Sensitivity of the Southern Hemisphere circumpolar jet response to Antarctic ozone depletion: prescribed versus interactive chemistry

Abstract. Southern Hemisphere lower-stratospheric ozone depletion has been shown to lead to a poleward shift of the tropospheric jet stream during austral summer, influencing surface atmosphere and ocean conditions, such as surface temperatures and sea ice extent. The characteristics of stratospheric and tropospheric responses to ozone depletion, however, differ among climate models depending on the representation of ozone in the models. The most appropriate way to represent ozone in a model is to calculate it interactively. However, due to computational costs, in particular for long-term coupled ocean–atmosphere model integrations, the more common way is to prescribe ozone from observations or calculated model fields. Here, we investigate the difference between an interactive and a specified chemistry version of the same atmospheric model in a fully coupled setup using a nine-member chemistry–climate model ensemble. In the specified chemistry version of the model the ozone fields are prescribed using the output from the interactive chemistry model version. We use daily resolved ozone fields in the specified chemistry simulations to achieve a very good comparability between the ozone forcing with and without interactive chemistry. We find that although the shortwave heating rate trend in response to ozone depletion is the same in the different chemistry settings, the interactive chemistry ensemble shows a stronger trend in polar cap stratospheric temperatures (by about 0.7 K decade−1) and circumpolar stratospheric zonal mean zonal winds (by about 1.6 m s−1 decade−1 as compared to the specified chemistry ensemble. This difference between interactive and specified chemistry in the stratospheric response to ozone depletion also affects the tropospheric response. However, an impact on the poleward shift of the tropospheric jet stream is not detected. We attribute part of the differences found in the experiments to the missing representation of feedbacks between chemistry and dynamics in the specified chemistry ensemble, which affect the dynamical heating rates, and part of it to the lack of spatial asymmetries in the prescribed ozone fields. This effect is investigated using a sensitivity ensemble that was forced by a three-dimensional instead of a two-dimensional ozone field. This study emphasizes the value of interactive chemistry for the representation of the Southern Hemisphere stratospheric-jet response to ozone depletion and infers that for periods with strong ozone variability (trends) the details of the ozone forcing could also have an influence on the representation of southern-hemispheric climate variability.

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Sensitivity of the southern hemisphere tropospheric jet response to Antarctic ozone depletion: prescribed versus interactive chemistry

10.5194/acp-2020-441 ◽

2020 ◽

Author(s):

Sabine Haase ◽

Jaika Fricke ◽

Tim Kruschke ◽

Sebastian Wahl ◽

Katja Matthes

Keyword(s):

Southern Hemisphere ◽

Ozone Depletion ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Austral Summer ◽

Jet Stream ◽

Heating Rates ◽

Sea Ice Extent ◽

Poleward Shift

Abstract. Southern hemisphere lower stratospheric ozone depletion has been shown to lead to a poleward shift of the tropospheric jet stream during austral summer, influencing surface atmosphere and ocean conditions, such as surface temperatures and sea ice extent. The characteristics of stratospheric and tropospheric responses to ozone depletion, however, differ largely among climate models depending on the representation of ozone in the models. The most accurate way to represent ozone in a model is to calculate it interactively. However, due to computational costs, in particular for long-term coupled ocean-atmosphere model integrations, the more common way is to prescribe ozone from observations or calculated model fields. Here, we investigate the difference between an interactive and a specified chemistry version of the same atmospheric model in a fully-coupled setup using a 9-member chemistry-climate model ensemble. In the specified chemistry version of the model the ozone fields are prescribed using the output from the interactive chemistry model version. In contrast to earlier studies, we use daily-resolved ozone fields in the specified chemistry simulations to achieve a better comparability between the ozone forcing with and without interactive chemistry. We find that although the short-wave heating rate trend in response to ozone depletion is the same in the different chemistry settings, the interactive chemistry ensemble shows a stronger trend in polar cap stratospheric temperatures (by about 0.7 K per decade) and circumpolar stratospheric zonal mean zonal winds (by about 1.6 m/s per decade) as compared to the specified chemistry ensemble. This difference between interactive and specified chemistry in the stratospheric response to ozone depletion also affects the tropospheric response, namely the poleward shift of the tropospheric jet stream. We attribute part of these differences to the missing representation of feedbacks between chemistry and dynamics in the specified chemistry ensemble, which affect the dynamical heating rates, and part of it to the lack of spatial asymmetries in the prescribed ozone fields. This effect is investigated using a sensitivity ensemble that was forced by a three-dimensional instead of a two–dimensional ozone field. This study emphasizes the value of interactive chemistry for the representation of the southern hemisphere tropospheric jet response to ozone depletion and infers that for periods with strong ozone variability (trends) the details of the ozone forcing can be crucial for representing southern hemispheric climate variability.

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Sensitivity of the southern hemisphere tropospheric jet response to ozone depletion: specified versus interactive chemistry

10.5194/egusphere-egu2020-2831 ◽

2020 ◽

Author(s):

Sabine Haase ◽

Jaika Fricke ◽

Katja Matthes

Keyword(s):

Southern Hemisphere ◽

Ozone Depletion ◽

Climate Models ◽

Stratospheric Ozone ◽

Austral Summer ◽

Atmospheric Model ◽

Short Wave ◽

Wave Heating ◽

Poleward Shift ◽

The Difference

Southern hemisphere lower stratospheric ozone depletion has been shown to lead to a poleward shift of the tropospheric jet stream during austral summer, influencing surface atmosphere and ocean conditions, such as surface temperatures and sea ice extend. The characteristics of stratospheric and tropospheric responses to ozone depletion, however, differ among climate models largely depending on the representation of ozone in the model.The most accurate way to represent ozone in a model is to calculate it interactively. However, due to computational costs, in particular for long-term coupled ocean-atmosphere model integrations, the more common way is to prescribe ozone from observations or calculated model fields.Here, we investigate the difference between an interactive chemistry and a specified chemistry version of the same atmospheric model in a fully-coupled setup using a large 9-member model ensemble. In contrast to most earlier studies, we use daily-resolved ozone fields in the specified chemistry simulations to achieve a better comparability between the ozone forcing with and without interactive chemistry. We find that although the short-wave heating rate trend in response to ozone depletion is the same in the different chemistry settings, the interactive chemistry ensemble shows a stronger trend in polar cap stratospheric temperatures and circumpolar stratospheric and tropospheric zonal mean zonal winds as compared to the specified chemistry ensemble. We attribute part of these differences to the missing representation of feedbacks between chemistry and dynamics in the specified chemistry ensemble and part of it to the lack of zonal asymmetries in the prescribed ozone fields.This study emphasizes the value of interactive chemistry for the representation of the southern hemisphere tropospheric jet response to ozone depletion.

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The Antarctic Sea Ice Response to the Ozone Hole in Climate Models

Journal of Climate ◽

10.1175/jcli-d-13-00590.1 ◽

2014 ◽

Vol 27 (3) ◽

pp. 1336-1342 ◽

Cited By ~ 50

Author(s):

Michael Sigmond ◽

John C. Fyfe

Keyword(s):

Sea Ice ◽

Southern Hemisphere ◽

Ozone Depletion ◽

Climate Models ◽

Stratospheric Ozone ◽

Coupled Model ◽

Ozone Hole ◽

Cmip5 Models ◽

Time Varying ◽

Sea Ice Extent

Abstract It has been suggested that the increase of Southern Hemisphere sea ice extent since the 1970s can be explained by ozone depletion in the Southern Hemisphere stratosphere. In a previous study, the authors have shown that in a coupled atmosphere–ocean–sea ice model the ozone hole does not lead to an increase but to a decrease in sea ice extent. Here, the robustness of this result is established through the analysis of models from phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Comparison of the mean sea ice trends in CMIP3 models with and without time-varying stratospheric ozone suggests that ozone depletion is associated with decreased sea ice extent, and ozone recovery acts to mitigate the future sea ice decrease associated with increasing greenhouse gases. All available historical simulations with CMIP5 models that were designed to isolate the effect of time-varying ozone concentrations show decreased sea ice extent in response to historical ozone trends. In most models, the historical sea ice extent trends are mainly driven by historical greenhouse gas forcing, with ozone forcing playing a secondary role.

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Evaluation of the Australian Community Climate and Earth-System Simulator Chemistry-Climate Model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-19161-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 19161-19196

Author(s):

K. A. Stone ◽

O. Morgenstern ◽

D. J. Karoly ◽

A. R. Klekociuk ◽

W. J. R. French ◽

...

Keyword(s):

Southern Hemisphere ◽

Zonal Wind ◽

Ozone Depletion ◽

Climate Model ◽

Stratospheric Ozone ◽

Similar Amount ◽

Earth System ◽

Total Column Ozone ◽

Australian Community ◽

Community Climate

Abstract. Chemistry climate models are important tools for addressing interactions of composition and climate in the Earth System. In particular, they are used for assessing the combined roles of greenhouse gases and ozone in Southern Hemisphere climate and weather. Here we present an evaluation of the Australian Community Climate and Earth System Simulator-Chemistry Climate Model, focusing on the Southern Hemisphere and the Australian region. This model is used for the Australian contribution to the international Chemistry-Climate Model Initiative, which is soliciting hindcast, future projection and sensitivity simulations. The model simulates global total column ozone (TCO) distributions accurately, with a slight delay in the onset and recovery of springtime Antarctic ozone depletion, and consistently higher ozone values. However, October averaged Antarctic TCO from 1960 to 2010 show a similar amount of depletion compared to observations. A significant innovation is the evaluation of simulated vertical profiles of ozone and temperature with ozonesonde data from Australia, New Zealand and Antarctica from 38 to 90° S. Excess ozone concentrations (up to 26.4 % at Davis during winter) and stratospheric cold biases (up to 10.1 K at the South Pole) outside the period of perturbed springtime ozone depletion are seen during all seasons compared to ozonesondes. A disparity in the vertical location of ozone depletion is seen: centered around 100 hPa in ozonesonde data compared to above 50 hPa in the model. Analysis of vertical chlorine monoxide profiles indicates that colder Antarctic stratospheric temperatures (possibly due to reduced mid-latitude heat flux) are artificially enhancing polar stratospheric cloud formation at high altitudes. The models inability to explicitly simulated supercooled ternary solution may also explain the lack of depletion at lower altitudes. The simulated Southern Annular Mode (SAM) index compares well with ERA-Interim data. Accompanying these modulations of the SAM, 50 hPa zonal wind differences between 2001–2010 and 1979–1998 show increasing zonal wind strength southward of 60° S during December for both the model simulations and ERA-Interim data. These model diagnostics shows that the model reasonably captures the stratospheric ozone driven chemistry-climate interactions important for Australian climate and weather while highlighting areas for future model development.

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Comparison of three vertically resolved ozone data sets: climatology, trends and radiative forcings

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-5533-2013 ◽

2013 ◽

Vol 13 (11) ◽

pp. 5533-5550 ◽

Cited By ~ 27

Author(s):

B. Hassler ◽

P. J. Young ◽

R. W. Portmann ◽

G. E. Bodeker ◽

J. S. Daniel ◽

...

Keyword(s):

Ozone Depletion ◽

Radiative Forcing ◽

Climate Models ◽

Linear Trend ◽

Piecewise Linear ◽

Stratospheric Ozone ◽

Data Sets ◽

Heating Rates ◽

Data Set ◽

Ozone Concentrations

Abstract. Climate models that do not simulate changes in stratospheric ozone concentrations require the prescription of ozone fields to accurately calculate UV fluxes and stratospheric heating rates. In this study, three different global ozone time series that are available for this purpose are compared: the data set of Randel and Wu (2007) (RW07), Cionni et al. (2011) (SPARC), and Bodeker et al. (2013) (BDBP). All three data sets represent multiple-linear regression fits to vertically resolved ozone observations, resulting in a spatially and temporally continuous stratospheric ozone field covering at least the period from 1979 to 2005. The main differences among the data sets result from regression models, which use different observations and include different basis functions. The data sets are compared against ozonesonde and satellite observations to assess how the data sets represent concentrations, trends and interannual variability. In the Southern Hemisphere polar region, RW07 and SPARC underestimate the ozone depletion in spring ozonesonde measurements. A piecewise linear trend regression is performed to estimate the 1979–1996 ozone decrease globally, covering a period of extreme depletion in most regions. BDBP overestimates Arctic and tropical ozone depletion over this period relative to the available measurements, whereas the depletion is underestimated in RW07 and SPARC. While the three data sets yield ozone concentrations that are within a range of different observations, there is a large spread in their respective ozone trends. One consequence of this is differences of almost a factor of four in the calculated stratospheric ozone radiative forcing between the data sets (RW07: −0.038 Wm−2, SPARC: −0.033 Wm−2, BDBP: −0.119 Wm−2), important in assessing the contribution of stratospheric ozone depletion to the total anthropogenic radiative forcing.

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Sensitivity of the Amundsen Sea Low to Stratospheric Ozone Depletion

Journal of Climate ◽

10.1175/jcli-d-13-00657.1 ◽

2014 ◽

Vol 27 (24) ◽

pp. 9383-9400 ◽

Cited By ~ 16

Author(s):

Ryan L. Fogt ◽

Elizabeth A. Zbacnik

Keyword(s):

Ozone Depletion ◽

Climate Models ◽

Stratospheric Ozone ◽

Austral Summer ◽

Lower Troposphere ◽

Southern Annular Mode ◽

Stratospheric Ozone Depletion ◽

Austral Spring ◽

Regional Warming ◽

Amundsen Sea

Abstract Dramatic sea ice loss in the Amundsen and Bellingshausen Seas and regional warming in West Antarctica and the Antarctica Peninsula have been observed over the last few decades. Both of these changes are strongly influenced by the presence of the Amundsen Sea low (ASL), a climatological region of low pressure in the Amundsen Sea. Studies have demonstrated a deepening of the ASL, particularly in austral spring and to a lesser extent autumn, the former related to decreases in the underlying cyclone central pressures and the latter previously suggested to be due to stratospheric ozone depletion. This study further investigates the sensitivity of the ASL to stratospheric ozone depletion using geopotential height from a suite of chemistry–climate models (CCMs) as well as historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Overall, both model types capture the mean characteristics of the ASL, although they have notable positive height biases at 850 hPa and a subdued seasonal cycle in its longitudinal position. Comparing across model simulations, it is observed that there is a pronounced influence of stratospheric ozone depletion in the vicinity of the ASL in the stratosphere through the lower troposphere during austral summer, consistent with the positive phase of the southern annular mode. In the autumn, the authors note a weaker, secondary influence of stratospheric ozone depletion on the ASL only in the CMIP5 simulations.

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Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion

10.5194/acp-2020-705 ◽

2020 ◽

Cited By ~ 1

Author(s):

Ioana Ivanciu ◽

Katja Matthes ◽

Sebastian Wahl ◽

Jan Harlaß ◽

Arne Biastoch

Keyword(s):

Greenhouse Gases ◽

Atmospheric Circulation ◽

Southern Hemisphere ◽

Ozone Depletion ◽

Climate Models ◽

Climate Model ◽

Ozone Hole ◽

Radiative Heating ◽

Austral Spring ◽

The Impact

Abstract. The Antarctic ozone hole has led to substantial changes in the Southern Hemisphere atmospheric circulation, such as the strengthening and poleward shift of the mid-latitude westerly jet. Ozone recovery during the twenty-first century is expected to continue to affect the jet's strength and position, leading to changes in the opposite direction compared to the twentieth century and competing with the effect of increasing greenhouse gases. Simulations of the Earth's past and future climate, such as those performed for the Coupled Model Intercomparison Project Phase 6 (CMIP6), require an accurate representation of these ozone effects. Climate models that use prescribed ozone fields lack the important feedbacks between ozone chemistry, radiative heating, dynamics, as well as transport. These limitations ultimately affect their climate response to ozone depletion. This study investigates the impact of prescribing the ozone field recommended for CMIP6 on the simulated effects of ozone depletion in the Southern Hemisphere. We employ a new, state-of the-art coupled climate model, FOCI, to compare simulations in which the CMIP6 ozone is prescribed with simulations in which the ozone chemistry is calculated interactively. At the same time, we compare the roles played by ozone depletion and by increasing concentrations of greenhouse gases in driving changes in the Southern Hemisphere atmospheric circulation, using a series of historical sensitivity simulations. FOCI reliably captures the known effects of ozone depletion, simulating an austral spring and summer intensification of the mid-latitude westerly winds and of the Brewer-Dobson circulation in the Southern Hemisphere. Ozone depletion is the primary driver of these historical circulation changes in FOCI. These changes are weaker in the simulations that prescribe the CMIP6 ozone field. We attribute this weaker response to the missing ozone-radiative-dynamical feedbacks and to a prescribed ozone hole that is displaced compared to the simulated polar vortex, altering the propagation of planetary wave activity. As a result, the dynamical contribution to the ozone-induced austral spring lower stratospheric cooling is suppressed, leading to a weaker cooling trend. Consequently, the intensification of the polar night jet is also weaker in the simulations with prescribed CMIP6 ozone. In addition, the persistence of the Southern Annular Mode is shorter in the prescribed ozone chemistry simulations. These results suggest that climate models which prescribe the CMIP6 ozone field still underestimate the historical ozone-induced dynamical changes in the Southern Hemisphere, while models that calculate the ozone chemistry interactively simulate an improved response to ozone depletion.

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Southern Hemisphere jet stream: emergent constraints on future shift in zonally varying framework

10.5194/egusphere-egu2020-10820 ◽

2020 ◽

Author(s):

Camille Li ◽

Fumiaki Ogawa ◽

Martin King ◽

Jerry Tjiputra ◽

Bjørnar Jensen ◽

...

Keyword(s):

Southern Hemisphere ◽

Climate Models ◽

Jet Stream ◽

Optimal Solutions ◽

Large Spread ◽

Shift Response ◽

Sample Data ◽

The Future ◽

Emergent Constraints ◽

Poleward Shift

IPCC climate models (CMIP3/5) predict a poleward shift of the Southern Hemisphere (SH) jet stream under global warming, with a large spread across the models. Efforts to find emergent constraints for the future jet shift (response) have relied on the simulated present-day jet position (observable). However, this has been investigated primarily in a zonal-mean framework, which averages out important zonal asymmetries. In this study, we revisit the problem allowing for variations in the longitude, height and season of the response to gain a better physical understanding of the nature of the future jet shift in individual models. Results from a manual data analysis will help guide an exploration of the problem using a big data approach, in particular, the application of a genetic algorithm that finds optimal solutions based on iterative random selection within large sample data spaces.

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The Transient Response of the Southern Ocean to Stratospheric Ozone Depletion

Journal of Climate ◽

10.1175/jcli-d-16-0198.1 ◽

2016 ◽

Vol 29 (20) ◽

pp. 7383-7396 ◽

Cited By ~ 17

Author(s):

William J. M. Seviour ◽

Anand Gnanadesikan ◽

Darryn W. Waugh

Keyword(s):

Southern Ocean ◽

Transient Response ◽

Ozone Depletion ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Natural Variability ◽

Stratospheric Ozone Depletion ◽

Initial State ◽

Cooling Period

Abstract Recent studies have suggested that the response of the Southern Ocean to stratospheric ozone depletion is nonmonotonic in time; consisting of an initial cooling followed by a long-term warming. This result may be significant for the attribution of observed Southern Ocean temperature and sea ice trends, but the time scale and magnitude of the response is poorly constrained, with a wide spread among climate models. Furthermore, a long-lived initial cooling period has only been observed in a model with idealized geometry and lacking an explicit representation of ozone. Here the authors calculate the transient response of the Southern Ocean to a step-change in ozone in a comprehensive coupled climate model, GFDL-ESM2Mc. The Southern Ocean responds to ozone depletion with an initial cooling, lasting 25 yr, followed by a warming. The authors extend previous studies to investigate the dependence of the response on the ozone forcing as well as the regional pattern of this response. The response of the Southern Ocean relative to natural variability is shown to be largely independent of the initial state. However, the magnitude of this response is much less than that of natural variability found in the model, which limits its influence and detectability.

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A Mechanistically Credible, Poleward Shift in Warm-Season Precipitation Projected for the U.S. Southern Great Plains?

Journal of Climate ◽

10.1175/jcli-d-16-0316.1 ◽

2017 ◽

Vol 30 (20) ◽

pp. 8275-8298 ◽

Cited By ~ 13

Author(s):

Melissa S. Bukovsky ◽

Rachel R. McCrary ◽

Anji Seth ◽

Linda O. Mearns

Keyword(s):

Great Plains ◽

Climate Models ◽

Climate Model ◽

Global Climate Model ◽

Regional Climate ◽

Warm Season ◽

Dry Season ◽

Wet Season ◽

Southern Great Plains ◽

Poleward Shift

Abstract Global and regional climate model ensembles project that the annual cycle of rainfall over the southern Great Plains (SGP) will amplify by midcentury. Models indicate that warm-season precipitation will increase during the early spring wet season but shift north earlier in the season, intensifying late summer drying. Regional climate models (RCMs) project larger precipitation changes than their global climate model (GCM) counterparts. This is particularly true during the dry season. The credibility of the RCM projections is established by exploring the larger-scale dynamical and local land–atmosphere feedback processes that drive future changes in the simulations, that is, the responsible mechanisms or processes. In this case, it is found that out of 12 RCM simulations produced for the North American Regional Climate Change Assessment Program (NARCCAP), the majority are mechanistically credible and consistent in the mean changes they are producing in the SGP. Both larger-scale dynamical processes and local land–atmosphere feedbacks drive an earlier end to the spring wet period and deepening of the summer dry season in the SGP. The midlatitude upper-level jet shifts northward, the monsoon anticyclone expands, and the Great Plains low-level jet increases in strength, all supporting a poleward shift in precipitation in the future. This dynamically forced shift causes land–atmosphere coupling to strengthen earlier in the summer, which in turn leads to earlier evaporation of soil moisture in the summer, resulting in extreme drying later in the summer.

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