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Lorenzo M Polvani - One of the best experts on this subject based on the ideXlab platform.
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stratospheric Ozone Depletion an unlikely driver of the regional trends in antarctic sea ice in austral fall in the late twentieth century
Geophysical Research Letters, 2017Co-Authors: Laura Landrum, Lorenzo M Polvani, Marika M. Holland, Marilyn N RaphaelAbstract:It has been suggested that recent regional trends in Antarctic sea ice might have been caused by the formation of the Ozone hole in the late twentieth century. Here we explore this by examining two ensembles of a climate model over the Ozone hole formation period (1955–2005). One ensemble includes all known historical forcings; the other is identical except for Ozone levels, which are fixed at 1955 levels. We demonstrate that the model is able to capture, on interannual and decadal timescales, the observed statistical relationship between summer Amundsen Sea Low strength (when Ozone loss causes a robust deepening) and fall sea ice concentrations (when observed trends are largest). In spite of this, the modeled regional trends caused by Ozone Depletion are found to be almost exactly opposite to the observed ones. We deduce that the regional character of observed sea ice trends is likely not caused by Ozone Depletion.
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dependence of model simulated response to Ozone Depletion on stratospheric polar vortex climatology
Geophysical Research Letters, 2017Co-Authors: Pu Lin, Lorenzo M Polvani, Gustavo Correa, David Paynter, Yi Ming, V RamaswamyAbstract:We contrast the responses to Ozone Depletion in two climate models: CAM3 and GFDL AM3. Although both models are forced with identical Ozone concentration changes, the stratospheric cooling simulated in CAM3 is 30% stronger than in AM3 in annual mean, and twice as strong in December. We find that this difference originates from the dynamical response to Ozone Depletion, and its strength can be linked to the timing of the climatological springtime polar vortex breakdown. This mechanism is further supported by a variant of the AM3 simulation in which the Southern stratospheric zonal wind climatology is nudged to be CAM3-like. Given that the delayed breakdown of the Southern polar vortex is a common bias among many climate models, previous model-based assessments of the forced responses to Ozone Depletion may have been somewhat overestimated.
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robustness of the simulated tropospheric response to Ozone Depletion
Journal of Climate, 2017Co-Authors: William J. M. Seviour, Lorenzo M Polvani, Darryn W Waugh, Gustavo P Correa, Chaim I. GarfinkelAbstract:AbstractRecent studies have shown large intermodel differences in the magnitude of the simulated response of the Southern Hemisphere tropospheric circulation to Ozone Depletion. This inconsistency may be a result of different model dynamics, different Ozone forcing, or statistical uncertainty. Here the summertime tropospheric response to Ozone Depletion is analyzed in an array of climate model simulations with incrementally increasing complexity. This allows the sensitivity of the response to a range of factors to be carefully tested, including the choice of model, the prescribed sea surface temperatures and greenhouse gas concentrations, the inclusion of a coupled ocean, the temporal resolution of the prescribed Ozone concentrations, and the inclusion of interactive chemistry. A consistent poleward shift of the extratropical jet is found in all simulations. All simulations also show a strengthening of the extratropical jet and a widening of the southern edge of the Hadley cell, but the magnitude of these...
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modeling evidence that Ozone Depletion has impacted extreme precipitation in the austral summer
Geophysical Research Letters, 2013Co-Authors: Sarah M Kang, Lorenzo M Polvani, Seok-woo Son, J C Fyfe, Michael Sigmond, Gustavo P CorreaAbstract:[1] The impacts of stratospheric Ozone Depletion on the extremes of daily precipitation in the austral summer are explored using two global climate models. Both models indicate that stratospheric Ozone losses since the late 1970s may have increased the frequency and intensity of very heavy precipitation in austral summer over southern high and subtropical latitudes, and may have decreased the frequency and intensity over southern midlatitudes. This hemispheric wide pattern of extreme precipitation response projects strongly onto a previously identified pattern of seasonal mean precipitation response, both of which are shown to be likely of dynamic rather than thermodynamic origin. Citation: Kang, S. M., L. M. Polvani, J. C. Fyfe, S.-W. Son, M. Sigmond, and G. J. P. Correa (2013), Modeling evidence that Ozone Depletion has impacted extreme precipitation in the austral summer, Geophys. Res. Lett., 40, 4054–4059, doi:10.1002/grl.50769.
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the signature of Ozone Depletion on tropical temperature trends as revealed by their seasonal cycle in model integrations with single forcings
Journal of Geophysical Research, 2012Co-Authors: Lorenzo M Polvani, Susan SolomonAbstract:[1] The effect of Ozone Depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the effect of increased greenhouse gases and warmer sea surface temperatures. Confirming and extending earlier studies we find that, over the second half of the 20th Century, the model's lower-stratospheric cooling caused by Ozone Depletion is several times larger than that induced by increasing greenhouse gases. Moreover, our model suggests that the response to different forcings is highly additive. Finally we demonstrate that when Ozone Depletion alone is prescribed in the model, the seasonal cycle of the resultant cooling trends in the lower stratosphere is quite similar to that recently reported in satellite and radiosonde observations: this constitutes strong, new evidence for the key role of Ozone Depletion on tropical lower-stratospheric temperature trends.
Susan Solomon - One of the best experts on this subject based on the ideXlab platform.
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Observing the Impact of Calbuco Volcanic Aerosols on South Polar Ozone Depletion in 2015
Journal of Geophysical Research: Atmospheres, 2017Co-Authors: Kane A. Stone, Susan Solomon, Doug Kinnison, Michael C. Pitts, Lamont R. Poole, Michael J. Mills, Anja Schmidt, Ryan R. Neely, Diane J. Ivy, Michael J. SchwartzAbstract:The Southern Hemisphere Antarctic stratosphere experienced two noteworthy events in 2015: a significant injection of sulfur from the Calbuco volcanic eruption in Chile in April, and a record-large Antarctic Ozone hole in October and November. Here, we quantify Calbuco's influence on stratospheric Ozone Depletion in austral spring 2015 using observations and an earth system model. We analyze Ozonesondes, as well as data from the Microwave Limb Sounder. We employ the Community Earth System Model, version 1, with the Whole Atmosphere Community Climate Model (CESM1(WACCM)) in a specified dynamics setup, which includes calculations of volcanic effects. The Cloud Aerosol Lidar with Orthogonal Polarization data indicate enhanced volcanic liquid sulfate 532 nm backscatter values as far poleward as 68°S during October and November (in broad agreement with WACCM). Comparison of the location of the enhanced aerosols to Ozone data supports the view that aerosols played a major role in increasing the Ozone hole size, especially at pressure levels between 150 and 100 hPa. Ozonesonde vertical Ozone profiles from the sites of Syowa, South Pole, and Neumayer, display the lowest individual October or November measurements at 150 hPa since the 1991 Mt. Pinatubo eruption period, with Davis showing similarly low values, but no available 1990s data. The analysis suggests that under the cold conditions ideal for Ozone Depletion, stratospheric volcanic aerosol particles from the moderate-magnitude eruption of Calbuco in 2015 greatly enhanced austral Ozone Depletion, particularly at 55–68°S, where liquid binary sulfate aerosols have a large influence on Ozone concentrations.
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simulation of polar Ozone Depletion an update
Journal of Geophysical Research, 2015Co-Authors: Susan Solomon, D E Kinnison, Justin Bandoro, Rolando R GarciaAbstract:We evaluate polar Ozone Depletion chemistry using the specified dynamics version of the Whole Atmosphere Community Climate Model for the year 2011. We find that total Ozone Depletion in both hemispheres is dependent on cold temperatures (below 192 K) and associated heterogeneous chemistry on polar stratospheric cloud particles. Reactions limited to warmer temperatures above 192 K, or on binary liquid aerosols, yield little modeled polar Ozone Depletion in either hemisphere. An imposed factor of three enhancement in stratospheric sulfate increases Ozone loss by up to 20 Dobson unit (DU) in the Antarctic and 15 DU in the Arctic in this model. Such enhanced sulfate loads are similar to those observed following recent relatively small volcanic eruptions since 2005 and imply impacts on the search for polar Ozone recovery. Ozone losses are strongly sensitive to temperature, with a test case cooler by 2 K producing as much as 30 DU additional Ozone loss in the Antarctic and 40 DU in the Arctic. A new finding of this paper is the use of the temporal behavior and variability of ClONO2 and HCl as indicators of the efficacy of heterogeneous chemistry. Transport of ClONO2 from the southern subpolar regions near 55–65°S to higher latitudes near 65–75°S provides a flux of NOx from more sunlit latitudes to the edge of the vortex and is important for Ozone loss in this model. Comparisons between modeled and observed total column and profile Ozone perturbations, ClONO2 abundances, and the rate of change of HCl bolster confidence in these conclusions.
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modeling the climate impact of southern hemisphere Ozone Depletion the importance of the Ozone data set
Geophysical Research Letters, 2014Co-Authors: Paul Young, Susan Solomon, Sean M Davis, Birgit Hassler, Karen H RosenlofAbstract:The Ozone hole is an important driver of recent Southern Hemisphere (SH) climate change, and capturing these changes is a goal of climate modeling. Most climate models are driven by off-line Ozone data sets. Previous studies have shown that there is a substantial range in estimates of SH Ozone Depletion, but the implications of this range have not been examined systematically. We use a climate model to evaluate the difference between using the Ozone forcing (Stratospheric Processes and their Role in Climate (SPARC)) used by many Intergovernmental Panel on Climate Change Fifth Assessment Report (Coupled Model Intercomparison Project) models and one at the upper end of the observed Depletion estimates (Binary Database of Profiles (BDBP)). In the stratosphere, we find that austral spring/summer polar cap cooling, geopotential height decreases, and zonal wind increases in the BDBP simulations are all doubled compared to the SPARC simulations, while tropospheric responses are 20–100% larger. These results are important for studies attempting to diagnose the climate fingerprints of Ozone Depletion.
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fundamental differences between arctic and antarctic Ozone Depletion
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Susan Solomon, Diane J. Ivy, J Haskins, Flora MinAbstract:Antarctic Ozone Depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. The deep Antarctic “hole” contrasts with the generally weaker Depletions observed in the warmer Arctic. An unusually cold Arctic stratospheric season occurred in 2011, raising the question of how the Arctic Ozone chemistry in that year compares with others. We show that the averaged Depletions near 20 km across the cold part of each pole are deeper in Antarctica than in the Arctic for all years, although 2011 Arctic values do rival those seen in less-depleted years in Antarctica. We focus not only on averages but also on extremes, to address whether or not Arctic Ozone Depletion can be as extreme as that observed in the Antarctic. This information provides unique insights into the contrasts between Arctic and Antarctic Ozone chemistry. We show that extreme Antarctic Ozone minima fall to or below 0.1 parts per million by volume (ppmv) at 18 and 20 km (about 70 and 50 mbar) whereas the lowest Arctic Ozone values are about 0.5 ppmv at these altitudes. At a higher altitude of 24 km (30-mbar level), no Arctic data below about 2 ppmv have been observed, including in 2011, in contrast to values more than an order of magnitude lower in Antarctica. The data show that the lowest Ozone values are associated with temperatures below −80 °C to −85 °C depending upon altitude, and are closely associated with reduced gaseous nitric acid concentrations due to uptake and/or sedimentation in polar stratospheric cloud particles.
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the signature of Ozone Depletion on tropical temperature trends as revealed by their seasonal cycle in model integrations with single forcings
Journal of Geophysical Research, 2012Co-Authors: Lorenzo M Polvani, Susan SolomonAbstract:[1] The effect of Ozone Depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the effect of increased greenhouse gases and warmer sea surface temperatures. Confirming and extending earlier studies we find that, over the second half of the 20th Century, the model's lower-stratospheric cooling caused by Ozone Depletion is several times larger than that induced by increasing greenhouse gases. Moreover, our model suggests that the response to different forcings is highly additive. Finally we demonstrate that when Ozone Depletion alone is prescribed in the model, the seasonal cycle of the resultant cooling trends in the lower stratosphere is quite similar to that recently reported in satellite and radiosonde observations: this constitutes strong, new evidence for the key role of Ozone Depletion on tropical lower-stratospheric temperature trends.
Mp Chipperfield - One of the best experts on this subject based on the ideXlab platform.
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unprecedented spring 2020 Ozone Depletion in the context of 20 years of measurements at eureka canada
Journal of Geophysical Research, 2021Co-Authors: Kristof Bognar, Mp Chipperfield, Sandip Dhomse, Wuhu Feng, Ramina Alwarda, Kimberly Strong, J R Drummond, Vitali Fioletov, Florence Goutail, Beatriz HerreraAbstract:In the winter and spring of 2019/2020, the unusually cold, strong, and stable polar vortex created favorable conditions for Ozone Depletion in the Arctic. Chemical Ozone loss started earlier than i...
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arctic Ozone Depletion in 2019 20 roles of chemistry dynamics and the montreal protocol
Geophysical Research Letters, 2021Co-Authors: Wuhu Feng, Sandip Dhomse, Carlo Arosio, M Weber, J P Burrows, M L Santee, Mp ChipperfieldAbstract:We use a 3‐D chemical transport model and satellite observations to investigate Arctic Ozone Depletion in winter/spring 2019/20 and compare with earlier years. Persistently low temperatures caused extensive chlorine activation through to March. March‐mean polar‐cap‐mean modelled chemical column Ozone loss reached 78 DU (local maximum loss of ∼108 DU in the vortex), similar to that in 2011. However, weak dynamical replenishment of only 59 DU from December to March was key to producing very low (<220 DU) column Ozone values. The only other winter to exhibit such weak transport in the past 20 years was 2010/11, so this process is fundamental to causing such low Ozone values. A model simulation with peak observed stratospheric total chlorine and bromine loading (from the mid‐1990s) shows that gradual recovery of the Ozone layer over the past two decades ameliorated the polar cap Ozone Depletion in March 2020 by ∼20 DU.
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Arctic Ozone Depletion in 2019/20: Roles of chemistry, dynamics and the Montreal Protocol
'American Geophysical Union (AGU)', 2021Co-Authors: Feng W, J P Burrows, M L Santee, Ss Dhomse, Arosio C, Weber M, Mp ChipperfieldAbstract:We use a 3‐D chemical transport model and satellite observations to investigate Arctic Ozone Depletion in winter/spring 2019/20 and compare with earlier years. Persistently low temperatures caused extensive chlorine activation through to March. March‐mean polar‐cap‐mean modelled chemical column Ozone loss reached 78 DU (local maximum loss of ∼108 DU in the vortex), similar to that in 2011. However, weak dynamical replenishment of only 59 DU from December to March was key to producing very low (
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On the Regional and Seasonal Ozone Depletion Potential of Chlorinated Very Short-Lived Substances
'American Geophysical Union (AGU)', 2019Co-Authors: Claxton T, Hossaini R, Wild O, Mp Chipperfield, Wilson CAbstract:Chloroform (CHCl ₃ ), dichloromethane (CH ₂ Cl ₂ ), perchloroethylene (C ₂ Cl ₄ ), and 1,2-dichloroethane (C ₂ H ₄ Cl ₂ ) are chlorinated Very Short-Lived Substances (Cl-VSLS) with a range of commercial/industrial applications. Recent studies highlight the increasing influence of Cl-VSLS on the stratospheric chlorine budget and therefore their possible role in Ozone Depletion. Here we evaluate the Ozone Depletion potential (ODP) of these Cl-VSLS using a three-dimensional chemical transport model and investigate sensitivity to emission location/season. The seasonal dependence of the ODPs is small, but ODPs vary by a factor of 2–3 depending on the continent of emission: 0.0143–0.0264 (CHCl ₃ ), 0.0097–0.0208 (CH ₂ Cl ₂ ), 0.0057–0.0198 (C ₂ Cl ₄ ), and 0.0029–0.0119 (C ₂ H ₄ Cl ₂ ). Asian emissions produce the largest ODPs owing to proximity to the tropics and efficient troposphere-to-stratosphere transport of air originating from industrialized East Asia. The Cl-VSLS ODPs are generally small, but the upper ends of the CHCl ₃ and CH ₂ Cl ranges are comparable to the mean ODP of methyl chloride (0.02), a longer-lived Ozone-depleting substance
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tropospheric jet response to antarctic Ozone Depletion an update with chemistry climate model initiative ccmi models
Environmental Research Letters, 2018Co-Authors: Seok-woo Son, Chaim I. Garfinkel, Boreum Han, Seoyeon Kim, Rokjin J Park, Luke N Abraham, Hideharu Akiyoshi, A T Archibald, N Butchart, Mp ChipperfieldAbstract:The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic Ozone Depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic Ozone Depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments exhibit quantitatively the same multi-model mean trend, irrespective of whether the ocean is coupled or prescribed. Results are also quantitatively similar to those derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) high-top model simulations in which the stratospheric Ozone is mostly prescribed with monthly- and zonally-averaged values. These results suggest that the Ozone-hole-induced SH-summer circulation changes are robust across the models irrespective of the specific chemistry-atmosphere-ocean coupling.
Rolando R Garcia - One of the best experts on this subject based on the ideXlab platform.
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simulation of polar Ozone Depletion an update
Journal of Geophysical Research, 2015Co-Authors: Susan Solomon, D E Kinnison, Justin Bandoro, Rolando R GarciaAbstract:We evaluate polar Ozone Depletion chemistry using the specified dynamics version of the Whole Atmosphere Community Climate Model for the year 2011. We find that total Ozone Depletion in both hemispheres is dependent on cold temperatures (below 192 K) and associated heterogeneous chemistry on polar stratospheric cloud particles. Reactions limited to warmer temperatures above 192 K, or on binary liquid aerosols, yield little modeled polar Ozone Depletion in either hemisphere. An imposed factor of three enhancement in stratospheric sulfate increases Ozone loss by up to 20 Dobson unit (DU) in the Antarctic and 15 DU in the Arctic in this model. Such enhanced sulfate loads are similar to those observed following recent relatively small volcanic eruptions since 2005 and imply impacts on the search for polar Ozone recovery. Ozone losses are strongly sensitive to temperature, with a test case cooler by 2 K producing as much as 30 DU additional Ozone loss in the Antarctic and 40 DU in the Arctic. A new finding of this paper is the use of the temporal behavior and variability of ClONO2 and HCl as indicators of the efficacy of heterogeneous chemistry. Transport of ClONO2 from the southern subpolar regions near 55–65°S to higher latitudes near 65–75°S provides a flux of NOx from more sunlit latitudes to the edge of the vortex and is important for Ozone loss in this model. Comparisons between modeled and observed total column and profile Ozone perturbations, ClONO2 abundances, and the rate of change of HCl bolster confidence in these conclusions.
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Ozone Depletion at mid latitudes coupling of volcanic aerosols and temperature variability to anthropogenic chlorine
Geophysical Research Letters, 1998Co-Authors: Stanley C Solomon, Lamont R. Poole, Rolando R Garcia, R W Portmann, William J Randel, R Nagatani, J F Gleason, L W Thomason, M P MccormickAbstract:Satellite observations of total Ozone at 40–60°N are presented from a variety of instruments over the time period 1979–1997. These reveal record low values in 1992–3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of Ozone Depletion. The observations are shown to be consistent with current understanding of the chemistry of Ozone Depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude Ozone Depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200–210K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude Ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol.
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Ozone Depletion at mid latitudes coupling of volcanic aerosols and temperature variability to anthropogenic chlorine
Geophysical Research Letters, 1998Co-Authors: Stanley C Solomon, Lamont R. Poole, Rolando R Garcia, R W Portmann, William J Randel, R Nagatani, J F Gleason, L W Thomason, M P MccormickAbstract:Satellite observations of total Ozone at 40-60 deg N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of Ozone Depletion. The observations are shown to be consistent with current understanding of the chemistry of Ozone Depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude Ozone Depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210 K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude Ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol.
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the role of aerosol variations in anthropogenic Ozone Depletion at northern midlatitudes
Journal of Geophysical Research, 1996Co-Authors: S C Solomon, Lamont R. Poole, Rolando R Garcia, R W Portmann, L W Thomason, M P MccormickAbstract:Aerosol surface area distributions inferred from satelliteborne 1-μm extinction measurements are used as input to a two-dimensional model to study the effects of heterogeneous chemistry upon anthropogenic Ozone Depletion at northern midlatitudes. It is shown that short-term (interannual) and longer-term (decadal) changes in aerosols very likely played a substantial role along with trends in anthropogenic chlorine and bromine in both triggering the Ozone losses observed at northern midlatitudes in the early 1980s and increasing the averaged long-term Ozone Depletions of the past decade or so. The use of observed aerosol distributions enhances the calculated Ozone Depletion due to halogen chemistry below about 25 km over much of the past decade, including many periods not generally thought to be affected by volcanic activity. Direct observations (especially the relationships of NO X /NO Y and ClO/Cl y ratios to aerosol content) confirm the key aspects of the model chemistry that is responsible for this behavior and demonstrate that aerosol changes alone are not a mechanism for Ozone losses in the absence of anthropogenic halogen inputs to the stratosphere. It is also suggested that aerosol-induced Ozone changes could be confused with 11-year solar cycle effects in some statistical analyses, resulting in an overestimate of the trends ascribed to solar activity. While the timing of the observed Ozone changes over about the past 15 years is in remarkable agreement with the model predictions that explicitly include observed aerosol changes, their magnitude is about 50% larger than calculated. Possible chemical and dynamical causes of this discrepancy are explored. On the basis of this work, it is shown that the timing and magnitude of future Ozone losses at midlatitudes in the northern hemisphere are likely to be strongly dependent upon volcanic aerosol variations as well as on future chlorine and bromine loading.
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Ozone Depletion and global warming potentials of CF3I
Journal of Geophysical Research, 1994Co-Authors: Susan Solomon, James B. Burkholder, A. R. Ravishankara, Rolando R GarciaAbstract:Laboratory measurements of the infrared and near-ultraviolet absorption characteristics of CF{sub 3}I (a potentially useful substitute for halons) are presented. Using these data together with a detailed photochemical model, it is shown that the lifetime of this gas in the sunlit atmosphere is less than a day. The chemistry of iodine in the stratosphere is evaluated, and it is shown that any iodine that reaches the stratosphere will be very effective for Ozone destruction here. However, the extremely short lifetime of CF{sub 3}I greatly limits its transport to the stratosphere when released at the surface, especially at midlatitudes, and the total anthropogenic surface release of CF{sub 3}I is likely to be far less than that of natural iodocarbons such as CH{sub 3}I on a global basis. It is highly probable that the steady-state Ozone Depletion potential (ODP) of CF{sub 3}I for surface releases is less than 0.008 and more likely baelow 0.0001. Measured infrared absorption data are also combined with the lifetime to show that the 20-year global warming potential (GWP) of this gas is likely to be very small, less than 5. Therefore this study suggests that neither the ODP nor the GWP of this gas represent significant obstaclesmore » to its use as a replacement for halons. 34 refs., 3 figs., 2 tabs.« less
Darryn W Waugh - One of the best experts on this subject based on the ideXlab platform.
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robustness of the simulated tropospheric response to Ozone Depletion
Journal of Climate, 2017Co-Authors: William J. M. Seviour, Lorenzo M Polvani, Darryn W Waugh, Gustavo P Correa, Chaim I. GarfinkelAbstract:AbstractRecent studies have shown large intermodel differences in the magnitude of the simulated response of the Southern Hemisphere tropospheric circulation to Ozone Depletion. This inconsistency may be a result of different model dynamics, different Ozone forcing, or statistical uncertainty. Here the summertime tropospheric response to Ozone Depletion is analyzed in an array of climate model simulations with incrementally increasing complexity. This allows the sensitivity of the response to a range of factors to be carefully tested, including the choice of model, the prescribed sea surface temperatures and greenhouse gas concentrations, the inclusion of a coupled ocean, the temporal resolution of the prescribed Ozone concentrations, and the inclusion of interactive chemistry. A consistent poleward shift of the extratropical jet is found in all simulations. All simulations also show a strengthening of the extratropical jet and a widening of the southern edge of the Hadley cell, but the magnitude of these...
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The Transient Response of the Southern Ocean to Stratospheric Ozone Depletion
Journal of Climate, 2016Co-Authors: William J. M. Seviour, Anand Gnanadesikan, Darryn W WaughAbstract:AbstractRecent 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 Sou...
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Drivers of the Recent Tropical Expansion in the Southern Hemisphere: Changing SSTs or Ozone Depletion?
Journal of Climate, 2015Co-Authors: Darryn W Waugh, Chaim I. GarfinkelAbstract:AbstractObservational evidence indicates that the southern edge of the Hadley cell (HC) has shifted southward during austral summer in recent decades. However, there is no consensus on the cause of this shift, with several studies reaching opposite conclusions as to the relative role of changes in sea surface temperatures (SSTs) and stratospheric Ozone Depletion in causing this shift. Here, the authors perform a meta-analysis of the extant literature on this subject and quantitatively compare the results of all published studies that have used single-forcing model integrations to isolate the role of different factors on the HC expansion during austral summer. It is shown that the weight of the evidence clearly points to stratospheric Ozone Depletion as the dominant driver of the tropical summertime expansion over the period in which an Ozone hole was formed (1979 to late 1990s), although SST trends have contributed to trends since then. Studies that have claimed SSTs as the major driver of tropical expans...
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stratospheric Ozone Depletion the main driver of twentieth century atmospheric circulation changes in the southern hemisphere
Journal of Climate, 2011Co-Authors: Lorenzo M Polvani, Gustavo Correa, Darryn W Waugh, Seok-woo SonAbstract:The importance of stratospheric Ozone Depletion on the atmospheric circulation of the troposphere is studied with an atmospheric general circulation model, the Community Atmospheric Model, version 3 (CAM3), for the second half of the twentieth century. In particular, the relative importance of Ozone Depletion is contrasted with that of increased greenhouse gases and accompanying sea surface temperature changes. By specifying Ozone and greenhouse gas forcings independently, and performing long, time-slice integrations,it is shown thatthe impactsof Ozone Depletionare roughly2‐3 times larger thanthoseassociated with increased greenhouse gases, for the Southern Hemisphere tropospheric summer circulation. The formation of the Ozone hole is shown to affect not only the polar tropopause and the latitudinal position of the midlatitude jet; it extends to the entire hemisphere, resulting in a broadening of the Hadley cell and a poleward extension of the subtropical dry zones. The CAM3 results are compared to and found to be in excellent agreement with those of the multimodel means of the recent Coupled Model Intercomparison Project (CMIP3) and Chemistry‐Climate Model Validation (CCMVal2) simulations. This study, therefore, strongly suggests that most Southern Hemisphere tropospheric circulation changes, in austral summerover the second half of the twentieth century, have been caused by polar stratospheric Ozone Depletion.
