OClO as observed by TROPOMI: a  comparison with meteorological parameters  and polar stratospheric cloud observations

Abstract. Chlorine dioxide (OClO) is a by-product of the ozone-depleting halogen chemistry in the stratosphere. Although it is rapidly photolysed at low solar zenith angles (SZAs), it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation on chlorine oxide (ClO). Here, we compare slant column densities (SCDs) of chlorine dioxide (OClO) retrieved by means of differential optical absorption spectroscopy (DOAS) from spectra measured by the TROPOspheric Monitoring Instrument (TROPOMI) with meteorological data for both Antarctic and Arctic regions for the first three winters in each of the hemispheres (November 2017–October 2020). TROPOMI, a UV–Vis–NIR–SWIR instrument on board of the Sentinel-5P satellite, monitors the Earth's atmosphere in a near-polar orbit at an unprecedented spatial resolution and signal-to-noise ratio and provides daily global coverage at the Equator and thus even more frequent observations at polar regions. The observed OClO SCDs are generally well correlated with the meteorological conditions in the polar winter stratosphere; for example, the chlorine activation signal appears as a sharp gradient in the time series of the OClO SCDs once the temperature drops to values well below the nitric acid trihydrate (NAT) existence temperature (TNAT). Also a relation of enhanced OClO values at lee sides of mountains can be observed at the beginning of the winters, indicating a possible effect of lee waves on chlorine activation. The dataset is also compared with CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) polar stratospheric cloud (PSC) observations. In general, OClO SCDs coincide well with CALIOP measurements for which PSCs are detected. Very high OClO levels are observed for the northern hemispheric winter 2019/20, with an extraordinarily long period with a stable polar vortex being even close to the values found for southern hemispheric winters. An extraordinary winter in the Southern Hemisphere was also observed in 2019, with a minor sudden stratospheric warming at the beginning of September. In this winter, similar OClO values were measured in comparison to the previous (usual) winter till that event but with a OClO deactivation that was 1–2 weeks earlier.

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OClO as observed by TROPOMI: a comparison with meteorological parameters and PSC observations

10.5194/acp-2021-600 ◽

2021 ◽

Author(s):

Jānis Puķīte ◽

Christian Borger ◽

Steffen Dörner ◽

Myojeong Gu ◽

Thomas Wagner

Keyword(s):

Chlorine Dioxide ◽

Signal To Noise Ratio ◽

Meteorological Data ◽

Polar Vortex ◽

Optical Absorption Spectroscopy ◽

Orthogonal Polarization ◽

Polar Regions ◽

Arctic Regions ◽

Lee Waves ◽

A Minor

Abstract. Chlorine dioxide (OClO) is a by-product of the ozone depleting halogen chemistry in the stratosphere. Although being rapidly photolysed at low solar zenith angles (SZAs) it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation to chlorine oxide (ClO). Here we compare slant column densities (SCDs) of chlorine dioxide (OClO) retrieved by means of differential optical absorption spectroscopy (DOAS) from spectra measured by the TROPOspheric Monitoring Instrument (TROPOMI) with meteorological data for both Antarctic and Arctic regions for the first three winters in each of the hemispheres (November 2017–October 2020). TROPOMI, a UV-VIS-NIR-SWIR instrument on board of the Sentinel-5P satellite monitors the Earth’s atmosphere in a near polar orbit at an unprecedented spatial resolution and signal to noise ratio and provides daily global coverage at the equator and thus even more frequent observations at polar regions. The observed OClO SCDs are generally well correlated with the meteorological conditions in the polar winter stratosphere: e.g. the chlorine activation signal appears as a sharp gradient in the time series of the OClO SCDs once the temperature drops to values well below the Nitric Acid Trihydrate (NAT) existence temperature TNAT. Also a relation of enhanced OClO values at lee sides of mountains can be observed at the beginning of the winters indicating a possible effect of occurring lee waves on chlorine activation. The dataset is also compared with CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) polar stratospheric cloud (PSC) observations. In general, OClO SCDs coincide well with CALIOP measurements for which PSCs are detected. Very high OClO levels are observed for the northern hemispheric winter 2019/2020 with an extraordinarly long period with a stable polar vortex being even close to the values found for Southern Hemispheric winters. Also the extraordinary winter in 2019 in the Southern Hemisphere with a minor sudden stratospheric warming at the beginning of September was observed. In this winter similar OClO values were measured in comparison to the previous (usual) winter till that event but with a 1–2 week earlier OClO deactivation.

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OClO as observed by TROPOMI on Sentinel 5P

10.5194/egusphere-egu2020-11831 ◽

2020 ◽

Author(s):

Janis Pukite ◽

Christian Borger ◽

Steffen Dörner ◽

Thomas Wagner

Keyword(s):

Chlorine Dioxide ◽

Meteorological Data ◽

Trace Gas ◽

Optical Absorption Spectroscopy ◽

Retrieval Algorithm ◽

Polar Regions ◽

Arctic Regions ◽

Halogen Chemistry ◽

Global Coverage ◽

Spectrally Resolved

The TROPOspheric Monitoring Instrument (TROPOMI) is an UV-VIS-NIR-SWIR instrument on board of Sentinel-5P satellite developed for monitoring the Earth&#8217;s atmosphere. It was launched on 13 October 2017 in a near polar orbit. It measures spectrally resolved earthshine radiances at an unprecedented spatial resolution of around 3.5x7.2 km2 (3.5x5.6 km2 starting from 6 Aug 2019) (near nadir) with a total swath width of ~2600 km on the Earth's surface providing daily global coverage. From the measured spectra high resolved trace gas distributions can be retrieved by means of differential optical absorption spectroscopy (DOAS).Chlorine dioxide (OClO) is a by-product of the ozone depleting halogen chemistry in the stratosphere. Although being rapidly photolysed at low solar zenith angles (SZAs) it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear relation of its formation to chlorine oxide (ClO).Here we present a new DOAS retrieval algorithm of the slant column densities (SCDs) of chlorine dioxide (OClO) and correlate this TROPOMI OClO signal with meteorological data for both Antarctic and Arctic regions.

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Retrieval algorithm for OClO from TROPOMI by Differential Optical Absorption Spectroscopy

10.5194/amt-2021-178 ◽

2021 ◽

Author(s):

Jānis Puķīte ◽

Christian Borger ◽

Steffen Dörner ◽

Myojeong Gu ◽

Udo Frieß ◽

...

Keyword(s):

Optical Absorption ◽

Absorption Spectroscopy ◽

Chlorine Dioxide ◽

Large Scale ◽

Order Term ◽

Differential Optical Absorption Spectroscopy ◽

Optical Absorption Spectroscopy ◽

Retrieval Algorithm ◽

Polar Regions ◽

Spectrally Resolved

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) is a UV-VIS-NIR-SWIR instrument on board of Sentinel-5P satellite developed for monitoring the Earth’s atmosphere. It was launched on 13 October 2017 in a near polar orbit. It measures spectrally resolved earthshine radiances at an unprecedented spatial resolution of around 3.5 x 7.2 km² (3.5 x 5.6 km² starting from 6 Aug 2019) (near nadir) with a total swath width of ~ 2600 km on the Earth's surface providing daily global coverage. From the measured spectra high resolved trace gas distributions can be retrieved by means of differential optical absorption spectroscopy (DOAS). Chlorine dioxide (OClO) is a by-product of the ozone depleting halogen chemistry in the stratosphere. Although being rapidly photolysed at low solar zenith angles (SZAs) it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation to chlorine oxide (ClO). Here we present a new retrieval algorithm of the slant column densities (SCDs) of chlorine dioxide (OClO) by DOAS. To achieve a substantially improved accuracy, which is especially important for OClO observations, accounting for absorber and pseudo absorber structures in optical depth even of the order of 10−4 is important. Therefore in comparison to existing retrievals, we include several additional fit parameters accounting for spectral effects like the temperature dependency of the Ring effect and Ring absorption effects, higher order term for the OClO SCD dependency on wavelength and account for the BrO absorption. We investigate the performance of different retrieval settings by an error analysis with respect to random variations, large scale systematic variations as function of solar zenith angle and also more localised systematic variations by a novel application of an autocorrelation analysis. The retrieved TROPOMI OClO SCDs show a very good agreement with ground based zenith sky measurements and are correlated well with preliminary data of the opeartional TROPOMI OClO retrieval algorithm currently being developed as part of ESA's S5p+I project.

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Retrieving the vertical distribution of stratospheric OClO from Odin/OSIRIS limb-scattered sunlight measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-2989-2005 ◽

2005 ◽

Vol 5 (3) ◽

pp. 2989-3046 ◽

Cited By ~ 1

Author(s):

P. Krecl ◽

C. S. Haley ◽

J. Stegman ◽

S. M. Brohede ◽

G. Berthet

Keyword(s):

Transport Model ◽

Polar Vortex ◽

Optical Absorption Spectroscopy ◽

Polar Regions ◽

Atmospheric Conditions ◽

Chemical Transport Model ◽

Austral Spring ◽

Data Set ◽

Spectral Window ◽

Window Selection

Abstract. The first vertical profiles of stratospheric OClO retrieved from Odin/OSIRIS limb-scattered sunlight radiances are presented. The retrieval method is based on a two-step approach, using differential optical absorption spectroscopy combined with the maximum a posteriori estimator. The details of the spectral window selection, spectral corrections and inversion technique are discussed. The results show that OClO can be detected inside the South polar vortex region between about 12 and 20 km altitude with a 2–5 km height resolution and an estimated retrieval error better than 60% at the peak. OClO concentrations are consistent with chemical transport model simulations and show the expected relation to the atmospheric conditions in the lower stratosphere in the austral spring 2002. This unique data set of OClO profiles is very promising to study the stratospheric chlorine activation in both polar regions.

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Separating tropospheric and stratospheric BrO columns over the Arctic using TROPOMI data

10.5194/egusphere-egu2020-20775 ◽

2020 ◽

Author(s):

Moritz Schöne ◽

Holger Sihler ◽

Simon Warnach ◽

Christian Borger ◽

Steffen Beirle ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Ozone Depletion ◽

Meteorological Data ◽

The Arctic ◽

Optical Absorption Spectroscopy ◽

Polar Regions ◽

Bromine Oxide ◽

Spatial Coverage ◽

Meteorological Influences ◽

Boundary Layer Ozone

Halogen radicals can drastically alter the atmospheric chemistry. In the polar regions, this is made evident, among others, by the almost complete destruction of boundary layer ozone during polar springs. These recurrent episodes of catalytic ozone depletion, referred to as Ozone Depletion Events (ODE), are caused by enhanced concentrations of reactive bromine compounds. The proposed mechanism by which these are released into the atmosphere is called bromine explosions - &#160;reactive bromine is formed autocatalytically from the condensed phase. Enhanced bromine oxide concentrations have been observed by ground-based measurements as well as from aircraft and satellite, where the large spatial coverage allows to study the spatial extent of the phenomenon and its correlation with meteorological data as well as climate change.The spatial resolution of S-5P/TROPOMI of 3,5 km x 7 km allows improved localization of these events and to resolve finer structures compared to previous satellite measurements. Together with the better than daily coverage over the polar regions, this allows investigations of the spatio-temporal variability of enhanced BrO levels and their relation to different possible bromine sources and release mechanisms.We present tropospheric BrO column densities retrieved from TROPOMI data using Differential Optical Absorption Spectroscopy (DOAS). Building on methods from statistical data analysis and machine learning, we separate the tropospheric partial column from the total column using solely data (BrO, O3 and NO2) measured by satellite. The observations are discussed with regards to sea ice coverage and meteorological influences.

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Location controls the findings of ground-based PSC observations

10.5194/acp-2020-930 ◽

2020 ◽

Author(s):

Matthias Tesche ◽

Peggy Achtert ◽

Michael C. Pitts

Keyword(s):

Signal To Noise Ratio ◽

The Arctic ◽

Orthogonal Polarization ◽

Microphysical Properties ◽

Polar Stratospheric Cloud ◽

Comprehensive Picture ◽

Ground Based Lidar ◽

Stratospheric Clouds ◽

The Antarctic ◽

Lidar Observations

Abstract. Spaceborne observations of Polar Stratospheric Clouds (PSCs) with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite provide a comprehensive picture of the occurrence of Arctic and Antarctic PSCs as well as their microphysical properties. However, advances in understanding PSC microphysics also require measurements with ground-based instruments, which are often superior to CALIOP in terms of, e.g. time resolution, measured parameters, and signal-to-noise ratio. This advantage is balanced by the location of ground-based PSC observations and their dependence on tropospheric cloudiness. CALIPSO observations during the boreal winters from December 2006 to February 2018 and the austral winters 2012 and 2015 are used to assess the representativeness of ground-based PSC observations with lidar in the Arctic and Antarctic, respectively. Information on tropospheric and stratospheric clouds from the CALIPSO Cloud Profile product (05kmCPro version 4.10) and the Polar Stratospheric Cloud (PSC) mask version 2, respectively, is combined on a profile-by-profile basis to identify conditions under which a ground-based lidar is likely to perform useful measurements for the analysis of PSC occurrence. It is found that the location of a ground-based measurement together with the related tropospheric cloudiness can have a profound impact on the derived PSC statistics and that these findings are rarely in agreement with polar-wide results from CALIOP observations. Considering the current polar research infrastructure, it is concluded that the most suitable sites for the expansion of capabilities for ground-based lidar observations of PSCs are Summit and Villum in the Arctic and Concordia, Troll, and Vostok in the Antarctic.

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Retrieval of chlorine dioxide columns from Sentinel-5p observations

10.5194/egusphere-egu2020-13715 ◽

2020 ◽

Author(s):

Andreas Carlos Meier ◽

Andreas Richter ◽

Gaia Pinardi ◽

Michel Van Roozendael ◽

John Philip Burrows

Keyword(s):

Chlorine Dioxide ◽

Signal To Noise Ratio ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Current Status ◽

Innovation Activity ◽

Signal To Noise ◽

Fine Spatial Resolution ◽

Global Coverage ◽

Good Signal

The Sentinel-5-precursor (S5p) satellite with the TROPOMI payload was launched on 13 October 2017. It is part of the European Copernicus program and provides a set of operational products of atmospheric constituents related to air quality and climate change with almost daily global coverage. The good signal to noise ratio of the instrument enables precise measurements despite the fine spatial resolution of 3.5 x 5.5 km2.&#160; The ESA S5p+ Innovation activity aims at extending the list of S5p products with scientific products, which are not yet part of the operational processor, to exploit the potential of the Sentinel-5p mission&#8217;s capabilities beyond its primary objectives. The retrieval of chlorine dioxide (OClO) from S5p is among the seven funded sub projects. Chlorine dioxide is an indicator for chlorine activation in the stratosphere and thus of importance for the understanding of stratospheric ozone chemistry, in particular in the polar vortex. Chlorine dioxide was retrieved from heritage instruments (GOME, SCIAMACHY, GOME2, OMI) and the S5p OClO product will act as a continuation of these time-series. Here we present the current status of the IUP-Bremen S5p OClO product developed within the ESA S5p+ Innovation framework. The new S5p product will be put into context with products from previous and current (e.g. GOME-2c) satellite missions as well as ground-based measurements used for validation.

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A global climatology of stratospheric OClO derived from GOMOS measurement

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-3511-2013 ◽

2013 ◽

Vol 6 (2) ◽

pp. 3511-3543

Author(s):

C. Tétard ◽

D. Fussen ◽

F. Vanhellemont ◽

C. Bingen ◽

E. Dekemper ◽

...

Keyword(s):

Near Infrared ◽

Signal To Noise Ratio ◽

Equatorial Region ◽

Optical Absorption Spectroscopy ◽

Polar Regions ◽

Signal To Noise ◽

Spectral Window ◽

Stellar Occultation ◽

Noise Ratio ◽

Window Selection

Abstract. The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European platform ENVISAT was dedicated to the study of the atmosphere of the Earth using the stellar occultation technique. The spectral range of the GOMOS spectrometer extends from the UV to the near infrared, allowing for the retrieval of species such as O3, NO2, NO3, H2O, O2, air density, aerosol extinction and OClO. Nevertheless, OClO can not be retrieved using a single GOMOS measurement because of the weak signal-to-noise ratio and the small optical thickness associated with this molecule. We present here the method used to detect this molecule by using several GOMOS measurements. It is based on a two-step approach. First, several co-located measurements are combined in a statistical way to build an averaged measurement with a higher signal-to-noise ratio. Then, a Differential Optical Absorption Spectroscopy (DOAS) method is applied to retrieve OClO slant column densities. The statistics of the sets of GOMOS measurements used to build the averaged measurement and the spectral window selection are analyzed. The obtained retrievals are compared to results from two balloon-borne instruments. It appears that the inter-comparisons of OClO are generally satisfying. Then, two nighttime climatologies of OClO slant column densities based on GOMOS averaged measurements are presented. The first depicts annual global pictures of OClO from 2003 to 2011. From this climatology, the presence of an OClO layer in the equatorial region at about 35 km is confirmed and strong concentrations of OClO in both polar regions are observed, a sign of chlorine activation. The second climatology is a monthly time series. It clearly shows the chlorine activation of the lower stratosphere during winter. Moreover the equatorial OClO layer is observed during all the years without any significant variations. Finally, the anti-correlation between OClO and NO2 is highlighted. This very promising method, applied on GOMOS measurements, allowed us to build the first nighttime climatology of OClO.

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Retrieving the vertical distribution of stratospheric OClO from Odin/OSIRIS limb-scattered sunlight measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-1879-2006 ◽

2006 ◽

Vol 6 (7) ◽

pp. 1879-1894 ◽

Cited By ~ 25

Author(s):

P. Krecl ◽

C. S. Haley ◽

J. Stegman ◽

S. M. Brohede ◽

G. Berthet

Keyword(s):

Polar Vortex ◽

Optical Absorption Spectroscopy ◽

Polar Regions ◽

Atmospheric Conditions ◽

Austral Spring ◽

Data Set ◽

Spectral Window ◽

Window Selection ◽

And Inversion ◽

The Vertical Distribution

Abstract. The first vertical profiles of stratospheric OClO retrieved from Odin/OSIRIS limb-scattered sunlight radiances are presented. The retrieval method is based on a two-step approach, using differential optical absorption spectroscopy combined with the maximum a posteriori estimator. The details of the spectral window selection, spectral corrections and inversion technique are discussed. The results show that OClO can be detected inside the South polar vortex region between about 14 and 22 km altitude with a 2–5 km height resolution and an estimated retrieval error better than 50% at the peak. OClO concentrations show the expected relation to the atmospheric conditions in the lower stratosphere in the austral spring 2002. This unique data set of OClO profiles is very promising to study the stratospheric chlorine activation in both polar regions.

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OClO slant column densities derived from GOMOS averaged transmittance measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-6-2953-2013 ◽

2013 ◽

Vol 6 (11) ◽

pp. 2953-2964 ◽

Cited By ~ 1

Author(s):

C. Tétard ◽

D. Fussen ◽

F. Vanhellemont ◽

C. Bingen ◽

E. Dekemper ◽

...

Keyword(s):

Near Infrared ◽

Signal To Noise Ratio ◽

Arctic Region ◽

Equatorial Region ◽

The Arctic ◽

Optical Absorption Spectroscopy ◽

Polar Regions ◽

Signal To Noise ◽

Spectral Window ◽

Noise Ratio

Abstract. The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European platform ENVISAT (ENVironment SATellite) was dedicated to the study of the of Earth's atmosphere using the stellar occultation technique. The spectral range of the GOMOS spectrometer extends from the UV (ultra violet) to the near infrared, allowing for the retrieval of species such as O3, NO2, NO3, H2O, O2, air density, aerosol extinction and OClO. Nevertheless, OClO cannot be retrieved using a single GOMOS measurement because of the weak signal-to-noise ratio and the small optical thickness associated with this molecule. We present here the method used to detect this molecule by using several GOMOS measurements. It is based on a two-step approach. First, several co-located measurements are combined in a statistical way to build an averaged measurement with a higher signal-to-noise ratio; then, a differential optical absorption spectroscopy (DOAS) method is applied to retrieve OClO slant column densities (SCD). The statistics of the sets of GOMOS measurements used to build the averaged measurement and the spectral window selection are analyzed. The obtained retrievals are compared to results from two balloon-borne instruments. It appears that the inter-comparisons of OClO are generally satisfying (relative differences are about 15–60%). Two nighttime climatologies of OClO based on GOMOS averaged measurements are presented. The first depicts annual global pictures of OClO from 2003 to 2011. From this climatology, the presence of an OClO SCD peak in the equatorial region at about 35 km is confirmed and strong OClO SCD in both polar regions are observed (more than 1016 cm−2 in the Antarctic region and slightly less in the Arctic region), a sign of chlorine activation. The second climatology is a monthly time series. It clearly shows the chlorine activation of the lower stratosphere during winter. Moreover the equatorial OClO SCD peak is observed during all years without any significant variations. This very promising method, applied on GOMOS measurements, allowed us to build the first nighttime climatology of OClO using limb-viewing instruments.

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