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  • 1
    Online Resource
    Online Resource
    Copernicus GmbH ; 2009
    In:  Atmospheric Chemistry and Physics Vol. 9, No. 8 ( 2009-04-23), p. 2679-2694
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 9, No. 8 ( 2009-04-23), p. 2679-2694
    Abstract: Abstract. In this study backward trajectories from the tropical lower stratosphere were calculated for the Northern Hemisphere (NH) winters 1995–1996, 1997–1998 (El Niño) and 1998–1999 (La Niña) and summers 1996, 1997 and 1999 using both ERA-40 reanalysis data of the European Centre for Medium-Range Weather Forecast (ECMWF) and coupled Chemistry-Climate Model (CCM) data. The calculated trajectories were analysed to determine the distribution of points where individual air masses encounter the minimum temperature and thus minimum water vapour mixing ratio during their ascent through the tropical tropopause layer (TTL) into the stratosphere. The geographical distribution of these dehydration points and the local conditions there determine the overall water vapour entry into the stratosphere. Results of two CCMs are presented: the ECHAM4.L39(DLR)/CHEM (hereafter: E39/C) from the German Aerospace Center (DLR) and the Freie Universität Berlin Climate Middle Atmosphere Model with interactive chemistry (hereafter: FUB-CMAM-CHEM). In the FUB-CMAM-CHEM model the minimum temperatures are overestimated by about 9 K in NH winter and about 3 K in NH summer, resulting in too high water vapour entry values compared to ERA-40. However, the geographical distribution of dehydration points is fairly similar to ERA-40 for NH winter 1995–1996 and 1998–1999. The distribution of dehydration points in the boreal summer 1996 suggests an influence of the Indian monsoon upon the water vapour transport. The E39/C model displays a temperature bias of about +5 K. Hence, the minimum water vapour mixing ratios are higher relative to ERA-40. The geographical distribution of dehydration points is fairly well in NH winter 1995–1996 and 1997–1998 with respect to ERA-40. The distribution is not reproduced for the NH winter 1998–1999 (La Niña event) compared to ERA-40. There is an excessive water vapour flux through warm regions e.g. Africa in the NH winter and summer. The possible influence of the Indian monsoon on the transport is not seen in the boreal summer 1996. Further, the residence times of air parcels in the TTL were derived from the trajectory calculations. The analysis of the residence times reveals that in both CCMs residence times in the TTL are lower compared to ERA-40 and the seasonal variation is hardly present.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2009
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  • 2
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2021
    In:  Nature Communications Vol. 12, No. 1 ( 2021-06-23)
    In: Nature Communications, Springer Science and Business Media LLC, Vol. 12, No. 1 ( 2021-06-23)
    Abstract: Chemical loss of Arctic ozone due to anthropogenic halogens is driven by temperature, with more loss occurring during cold winters favourable for formation of polar stratospheric clouds (PSCs). We show that a positive, statistically significant rise in the local maxima of PSC formation potential (PFP LM ) for cold winters is apparent in meteorological data collected over the past half century. Output from numerous General Circulation Models (GCMs) also exhibits positive trends in PFP LM over 1950 to 2100, with highest values occurring at end of century, for simulations driven by a large rise in the radiative forcing of climate from greenhouse gases (GHGs). We combine projections of stratospheric halogen loading and humidity with GCM-based forecasts of temperature to suggest that conditions favourable for large, seasonal loss of Arctic column O 3 could persist or even worsen until the end of this century, if future abundances of GHGs continue to steeply rise.
    Type of Medium: Online Resource
    ISSN: 2041-1723
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2553671-0
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  • 3
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 23 ( 2020-12-02), p. 14695-14715
    Abstract: Abstract. We present the first high-resolution measurements of pollutant trace gases in the Asian summer monsoon upper troposphere and lowermost stratosphere (UTLS) from the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) campaign based in Kathmandu, Nepal, 2017. Measurements of peroxyacetyl nitrate (PAN), acetylene (C2H2), and formic acid (HCOOH) show strong local enhancements up to altitudes of 16 km. More than 500 pptv of PAN, more than 200 pptv of C2H2, and more than 200 pptv of HCOOH are observed. Air masses with increased volume mixing ratios of PAN and C2H2 at altitudes up to 18 km, reaching to the lowermost stratosphere, were present at these altitudes for more than 10 d, as indicated by trajectory analysis. A local minimum of HCOOH is correlated with a previously reported maximum of ammonia (NH3), which suggests different washout efficiencies of these species in the same air masses. A backward trajectory analysis based on the models Alfred Wegener InsTitute LAgrangian Chemistry/Transport System (ATLAS) and TRACZILLA, using advanced techniques for detection of convective events, and starting at geolocations of GLORIA measurements with enhanced pollution trace gas concentrations, has been performed. The analysis shows that convective events along trajectories leading to GLORIA measurements with enhanced pollutants are located close to regions where satellite measurements by the Ozone Monitoring Instrument (OMI) indicate enhanced tropospheric columns of nitrogen dioxide (NO2) in the days prior to the observation. A comparison to the global atmospheric models Copernicus Atmosphere Monitoring Service (CAMS) and ECHAM/MESSy Atmospheric Chemistry (EMAC) has been performed. It is shown that these models are able to reproduce large-scale structures of the pollution trace gas distributions for one part of the flight, while the other part of the flight reveals large discrepancies between models and measurement. These discrepancies possibly result from convective events that are not resolved or parameterized in the models, uncertainties in the emissions of source gases, and uncertainties in the rate constants of chemical reactions.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2092549-9
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  • 4
    Online Resource
    Online Resource
    American Geophysical Union (AGU) ; 2013
    In:  Journal of Geophysical Research: Atmospheres Vol. 118, No. 20 ( 2013-10-27)
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 118, No. 20 ( 2013-10-27)
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Issue
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2013
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    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 2969341-X
    SSG: 16,13
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  • 5
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 16, No. 5 ( 2016-03-14), p. 3311-3325
    Abstract: Abstract. We examined observations of polar stratospheric clouds (PSCs) by CALIPSO, and of HCl and ClO by MLS along air mass trajectories, to investigate the dependence of the inferred PSC composition on the temperature history of the air parcels and the dependence of the level of chlorine activation on PSC composition. Several case studies based on individual trajectories from the Arctic winter 2009/2010 were conducted, with the trajectories chosen such that the first processing of the air mass by PSCs in this winter occurred on the trajectory. Transitions of PSC composition classes were observed to be highly dependent on the temperature history. In cases of a gradual temperature decrease, nitric acid trihydrate (NAT) and super-cooled ternary solution (STS) mixture clouds were observed. In cases of rapid temperature decrease, STS clouds were first observed, followed by NAT/STS mixture clouds. When temperatures dropped below the frost point, ice clouds formed and then transformed into NAT/STS mixture clouds when temperature increased above the frost point. The threshold temperature for rapid chlorine activation on PSCs is approximately 4 K below the NAT existence temperature, TNAT. Furthermore, simulations of the ATLAS chemistry and transport box model along the trajectories were used to corroborate the measurements and show good agreement with the observations. Rapid chlorine activation was observed when an air mass encountered PSCs. Usually, chlorine activation was limited by the amount of available ClONO2. Where ClONO2 was not the limiting factor, a large dependence on temperature was evident.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
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  • 6
    Online Resource
    Online Resource
    Copernicus GmbH ; 2017
    In:  Geoscientific Model Development Vol. 10, No. 7 ( 2017-07-13), p. 2671-2689
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 10, No. 7 ( 2017-07-13), p. 2671-2689
    Abstract: Abstract. The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in polar winter. It is intended for use in global climate models (GCMs) and Earth system models (ESMs) to enable the simulation of mutual interactions between the ozone layer and climate. To date, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. Polar SWIFT is based on a set of coupled differential equations, which simulate the polar vortex-averaged mixing ratios of the key species involved in polar ozone depletion on a given vertical level. These species are O3, chemically active chlorine (ClOx), HCl, ClONO2 and HNO3. The only external input parameters that drive the model are the fraction of the polar vortex in sunlight and the fraction of the polar vortex below the temperatures necessary for the formation of polar stratospheric clouds. Here, we present an update of the Polar SWIFT model introducing several improvements over the original model formulation. In particular, the model is now trained on vortex-averaged reaction rates of the ATLAS Chemistry and Transport Model, which enables a detailed look at individual processes and an independent validation of the different parameterizations contained in the differential equations. The training of the original Polar SWIFT model was based on fitting complete model runs to satellite observations and did not allow for this. A revised formulation of the system of differential equations is developed, which closely fits vortex-averaged reaction rates from ATLAS that represent the main chemical processes influencing ozone. In addition, a parameterization for the HNO3 change by denitrification is included. The rates of change of the concentrations of the chemical species of the Polar SWIFT model are purely chemical rates of change in the new version, whereas in the original Polar SWIFT model, they included a transport effect caused by the original training on satellite data. Hence, the new version allows for an implementation into climate models in combination with an existing stratospheric transport scheme. Finally, the model is now formulated on several vertical levels encompassing the vertical range in which polar ozone depletion is observed. The results of the Polar SWIFT model are validated with independent Microwave Limb Sounder (MLS) satellite observations and output from the original detailed chemistry model of ATLAS.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2456725-5
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  • 7
    In: Nature Geoscience, Springer Science and Business Media LLC, Vol. 12, No. 8 ( 2019-8), p. 608-612
    Type of Medium: Online Resource
    ISSN: 1752-0894 , 1752-0908
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
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    detail.hit.zdb_id: 2405323-5
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    American Geophysical Union (AGU) ; 2000
    In:  Geophysical Research Letters Vol. 27, No. 24 ( 2000-12-15), p. 4093-4096
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 27, No. 24 ( 2000-12-15), p. 4093-4096
    Abstract: Observations of stratospheric chlorine monoxide (ClO) were performed at the Arctic station of the ‘Network for the detection of Stratospheric Change” (NDSC). A ground based millimeter wave radiometer was routinely operated in Ny‐Ålesund, Spitsbergen (78.9°N, 11.9°E). In 1998 a period with enhanced ClO in a layer around 22 km altitude was detected from February 16 to March 9. Calculations using the three dimensional chemical transport model SLIMCAT are consistent with the observations. In 1999 no significant chlorine activation was observed while SLIMCAT calculations predicted a rather strong chlorine activation in February 1999, when the polar vortex was situated above Ny‐Ålesund. Deviations of SLIMCAT calculations for 1999 from the observations could be attributed to differences in temperatures obtained from the United Kingdom Meteorological office (UKMO) used in the model, and temperatures obtained from other sources. UKMO temperatures were compared to temperatures obtained from the National Center for Environmental Predictions (NCEP), the European Centre for Medium Range Weather Forecast (ECMWF) and radio soundings in Ny‐Ålesund. A low bias of 1 to 2 K in UKMO temperatures was detected during the preconditioning phase of the vortex air at the altitude were the ClO activation was modeled. No systematic deviation from the radio sonde temperatures were found in the other data sets. In UKMO data temperature differences reach up to 8 K during the investigated time period.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Copernicus GmbH ; 2017
    In:  Atmospheric Chemistry and Physics Vol. 17, No. 17 ( 2017-09-08), p. 10535-10563
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 17, No. 17 ( 2017-09-08), p. 10535-10563
    Abstract: Abstract. We present a quantitative analysis of the chemical reactions involved in polar ozone depletion in the stratosphere and of the relevant reaction pathways and cycles. While the reactions involved in polar ozone depletion are well known, quantitative estimates of the importance of individual reactions or reaction cycles are rare. In particular, there is no comprehensive and quantitative study of the reaction rates and cycles averaged over the polar vortex under conditions of heterogeneous chemistry so far. We show time series of reaction rates averaged over the core of the polar vortex in winter and spring for all relevant reactions and indicate which reaction pathways and cycles are responsible for the vortex-averaged net change of the key species involved in ozone depletion, i.e., ozone, chlorine species (ClOx, HCl, ClONO2), bromine species, nitrogen species (HNO3, NOx) and hydrogen species (HOx). For clarity, we focus on one Arctic winter (2004–2005) and one Antarctic winter (2006) in a layer in the lower stratosphere around 54 hPa and show results for additional pressure levels and winters in the Supplement. Mixing ratios and reaction rates are obtained from runs of the ATLAS Lagrangian chemistry and transport model (CTM) driven by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis data. An emphasis is put on the partitioning of the relevant chemical families (nitrogen, hydrogen, chlorine, bromine and odd oxygen) and activation and deactivation of chlorine.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 10
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 1 ( 2019-01-16), p. 577-601
    Abstract: Abstract. Stratospheric ozone loss inside the Arctic polar vortex for the winters between 2004–2005 and 2012–2013 has been quantified using measurements from the space-borne Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). For the first time, an evaluation has been performed of six different ozone loss estimation methods based on the same single observational dataset to determine the Arctic ozone loss (mixing ratio loss profiles and the partial-column ozone losses between 380 and 550 K). The methods used are the tracer-tracer correlation, the artificial tracer correlation, the average vortex profile descent, and the passive subtraction with model output from both Lagrangian and Eulerian chemical transport models (CTMs). For the tracer-tracer, the artificial tracer, and the average vortex profile descent approaches, various tracers have been used that are also measured by ACE-FTS. From these seven tracers investigated (CH4, N2O, HF, OCS, CFC-11, CFC-12, and CFC-113), we found that CH4, N2O, HF, and CFC-12 are the most suitable tracers for investigating polar stratospheric ozone depletion with ACE-FTS v3.5. The ozone loss estimates (in terms of the mixing ratio as well as total column ozone) are generally in good agreement between the different methods and among the different tracers. However, using the average vortex profile descent technique typically leads to smaller maximum losses (by approximately 15–30 DU) compared to all other methods. The passive subtraction method using output from CTMs generally results in slightly larger losses compared to the techniques that use ACE-FTS measurements only. The ozone loss computed, using both measurements and models, shows the greatest loss during the 2010–2011 Arctic winter. For that year, our results show that maximum ozone loss (2.1–2.7 ppmv) occurred at 460 K. The estimated partial-column ozone loss inside the polar vortex (between 380 and 550 K) using the different methods is 66–103, 61–95, 59–96, 41–89, and 85–122 DU for March 2005, 2007, 2008, 2010, and 2011, respectively. Ozone loss is difficult to diagnose for the Arctic winters during 2005–2006, 2008–2009, 2011–2012, and 2012–2013, because strong polar vortex disturbance or major sudden stratospheric warming events significantly perturbed the polar vortex, thereby limiting the number of measurements available for the analysis of ozone loss.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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