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 PSCs initiated by mountain waves in a global chemistry-climate model: A missing piece in fully modelling polar stratospheric ozone depletion

2020 ◽  
Author(s):  
Andrew Orr ◽  
J. Scott Hosking ◽  
Aymeric Delon ◽  
Lars Hoffmann ◽  
Reinhold Spang ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Stratospheric Ozone Depletion ◽  
Synoptic Scale ◽  
Mountain Waves ◽  
Cooling Phase ◽  
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 from 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/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/early austral winter and early austral spring, and without the additional cooling-phase the ice frost point is rarely exceeded 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 NAT particles it was only during October that the additional cooling is required for the NAT temperature threshold to be exceeded (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 Inclusion of mountain wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

2014 ◽  
Vol 14 (12) ◽  
pp. 18277-18314 ◽  
Author(s):  
A. Orr ◽  
J. S. Hosking ◽  
L. Hoffmann ◽  
J. Keeble ◽  
S. M. Dean ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Horizontal Resolution ◽  
Measured Temperature ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Induced ◽  
The Antarctic

Abstract. An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves. However, this formation mechanism is usually missing in chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of stratospheric mountain wave-induced temperature fluctuations by the UK Met Office Unified Model (UM) at high and low spatial resolution against Atmospheric Infrared Sounder satellite observations for three case studies over the Antarctic Peninsula. At a high horizontal resolution (4 km) the mesoscale configuration of the UM correctly simulates the magnitude, timing, and location of the measured temperature fluctuations. By comparison, at a low horizontal resolution (2.5° × 3.75°) the climate configuration fails to resolve such disturbances. However, it is demonstrated that the temperature fluctuations computed by a mountain wave parameterisation scheme inserted into the climate configuration (which computes the temperature fluctuations due to unresolved mountain waves) are in excellent agreement with the mesoscale configuration responses. The parameterisation was subsequently used to compute the local mountain wave-induced cooling phases in the chemistry–climate configuration of the UM. This increased stratospheric cooling was passed to the PSC scheme of the chemistry–climate model, and caused a 30–50% increase in PSC surface area density over the Antarctic Peninsula compared to a 30 year control simulation.

scholarly journals Inclusion of mountain-wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

2015 ◽  
Vol 15 (2) ◽  
pp. 1071-1086 ◽  
Author(s):  
A. Orr ◽  
J. S. Hosking ◽  
L. Hoffmann ◽  
J. Keeble ◽  
S. M. Dean ◽  
...  
Keyword(s):  
Case Studies ◽  
Antarctic Peninsula ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Horizontal Resolution ◽  
Measured Temperature ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Induced ◽  
The Antarctic

Abstract. An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves. However, this formation mechanism is usually missing in chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of stratospheric mountain-wave-induced temperature fluctuations by the UK Met Office Unified Model (UM) at climate scale and mesoscale against Atmospheric Infrared Sounder satellite observations for three case studies over the Antarctic Peninsula. At a high horizontal resolution (4 km) the regional mesoscale configuration of the UM correctly simulates the magnitude, timing, and location of the measured temperature fluctuations. By comparison, at a low horizontal resolution (2.5° × 3.75°) the global climate configuration fails to resolve such disturbances. However, it is demonstrated that the temperature fluctuations computed by a mountain wave parameterisation scheme inserted into the climate configuration (which computes the temperature fluctuations due to unresolved mountain waves) are in relatively good agreement with the mesoscale configuration responses for two of the three case studies. The parameterisation was used to include the simulation of mountain-wave-induced PSCs in the global chemistry–climate configuration of the UM. A subsequent sensitivity study demonstrated that regional PSCs increased by up to 50% during July over the Antarctic Peninsula following the inclusion of the local mountain-wave-induced cooling phase.

Mountain-wave Induced Polar Stratospheric Clouds with ICON-ART: An Example at the Antarctic Peninsula

2020 ◽  
Author(s):  
Michael Weimer ◽  
Jennifer Schröter ◽  
Lars Hoffmann ◽  
Oliver Kirner ◽  
Roland Ruhnke ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Ozone Depletion ◽  
Grid Refinement ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Local Grid Refinement ◽  
Local Grid ◽  
Stratospheric Clouds ◽  
Wave Induced ◽  
The Antarctic

<p>Polar Stratospheric Clouds (PSCs) play a key role in explaining ozone depletion on large<br>scales as well as on regional scales. Mountain waves can be formed in the lee of a mountain<br>in a stably stratified atmosphere. They can propagate upwards into the stratosphere and<br>induce temperature changes in the order of 10 to 15 K. Thus, large PSCs localised around the<br>mountain ridge can be formed, leading to increased chlorine activation and subsequently to<br>a larger ozone depletion. It was estimated that 30 % of the southern hemispheric PSCs can<br>be explained by mountain waves. However, for the direct simulation of mountain-wave<br>induced PSCs, the mountains have to be represented adequately in global chemistry climate<br>models which was a challenge in the past due to too low horizontal resolution.</p><p><br>The ICOsahedral Nonhydrostatic (ICON) modelling framework with its extension for Aerosols<br>and Reactive Trace gases (ART) includes a PSC scheme coupled to the atmospheric chemistry<br>in the model. The PSC scheme calculates the formation of all three PSC types independently<br>resulting in the calculation of the heterogeneous reaction rates of chlorine and bromine<br>species on the surface of PSCs. ICON-ART provides the possibility of local grid refinement<br>with two-way interaction. With this, the grid around a mountain can be refined so that<br>mountain waves can be directly simulated in this region with a feedback to the coarser<br>global resolution.</p><p><br>In this study, we show the formation of mountain-wave induced PSCs with ICON-ART for the<br>example of a mountain wave event in July 2008 around the Antarctic Peninsula. It is<br>evaluated with satellite measurements of AIRS and CALIOP and its impact on chlorine and<br>bromine activation as well as on the ozone depletion in the southern hemisphere are<br>analysed. We demonstrate that the effect of mountain-wave induced PSCs can be<br>represented in the coarser global grid by using local grid refinement with two-way<br>interaction. Thus, this study bridges the gap between directly simulated mountain-wave<br>induced PSCs and their representation in a global simulation.</p>

scholarly journals Mountain-wave-induced polar stratospheric clouds and their representation in the global chemistry model ICON-ART

2021 ◽  
Vol 21 (12) ◽  
pp. 9515-9543
Author(s):  
Michael Weimer ◽  
Jennifer Buchmüller ◽  
Lars Hoffmann ◽  
Ole Kirner ◽  
Beiping Luo ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Scale Effects ◽  
Hot Spot ◽  
Orthogonal Polarization ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Stratospheric Clouds ◽  
Wave Induced ◽  
The Antarctic

Abstract. Polar stratospheric clouds (PSCs) are a driver for ozone depletion in the lower polar stratosphere. They provide surface for heterogeneous reactions activating chlorine and bromine reservoir species during the polar night. The large-scale effects of PSCs are represented by means of parameterisations in current global chemistry–climate models, but one process is still a challenge: the representation of PSCs formed locally in conjunction with unresolved mountain waves. In this study, we investigate direct simulations of PSCs formed by mountain waves with the ICOsahedral Nonhydrostatic modelling framework (ICON) with its extension for Aerosols and Reactive Trace gases (ART) including local grid refinements (nesting) with two-way interaction. Here, the nesting is set up around the Antarctic Peninsula, which is a well-known hot spot for the generation of mountain waves in the Southern Hemisphere. We compare our model results with satellite measurements of PSCs from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and gravity wave observations of the Atmospheric Infrared Sounder (AIRS). For a mountain wave event from 19 to 29 July 2008 we find similar structures of PSCs as well as a fairly realistic development of the mountain wave between the satellite data and the ICON-ART simulations in the Antarctic Peninsula nest. We compare a global simulation without nesting with the nested configuration to show the benefits of adding the nesting. Although the mountain waves cannot be resolved explicitly at the global resolution used (about 160 km), their effect from the nested regions (about 80 and 40 km) on the global domain is represented. Thus, we show in this study that the ICON-ART model has the potential to bridge the gap between directly resolved mountain-wave-induced PSCs and their representation and effect on chemistry at coarse global resolutions.

Study of mountain-wave-induced stratospheric cooling over the Antarctic Peninsula using a parameterisation scheme in the UM-UKCA chemistry climate model

2020 ◽  
Author(s):  
Andrew Orr ◽  
Scott Hosking ◽  
Aymeric Delon ◽  
Tracy Moffat-Griffin ◽  
Lars Hoffman ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Models ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Temperature Threshold ◽  
Mountain Wave ◽  
Stratospheric Cooling ◽  
Wave Induced ◽  
The Antarctic

<p>An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves, enabling stratospheric temperatures to fall below the threshold value for PSC formation in the cold phases of these waves even if the synoptic-scale temperatures are too high. However, this formation mechanism is usually missing in chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of parameterised stratospheric mountain-wave-induced temperature fluctuations over the Antarctic Peninsula from a 30-year run of the global chemistry-climate configuration of the UM-UKCA model against climatologies of Atmospheric Infrared Sounder (AIRS) radiance measurements and high-resolution radiosonde temperature soundings from Rothera. The results demonstrate that the local mountain wave-induced cooling phases computed by the scheme are in relatively good agreement with both sets of observations. For example, the scheme is able to capture the observed probability distribution of the temperature fluctuations, particularly the cold tails of the distribution that are critical for exceeding the temperature threshold for PSC formation. Further analysis shows that the increased stratospheric cooling induced by the scheme results in a large increase in total PSC ‘pseudo-volume’ of the area over the Antarctic Peninsula where the model temperature exceeds the temperature threshold of formation of PSCs.</p>

scholarly journals Mountain-wave induced polar stratospheric clouds and their representation in the global chemistry model ICON-ART

2020 ◽  
Author(s):  
Michael Weimer ◽  
Jennifer Buchmüller ◽  
Lars Hoffmann ◽  
Ole Kirner ◽  
Beiping Luo ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Models ◽  
Hot Spot ◽  
Heterogeneous Reactions ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Stratospheric Clouds ◽  
Wave Induced ◽  
The Antarctic

Abstract. Polar stratospheric clouds (PSCs) are a driver for ozone depletion in the lower polar stratosphere. They provide surfaces for heterogeneous reactions activating chlorine and bromine reservoir species during the polar night. PSCs are represented in current global chemistry-climate models, but one process is still a challenge: the representation of PSCs formed locally in conjunction with unresolved mountain waves. In this study, we present simulations with the ICOsahedral Nonhydrostatic modelling framework (ICON) with its extension for Aerosols and Reactive Trace gases (ART) that include local grid refinements (nesting) with two-way interaction. Here, the nesting is set up around the Antarctic Peninsula which is a well-known hot spot for the generation of mountain waves in the southern hemisphere. We compare our model results with satellite measurements from the Cloud-Aerosol LIdar with Orthogonal Polarisation (CALIOP) and the Atmospheric InfraRed Sounder (AIRS). We study a mountain wave event that took place from 19 to 29 July 2008 and find similar structures of PSCs as well as a fairly realistic development of the mountain wave in the Antarctic Peninsula nest. We compare a global simulation without nesting with the nested configuration to show the benefit. Although the mountain waves cannot be resolved adequately in the used global resolution (about 160 km), their effect from the nested regions (about 80 and 40 km) on the global domain is represented. Thus, we show in this study that by using the two-way nesting technique the gap between directly resolved mountain-wave induced PSCs and their representation and effect on chemistry in coarse global resolutions can be bridged by the ICON-ART model.

scholarly journals Can gravity waves significantly impact PSC occurrence in the Antarctic?

2009 ◽  
Vol 9 (22) ◽  
pp. 8825-8840 ◽  
Author(s):  
A. J. McDonald ◽  
S. E. George ◽  
R. M. Woollands
Keyword(s):  
Antarctic Peninsula ◽  
Gravity Waves ◽  
Clustering Algorithm ◽  
Small Scale ◽  
Temperature Threshold ◽  
Aerosol Extinction ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Stratospheric Clouds ◽  
The Antarctic

Abstract. A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs). POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm. A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (TNAT), shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed. Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses). For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to TNAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The latitudinal variation of POAM III observations means that we only observe this region in June–July, and thus the true pattern of enhanced PSC production may continue operating into later months. The analysis has shown that early in the Antarctic winter stratospheric background temperatures are close to the TNAT threshold (and PSC formation), and are thus sensitive to temperature perturbations associated with mountain wave activity near the Antarctic peninsula (40% of PSC formation). Later in the season, and at latitudes away from the peninsula, temperature perturbations associated with gravity waves contribute to about 15% of the observed PSC (a value which corresponds well to several previous studies). This lower value is likely to be due to colder background temperatures already achieving the TNAT threshold unaided. Additionally, there is a reduction in the magnitude of gravity waves perturbations observed as POAM III samples poleward of the peninsula.

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 Possible Effects of Ozone Depletion on the Global Carbon Cycle

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 772-779 ◽  
Author(s):  
Tsung-Hung Peng
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Maximum Effect ◽  
Antarctic Ocean ◽  
Box Models ◽  
Marine Productivity ◽  
Business As Usual ◽  
The Antarctic ◽  
Global Oceans ◽  
Global Carbon

The increase of UV-B radiation resulting from ozone depletion is considered to have damaging effects on marine ecosystems. A cutback of marine productivity would tend to reduce the oceanic uptake of atmospheric CO2. Box models of the global oceans based on the distribution of bomb-produced 14C are used to evaluate the possible effects of ozone depletion on the atmospheric CO2 concentration. The maximum effect presumably takes place if the ozone hole reduces the marine productivity to zero in the Antarctic Ocean. In a business-as-usual scenario of future CO2 emissions, the atmospheric CO2 partial pressure (pCO2) would increase by an additional 37 μatm over the course of the next century. This increase corresponds to 4.6% of the projected atmospheric pCO2 in the year 2090. However, if the damaging effect caused by the destruction of the stratospheric ozone layer is assumed to lower the productivity over the Antarctic Ocean by 10%, the atmospheric pCO2 would rise by less than 3 μatm over the expected atmospheric level in the next century.

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