Retrieval of stratospheric and tropospheric BrO columns from multi-axis DOAS measurements at Reunion Island (21° S, 56° E)

Abstract. Spectral measurements of BrO using zenith-sky and off-axis viewing geometries are combined in a linear multiple regression retrieval algorithm to provide stratospheric and tropospheric BrO vertical columns. One year of measurement data are investigated over Reunion-Island (20.9° S, 55.5° E), from July 2004 to July 2005. No seasonal variations of the retrieved BrO columns could be observed, in line with previous studies. A comparison between the stratospheric columns retrieved at 45°, 80°, 85°, 87.5° and 92.5° solar zenith angles and photochemical simulations initialized by chemical fields from the 3-D-CTM SLIMCAT and further constrained by observed NO2 profiles shows a good agreement only by considering a contribution from the very short-lived organic bromine substances to the stratospheric inorganic bromine budget, of 6 to 8 pptv. Furthermore, stratospheric BrO profiles retrieved from late twilight zenith-sky observations are consistent with a total inorganic bromine (Bry) loading of approximately 23 pptv. This represents 6 to 7 pptv more than can be supplied by long-lived organic bromine sources, and therefore supports an added contribution from very short-lived organic bromine substances as recently suggested in several other studies. Moreover strong evidences are presented for the existence of a substantial amount of BrO in the tropical free-troposphere, around 6 km altitude, possibly supplied by the decomposition of short-lived biogenic bromine organic compounds. Tropospheric BrO vertical columns of 1.1±0.45×1013 molec/cm2 are derived for the entire observation period. Comparisons between ground-based BrO vertical columns and total BrO columns derived from SCIAMACHY (onboard the ENVISAT satellite) nadir observations in a latitudinal band centered around 21° S present a good level of consistency, which further strengthens the conclusions of our study.

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Retrieval of stratospheric and tropospheric BrO columns from multi-axis DOAS measurements at Reunion Island (21° S, 56° E)

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-4733-2007 ◽

2007 ◽

Vol 7 (18) ◽

pp. 4733-4749 ◽

Cited By ~ 76

Author(s):

N. Theys ◽

M. Van Roozendael ◽

F. Hendrick ◽

C. Fayt ◽

C. Hermans ◽

...

Keyword(s):

Measurement Data ◽

Retrieval Algorithm ◽

Reunion Island ◽

Spectral Measurements ◽

Réunion Island ◽

One Year ◽

Chemical Fields ◽

Latitudinal Band ◽

Observation Period ◽

Good Agreement

Abstract. Spectral measurements of BrO using zenith-sky and off-axis viewing geometries are combined in a linear multiple regression retrieval algorithm to provide stratospheric and tropospheric BrO vertical columns. One year of measurement data are investigated over Reunion-Island (20.9° S, 55.5° E), from August 2004 to June 2005. A comparison between the stratospheric columns retrieved at 45°, 80°, 85°, 87.5° and 92.5° solar zenith angles and photochemical simulations initialized by chemical fields from the 3-D-CTM SLIMCAT and further constrained by observed NO2 profiles shows a good agreement only by considering a contribution from the very short-lived organic bromine substances to the stratospheric inorganic bromine budget, of 6 to 8 pptv. Furthermore, stratospheric BrO profiles retrieved from late twilight zenith-sky observations are consistent with a total inorganic bromine (Bry) loading of approximately 23 pptv. This represents 6 to 7 pptv more than can be supplied by long-lived organic bromine sources, and therefore supports an added contribution from very short-lived organic bromine substances as recently suggested in several other studies. Moreover strong evidences are presented for the existence of a substantial amount of BrO in the tropical free-troposphere, around 6 km altitude, possibly supplied by the decomposition of short-lived biogenic bromine organic compounds. Tropospheric BrO vertical columns of 1.1±0.45×1013 molec/cm² are derived for the entire observation period. Comparisons between ground-based BrO vertical columns and total BrO columns derived from SCIAMACHY (onboard the ENVISAT satellite) nadir observations in a latitudinal band centered around 21° S present a good level of consistency, which further strengthens the conclusions of our study.

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Validation of the Water Vapor Profiles of the Raman Lidar at the Maïdo Observatory (Reunion Island) Calibrated with Global Navigation Satellite System Integrated Water Vapor

Atmosphere ◽

10.3390/atmos10110713 ◽

2019 ◽

Vol 10 (11) ◽

pp. 713 ◽

Cited By ~ 1

Author(s):

Hélène Vérèmes ◽

Guillaume Payen ◽

Philippe Keckhut ◽

Valentin Duflot ◽

Jean-Luc Baray ◽

...

Keyword(s):

Water Vapor ◽

Global Navigation Satellite System ◽

Satellite System ◽

Navigation Satellite ◽

Reunion Island ◽

Raman Lidar ◽

Réunion Island ◽

Global Navigation ◽

Global Navigation Satellite ◽

Good Agreement

The Maïdo high-altitude observatory located in Reunion Island (21 ∘ S, 55.5 ∘ E) is equipped with the Lidar1200, an innovative Raman lidar designed to measure the water vapor mixing ratio in the troposphere and the lower stratosphere, to perform long-term survey and processes studies in the vicinity of the tropopause. The calibration methodology is based on a GNSS (Global Navigation Satellite System) IWV (Integrated Water Vapor) dataset. The lidar water vapor measurements from November 2013 to October 2015 have been calibrated according to this methodology and used to evaluate the performance of the lidar. The 2-year operation shows that the calibration uncertainty using the GNSS technique is in good agreement with the calibration derived using radiosondes. During the MORGANE (Maïdo ObservatoRy Gaz and Aerosols NDACC Experiment) campaign (Reunion Island, May 2015), CFH (Cryogenic Frost point Hygrometer) radiosonde and Raman lidar profiles are compared and show good agreement up to 22 km asl; no significant biases are detected and mean differences are smaller than 9% up to 22 km asl.

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Long-range isentropic transport of stratospheric aerosols over Southern Hemisphere following the Calbuco eruption in April 2015

10.5194/acp-2017-544 ◽

2017 ◽

Cited By ~ 1

Author(s):

Nelson Bègue ◽

Damien Vignelles ◽

Gwenaël Berthet ◽

Thierry Portafaix ◽

Guillaume Payen ◽

...

Keyword(s):

Southern Hemisphere ◽

Transient Behavior ◽

Stratospheric Aerosol ◽

Aerosol Layer ◽

Reunion Island ◽

Volcanic Aerosol ◽

Réunion Island ◽

One Year ◽

The Impact ◽

Aerosol Plume

Abstract. After 43 years of inactivity, the Calbuco volcano which is located in the southern part of Chile erupted on 22 April 2015. The space-time evolutions (distribution and transport) of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS), in situ aerosol counting (LOAC OPC) and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21° S; 55.5° E), the aerosol signal was unambiguously enhanced in comparison with "background" conditions with a volcanic aerosol layer extending from 18 km to 21 km during the May–July period. All the data reveal an increase by a factor of ~ 2 in the SAOD (Stratospheric Aerosol Optical Depth) with respect to values observed before the eruption. The aerosol e-folding time is approximately 90 days. Microphysical measurements obtained before, during and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over Reunion site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.16 ± 0.02 µm with an unimodal lognormal size distribution and the aerosol number concentration appears 20 times higher than before and one year after the eruption. A tendency toward "background" conditions has been observed about one year after the eruption, by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island between May and July 2015 reflects an inhomogeneous geographical distribution of the plume which is controlled by the latitudinal motion of these dynamical barriers.

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Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-7531-2016 ◽

2016 ◽

Vol 16 (12) ◽

pp. 7531-7543 ◽

Cited By ~ 8

Author(s):

Susana Fernandez ◽

Rolf Rüfenacht ◽

Niklaus Kämpfer ◽

Thierry Portafaix ◽

Françoise Posny ◽

...

Keyword(s):

Middle Atmosphere ◽

Microwave Radiometer ◽

Optimal Estimation ◽

Reunion Island ◽

Model Data ◽

Data Set ◽

North East ◽

Réunion Island ◽

Wind Profiles ◽

Good Agreement

Abstract. Ozone performs a key role in the middle atmosphere and its monitoring is thus necessary.At the Institute of Applied Physics of the University of Bern, Switzerland, we built a new ground-based microwave radiometer, GROMOS-C (GRound based Ozone MOnitoring System for Campaigns). It has a compact design and can be operated remotely with very little maintenance requirements, being therefore suitable for remote deployments. It has been conceived to measure the vertical distribution of ozone in the middle atmosphere, by observing pressure-broadened emission spectra at a frequency of 110.836 GHz. In addition, meridional and zonal wind profiles can be retrieved, based on the Doppler shift of the ozone line measured in the four directions of observation (north, east, south and west).In June 2014 the radiometer was installed at the Maïdo observatory, on Réunion island (21.2° S, 55.5° E). High-resolution ozone spectra were recorded continuously over 7 months. Vertical profiles of ozone have been retrieved through an optimal estimation inversion process, using the Atmospheric Radiative Transfer Simulator ARTS2 as the forward model. The validation is performed against ozone profiles from the Microwave Limb Sounder (MLS) on the Aura satellite, the ozone lidar located at the observatory and with ozone profiles from weekly radiosondes. Zonal and meridional winds retrieved from GROMOS-C data are validated against another wind radiometer located in situ, WIRA. In addition, we compare both ozone and winds with ECMWF (European Centre for Medium-Range Weather Forecasts) model data. Results show that GROMOS-C provides reliable ozone profiles between 30 and 0.02 hPa. The comparison with lidar profiles shows a very good agreement at all levels. The accordance with the MLS data set is within 5 % for pressure levels between 25 and 0.2 hPa. GROMOS-C's wind profiles are in good agreement with the observations by WIRA and with the model data, differences are below 5 m s−1 for both.

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Atmospheric CO and CH<sub>4</sub> time series and seasonal variations on Reunion Island from ground-based in situ and FTIR (NDACC and TCCON) measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-13881-2018 ◽

2018 ◽

Vol 18 (19) ◽

pp. 13881-13901 ◽

Cited By ~ 6

Author(s):

Minqiang Zhou ◽

Bavo Langerock ◽

Corinne Vigouroux ◽

Mahesh Kumar Sha ◽

Michel Ramonet ◽

...

Keyword(s):

Time Series ◽

Indian Ocean ◽

Mole Fraction ◽

Seasonal Cycles ◽

Reunion Island ◽

Time Period ◽

Réunion Island ◽

The Indian Ocean ◽

Good Agreement

Abstract. Atmospheric carbon monoxide (CO) and methane (CH4) mole fractions are measured by ground-based in situ cavity ring-down spectroscopy (CRDS) analyzers and Fourier transform infrared (FTIR) spectrometers at two sites (St Denis and Maïdo) on Reunion Island (21∘ S, 55∘ E) in the Indian Ocean. Currently, the FTIR Bruker IFS 125HR at St Denis records the direct solar spectra in the near-infrared range, contributing to the Total Carbon Column Observing Network (TCCON). The FTIR Bruker IFS 125HR at Maïdo records the direct solar spectra in the mid-infrared (MIR) range, contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). In order to understand the atmospheric CO and CH4 variability on Reunion Island, the time series and seasonal cycles of CO and CH4 from in situ and FTIR (NDACC and TCCON) measurements are analyzed. Meanwhile, the difference between the in situ and FTIR measurements are discussed. The CO seasonal cycles observed from the in situ measurements at Maïdo and FTIR retrievals at both St Denis and Maïdo are in good agreement with a peak in September–November, primarily driven by the emissions from biomass burning in Africa and South America. The dry-air column averaged mole fraction of CO (XCO) derived from the FTIR MIR spectra (NDACC) is about 15.7 ppb larger than the CO mole fraction near the surface at Maïdo, because the air in the lower troposphere mainly comes from the Indian Ocean while the air in the middle and upper troposphere mainly comes from Africa and South America. The trend for CO on Reunion Island is unclear during the 2011–2017 period, and more data need to be collected to get a robust result. A very good agreement is observed in the tropospheric and stratospheric CH4 seasonal cycles between FTIR (NDACC and TCCON) measurements, and in situ and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements, respectively. In the troposphere, the CH4 mole fraction is high in August–September and low in December–January, which is due to the OH seasonal variation. In the stratosphere, the CH4 mole fraction has its maximum in March–April and its minimum in August–October, which is dominated by vertical transport. In addition, the different CH4 mole fractions between the in situ, NDACC and TCCON CH4 measurements in the troposphere are discussed, and all measurements are in good agreement with the GEOS-Chem model simulation. The trend of XCH4 is 7.6±0.4 ppb yr−1 from the TCCON measurements over the 2011 to 2017 time period, which is consistent with the CH4 trend of 7.4±0.5 ppb yr−1 from the in situ measurements for the same time period at St Denis.

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CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Réunion Island and comparisons with MIPAS/ENVISAT data

Atmospheric Measurement Techniques ◽

10.5194/amt-9-5621-2016 ◽

2016 ◽

Vol 9 (11) ◽

pp. 5621-5636 ◽

Cited By ~ 12

Author(s):

Minqiang Zhou ◽

Corinne Vigouroux ◽

Bavo Langerock ◽

Pucai Wang ◽

Geoff Dutton ◽

...

Keyword(s):

Michelson Interferometer ◽

Species Group ◽

Reunion Island ◽

Solar Absorption ◽

Trace Species ◽

Réunion Island ◽

Peak Sensitivity ◽

Random Uncertainties ◽

Absorption Measurements ◽

Good Agreement

Abstract. Profiles of CFC-11 (CCl3F), CFC-12 (CCl2F2) and HCFC-22 (CHF2Cl) have been obtained from Fourier transform infrared (FTIR) solar absorption measurements above the Saint-Denis (St Denis) and Maïdo sites at Réunion Island (21° S, 55° E) with low vertical resolution. FTIR profile retrievals are performed by the well-established SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12 and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 km. The ground-based FTIR data have been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT) data and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6–30 km) are (−4.3 and 4.4 %), (−2.9 and 4.6 %) and (−0.7 and 4.8 %) for CFC-11, CFC-12 and HCFC-22, respectively, which are within the combined error budgets from both measurements. The season cycles of CFC-11, CFC-12 and HCFC-22 from FTIR measurements and MIPAS data show a similar variation: concentration is highest in February–April and lowest in August–October. The trends derived from the combined St Denis and Maïdo FTIR time series are −0.86 ± 0.12 and 2.84 ± 0.06 % year−1 for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016, and −0.76 ± 0.05 % year−1 for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division's (GMD) Halocarbons & other Atmospheric Trace Species Group (HATS) measurements at Samoa (14.2° S, 170.5° W) for CFC-11 (−0.87 ± 0.04 % year−1), but slightly weaker for HCFC-22 (3.46 ± 0.05 %) year−1 and stronger for CFC-12 (−0.60 ± 0.02 % year−1).

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A one year prevalence study of schizophrenia on Reunion Island

European Psychiatry ◽

10.1016/s0924-9338(97)84787-6 ◽

1997 ◽

Vol 12 (6) ◽

pp. 284-288 ◽

Cited By ~ 5

Author(s):

M Jay ◽

P Gorwood ◽

J Feingold ◽

M Leboyer

Keyword(s):

Prevalence Study ◽

Limited Area ◽

Reunion Island ◽

High Prevalence ◽

Range Difference ◽

Réunion Island ◽

The Indian Ocean ◽

Highly Correlated ◽

One Year ◽

Low Prevalence

SummaryReview of geographical comparisons of the prevalence of schizophrenic disorders found a ten-fold range difference between geographical contiguous groups, with high and low prevalence pockets. We performed a 1-year prevalence study of schizophrenia in a limited area of Reunion Island in the Indian Ocean, and analysed the prevalence variability in contiguous regions of this area. We found one of the highest reported age-corrected (above 15 years) 1-year prevalence of schizophrenia (14.9 per thousand). Large discrepancies in the distribution of prevalence rates of schizophrenia were observed between the five towns analysed. Interestingly, when a higher prevalence was observed, it was highly correlated with an increase of the percentage of familial cases (r = 0.989, df = 3, P = 0.0014). Presence of founder effect often described in geographical isolates could explain the high prevalence rate and the heterogeneity between towns observed in our sample.

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Atmospheric CO and CH<sub>4</sub> time series and seasonal variations on Reunion Island from ground-based in-situ and FTIR (NDACC and TCCON) measurements

10.5194/acp-2018-218 ◽

2018 ◽

Author(s):

Minqiang Zhou ◽

Bavo Langerock ◽

Corinne Vigouroux ◽

Mahesh Kumar Sha ◽

Michel Ramonet ◽

...

Keyword(s):

Mole Fraction ◽

Infrared Range ◽

Seasonal Cycles ◽

Reunion Island ◽

Time Period ◽

Réunion Island ◽

The Indian Ocean ◽

Ch4 Concentration ◽

Good Agreement

Abstract. Atmospheric carbon monoxide (CO) and methane (CH4) concentrations are measured by ground-based in-situ Cavity Ring-Down Spectroscopy (CRDS) analyzers and Fourier transform infrared (FTIR) spectrometers at two sites (St Denis and Maïdo) on Reunion Island (21° S, 55° E) in the Indian Ocean. Currently, the FTIR Bruker IFS 125HR at St Denis records the direct solar spectra in the near-infrared range, contributing to the Total Carbon Column Observing Network (TCCON). The FTIR Bruker IFS 125HR at Maïdo records the direct solar spectra in the mid-infrared range, contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). In order to understand the atmospheric CO and CH4 variability on Reunion Island, the time series and seasonal cycles of CO and CH4 from in-situ and FTIR (NDACC and TCCON) measurements are analysed. Meanwhile, the difference between the in-situ and FTIR measurements are discussed. The CO seasonal cycles observed from the in-situ measurements at Maïdo and FTIR retrievals both at St Denis and Maïdo are in good agreement with a peak in September–November, primarily driven by the emissions from biomass burning in Africa and South America. The dry-air column averaged mole fraction of CO (XCO) derived from the FTIR MIR spectra (NDACC) is about 15.7 ppb larger than the CO mole fraction near the surface at Maïdo, because the air in the lower troposphere mainly comes from the Indian Ocean while the air in the middle and upper troposphere mainly comes from Africa and South America. The trend for CO on Reunion Island is unclear during 2011–2017, and more data need to be collected to get a robust result. A very good agreement is observed in the tropospheric and stratospheric CH4 seasonal cycles between FTIR (NDACC and TCCON) measurements, and in-situ and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite measurements, respectively. In the troposphere, the CH4 mole fraction is high in August–September and low in December–January, which is due to the OH seasonal variation. In the stratosphere, CH4 concentration has its maximum in March–April and its minimum in August–October, which is dominated by the vertical transport. In addition, the different CH4 concentration between the in-situ, NDACC and TCCON CH4 measurements in the troposphere are discussed, and all measurements are in good agreement with the GEOS-Chem model simulation. The trend of XCH4 is 7.6 ± 0.4 ppb/year from the TCCON measurements over the 2011–2017 time period, which is consistent with the CH4 of 7.4 ± 0.5 ppb/year from the in-situ measurements for the same time period at St Denis.

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Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): system description, instrumental performance and result comparison with ozone external data set

Atmospheric Measurement Techniques ◽

10.5194/amt-10-3359-2017 ◽

2017 ◽

Vol 10 (9) ◽

pp. 3359-3373 ◽

Cited By ~ 1

Author(s):

Valentin Duflot ◽

Jean-Luc Baray ◽

Guillaume Payen ◽

Nicolas Marquestaut ◽

Francoise Posny ◽

...

Keyword(s):

Current System ◽

Atmospheric Composition ◽

Integration Time ◽

Data Sets ◽

Buffer Gas ◽

Reunion Island ◽

Data Set ◽

Upper Troposphere ◽

Réunion Island ◽

Good Agreement

Abstract. In order to recognize the importance of ozone (O3) in the troposphere and lower stratosphere in the tropics, a DIAL (differential absorption lidar) tropospheric O3 lidar system (LIO3TUR) was developed and installed at the Université de la Réunion campus site (close to the sea) on Reunion Island (southern tropics) in 1998. From 1998 to 2010, it acquired 427 O3 profiles from the low to the upper troposphere and has been central to several studies. In 2012, the system was moved up to the new Maïdo Observatory facility (2160 m a.m.s.l. – metres above mean sea level) where it started operation in February 2013. The current system (LIO3T) configuration generates a 266 nm beam obtained with the fourth harmonic of a Nd:YAG laser sent into a Raman cell filled up with deuterium (using helium as buffer gas), generating the 289 and 316 nm beams to enable the use of the DIAL method for O3 profile measurements. The optimal range for the actual system is 6–19 km a.m.s.l., depending on the instrumental and atmospheric conditions. For a 1 h integration time, vertical resolution varies from 0.7 km at 6 km a.m.s.l. to 1.3 km at 19 km a.m.s.l., and mean uncertainty within the 6–19 km range is between 6 and 13 %. Comparisons with eight electrochemical concentration cell (ECC) sondes simultaneously launched from the Maïdo Observatory show good agreement between data sets with a 6.8 % mean absolute relative difference (D) between 6 and 17 km a.m.s.l. (LIO3T lower than ECC). Comparisons with 37 ECC sondes launched from the nearby Gillot site during the daytime in a ±24 h window around lidar shooting result in a 9.4 % D between 6 and 19 km a.m.s.l. (LIO3T lower than ECC). Comparisons with 11 ground-based Network for Detection of Atmospheric Composition Change (NDACC) Fourier transform infrared (FTIR) spectrometer measurements acquired during the daytime in a ±24 h window around lidar shooting show good agreement between data sets with a D of 11.8 % for the 8.5–16 km partial column (LIO3T higher than FTIR), and comparisons with 39 simultaneous Infrared Atmospheric Sounding Interferometer (IASI) observations over Reunion Island show good agreement between data sets with a D of 11.3 % for the 6–16 km partial column (LIO3T higher than IASI). ECC, LIO3TUR and LIO3T O3 monthly climatologies all exhibit the same range of values and patterns. In particular, the Southern Hemisphere biomass burning seasonal enhancement and the ozonopause altitude decrease in late austral winter–spring, as well as the sign of deep convection bringing boundary layer O3-poor air masses up to the middle–upper troposphere in late austral summer, are clearly visible in all data sets.

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TOC intercomparison of Brewer, Dobson and BTS Solar at Hohenpeißenberg and Davos 2019/2020

10.5194/amt-2021-52 ◽

2021 ◽

Author(s):

Ralf Zuber ◽

Ulf Köhler ◽

Luca Egli ◽

Mario Ribnitzky ◽

Wolfgang Steinbrecht ◽

...

Keyword(s):

Standard Deviation ◽

Total Ozone ◽

Retrieval Algorithm ◽

Spectral Measurements ◽

Measurement Campaign ◽

Stratospheric Temperature ◽

Retrieval Algorithms ◽

One Year ◽

Double Monochromator ◽

Ozone Column

Abstract. In the 2019/2020 measurement campaign at Hohenpeißenberg (Germany) and Davos (Switzerland) we compared the well-established Dobson and Brewer spectrometers (single and double monochromator Brewer) with newer BTS array spectroradiometer based systems in terms of total ozone column (TOC) determination. The aim of this study is to validate the BTS performance in a longer-term TOC analysis over more than one year with seasonal and weather influences. Two different BTS setups have been used. A fibre coupled entrance optic version by PMOD/WRC called Koherent and a diffusor optic which proved to be simpler in terms of calibration from Gigahertz-Optik GmbH called BTS Solar. The array-spectrometer based BTS systems have been traceable calibrated to National Metrology Institutes (NMI) and the used TOC retrieval algorithms are based on spectral measurements in the range of 305 nm and 350 nm instead of single wavelength measurements as for Brewer or Dobson. The two BTS based systems, however, used fundamentally different retrieval algorithms for the TOC assessment, whereby the retrieval of the BTS solar turned out to achieve significantly smaller seasonal drifts. The intercomparison showed a deviation of the BTS Solar to Brewers of < 0.1 % with an expanded standard deviation of < 1.5 % within the whole measurement campaign. Koherent showed a deviation of 1.7 % with an expanded standard deviation of 2.7 % mostly given by a significant seasonal drift. Resulting, the BTS Solar performance is comparable to Brewers at the comparison in Hohenpeißenberg. The slant path slope is in-between double monochromator and single monochromator Brewer. Koherent shows a strong seasonal variation in Davos due to the sensitivity of its ozone retrieval algorithm to stratospheric temperature similar to the Dobson results.

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