The importance of interactive chemistry for stratosphere–troposphere coupling

Abstract. Recent observational and modeling studies suggest that stratospheric ozone depletion not only influences the surface climate in the Southern Hemisphere (SH), but also impacts Northern Hemisphere (NH) spring, which implies a strong interaction between dynamics and chemistry. Here, we systematically analyze the importance of interactive chemistry with respect to the representation of stratosphere–troposphere coupling and in particular the effects on NH surface climate during the recent past. We use the interactive and specified chemistry version of NCAR's Whole Atmosphere Community Climate Model coupled to an ocean model to investigate differences in the mean state of the NH stratosphere as well as in stratospheric extreme events, namely sudden stratospheric warmings (SSWs), and their surface impacts. To be able to focus on differences that arise from two-way interactions between chemistry and dynamics in the model, the specified chemistry model version uses a time-evolving, model-consistent ozone field generated by the interactive chemistry model version. We also test the effects of zonally symmetric versus asymmetric prescribed ozone, evaluating the importance of ozone waves in the representation of stratospheric mean state and variability. The interactive chemistry simulation is characterized by a significantly stronger and colder polar night jet (PNJ) during spring when ozone depletion becomes important. We identify a negative feedback between lower stratospheric ozone and atmospheric dynamics during the breakdown of the stratospheric polar vortex in the NH, which contributes to the different characteristics of the PNJ between the simulations. Not only the mean state, but also stratospheric variability is better represented in the interactive chemistry simulation, which shows a more realistic distribution of SSWs as well as a more persistent surface impact afterwards compared with the simulation where the feedback between chemistry and dynamics is switched off. We hypothesize that this is also related to the feedback between ozone and dynamics via the intrusion of ozone-rich air into polar latitudes during SSWs. The results from the zonally asymmetric ozone simulation are closer to the interactive chemistry simulations, implying that under a model-consistent ozone forcing, a three-dimensional (3-D) representation of the prescribed ozone field is desirable. This suggests that a 3-D ozone forcing, as recommended for the upcoming CMIP6 simulations, has the potential to improve the representation of stratospheric dynamics and chemistry. Our findings underline the importance of the representation of interactive chemistry and its feedback on the stratospheric mean state and variability not only in the SH but also in the NH during the recent past.

Download Full-text

The importance of interactive chemistry for stratosphere–troposphere–coupling

10.5194/acp-2018-1052 ◽

2018 ◽

Author(s):

Sabine Haase ◽

Katja Matthes

Keyword(s):

Ozone Depletion ◽

Climate Model ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Ocean Model ◽

Recent Past ◽

Stratospheric Polar Vortex ◽

Surface Climate ◽

The Mean ◽

Mean State

Abstract. Recent observational and modeling studies suggest that not only southern hemispheric surface climate is influenced by stratospheric ozone depletion but also northern hemisphere (NH) spring, implying a strong interaction between dynamics and chemistry. Here, we systematically analyze the importance of interactive chemistry for the representation of stratosphere–troposphere–coupling and in particular the effects on NH surface climate during the recent past. We use the interactive and specified chemistry version of NCAR's Whole Atmosphere Community Climate Model coupled to an ocean model to investigate differences in the mean state of the NH stratosphere as well as in stratospheric extreme events, namely sudden stratospheric warmings (SSWs), and their surface impacts. We also test the effects of zonally symmetric versus asymmetric prescribed ozone, testing the importance of ozone waves for the representation of stratospheric mean state and variability. The interactive chemistry simulation is characterized by a statistically significant stronger and colder polar night jet (PNJ) during spring when ozone depletion becomes important. We identify a negative feedback between lower stratospheric ozone and atmospheric dynamics during the break down of the stratospheric polar vortex in the NH, which contributes to the different characteristics of the PNJ between the simulations. Not only the mean state, but also stratospheric variability is better represented in the interactive chemistry simulation, which shows a more realistic distribution of SSWs as well as a more persisting surface impact afterwards compared to the simulation where the feedback between chemistry and dynamics is switched off. We hypothesize that this is also related to the feedback between ozone and dynamics through the intrusion of ozone rich air into polar latitudes during SSWs. The results from the zonally asymmetric ozone simulation are closer to the interactive chemistry simulations, implying that a three-dimensional representation of prescribed ozone is necessary and desirable in case interactive chemistry is not available or possible for (multi-) centennial simulations. Our findings underline the importance of the representation of interactive chemistry and its feedback on the stratospheric mean state and variability not only on the SH but also on the NH during the recent past.

Download Full-text

Robust effects of springtime Arctic ozone depletion on surface climate

10.21203/rs.3.rs-496081/v1 ◽

2021 ◽

Author(s):

Marina Friedel ◽

Gabriel Chiodo ◽

Andrea Stenke ◽

Daniela Domeisen ◽

Stephan Fueglistaler ◽

...

Keyword(s):

Ozone Depletion ◽

Climate Model ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Negative Temperature ◽

Significant Degree ◽

The Arctic ◽

Surface Climate ◽

Northern Hemispheric ◽

The Impact

Abstract Massive spring ozone loss due to anthropogenic emissions of ozone depleting substances is not limited to the austral hemisphere, but can also occur in the Arctic. Previous studies have suggested a link between springtime Arctic ozone depletion and Northern Hemispheric surface climate, which might add surface predictability. However, so far it has not been possible to isolate the role of stratospheric ozone from dynamical downward impacts. For the first time, we quantify the impact of springtime Arctic ozone depletion on surface climate using observations and targeted chemistry-climate model experiments to isolate the effects of ozone feedbacks. We find that springtime stratospheric ozone depletion is followed by surface anomalies in precipitation and temperature resembling a positive Arctic Oscillation. Most notably, we show that these anomalies, affecting large portions of the Northern Hemisphere, cannot be explained by dynamical variability alone, but are to a significant degree driven by stratospheric ozone. The surface signal is linked to reduced shortwave absorption by stratospheric ozone, forcing persistent negative temperature anomalies in the lower stratosphere and a delayed breakup of the polar vortex - analogous to ozone-surface coupling in the Southern Hemisphere.These results suggest that Arctic stratospheric ozone actively forces springtime Northern Hemispheric surface climate and thus provides a source of predictability on seasonal scales.

Download Full-text

Emergence of Southern Hemisphere circulation changes in response to ozone recovery

10.5194/egusphere-egu2020-22211 ◽

2020 ◽

Author(s):

Brian Zambri ◽

Susan Solomon ◽

David Thompson ◽

Qiang Fu

Keyword(s):

Southern Hemisphere ◽

Ozone Depletion ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Montreal Protocol ◽

Stratospheric Polar Vortex ◽

Surface Climate ◽

Antarctic Ozone ◽

Ozone Depleting Substances ◽

Circulation Changes

<p>Ozone depletion in the Southern Hemisphere (SH) stratosphere in the late 20<sup>th</sup> century cooled the air there, strengthening the SH stratospheric westerly winds near 60&#186;S and altering SH surface climate. Since ~1999, trends in Antarctic ozone have begun to recover, exhibiting a flattening followed by a sign reversal in response to decreases in stratospheric chlorine concentration due to the Montreal Protocol, an international treaty banning the production and consumption of ozone-depleting substances. Here we show that the post&#8211;1999 increase in ozone has resulted in thermal and circulation changes of opposite sign to those that resulted from stratospheric ozone losses, including a warming of the SH polar lower stratosphere and a weakening of the SH stratospheric polar vortex.&#160; Further, these altered trends extend to the upper troposphere, albeit of smaller magnitudes. &#160;Observed post&#8211;1999 trends of temperature and circulation in the stratosphere are about 20&#8211;25% the magnitude of those of the ozone depletion era, and are broadly consistent with expectations based on modeled depletion-era trends and variability of both ozone and reactive chlorine, thereby indicating the emergence of healing of dynamical impacts of the Antarctic ozone hole.</p>

Download Full-text

Projected increases in surface melt and ice loss for the Northern and Southern Patagonian Icefields

Scientific Reports ◽

10.1038/s41598-021-95725-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Claudio Bravo ◽

Deniz Bozkurt ◽

Andrew N. Ross ◽

Duncan J. Quincey

Keyword(s):

Climate Model ◽

Regional Climate ◽

Historical Period ◽

Emission Scenarios ◽

Recent Past ◽

Model Data ◽

Surface Mass ◽

The Mean ◽

Surface Melt ◽

Frontal Ablation

AbstractThe Northern Patagonian Icefield (NPI) and the Southern Patagonian Icefield (SPI) have increased their ice mass loss in recent decades. In view of the impacts of glacier shrinkage in Patagonia, an assessment of the potential future surface mass balance (SMB) of the icefields is critical. We seek to provide this assessment by modelling the SMB between 1976 and 2050 for both icefields, using regional climate model data (RegCM4.6) and a range of emission scenarios. For the NPI, reductions between 1.5 m w.e. (RCP2.6) and 1.9 m w.e. (RCP8.5) were estimated in the mean SMB during the period 2005–2050 compared to the historical period (1976–2005). For the SPI, the estimated reductions were between 1.1 m w.e. (RCP2.6) and 1.5 m w.e. (RCP8.5). Recently frontal ablation estimates suggest that mean SMB in the SPI is positively biased by 1.5 m w.e., probably due to accumulation overestimation. If it is assumed that frontal ablation rates of the recent past will continue, ice loss and sea-level rise contribution will increase. The trend towards lower SMB is mostly explained by an increase in surface melt. Positive ice loss feedbacks linked to increasing in meltwater availability are expected for calving glaciers.

Download Full-text

Impact of Resolution on the Tropical Pacific Circulation in a Matrix of Coupled Models

Journal of Climate ◽

10.1175/2008jcli2537.1 ◽

2009 ◽

Vol 22 (10) ◽

pp. 2541-2556 ◽

Cited By ~ 69

Author(s):

Malcolm J. Roberts ◽

A. Clayton ◽

M.-E. Demory ◽

J. Donners ◽

P. L. Vidale ◽

...

Keyword(s):

Coupled Model ◽

Walker Circulation ◽

Ocean Model ◽

Tropical Pacific ◽

Coupled Models ◽

Model Stability ◽

The Mean ◽

The Impact ◽

Mean State ◽

The Tropical Pacific

Abstract Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation. Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean. These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.

Download Full-text

Influence of Arctic Stratospheric Ozone on Surface Climate in CCMI models

10.5194/acp-2018-1031 ◽

2018 ◽

Author(s):

Ohad Harari ◽

Chaim I. Garfinkel ◽

Olaf Morgenstern ◽

Guang Zeng ◽

Simone Tilmes ◽

...

Keyword(s):

Lower Stratosphere ◽

Climate Model ◽

Southern Oscillation ◽

Stratospheric Ozone ◽

Internal Variability ◽

Tropical Circulation ◽

Polar Cap ◽

Sea Level Pressure ◽

Surface Climate ◽

Stratospheric Variability

Abstract. The Northern Hemisphere and tropical circulation response to interannual variability in Arctic stratospheric ozone is analyzed in a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models simulate a connection between ozone variability and temperature/geopotential height in the lower stratosphere similar to that observed. A connection between Arctic ozone variability and polar cap sea-level pressure is also found, but additional analysis suggests that it is mediated by the dynamical variability that typically drives the anomalous ozone concentrations. The CCMI models also show a connection between Arctic stratospheric ozone and the El Nino Southern Oscillation (ENSO): the CCMI models show a tendency of Arctic stratospheric ozone variability to lead ENSO variability one to two years later. While this effect is much weaker than that observed, it is still statistically significant. Overall, Arctic stratospheric ozone is related to lower stratospheric variability and may also influence the surface in both polar and tropical latitudes, though these impacts can be masked by internal variability if data is only available for ~ 40 years.

Download Full-text

Ozone database in support of CMIP5 simulations: results and corresponding radiative forcing

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-10875-2011 ◽

2011 ◽

Vol 11 (4) ◽

pp. 10875-10933 ◽

Cited By ~ 26

Author(s):

I. Cionni ◽

V. Eyring ◽

J. F. Lamarque ◽

W. J. Randel ◽

D. S. Stevenson ◽

...

Keyword(s):

Time Series ◽

Ozone Depletion ◽

Tropospheric Ozone ◽

Radiative Forcing ◽

Climate Model ◽

Stratospheric Ozone ◽

Satellite Observations ◽

High Latitudes ◽

The Future ◽

Column Ozone

Abstract. A continuous tropospheric and stratospheric vertically resolved ozone time series, from 1850 to 2099, has been generated to be used as forcing in global climate models that do not include interactive chemistry. A multiple linear regression analysis of SAGE I+II satellite observations and polar ozonesonde measurements is used for the stratospheric zonal mean dataset during the well-observed period from 1979 to 2009. In addition to terms describing the mean annual cycle, the regression includes terms representing equivalent effective stratospheric chlorine (EESC) and the 11-yr solar cycle variability. The EESC regression fit coefficients, together with pre-1979 EESC values, are used to extrapolate the stratospheric ozone time series backward to 1850. While a similar procedure could be used to extrapolate into the future, coupled chemistry climate model (CCM) simulations indicate that future stratospheric ozone abundances are likely to be significantly affected by climate change, and capturing such effects through a regression model approach is not feasible. Therefore, the stratospheric ozone dataset is extended into the future (merged in 2009) with multi-model mean projections from 13 CCMs that performed a simulation until 2099 under the SRES (Special Report on Emission Scenarios) A1B greenhouse gas scenario and the A1 adjusted halogen scenario in the second round of the Chemistry-Climate Model Validation (CCMVal-2) Activity. The stratospheric zonal mean ozone time series is merged with a three-dimensional tropospheric data set extracted from simulations of the past by two CCMs (CAM3.5 and PUCCINI) and of the future by one CCM (CAM3.5). The future tropospheric ozone time series continues the historical CAM3.5 simulation until 2099 following the four different Representative Concentration Pathways (RCPs). Generally good agreement is found between the historical segment of the ozone database and satellite observations, although it should be noted that total column ozone is overestimated in the southern polar latitudes during spring and tropospheric column ozone is slightly underestimated. Vertical profiles of tropospheric ozone are broadly consistent with ozonesondes and in-situ measurements, with some deviations in regions of biomass burning. The tropospheric ozone radiative forcing (RF) from the 1850s to the 2000s is 0.23 W m−2, lower than previous results. The lower value is mainly due to (i) a smaller increase in biomass burning emissions; (ii) a larger influence of stratospheric ozone depletion on upper tropospheric ozone at high southern latitudes; and possibly (iii) a larger influence of clouds (which act to reduce the net forcing) compared to previous radiative forcing calculations. Over the same period, decreases in stratospheric ozone, mainly at high latitudes, produce a RF of −0.08 W m−2, which is more negative than the central Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) value of −0.05 W m−2, but which is within the stated range of −0.15 to +0.05 W m−2. The more negative value is explained by the fact that the regression model simulates significant ozone depletion prior to 1979, in line with the increase in EESC and as confirmed by CCMs, while the AR4 assumed no change in stratospheric RF prior to 1979. A negative RF of similar magnitude persists into the future, although its location shifts from high latitudes to the tropics. This shift is due to increases in polar stratospheric ozone, but decreases in tropical lower stratospheric ozone, related to a strengthening of the Brewer-Dobson circulation, particularly through the latter half of the 21st century. Differences in trends in tropospheric ozone among the four RCPs are mainly driven by different methane concentrations, resulting in a range of tropospheric ozone RFs between 0.4 and 0.1 W m−2 by 2100. The ozone dataset described here has been released for the Coupled Model Intercomparison Project (CMIP5) model simulations in netCDF Climate and Forecast (CF) Metadata Convention at the PCMDI website (http://cmip-pcmdi.llnl.gov/).

Download Full-text

Stratospheric ozone in the post-CFC era

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-20223-2008 ◽

2008 ◽

Vol 8 (6) ◽

pp. 20223-20237 ◽

Cited By ~ 3

Author(s):

F. Li ◽

R. S. Stolarski ◽

P. A. Newman

Keyword(s):

Greenhouse Gas ◽

21St Century ◽

Crucial Role ◽

Climate Model ◽

Stratospheric Ozone ◽

Advective Transport ◽

Recent Past ◽

Column Ozone ◽

The Tropics

Abstract. Vertical and latitudinal changes in the stratospheric ozone in the post-chlorofluorocarbon (CFC) era are investigated using simulations of the recent past and the 21st century with a coupled chemistry-climate model. Model results reveal that, in the 2060s when the stratospheric halogen loading is projected to return to its 1980 values, the extratropical column ozone is significantly higher than that in 1975–1984, but the tropical column ozone does not recover to 1980 values. Upper and lower stratospheric ozone changes in the post-CFC era have very different patterns. Above 15 hPa ozone increases almost latitudinally uniformly by 6 Dobson Unit (DU), whereas below 15 hPa ozone decreases in the tropics by 8 DU and increases in the extratropics by up to 16 DU. The upper stratospheric ozone increase is a photochemical response to greenhouse gas induced strong cooling, and the lower stratospheric ozone changes are consistent with enhanced mean advective transport due to a stronger Brewer-Dobson circulation. The model results suggest that the strengthening of the Brewer-Dobson circulation plays a crucial role in ozone recovery and ozone distributions in the post-CFC era.

Download Full-text

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.

Download Full-text

The Meridional Mode in an Idealized Aquaplanet Model: Dependence on the Mean State

Journal of Climate ◽

10.1175/jcli-d-15-0399.1 ◽

2016 ◽

Vol 29 (8) ◽

pp. 2889-2905 ◽

Cited By ~ 5

Author(s):

Honghai Zhang ◽

Amy Clement ◽

Brian Medeiros

Keyword(s):

Climate Variability ◽

Coupled System ◽

Ocean Model ◽

Seasonal Migration ◽

Trade Winds ◽

Zonal Asymmetry ◽

The Mean ◽

Meridional Mode ◽

Mean Climate ◽

Mean State

Abstract The meridional mode provides a source of predictability for the tropical climate variability and change on seasonal and longer time scales by transporting extratropical climate signals into the tropics. Previous research shows that the tropical imprint of the meridional mode is constrained by the interhemispheric asymmetry of the tropical mean climate state. In this study the constraint of the zonal asymmetry is investigated in an AGCM thermodynamically coupled with an aquaplanet slab ocean model. The strategy is to modify the zonal asymmetry of the mean climate state and examine the response of the meridional mode. Presented here are two simulations of different zonal asymmetries in the mean state. In the zonally symmetric case, the meridional mode operates throughout the subtropics but only becomes evident after removing a dominant global-scale eastward-propagating mode. In the zonally asymmetric case, the meridional mode operates only in regions where trade winds converge onto the equator and has an enlarged spatial scale due to the modified mean climate including cold sea surface and weak trade winds. In both simulations, the tropical imprint of the meridional mode is constrained by the north–south seasonal migration of the intertropical convergence zone. These results suggest that the meridional mode does not require the zonal asymmetry of the mean state but is intrinsic to the subtropical ocean–atmosphere coupled system with its characteristics subject to the mean climate state. The implication is that the internal climate variability needs to be assessed in the context of the mean climate state.

Download Full-text