scholarly journals Temperature thresholds for polar stratospheric ozone loss

2010 ◽  
Vol 10 (11) ◽  
pp. 28687-28720 ◽  
Author(s):  
K. Drdla ◽  
R. Müller
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Reaction Rates ◽  
Threshold Temperature ◽  
Temperature Threshold ◽  
Detailed Model ◽  
Significant Uptake ◽  
Stratospheric Clouds ◽  
Polar Ozone

Abstract. Low stratospheric temperatures are known to be responsible for heterogeneous chlorine activation that leads to polar ozone depletion. Here, we discuss the temperature threshold below which substantial chlorine activation occurs. We suggest that the onset of chlorine activation is dominated by reactions on cold binary aerosol particles, without formation of polar stratospheric clouds (PSCs), i.e. without significant uptake of HNO3 from the gas-phase. Using reaction rates on cold binary aerosol, a chlorine activation threshold temperature, TACL, is derived. At typical stratospheric conditions, TACL is similar in value to TNAT the highest temperature at which nitric acid trihydrate (NAT) can theoretically condense to form PSCs. TACL is still in use as parameterization for the threshold temperature for the onset of chlorine activation. However, perturbations can cause TACL to differ from TNAT: TACL is dependent upon H2O, potential temperature, and the sulphate aerosol loading, but unlike TNAT is not dependent upon HNO3. A parameterization of TACL is provided here, allowing it to be calculated over a comprehensive range of stratospheric conditions. Although considering TACL as a proxy for chlorine activation can be no substitute for a detailed model calculation, TACL provides a more accurate description of the temperature conditions necessary for polar ozone depletion than TNAT and can readily be used in place of TNAT.

scholarly journals Temperature thresholds for chlorine activation and ozone loss in the polar stratosphere

2012 ◽  
Vol 30 (7) ◽  
pp. 1055-1073 ◽  
Author(s):  
K. Drdla ◽  
R. Müller
Keyword(s):  
Potential Temperature ◽  
Volcanic Eruptions ◽  
Reaction Rates ◽  
Threshold Temperature ◽  
Temperature Threshold ◽  
Detailed Model ◽  
Ozone Loss ◽  
Polar Stratosphere ◽  
The Impact ◽  
Polar Ozone

Abstract. Low stratospheric temperatures are known to be responsible for heterogeneous chlorine activation that leads to polar ozone depletion. Here, we discuss the temperature threshold below which substantial chlorine activation occurs. We suggest that the onset of chlorine activation is dominated by reactions on cold binary aerosol particles, without the formation of polar stratospheric clouds (PSCs), i.e. without any significant uptake of HNO3 from the gas phase. Using reaction rates on cold binary aerosol in a model of stratospheric chemistry, a chlorine activation threshold temperature, TACL, is derived. At typical stratospheric conditions, TACL is similar in value to TNAT (within 1–2 K), the highest temperature at which nitric acid trihydrate (NAT) can exist. TNAT is still in use to parameterise the threshold temperature for the onset of chlorine activation. However, perturbations can cause TACL to differ from TNAT: TACL is dependent upon H2O and potential temperature, but unlike TNAT is not dependent upon HNO3. Furthermore, in contrast to TNAT, TACL is dependent upon the stratospheric sulfate aerosol loading and thus provides a means to estimate the impact on polar ozone of strong volcanic eruptions and some geo-engineering options, which are discussed. A parameterisation of TACL is provided here, allowing it to be calculated for low solar elevation (or high solar zenith angle) over a comprehensive range of stratospheric conditions. Considering TACL as a proxy for chlorine activation cannot replace a detailed model calculation, and polar ozone loss is influenced by other factors apart from the initial chlorine activation. However, TACL provides a more accurate description of the temperature conditions necessary for chlorine activation and ozone loss in the polar stratosphere than TNAT.

scholarly journals Polar Stratospheric Clouds: Satellite Observations, Processes, and Role in Ozone Depletion

2021 ◽  
Author(s):  
Ines Tritscher ◽  
Michael C. Pitts ◽  
Lamont R. Poole ◽  
Thomas Peter ◽  
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Michelson Interferometer ◽  
Orthogonal Polarization ◽  
Polar Stratospheric Clouds ◽  
Spatial And Temporal Distributions ◽  
Stratospheric Clouds ◽  
Polar Ozone ◽  
Made In

<p>The important role of polar stratospheric clouds (PSCs) in stratospheric ozone depletion during winter and spring at high latitudes has been known since the 1980s. However, contemporary observations by the spaceborne instruments MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), MLS (Microwave Limb Sounder), and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) have brought about a comprehensive and clearer understanding of PSC spatial and temporal distributions, their conditions of existence, and the processes through which they impact polar ozone. Within the SPARC (Stratosphere-troposphere Processes And their Role in Climate) PSC initiative (PSCi), those datasets have been synthesized and discussed in depth with the result of a new vortex-wide climatology of PSC occurrence and composition. We will present our results within this vPICO together with a review of the significant progress that has been made in our understanding of PSC nucleation, related dynamical processes, and heterogeneous chlorine activation. Moreover, we have compiled different techniques for parameterizing PSCs and we will show their effects in global models.</p>

scholarly journals A quantitative analysis of the reactions involved in stratospheric ozone depletion in the polar vortex core

2017 ◽  
Vol 17 (17) ◽  
pp. 10535-10563 ◽  
Author(s):  
Ingo Wohltmann ◽  
Ralph Lehmann ◽  
Markus Rex
Keyword(s):  
Quantitative Analysis ◽  
Ozone Depletion ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Reaction Rates ◽  
Reanalysis Data ◽  
Reaction Pathways ◽  
Key Species ◽  
Polar Ozone

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.

scholarly journals Quantification of the impact in mid-latitudes of chemical ozone depletion in the 1999/2000 Arctic polar vortex prior to the vortex breakup

2004 ◽  
Vol 4 (2) ◽  
pp. 1911-1940 ◽  
Author(s):  
G. Koch ◽  
H. Wernli ◽  
S. Buss ◽  
J. Staehelin ◽  
T. Peter ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Polar Vortex ◽  
Model Calculations ◽  
Air Masses ◽  
Future Evolution ◽  
Ozone Destruction ◽  
The Impact ◽  
Polar Ozone

Abstract. For the winter 1999/2000 transport of air masses out of the vortex to mid-latitudes and ozone destruction inside and outside the northern polar vortex is studied to quantify the impact of earlier winter (before March) polar ozone destruction on mid-latitude ozone. Nearly 112 000 trajectories are started on 1 December 1999 on 6 different potential temperature levels between 500–600 K and for a subset of these trajectories photo-chemical box-model calculations are performed. We linked a decline of −0.9% of mid-latitude ozone in this layer occurring in January and February 2000 to ozone destruction inside the vortex and successive transport of these air masses to mid-latitudes. Further, the impact of denitrification, PSC-occurrence and anthropogenic chlorine loading on future stratospheric ozone is determined by applying various scenarios. Lower stratospheric temperatures and denitrification were found to play the most important role in the future evolution of polar ozone depletion.

scholarly journals Update of the SWIFT model for polar stratospheric ozone loss (SWIFT version 2)

2017 ◽  
Author(s):  
Ingo Wohltmann ◽  
Ralph Lehmann ◽  
Markus Rex
Keyword(s):  
Differential Equations ◽  
Ozone Depletion ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Reaction Rates ◽  
Satellite Observations ◽  
Rates Of Change ◽  
Key Species ◽  
Polar Ozone

Abstract. The 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 interactions between the ozone layer and climate. So far, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. 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, 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 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 single processes and an independent validation of the different parameterizations for the single processes contained in the differential equations. The training of the original SWIFT model was based on fitting complete model runs to satellite observations and did not allow 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 SWIFT model are purely chemical rates of change in the new version, while the rates of change in the original SWIFT version 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 SWIFT model are validated with independent MLS satellite observations and the results of the original detailed chemistry model of ATLAS.

scholarly journals Update of the Polar SWIFT model for polar stratospheric ozone loss (Polar SWIFT version 2)

2017 ◽  
Vol 10 (7) ◽  
pp. 2671-2689 ◽  
Author(s):  
Ingo Wohltmann ◽  
Ralph Lehmann ◽  
Markus Rex
Keyword(s):  
Differential Equations ◽  
Ozone Depletion ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Reaction Rates ◽  
Satellite Observations ◽  
Rates Of Change ◽  
Key Species ◽  
Polar Ozone

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.

Record springtime stratospheric ozone depletion at 80°N in 2020

2021 ◽  
Author(s):  
Ramina Alwarda ◽  
Kristof Bognar ◽  
Kimberly Strong ◽  
Martyn Chipperfield ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
The Arctic ◽  
Optical Absorption Spectroscopy ◽  
Chemical Transport Model ◽  
Polar Stratospheric Clouds ◽  
Ozone Loss ◽  
Stratospheric Clouds

<p>The Arctic winter of 2019-2020 was characterized by an unusually persistent polar vortex and temperatures in the lower stratosphere that were consistently below the threshold for the formation of polar stratospheric clouds (PSCs). These conditions led to ozone loss that is comparable to the Antarctic ozone hole. Ground-based measurements from a suite of instruments at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Canada (80.05°N, 86.42°W) were used to investigate chemical ozone depletion. The vortex was located above Eureka longer than in any previous year in the 20-year dataset and lidar measurements provided evidence of polar stratospheric clouds (PSCs) above Eureka. Additionally, UV-visible zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements showed record ozone loss in the 20-year dataset, evidence of denitrification along with the slowest increase of NO<sub>2</sub> during spring, as well as enhanced reactive halogen species (OClO and BrO). Complementary measurements of HCl and ClONO<sub>2</sub> (chlorine reservoir species) from a Fourier transform infrared (FTIR) spectrometer showed unusually low columns that were comparable to 2011, the previous year with significant chemical ozone depletion. Record low values of HNO<sub>3</sub> in the FTIR dataset are in accordance with the evidence of PSCs and a denitrified atmosphere. Estimates of chemical ozone loss were derived using passive ozone from the SLIMCAT offline chemical transport model to account for dynamical contributions to the stratospheric ozone budget.</p>

scholarly journals Stratospheric Aerosols, Polar Stratospheric Clouds, and Polar Ozone Depletion After the Mount Calbuco Eruption in 2015

2018 ◽  
Vol 123 (21) ◽  
pp. 12,308-12,331 ◽  
Author(s):  
Yunqian Zhu ◽  
Owen Brian Toon ◽  
Douglas Kinnison ◽  
V. Lynn Harvey ◽  
Michael J. Mills ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Polar Stratospheric Clouds ◽  
Stratospheric Clouds ◽  
Polar Ozone ◽  
Stratospheric Aerosols

scholarly journals Polar stratospheric clouds initiated by mountain waves in a global chemistry–climate model: a missing piece in fully modelling polar stratospheric ozone depletion

2020 ◽  
Vol 20 (21) ◽  
pp. 12483-12497
Author(s):  
Andrew Orr ◽  
J. Scott Hosking ◽  
Aymeric Delon ◽  
Lars Hoffmann ◽  
Reinhold Spang ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Synoptic Scale ◽  
Mountain Waves ◽  
Cooling Phase ◽  
Stratospheric Clouds ◽  
Ice Water ◽  
The Antarctic

Abstract. An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is the temperature fluctuations induced by mountain waves. These enable stratospheric temperatures to fall below the threshold value for PSC formation in regions of negative temperature perturbations or cooling phases induced by the waves even if the synoptic-scale temperatures are too high. However, this formation mechanism is usually missing in global chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate in detail the episodic and localised wintertime stratospheric cooling events produced over the Antarctic Peninsula by a parameterisation of mountain-wave-induced temperature fluctuations inserted into a 30-year run of the global chemistry–climate configuration of the UM-UKCA (Unified Model – United Kingdom Chemistry and Aerosol) model. Comparison of the probability distribution of the parameterised cooling phases with those derived from climatologies of satellite-derived AIRS brightness temperature measurements and high-resolution radiosonde temperature soundings from Rothera Research Station on the Antarctic Peninsula shows that they broadly agree with the AIRS observations and agree well with the radiosonde observations, particularly in both cases for the “cold tails” of the distributions. It is further shown that adding the parameterised cooling phase to the resolved and synoptic-scale temperatures in the UM-UKCA model results in a considerable increase in the number of instances when minimum temperatures fall below the formation temperature for PSCs made from ice water during late austral autumn and early austral winter and early austral spring, and without the additional cooling phase the temperature rarely falls below the ice frost point temperature above the Antarctic Peninsula in the model. Similarly, it was found that the formation potential for PSCs made from ice water was many times larger if the additional cooling is included. For PSCs made from nitric acid trihydrate (NAT) particles it was only during October that the additional cooling is required for temperatures to fall below the NAT formation temperature threshold (despite more NAT PSCs occurring during other months). The additional cooling phases also resulted in an increase in the surface area density of NAT particles throughout the winter and early spring, which is important for chlorine activation. The parameterisation scheme was finally shown to make substantial differences to the distribution of total column ozone during October, resulting from a shift in the position of the polar vortex.

scholarly journals Simulation of the record Arctic stratospheric ozone depletion in 2020

2021 ◽  
Author(s):  
Jens-Uwe Grooß ◽  
Rolf Müller
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
Polar Regions ◽  
Ozone Monitoring Instrument ◽  
Polar Stratosphere ◽  
Year 2000

<p>In Arctic winter/spring 2019/2020, the stratospheric temperatures  were exceptionally low until early April and the polar vortex was  very stable.  As a consequence, significant chemical ozone depletion  occurred in Northern polar regions in spring 2020.  Here, we present  simulations by the Chemical Lagrangian Model of the Stratosphere  (CLaMS) that address the development of chlorine compounds and  ozone in the polar stratosphere in 2020.  The simulation reproduces  relevant observations of ozone and chlorine compounds, as shown by  comparisons with data from Microwave Limb Sounder (MLS), Atmospheric  Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS),  in-situ ozone sondes and the Ozone Monitoring Instrument (OMI).  Although the concentration of chlorine and bromine compounds in the  polar stratosphere has decreased by more than 10% compared to the  peak values around the year 2000, the meteorological conditions in  winter/spring 2019/2020 caused an unprecedented ozone depletion. The  simulated lowest ozone mixing ratio was around 0.05 ppmv and the  calculated partial ozone column depletion in the vortex core in the  lower stratosphere reached 141 Dobson Units between 350 and 600 K  potential temperature, which is more than the  loss in the years 2011 and 2016 which until 2020 had seen the  largest Arctic ozone depletion on record.</p>

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