scholarly journals On the impact of future climate change on tropopause folds and tropospheric ozone

2019 ◽  
Vol 19 (22) ◽  
pp. 14387-14401 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis
Keyword(s):  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Future Climate Change ◽  
Identification Algorithm ◽  
The Future ◽  
Projected Changes ◽  
The Impact

Abstract. Using a transient simulation for the period 1960–2100 with the state-of-the-art ECHAM5/MESSy Atmospheric Chemistry (EMAC) global model and a tropopause fold identification algorithm, we explore the future projected changes in tropopause folds, stratosphere-to-troposphere transport (STT) of ozone, and tropospheric ozone under the RCP6.0 scenario. Statistically significant changes in tropopause fold frequencies from 1970–1999 to 2070–2099 are identified in both hemispheres, regionally exceeding 3 %, and are associated with the projected changes in the position and intensity of the subtropical jet streams. A strengthening of ozone STT is projected for the future in both hemispheres, with an induced increase in transported stratospheric ozone tracer throughout the whole troposphere, reaching up to 10 nmol mol−1 in the upper troposphere, 8 nmol mol−1 in the middle troposphere, and 3 nmol mol−1 near the surface. Notably, the regions exhibiting the largest changes of ozone STT at 400 hPa coincide with those with the highest fold frequency changes, highlighting the role of the tropopause folding mechanism in STT processes under a changing climate. For both the eastern Mediterranean and Middle East (EMME) and Afghanistan (AFG) regions, which are known as hotspots of fold activity and ozone STT during the summer period, the year-to-year variability of middle-tropospheric ozone with stratospheric origin is largely explained by the short-term variations in ozone at 150 hPa and tropopause fold frequency. Finally, ozone in the lower troposphere is projected to decrease under the RCP6.0 scenario during MAM (March, April, and May) and JJA (June, July, and August) in the Northern Hemisphere and during DJF (December, January, and February) in the Southern Hemisphere, due to the decline of ozone precursor emissions and the enhanced ozone loss from higher water vapour abundances, while in the rest of the troposphere ozone shows a remarkable increase owing mainly to the STT strengthening and the stratospheric ozone recovery.

scholarly journals On the impact of future climate change on tropopause folds and tropospheric ozone

2019 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis
Keyword(s):  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Future Climate Change ◽  
Identification Algorithm ◽  
Jet Streams ◽  
Projected Changes ◽  
The Impact

Abstract. Using a transient simulation for the period 1960–2100 with the state-of-the-art ECHAM5/MESSy Atmospheric Chemistry (EMAC) global model and a tropopause fold identification algorithm, we explore the future projected changes in tropopause folds, Stratosphere-to-Troposphere Transport (STT) of ozone and tropospheric ozone under the RCP6.0 scenario. Statistically significant changes in tropopause fold frequencies are identified in both Hemispheres, occasionally exceeding 3 %, which are associated with the projected changes in the position and intensity of the subtropical jet streams. A strengthening of ozone STT is projected for future at both Hemispheres, with an induced increase of transported stratospheric ozone tracer throughout the whole troposphere, reaching up to 10 nmol/mol in the upper troposphere, 8 nmol/mol in the middle troposphere and 3 nmol/mol near the surface. Notably, the regions exhibiting the maxima changes of ozone STT at 400 hPa, coincide with that of the highest fold frequencies, highlighting the role of tropopause folding mechanism in STT process under a changing climate. For both the eastern Mediterranean and Middle East (EMME), and the Afghanistan (AFG) regions, which are known as hotspots of fold activity and ozone STT during the summer period, the year-to-year variability of middle tropospheric ozone with stratospheric origin is largely explained by the short-term variations of ozone at 150 hPa and tropopause folds frequency. Finally, ozone in the lower troposphere is projected to decrease under the RCP6.0 scenario during MAM (March, April and May) and JJA (June, July and August) at the Northern Hemisphere, and during DJF (December, January and February) at the Southern Hemisphere, due to the decline of ozone precursors emissions, while in the rest of the troposphere ozone shows a remarkable increase owing to the STT strengthening.

scholarly journals On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

2016 ◽  
Vol 16 (21) ◽  
pp. 14025-14039 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis ◽  
Evangelos Tyrlis ◽  
Bojan Škerlak ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Free Troposphere ◽  
Near Surface ◽  
Grid Points ◽  
High Concentrations

Abstract. We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model. Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle and lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the southeast and decreasing altitude. We find that the interannual variability of near-surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

scholarly journals Stratospheric impact on the Northern Hemisphere winter and spring ozone interannual variability in the troposphere

2019 ◽  
Author(s):  
Junhua Liu ◽  
Jose M. Rodriguez ◽  
Luke D. Oman ◽  
Anne R. Douglass ◽  
Mark A. Olsen ◽  
...  
Keyword(s):  
North America ◽  
Tropospheric Ozone ◽  
Interannual Variation ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
The Arctic ◽  
Vertical Extent ◽  
Pinatubo Eruption ◽  
Tropospheric O3 ◽  
The Impact

Abstract. In this study we use O3 and stratospheric O3 tracer simulations from the high-resolution Goddard Earth Observing System, Version 5 (GEOS-5) Replay run (MERRA-2 GMI at 0.5° model resolution ~ 50 km) and observations from ozonesondes to investigate the interannual variation and vertical extent of the stratospheric ozone impact on tropospheric ozone. Our work focuses on the winter and spring seasons over North America and Europe. The model reproduces the observed interannual variation of tropospheric O3, except for the Pinatubo period from 1991 to 1995 over the region of North America. Ozonesonde data show a negative ozone anomaly in 1992–1994 following the Pinatubo eruption, with recovery thereafter. The simulated anomaly is only half the magnitude of that observed. Our analysis suggests that the simulated Stratosphere-troposphere exchange (STE) flux deduced from the analysis might be too strong over the North American (50° N–70° N) region after the Mt. Pinatubo eruption in the early 1990s, masking the impact of lower stratospheric O3 concentration on tropospheric O3. European ozonesonde measurements show a similar but weaker O3 depletion after the Mt. Pinatubo eruption, which is fully reproduced by the model. Analysis based on a stratospheric O3 tracer (StratO3) identifies differences in strength and vertical extent of stratospheric ozone influence on the tropospheric ozone interannual variation (IAV) between North America and Europe. Over North America, the StratO3 IAV has a significant impact on tropospheric O3 from the upper to lower troposphere and explains about 60 % and 66 % of simulated O3 IAV at 400 hPa, ~ 11 % and 34 % at 700 hPa in winter and spring respectively. Over Europe, the influence is limited to the middle to upper troposphere, and becomes much smaller at 700 hPa. The stronger and deeper stratospheric contributions in the tropospheric O3 IAV over North America shown by the model is likely related to ozonesondes' being closer to the polar vortex in winter with lower geopotential height, lower tropopause height, and stronger coupling to the Arctic Oscillation in the lower troposphere (LT) than over Europe.

scholarly journals Lightning NO<sub>x</sub>, a key chemistry–climate interaction: impacts of future climate change and consequences for tropospheric oxidising capacity

2014 ◽  
Vol 14 (18) ◽  
pp. 9871-9881 ◽  
Author(s):  
A. Banerjee ◽  
A. T. Archibald ◽  
A. C. Maycock ◽  
P. Telford ◽  
N. L. Abraham ◽  
...  
Keyword(s):  
Climate Change ◽  
Tropospheric Ozone ◽  
Stratospheric Ozone ◽  
Future Climate ◽  
Ozone Production ◽  
Future Climate Change ◽  
Surface Boundary ◽  
Rcp Scenarios ◽  
Simple Estimate ◽  
The Impact

Abstract. Lightning is one of the major natural sources of NOx in the atmosphere. A suite of time slice experiments using a stratosphere-resolving configuration of the Unified Model (UM), containing the United Kingdom Chemistry and Aerosols sub-model (UKCA), has been performed to investigate the impact of climate change on emissions of NOx from lightning (LNOx) and to highlight its critical impacts on photochemical ozone production and the oxidising capacity of the troposphere. Two Representative Concentration Pathway (RCP) scenarios (RCP4.5 and RCP8.5) are explored. LNOx is simulated to increase in a year-2100 climate by 33% (RCP4.5) and 78% (RCP8.5), primarily as a result of increases in the depth of convection. The total tropospheric chemical odd oxygen production (P(Ox)) increases linearly with increases in total LNOx and consequently, tropospheric ozone burdens of 29 ± 4 Tg(O3) (RCP4.5) and 46 ± 4 Tg(O3) (RCP8.5) are calculated here. By prescribing a uniform surface boundary concentration for methane in these simulations, methane-driven feedbacks are essentially neglected. A simple estimate of the contribution of the feedback reduces the increase in ozone burden to 24 and 33 Tg(O3), respectively. We thus show that, through changes in LNOx, the effects of climate change counteract the simulated mitigation of the ozone burden, which results from reductions in ozone precursor emissions as part of air quality controls projected in the RCP scenarios. Without the driver of increased LNOx, our simulations suggest that the net effect of climate change would be to lower free tropospheric ozone. In addition, we identify large climate-change-induced enhancements in the concentration of the hydroxyl radical (OH) in the tropical upper troposphere (UT), particularly over the Maritime Continent, primarily as a consequence of greater LNOx. The OH enhancement in the tropics increases oxidation of both methane (with feedbacks onto chemistry and climate) and very short-lived substances (VSLS) (with implications for stratospheric ozone depletion). We emphasise that it is important to improve our understanding of LNOx in order to gain confidence in model projections of composition change under future climate.

scholarly journals Summertime free tropospheric ozone pool over the Eastern Mediterranean/Middle East

2013 ◽  
Vol 13 (8) ◽  
pp. 22025-22058 ◽  
Author(s):  
P. Zanis ◽  
P. Hadjinicolaou ◽  
A. Pozzer ◽  
E. Tyrlis ◽  
S. Dafka ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Eastern Mediterranean Region ◽  
Near Surface ◽  
Ozone Data ◽  
The Mediterranean

Abstract. Observations show that the Mediterranean troposphere is characterized by a marked enhancement in summertime ozone with a maximum over the Eastern Mediterranean. This has been linked to enhanced ozone photochemical production and subsidence under cloud-free anticyclonic conditions. The Eastern Mediterranean region has among the highest levels of background tropospheric ozone around the globe and it can be considered as a global air pollution hotspot. A 12 yr climatological analysis (1998–2009) of free tropospheric ozone was carried out over the region based on ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-interim reanalysis data and simulations with the EMAC (ECHAM5-MESSy for Atmospheric Chemistry) atmospheric chemistry climate model. EMAC is nudged towards the ECMWF analysis data and includes a stratospheric ozone tracer. A characteristic summertime pool with high ozone concentrations is found in the middle troposphere over the Eastern Mediterranean/Middle East (EMME) by ERA-interim ozone data, which is supported by Tropospheric Emission Spectrometer (TES) satellite ozone data and simulations with EMAC. The enhanced ozone over the EMME is a robust feature, propagating down to lower free tropospheric levels. The investigation of ozone in relation to potential vorticity and water vapour and the stratospheric ozone tracer indicates that the dominant mechanism causing the free tropospheric ozone pool is downward transport from the upper troposphere and lower stratosphere associated with the enhanced subsidence and the limited outflow transport that dominates the summertime EMME circulation. The implications of these summertime high free tropospheric ozone values on the seasonal cycle of near surface ozone over the Mediterranean are discussed.

scholarly journals Future impact of traffic emissions on atmospheric ozone and OH based on two scenarios

2012 ◽  
Vol 12 (8) ◽  
pp. 20975-21012
Author(s):  
Ø. Hodnebrog ◽  
T. K. Berntsen ◽  
O. Dessens ◽  
M. Gauss ◽  
V. Grewe ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Road Traffic ◽  
North Atlantic Ocean ◽  
Lower Troposphere ◽  
Traffic Emissions ◽  
Transport Sector ◽  
Atmospheric Ozone ◽  
The Future ◽  
The Impact

Abstract. The future impact of traffic emissions on atmospheric ozone and OH has been investigated separately for the three sectors AIRcraft, maritime SHIPping and ROAD traffic. To reduce uncertainties we present results from an ensemble of six different atmospheric chemistry models, each simulating the atmospheric chemical composition in a possible high emission scenario (A1B), and with emissions from each transport sector reduced by 5% to estimate sensitivities. Our results are compared with optimistic future emission scenarios (B1 and B1 ACARE), presented in a companion paper, and with the recent past (year 2000). Present-day activity indicates that anthropogenic emissions so far evolve closer to A1B than the B1 scenario. As a response to expected changes in emissions, AIR and SHIP will have increased impacts on atmospheric O3 and OH in the future while the impact of ROAD traffic will decrease substantially as a result of technological improvements. In 2050, maximum aircraft-induced O3 occurs near 80° N in the UTLS region and could reach 9 ppbv in the zonal mean during summer. Emissions from ship traffic have their largest O3 impact in the maritime boundary layer with a maximum of 6 ppbv over the North Atlantic Ocean during summer in 2050. The O3 impact of road traffic emissions in the lower troposphere peaks at 3 ppbv over the Arabian Peninsula, much lower than the impact in 2000. Radiative Forcing (RF) calculations show that the net effect of AIR, SHIP and ROAD combined will change from a~marginal cooling of −0.38 ± 13 mW m−2 in 2000 to a relatively strong cooling of −32 ± 8.9 (B1) or −31 ± 20 mW m−2 (A1B) in 2050, when taking into account RF due to changes in O3, CH4 and CH4-induced O3. This is caused both by the enhanced negative net RF from SHIP, which will change from −20 ± 5.4 mW m−2 in 2000 to −31 ± 4.8 (B1) or −40 ± 11 mW m−2 (A1B) in 2050, and from reduced O3 warming from ROAD, which is likely to turn from a positive net RF of 13 ± 7.9 mW m−2 in 2000 to a slightly negative net RF of −2.9 ± 1.7 (B1) or −3.3 ± 3.8 (A1B) mW m−2 in the middle of this century. The negative net RF from ROAD is temporary and induced by the strong decline in ROAD emissions prior to 2050, which only affects the methane cooling term due to the longer lifetime of CH4 compared to O3. The O3 RF from AIR in 2050 is strongly dependent on scenario and ranges from 19 ± 6.8 (B1 ACARE) to 62 ± 13.6 mW m−2 (A1B). There is also a considerable span in the net RF from AIR in 2050, ranging from −0.54 ± 4.6 (B1 ACARE) to 12 ± 11 (A1B) mW m−2 compared to 6.5 ± 2.1 mW m−2 in 2000.

scholarly journals Future impact of traffic emissions on atmospheric ozone and OH based on two scenarios

2012 ◽  
Vol 12 (24) ◽  
pp. 12211-12225 ◽  
Author(s):  
Ø. Hodnebrog ◽  
T. K. Berntsen ◽  
O. Dessens ◽  
M. Gauss ◽  
V. Grewe ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Road Traffic ◽  
North Atlantic Ocean ◽  
Lower Troposphere ◽  
Traffic Emissions ◽  
Transport Sector ◽  
Atmospheric Ozone ◽  
The Future ◽  
The Impact

Abstract. The future impact of traffic emissions on atmospheric ozone and OH has been investigated separately for the three sectors AIRcraft, maritime SHIPping and ROAD traffic. To reduce uncertainties we present results from an ensemble of six different atmospheric chemistry models, each simulating the atmospheric chemical composition in a possible high emission scenario (A1B), and with emissions from each transport sector reduced by 5% to estimate sensitivities. Our results are compared with optimistic future emission scenarios (B1 and B1 ACARE), presented in a companion paper, and with the recent past (year 2000). Present-day activity indicates that anthropogenic emissions so far evolve closer to A1B than the B1 scenario. As a response to expected changes in emissions, AIR and SHIP will have increased impacts on atmospheric O3 and OH in the future while the impact of ROAD traffic will decrease substantially as a result of technological improvements. In 2050, maximum aircraft-induced O3 occurs near 80° N in the UTLS region and could reach 9 ppbv in the zonal mean during summer. Emissions from ship traffic have their largest O3 impact in the maritime boundary layer with a maximum of 6 ppbv over the North Atlantic Ocean during summer in 2050. The O3 impact of road traffic emissions in the lower troposphere peaks at 3 ppbv over the Arabian Peninsula, much lower than the impact in 2000. Radiative forcing (RF) calculations show that the net effect of AIR, SHIP and ROAD combined will change from a marginal cooling of −0.44 ± 13 mW m−2 in 2000 to a relatively strong cooling of −32 ± 9.3 (B1) or −32 ± 18 mW m−2 (A1B) in 2050, when taking into account RF due to changes in O3, CH4 and CH4-induced O3. This is caused both by the enhanced negative net RF from SHIP, which will change from −19 ± 5.3 mW m−2 in 2000 to −31 ± 4.8 (B1) or −40 ± 9 mW m−2 (A1B) in 2050, and from reduced O3 warming from ROAD, which is likely to turn from a positive net RF of 12 ± 8.5 mW m−2 in 2000 to a slightly negative net RF of −3.1 ± 2.2 (B1) or −3.1 ± 3.4 (A1B) mW m−2 in the middle of this century. The negative net RF from ROAD is temporary and induced by the strong decline in ROAD emissions prior to 2050, which only affects the methane cooling term due to the longer lifetime of CH4 compared to O3. The O3 RF from AIR in 2050 is strongly dependent on scenario and ranges from 19 ± 6.8 (B1 ACARE) to 61 ± 14 mW m−2 (A1B). There is also a considerable span in the net RF from AIR in 2050, ranging from −0.54 ± 4.6 (B1 ACARE) to 12 ± 11 (A1B) mW m−2 compared to 6.6 ± 2.2 mW m−2 in 2000.

scholarly journals Summertime free-tropospheric ozone pool over the eastern Mediterranean/Middle East

2014 ◽  
Vol 14 (1) ◽  
pp. 115-132 ◽  
Author(s):  
P. Zanis ◽  
P. Hadjinicolaou ◽  
A. Pozzer ◽  
E. Tyrlis ◽  
S. Dafka ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Ozone Production ◽  
Near Surface ◽  
Ozone Data ◽  
The Mediterranean

Abstract. Observations show that the Mediterranean troposphere is characterized by a marked enhancement in summertime ozone, with a maximum over the eastern Mediterranean. This has been linked to enhanced photochemical ozone production and subsidence under cloud-free anticyclonic conditions. The eastern Mediterranean is among the regions with the highest levels of background tropospheric ozone worldwide. A 12 yr climatological analysis (1998–2009) of free-tropospheric ozone was carried out over the region based on the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data and simulations with the EMAC (ECHAM5–MESSy) atmospheric chemistry–climate model. EMAC is nudged towards the ECMWF analysis data and includes a stratospheric ozone tracer. A characteristic summertime pool with high ozone concentrations is found in the middle troposphere over the eastern Mediterranean–Middle East (EMME) in the ERA-Interim ozone data, Tropospheric Emission Spectrometer (TES) satellite ozone data and simulations with EMAC. The enhanced ozone over the EMME during summer is a robust feature, extending down to lower free-tropospheric levels. The investigation of ozone in relation to potential vorticity and water vapour and the stratospheric ozone tracer indicates that the dominant mechanism causing the free-tropospheric ozone pool is the downward transport from the upper troposphere and lower stratosphere, in association with the enhanced subsidence and the limited horizontal divergence observed over the region. The implications of these high free-tropospheric ozone levels on the seasonal cycle of near-surface ozone over the Mediterranean are discussed.

scholarly journals Stratospheric impact on the Northern Hemisphere winter and spring ozone interannual variability in the troposphere

2020 ◽  
Vol 20 (11) ◽  
pp. 6417-6433
Author(s):  
Junhua Liu ◽  
Jose M. Rodriguez ◽  
Luke D. Oman ◽  
Anne R. Douglass ◽  
Mark A. Olsen ◽  
...  
Keyword(s):  
North America ◽  
Interannual Variability ◽  
Northern Hemisphere ◽  
North American ◽  
Tropospheric Ozone ◽  
Interannual Variation ◽  
Stratospheric Ozone ◽  
Lower Troposphere ◽  
Pinatubo Eruption ◽  
The Impact

Abstract. In this study we use ozone and stratospheric ozone tracer simulations from the high-resolution (0.5∘×0.5∘) Goddard Earth Observing System, Version 5 (GEOS-5), in a replay mode to study the impact of stratospheric ozone on tropospheric ozone interannual variability (IAV). We use these simulations in conjunction with ozonesonde measurements from 1990 to 2016 during the winter and spring seasons. The simulations include a stratospheric ozone tracer (StratO3) to aid in the evaluation of the impact of stratospheric ozone IAV on the IAV of tropospheric ozone at different altitudes and locations. The model is in good agreement with the observed interannual variation in tropospheric ozone, except for the post-Pinatubo period (1992–1994) over the region of North America. Ozonesonde data show a negative ozone anomaly in 1992–1994 following the Pinatubo eruption, with recovery thereafter. The simulated anomaly is only half the magnitude of that observed. Our analysis suggests that the simulated stratosphere–troposphere exchange (STE) flux deduced from the analysis might be too strong over the North American (50–70∘ N) region after the Mt. Pinatubo eruption in the early 1990s, masking the impact of lower stratospheric ozone concentration on tropospheric ozone. European ozonesonde measurements show a similar but weaker ozone depletion after the Mt. Pinatubo eruption, which is fully reproduced by the model. Analysis based on the stratospheric ozone tracer identifies differences in strength and vertical extent of stratospheric ozone impact on the tropospheric ozone interannual variation (IAV) between North America and Europe. Over North American stations, the StratO3 IAV has a significant impact on tropospheric ozone from the upper to lower troposphere and explains about 60 % and 66 % of the simulated ozone IAV at 400 hPa and ∼11 % and 34 % at 700 hPa in winter and spring, respectively. Over European stations, the influence is limited to the middle to upper troposphere and becomes much smaller at 700 hPa. The Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), assimilated fields exhibit strong longitudinal variations over Northern Hemisphere (NH) mid-high latitudes, with lower tropopause height and lower geopotential height over North America than over Europe. These variations associated with the relevant variations in the location of tropospheric jet flows are responsible for the longitudinal differences in the stratospheric ozone impact, with stronger effects over North America than over Europe.

scholarly journals On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East

2016 ◽  
Author(s):  
Dimitris Akritidis ◽  
Andrea Pozzer ◽  
Prodromos Zanis ◽  
Evangelos Tyrlis ◽  
Bojan Škerlak ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Climate Model ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Free Troposphere ◽  
Near Surface ◽  
Grid Points

Abstract. We study the contribution of tropopause folds in the summertime pool of tropospheric ozone over the eastern Mediterranean and the Middle East (EMME) with the aid of the atmospheric chemistry climate model ECHAM5/MESSy (EMAC). Tropopause fold events in EMAC simulations were identified with a 3-D labeling algorithm that detects folds at grid points where multiple crossings of the dynamical tropopause are computed. Subsequently the events featuring the largest horizontal and vertical extent were selected for further study. For the selection of these events we identified a significant contribution of the stratospheric ozone reservoir to the high concentrations of ozone in the middle/lower free troposphere over the EMME. A distinct increase of ozone is found over the EMME in the middle troposphere during summer as a result of the fold activity, shifting towards the south-east and decreasing altitude. We find that the interannual variability of near surface ozone over the eastern Mediterranean (EM) during summer is related to that of both tropopause folds and ozone in the free troposphere.

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