Consistency of total column ozone measurements between the Brewer and Dobson spectroradiometers of the LKO Arosa and PMOD/WRC Davos

Abstract. Total column ozone measured by Brewer and Dobson spectroradiometers at Arosa and Davos, Switzerland, have systematic seasonal variations of around 1.5 % using the standard operational data processing. Most of this variability can be attributed to the temperature sensitivity of approx. +0.1 %/K of the ozone absorption coefficient of the Dobson spectroradiometer (in this study D101). While the currently used Bass&Paur ozone absorption cross-sections produce inconsistent results for Dobson and Brewer, the use of the ozone absorption cross-sections from Serdyuchenko et al. (2013) in conjunction with an effective ozone temperature dataset produces excellent agreement between the investigated four Brewers (of which two double Brewers), and Dobson D101. Even though other ozone absorption cross-sections available in the literature are able to reduce the seasonal variability, all of those investigated produce systematic biases in total column ozone between Brewer and Dobson of 1.1 % to 3.1 %. The highest consistency of total column ozone from Brewers and Dobson D101 at Arosa/Davos of 0.1 % is obtained by applying the Rayleigh scattering cross-sections from Bodhaine et al. (1999), the ozone absorption cross-sections from Serdyuchenko et al. (2013), the effective ozone temperature from either ozonesondes or ECMWF, and the measured line-spread functions of Brewer and Dobson. The variability between Brewer and Dobson for single measurements of 0.9 % can be reduced to less than 0.5 % for monthly means and 0.3 % on yearly means. As show here, the proposed methodology produces consistent total column ozone datasets between Brewer and Dobson spectroradiometers of better than 1 %. For colocated Brewer and Dobson spectroradiometers, as is the case for the Arosa/Davos total column ozone times series, this allows the merging of these two distinct datasets to produce a homogeneous time series of total column ozone measurements. Furthermore, it guarantees the long-term future of this longest total column ozone time-series, by proposing a methodology how to eventually replace the ageing Dobson spectroradiometer with the state-of-the art Brewer spectroradiometer.

Download Full-text

Optical Characterization of Three Reference Dobsons in the ATMOZ Project – Verification of G. M. B. Dobson's Original Specifications

10.5194/amt-2017-411 ◽

2017 ◽

Author(s):

Ulf Köhler ◽

Saulius Nevas ◽

Glen McConville ◽

Robert Evans ◽

Marek Smid ◽

...

Keyword(s):

Cross Sections ◽

Ozone Absorption ◽

Total Column Ozone ◽

Satellite Validation ◽

World Standard ◽

Column Ozone ◽

Ozone Column ◽

Positive Effect ◽

Total Column

Abstract. Three reference Dobsons (regional standards Dobsons No. 064 Hohenpeissenberg – Germany and No. 074 Hradec Kralove – Czech Republic and primary = world standard Dobson No. 083 Boulder – USA) were optically characterized at PTB (Physikalisch-Technische Bundesanstalt in Braunschweig) in 2015 and at CMI (Czech Metrology Institute in Prague) in 2016 within the EMRP ENV 059 project Traceability for the total column ozone. Bandpass functions and the related parameters of the instruments were measured and compared with G. M. B. Dobson's specification in his handbook. A predominantly good match of the bandpass functions and the peak (centroid) wavelengths of D083, D064 and D074 with the nominal values could be observed. Slightly larger deviations from the nominal Dobson data can be seen in the longer wavelengths, especially in the D-wavelength. As consequence of these findings the differences of the derived Effective Absorptions Coefficients (EACs) for ozone to Dobson's nominal ones are not too large in both old Bass-Paur (BP) and new IUP-ozone absorption cross sections. Their consideration in the calculation of the total ozone column (TOC) leads to improvements of significantly less than ±1 % in the AD- and between −1 % and −2 % in the CD-wavelengths pairs. Besides this positive effect of the achievement of data with higher quality needed for trend analyses and satellite validation, it will be possible to explain uncommon behaviours of field Dobsons during calibration services.

Download Full-text

Scattering and Absorption Cross-sections of Atmospheric Gases in the Ultraviolet-Visible Wavelength Range (307–725 nm)

10.5194/acp-2020-941 ◽

2020 ◽

Author(s):

Quanfu He ◽

Zheng Fang ◽

Ofir Shoshamin ◽

Steven S. Brown ◽

Yinon Rudich

Keyword(s):

Refractive Index ◽

Wavelength Range ◽

Cross Sections ◽

Rayleigh Scattering ◽

Dispersion Relations ◽

Optical Absorption Spectroscopy ◽

Absorption Cross ◽

Atmospheric Gases ◽

Scattering Cross ◽

Scattering Cross Sections

Abstract. Accurate Rayleigh scattering and absorption cross-sections of atmospheric gases are essential for understanding the propagation of electromagnetic radiation in planetary atmospheres. Accurate extinction cross-sections are also essential for calibrating high finesse optical cavities and differential optical absorption spectroscopy and for accurate remote sensing. In this study, we measured the scattering and absorption cross-sections of carbon dioxide, nitrous oxide, sulfur hexafluoride, oxygen, and methane in the continuous wavelength range of 307–725 nm using Broadband Cavity Enhanced Spectroscopy (BBCES). The experimentally derived Rayleigh scattering cross-sections for CO2, N2O, SF6, O2, and CH4 agree with refractive index-based calculations, with a difference of 1.5 % and 1.1 %, 1.5 %, 2.9 %, and 1.4 % on average, respectively. The O2-O2 collision-induced absorption and absorption by methane are obtained with high precision at the 0.8 nm resolution of our BBCES instrument in the 307–725 nm wavelength range. New dispersion relations for N2O, SF6, and CH4 were derived using data in the UV-vis wavelength range. This study provides improved refractive index dispersion relations, n-based Rayleigh scattering cross-sections, and absorption cross-sections for these gases.

Download Full-text

Wavelength calibration of Brewer spectrophotometer using a tuneable pulsed laser and implications to the Brewer ozone retrieval

10.5194/amt-2017-459 ◽

2018 ◽

Cited By ~ 1

Author(s):

Alberto Redondas ◽

Saulius Nevas ◽

Alberto Berjón ◽

Meelis-Mait Sildoja ◽

Sergio Fabian León-Luis ◽

...

Keyword(s):

Standard Procedure ◽

Pulsed Laser ◽

Laser Source ◽

Ozone Absorption ◽

Total Column Ozone ◽

Wavelength Calibration ◽

Brewer Spectrophotometer ◽

Wavelength Scale ◽

Column Ozone ◽

Total Column

Abstract. In this contribution we present the wavelength calibration of the traveling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe (RBCC-E) at PTB in Braunschweig, Germany. The wavelength calibration is needed for the calculation of the ozone absorption coefficients used by the Brewer ozone algorithm. In order to validate the standard procedure for determining Brewer’s wavelength scale, a calibration has been performed by using a tuneable laser source at PTB in the framework of the EMRP project ENV59 ATMOZ Traceability for the total column ozone. Here we compare these results to those of the standard procedure for the wavelength calibration of the Brewer instrument. Such a comparison allows validating the standard methodology used for measuring the ozone absorption coefficient with respect to several assumptions. The results of the laser-based calibrations reproduces those obtained by the standard operational methodology and shows that there is a underestimation of 0.8 % due the use of the parametrized slit functions.

Download Full-text

OMI total column ozone: extending the long-term data record

Atmospheric Measurement Techniques ◽

10.5194/amt-8-4845-2015 ◽

2015 ◽

Vol 8 (11) ◽

pp. 4845-4850 ◽

Cited By ~ 37

Author(s):

R. D. McPeters ◽

S. Frith ◽

G. J. Labow

Keyword(s):

Cross Sections ◽

Total Ozone ◽

Retrieval Algorithm ◽

Data Set ◽

Total Column Ozone ◽

Ozone Data ◽

Combining Data ◽

Data Record ◽

Column Ozone ◽

Total Column

Abstract. The ozone data record from the Ozone Monitoring Instrument (OMI) onboard the NASA Earth Observing System (EOS) Aura satellite has proven to be very stable over the 10-plus years of operation. The OMI total column ozone processed through the Total Ozone Mapping Spectrometer (TOMS) ozone retrieval algorithm (version 8.5) has been compared with ground-based measurements and with ozone from a series of SBUV/2 (Solar Backscatter Ultraviolet) instruments. Comparison with an ensemble of Brewer–Dobson sites shows an absolute offset of about 1.5 % and almost no relative trend. Comparison with a merged ozone data set (MOD) created by combining data from a series of SBUV/2 instruments again shows an offset, of about 1 %, and a relative trend of less than 0.5 % over 10 years. The offset is mostly due to the use of the old Bass–Paur ozone cross sections in the OMI retrievals rather than the Brion–Daumont–Malicet cross sections that are now recommended. The bias in the Southern Hemisphere is smaller than that in the Northern Hemisphere, 0.9 % vs. 1.5 %, for reasons that are not completely understood. When OMI was compared with the European realization of a multi-instrument ozone time series, the GTO (GOME type Total Ozone) data set, there was a small trend of about −0.85 % decade−1. Since all the comparisons of OMI relative to other ozone measuring systems show relative trends that are less than 1 % decade−1, we conclude that the OMI total column ozone data are sufficiently stable that they can be used in studies of ozone trends.

Download Full-text

Solar Backscatter UV (SBUV) total ozone and profile algorithm

Atmospheric Measurement Techniques ◽

10.5194/amt-6-2533-2013 ◽

2013 ◽

Vol 6 (10) ◽

pp. 2533-2548 ◽

Cited By ~ 91

Author(s):

P. K. Bhartia ◽

R. D. McPeters ◽

L. E. Flynn ◽

S. Taylor ◽

N. A. Kramarova ◽

...

Keyword(s):

Cross Sections ◽

Total Ozone ◽

Lower Atmosphere ◽

Quasi Biennial Oscillation ◽

Total Column Ozone ◽

Best Estimate ◽

Current Algorithm ◽

Previous Algorithm ◽

Column Ozone ◽

Total Column

Abstract. We describe the algorithm that has been applied to develop a 42 yr record of total ozone and ozone profiles from eight Solar Backscatter UV (SBUV) instruments launched on NASA and NOAA satellites since April 1970. The Version 8 (V8) algorithm was released more than a decade ago and has been in use since then at NOAA to produce their operational ozone products. The current algorithm (V8.6) is basically the same as V8, except for updates to instrument calibration, incorporation of new ozone absorption cross-sections, and new ozone and cloud height climatologies. Since the V8 algorithm has been optimized for deriving monthly zonal mean (MZM) anomalies for ozone assessment and model comparisons, our emphasis in this paper is primarily on characterizing the sources of errors that are relevant for such studies. When data are analyzed this way the effect of some errors, such as vertical smoothing of short-term variability, and noise due to clouds and aerosols diminish in importance, while the importance of others, such as errors due to vertical smoothing of the quasi-biennial oscillation (QBO) and other periodic and aperiodic variations, become more important. With V8.6 zonal mean data we now provide smoothing kernels that can be used to compare anomalies in SBUV profile and partial ozone columns with models. In this paper we show how to use these kernels to compare SBUV data with Microwave Limb Sounder (MLS) ozone profiles. These kernels are particularly useful for comparisons in the lower stratosphere where SBUV profiles have poor vertical resolution but partial column ozone values have high accuracy. We also provide our best estimate of the smoothing errors associated with SBUV MZM profiles. Since smoothing errors are the largest source of uncertainty in these profiles, they can be treated as error bars in deriving interannual variability and trends using SBUV data and for comparing with other measurements. In the V8 and V8.6 algorithms we derive total column ozone by integrating the SBUV profiles, rather than from a separate set of wavelengths, as was done in previous algorithm versions. This allows us to extend the total ozone retrieval to 88° solar zenith angle (SZA). Since the quality of total column data is affected by reduced sensitivity to ozone in the lower atmosphere by cloud and Rayleigh attenuation, which gets worse with increasing SZA, we provide our best estimate of these errors, as well as the kernels that can be used to test the sensitivity of the derived columns to long-term changes in ozone in the lower atmosphere.

Download Full-text

Impact of using different ozone cross sections on ozone profile retrievals from Global Ozone Monitoring Experiment (GOME) ultraviolet measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3571-2007 ◽

2007 ◽

Vol 7 (13) ◽

pp. 3571-3578 ◽

Cited By ~ 49

Author(s):

X. Liu ◽

K. Chance ◽

C. E. Sioris ◽

T. P. Kurosu

Keyword(s):

Cross Section ◽

Cross Sections ◽

Data Sets ◽

Total Column Ozone ◽

Section Data ◽

Ozone Profile ◽

Ozone Monitoring ◽

Column Ozone ◽

Flight Model ◽

Total Column

Abstract. We investigate the effect of using three different cross section data sets on ozone profile retrievals from Global Ozone Monitoring Experiment (GOME) ultraviolet measurements (289–307 nm, 326–337 nm). These include Bass-Paur, Brion, and GOME flight model cross sections (references below). Using different cross sections can significantly affect the retrievals, by up to 12 Dobson Units (DU, 1 DU=2.69×1016 molecules cm−2) in total column ozone, up to 10 DU in tropospheric column ozone, and up to 100% in retrieved ozone values for individual atmospheric layers. Compared to using the Bass-Paur and GOME flight model cross sections, using the Brion cross sections not only reduces fitting residuals by 15–60% in the Huggins bands, but also improves retrievals, especially in the troposphere, as seen from validation against ozonesonde measurements. Therefore, we recommend using the Brion cross section for ozone profile retrievals from ultraviolet measurements. The total column ozone retrieved using the GOME flight model cross sections is systematically lower, by 7–10 DU, than that retrieved using the Brion and Bass-Paur cross sections and is also systematically lower than Total Ozone Mapping Spectrometer (TOMS) observations. This study demonstrates the need for improved ozone cross section measurements in the ultraviolet to improve profile retrievals of this key atmospheric constituent.

Download Full-text

OMI total column ozone: extending the long term data record

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-7491-2015 ◽

2015 ◽

Vol 8 (7) ◽

pp. 7491-7510 ◽

Cited By ~ 1

Author(s):

R. D. McPeters ◽

S. Frith ◽

G. J. Labow

Keyword(s):

Cross Sections ◽

Retrieval Algorithm ◽

Ozone Monitoring Instrument ◽

Data Set ◽

Total Column Ozone ◽

Ozone Data ◽

Combining Data ◽

Data Record ◽

Column Ozone ◽

Total Column

Abstract. The ozone data record from the Ozone Monitoring Instrument (OMI) onboard the NASA EOS-Aura satellite has proven to be very stable over the ten plus years of operation. The OMI total column ozone processed through the TOMS ozone retrieval algorithm (version 8.5) has been compared with ground based measurements and with ozone from a series of SBUV/2 instruments. Comparison with an ensemble of Brewer and Dobson sites shows an absolute offset of about 1.5 % but stability over the ten years to better than half a percent. Comparison with a merged ozone (MOD) data set created by combining data from a series of SBUV/2 instruments again shows an offset, of about 1 %, and a relative trend of less than half a percent over ten years. The offset is mostly due to the use of the old Bass and Paur ozone cross sections in the OMI retrievals rather than the Brion/Daumont/Malicet cross sections that are now recommended. The bias in the Southern Hemisphere is smaller than that in the Northern Hemisphere, 1 vs. 1.5 %, for reasons that are not completely understood. When OMI was compared with the European realization of a multi-instrument ozone time series, the GTO (GOME type ozone) dataset, there was a small trend of about −0.85 % decade−1. Since all the comparisons of OMI relative to other ozone measuring systems show relative trends that are less than 1 % decade−1, we conclude that the OMI total column ozone data are sufficiently stable that they can be used in studies of ozone trends.

Download Full-text

Impact of using different ozone cross sections on ozone profile retrievals from Global Ozone Monitoring Experiment (GOME) ultraviolet measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-971-2007 ◽

2007 ◽

Vol 7 (1) ◽

pp. 971-993

Author(s):

X. Liu ◽

K. Chance ◽

C. E. Sioris ◽

T. P. Kurosu

Keyword(s):

Cross Section ◽

Cross Sections ◽

Data Sets ◽

Total Column Ozone ◽

Section Data ◽

Ozone Profile ◽

Ozone Monitoring ◽

Column Ozone ◽

Flight Model ◽

Total Column

Download Full-text

Wavelength calibration of Brewer spectrophotometer using a tunable pulsed laser and implications to the Brewer ozone retrieval

Atmospheric Measurement Techniques ◽

10.5194/amt-11-3759-2018 ◽

2018 ◽

Vol 11 (6) ◽

pp. 3759-3768 ◽

Cited By ~ 2

Author(s):

Alberto Redondas ◽

Saulius Nevas ◽

Alberto Berjón ◽

Meelis-Mait Sildoja ◽

Sergio Fabian León-Luis ◽

...

Keyword(s):

Standard Procedure ◽

Tunable Laser ◽

Laser Source ◽

Absorption Coefficients ◽

Ozone Absorption ◽

Total Column Ozone ◽

Wavelength Calibration ◽

Wavelength Scale ◽

Column Ozone ◽

Total Column

Abstract. In this contribution we present the wavelength calibration of the travelling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe (RBCC-E) at PTB in Braunschweig, Germany. The wavelength calibration is needed for the calculation of the ozone absorption coefficients used by the Brewer ozone algorithm. In order to validate the standard procedure for determining Brewer's wavelength scale, a calibration has been performed by using a tunable laser source at PTB in the framework of the EMRP project ENV59 ATMOZ “Traceability for the total column ozone”. Here we compare these results to those of the standard procedure for the wavelength calibration of the Brewer instrument. Such a comparison allows validating the standard methodology used for measuring the ozone absorption coefficient with respect to several assumptions. The results of the laser-based calibrations reproduces those obtained by the standard operational methodology and shows that there is an underestimation of 0.8 % of the ozone absorption coefficients due to the use of the parametrized slit functions.

Download Full-text