| publications-1421 |
PEER REVIEWED ARTICLE |
2015 |
Marta Abalos , Bernard Legras , Felix Ploeger , William J. Randel |
Evaluating the advective Brewer-Dobson circulation in three reanalyses for the period 1979-2012 |
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10.1002/2015jd023182 |
Data Management & Analytics |
River Basins |
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AbstractMost chemistry‐climate models show an intensification of the Brewer‐Dobson circulation (BDC) in the stratosphere associated with increasing greenhouse gas emissions and ozone depletion in the last decades, but this trend remains to be confirmed in observational data. In this work the evolution of the advective BDC for the period 1979–2012 is evaluated and compared in three modern reanalyses (ERA‐Interim, MERRA, and JRA‐55). Three different estimates of the BDC are computed for each reanalysis, one based on the definition of the residual circulation and two indirect estimates derived from momentum and thermodynamic balances. The comparison among the nine estimates shows substantial uncertainty in the mean magnitude (∼40%) but significant common variability. The tropical upwelling series show variability linked to the stratospheric quasi‐biennial oscillation and to El Niño–Southern Oscillation (ENSO) and also reflect extreme events such as major sudden stratospheric warmings and volcanic eruptions. The trend analysis suggests a strengthening of tropical upwelling of around 2–5%/decade throughout the layer 100–10 hPa. The global spatial structure of the BDC trends provides evidence of an overall acceleration of the circulation in both hemispheres, with qualitative agreement among the estimates. The global BDC trends are mainly linked to changes in the boreal winter season and can be tracked to long‐term increases in the resolved wave drag in both hemispheres. |
603557 |
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| publications-1422 |
PEER REVIEWED ARTICLE |
2015 |
Bossay, S., S. Bekki, M. Marchand, V. Poulain, and R. Toumi |
Sensitivity of tropical stratospheric ozone to rotational UV variations estimated from UARS and Aura MLS observations during the declining phases of solar cycles 22 and 23 |
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10.1016/j.jastp.2015.05.014 |
Uncategorized |
Uncategorized |
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No abstract available |
603557 |
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| publications-1423 |
PEER REVIEWED ARTICLE |
2015 |
Anita Cadoux , Bruno Scaillet , Slimane Bekki , Clive Oppenheimer , Timothy H. Druitt |
Stratospheric Ozone destruction by the Bronze-Age Minoan eruption (Santorini Volcano, Greece) |
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10.1038/srep12243 |
Simulation & Modeling |
River Basins |
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AbstractThe role of volcanogenic halogen-bearing (i.e. chlorine and bromine) compounds in stratospheric ozone chemistry and climate forcing is poorly constrained. While the 1991 eruption of Pinatubo resulted in stratospheric ozone loss, it was due to heterogeneous chemistry on volcanic sulfate aerosols involving chlorine of anthropogenic rather than volcanogenic origin, since co-erupted chlorine was scavenged within the plume. Therefore, it is not known what effect volcanism had on ozone in pre-industrial times, nor what will be its role on future atmospheres with reduced anthropogenic halogens present. By combining petrologic constraints on eruption volatile yields with a global atmospheric chemistry-transport model, we show here that the Bronze-Age ‘Minoan’ eruption of Santorini Volcano released far more halogens than sulfur and that, even if only 2% of these halogens reached the stratosphere, it would have resulted in strong global ozone depletion. The model predicts reductions in ozone columns of 20 to >90% at Northern high latitudes and an ozone recovery taking up to a decade. Our findings emphasise the significance of volcanic halogens for stratosphere chemistry and suggest that modelling of past and future volcanic impacts on Earth’s ozone, climate and ecosystems should systematically consider volcanic halogen emissions in addition to sulfur emissions. |
603557 |
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| publications-1424 |
PEER REVIEWED ARTICLE |
2015 |
N Calvo , L M Polvani , S Solomon |
On the surface impact of Arctic stratospheric ozone extremes |
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10.1088/1748-9326/10/9/094003 |
Data Management & Analytics |
Precipitation & Ecological Systems |
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No abstract available |
603557 |
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| publications-1425 |
PEER REVIEWED ARTICLE |
2016 |
G Chiodo , R García-Herrera , N Calvo , J M Vaquero , J A Añel , D Barriopedro , K Matthes |
The impact of a future solar minimum on climate change projections in the Northern Hemisphere |
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10.1088/1748-9326/11/3/034015 |
Simulation & Modeling |
River Basins |
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No abstract available |
603557 |
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| publications-1426 |
PEER REVIEWED ARTICLE |
2015 |
Steven C. Hardiman , Ian A. Boutle , Andrew C. Bushell , Neal Butchart , Mike J. P. Cullen , Paul R. Field , Kalli Furtado , James C. Manners , Sean F |
Processes Controlling Tropical Tropopause Temperature and Stratospheric Water Vapor in Climate Models |
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10.1175/jcli-d-15-0075.1 |
Simulation & Modeling |
River Basins |
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Abstract A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations. |
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| publications-1427 |
PEER REVIEWED ARTICLE |
2015 |
Maddalen Iza , Natalia Calvo |
Role of Stratospheric Sudden Warmings on the response to Central Pacific El Niño |
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10.1002/2014gl062935 |
Data Management & Analytics |
Precipitation & Ecological Systems |
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AbstractThe Northern Hemisphere (NH) polar stratospheric response to Central Pacific El Niño (CP‐El Niño) events remains unclear. Contradictory results have been reported depending on the definition and events considered. We show that this is due to the prominent role of Stratospheric Sudden Warmings (SSWs), whose signal dominates the NH winter polar stratospheric response to CP‐El Niño. In fact, the CP‐El Niño signal is robust when the events are classified according to the occurrence of SSWs and displays opposite response in winters with and without SSWs. In the absence of SSWs, polar stratospheric responses to Central Pacific and Eastern Pacific El Niño are clearly distinguishable in early winter, in relation to differences in the Pacific‐North American pattern. Our results demonstrate that the occurrence of SSWs needs to be taken into account when studying the stratospheric response to CP‐El Niño and explain why different responses to CP‐El Niño have been reported previously. |
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| publications-1428 |
PEER REVIEWED ARTICLE |
2016 |
Maddalen Iza , Natalia Calvo , Elisa Manzini |
The Stratospheric Pathway of La Niña |
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10.1175/jcli-d-16-0230.1 |
Data Management & Analytics |
Natural Water Bodies |
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Abstract A Northern Hemisphere (NH) polar stratospheric pathway for La Niña events is established during wintertime based on reanalysis data for the 1958–2012 period. A robust polar stratospheric response is observed in the NH during strong La Niña events, characterized by a significantly stronger and cooler polar vortex. Significant wind anomalies reach the surface, and a robust impact on the North Atlantic–European (NAE) region is observed. A dynamical analysis reveals that the stronger polar stratospheric winds during La Niña winters are due to reduced upward planetary wave activity into the stratosphere. This finding is the result of destructive interference between the climatological and the anomalous La Niña tropospheric stationary eddies over the Pacific–North American region. In addition, the lack of a robust stratospheric signature during La Niña winters reported in previous studies is investigated. It is found that this is related to the lower threshold used to detect the events, which signature is consequently more prone to be obscured by the influence of other sources of variability. In particular, the occurrence of stratospheric sudden warmings (SSWs), partly linked to the phase of the quasi-biennial oscillation, modulates the observed stratospheric signal. In the case of La Niña winters defined by a lower threshold, a robust stratospheric cooling is found only in the absence of SSWs. Therefore, these results highlight the importance of using a relatively restrictive threshold to define La Niña events in order to obtain a robust surface response in the NAE region through the stratosphere. |
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| publications-1429 |
PEER REVIEWED ARTICLE |
2016 |
Patrick Jöckel , Holger Tost , Andrea Pozzer , Markus Kunze , Oliver Kirner , Carl A. M. Brenninkmeijer , Sabine Brinkop , Duy S. Cai , Christoph Dyr |
Earth System Chemistry integrated Modelling (ESCiMo) with the Modular Earth Submodel System (MESSy) version 2.51 |
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10.5194/gmd-9-1153-2016 |
Data Management & Analytics |
Uncategorized |
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Abstract. Three types of reference simulations, as recommended by the Chemistry–Climate Model Initiative (CCMI), have been performed with version 2.51 of the European Centre for Medium-Range Weather Forecasts – Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model: hindcast simulations (1950–2011), hindcast simulations with specified dynamics (1979–2013), i.e. nudged towards ERA-Interim reanalysis data, and combined hindcast and projection simulations (1950–2100). The manuscript summarizes the updates of the model system and details the different model set-ups used, including the on-line calculated diagnostics. Simulations have been performed with two different nudging set-ups, with and without interactive tropospheric aerosol, and with and without a coupled ocean model. Two different vertical resolutions have been applied. The on-line calculated sources and sinks of reactive species are quantified and a first evaluation of the simulation results from a global perspective is provided as a quality check of the data. The focus is on the intercomparison of the different model set-ups. The simulation data will become publicly available via CCMI and the Climate and Environmental Retrieval and Archive (CERA) database of the German Climate Computing Centre (DKRZ). This manuscript is intended to serve as an extensive reference for further analyses of the Earth System Chemistry integrated Modelling (ESCiMo) simulations. |
603557 |
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| publications-1430 |
PEER REVIEWED ARTICLE |
2016 |
Matthias Nützel , Martin Dameris , Hella Garny |
Movement, drivers and bimodality of the South Asian High |
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10.5194/acp-16-14755-2016 |
Simulation & Modeling |
Precipitation & Ecological Systems |
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Abstract. The South Asian High (SAH) is an important component of the summer monsoon system in Asia. In this study we investigate the location and drivers of the SAH at 100 hPa during the boreal summers of 1979 to 2014 on interannual, seasonal and synoptic timescales using seven reanalyses and observational data. Our comparison of the different reanalyses focuses especially on the bimodality of the SAH, i.e. the two preferred modes of the SAH centre location: the Iranian Plateau to the west and the Tibetan Plateau to the east. We find that only the National Centers for Environmental Prediction–National Center of Atmospheric Research (NCEP–NCAR) reanalysis shows a clear bimodal structure of the SAH centre distribution with respect to daily and pentad (5 day) mean data. Furthermore, the distribution of the SAH centre location is highly variable from year to year. As in simple model studies, which connect the SAH to heating in the tropics, we find that the mean seasonal cycle of the SAH and its centre are dominated by the expansion of convection in the South Asian region (70–130° E × 15–30° N) on the south-eastern border of the SAH. A composite analysis of precipitation and outgoing long-wave radiation data with respect to the location of the SAH centre reveals that a more westward (eastward) location of the SAH is related to stronger (weaker) convection and rainfall over India and weaker (stronger) precipitation over the western Pacific. |
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