional methodology based on the internal halogen lamps is not sensitive
to the temperature-caused changes in the spectrum of the internal light
source. The three methodologies yielded equivalents results, with differences
in total ozone column below 0.08 % for a mean diurnal temperature variation
of 10 °C