scholarly journals A twentieth century perspective on summer Antarctic pressure change and variability and contributions from tropical SSTs and ozone depletion

2017 ◽  
Vol 44 (19) ◽  
pp. 9918-9927 ◽  
Author(s):  
Ryan L. Fogt ◽  
Chad A. Goergens ◽  
Julie M. Jones ◽  
David P. Schneider ◽  
Julien P. Nicolas ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Ozone Depletion ◽  
Pressure Change ◽  
Tropical Ssts

scholarly journals Comparing the Impacts of Tropical SST Variability and Polar Stratospheric Ozone Loss on the Southern Ocean Westerly Winds*

2015 ◽  
Vol 28 (23) ◽  
pp. 9350-9372 ◽  
Author(s):  
David P. Schneider ◽  
Clara Deser ◽  
Tingting Fan
Keyword(s):  
Southern Ocean ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Austral Summer ◽  
Southern Annular Mode ◽  
Forced Response ◽  
Coupled Models ◽  
Ozone Loss ◽  
The Pacific ◽  
Tropical Ssts

Abstract Westerly wind trends at 850 hPa over the Southern Ocean during 1979–2011 exhibit strong regional and seasonal asymmetries. On an annual basis, trends in the Pacific sector (40°–60°S, 70°–160°W) are 3 times larger than zonal-mean trends related to the increase in the southern annular mode (SAM). Seasonally, the SAM-related trend is largest in austral summer, and many studies have linked this trend with stratospheric ozone depletion. In contrast, the Pacific sector trends are largest in austral autumn. It is proposed that these asymmetries can be explained by a combination of tropical teleconnections and polar ozone depletion. Six ensembles of transient atmospheric model experiments, each forced with different combinations of time-dependent radiative forcings and SSTs, support this idea. In summer, the model simulates a positive SAM-like pattern, to which ozone depletion and tropical SSTs (which contain signatures of internal variability and warming from greenhouse gasses) contribute. In autumn, the ensemble-mean response consists of stronger westerlies over the Pacific sector, explained by a Rossby wave originating from the central equatorial Pacific. While these responses resemble observations, attribution is complicated by intrinsic atmospheric variability. In the experiments forced only with tropical SSTs, individual ensemble members exhibit wind trend patterns that mimic the forced response to ozone. When the analysis presented herein is applied to 1960–2000, the primary period of ozone loss, ozone depletion largely explains the model’s SAM-like zonal wind trend. The time-varying importance of these different drivers has implications for relating the historical experiments of free-running, coupled models to observations.

scholarly journals Stratospheric Ozone Depletion: The Main Driver of Twentieth-Century Atmospheric Circulation Changes in the Southern Hemisphere

2011 ◽  
Vol 24 (3) ◽  
pp. 795-812 ◽  
Author(s):  
Lorenzo M. Polvani ◽  
Darryn W. Waugh ◽  
Gustavo J. P. Correa ◽  
Seok-Woo Son
Keyword(s):  
Twentieth Century ◽  
Greenhouse Gases ◽  
Atmospheric Circulation ◽  
Southern Hemisphere ◽  
Ozone Depletion ◽  
General Circulation ◽  
Stratospheric Ozone ◽  
Hadley Cell ◽  
Stratospheric Ozone Depletion ◽  
Circulation Changes

Abstract 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 that the impacts of ozone depletion are roughly 2–3 times larger than those associated 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 summer over the second half of the twentieth century, have been caused by polar stratospheric ozone depletion.

Shedding new light on the radiative impacts of ozone-depleting substances

2020 ◽  
Author(s):  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Twentieth Century ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Walker Circulation ◽  
Climate Impacts ◽  
The Arctic ◽  
Temperature Structure ◽  
Stratospheric Ozone Depletion ◽  
Ozone Depleting Substances ◽  
The Walker Circulation

<p>It is well established that ozone-depleting substances (ODS) have been the primary cause of stratospheric ozone depletion. It is also widely accepted that stratospheric ozone depletion has been the primary driver of summertime circulation trends in the Austral Hemisphere in the second half of the twentieth century. However, the climate impacts of ODS that are independent of ozone depletion have received little attention. It has long been known that, while much less abundant than carbon dioxide, ODS have a much higher global warming potential (GWP) ecent studies have indicated that ODS may have played a key-role in the observed weakening trends of the Walker circulation (Polvani and Bellomo, 2019), and in the warming of the Arctic and the associated sea ice loss (Polvani et al., 2020). <span>that the climate efficacy of ODS may be much larger than previously thought, but </span><span>.</span></p><p>Here, we seek to better understand the radiative effect of ODS in the global atmosphere. Instead of confining our attention on a single metric, e.g. globally averaged radiative forcing (RF) or GWP which are typically reported in the IPCC Assessment Reports, we seek to understand how ODS alter the temperature structure of the entire atmosphere. Focusing on the half-century 1950-2000, which saw the largest growth of ODS concentrations in the atmosphere, we start by performing careful computations of the RF of individual ODS, including the effects of rapid temperature adjustments. We then explore how the vertical and latitudinal distribution of ODS (which are not well mixed in the stratosphere) affects their RF, and what temperature responses are associated with those changes. These calculations are repeated individually for each of the other well-mixed GHG, as well as for other composition changes arising from ODS (ozone depletion). It is shown that ODS, in contrast to other GHG, warm the lower stratosphere, implying a different fingerprint from CO2. Furthermore, the RF of ODS exhibits the largest meridional gradient of any other well-mixed GHG. Implications for the climate efficacy of ODS, and more generally for climate sensitivity, will be discussed.</p><p>References</p><p>Polvani, L.M and K. Bellomo: The key role of ozone depleting substances in weakening the Walker circulation in the second half of the 20th century, <em>J. Climate</em>, <strong>32</strong>, 1411-1418 (2019).</p><p>Polvani et al.,: Substantial twentieth-century Arctic warmng caused by ozone depleting substances, <em>Nature Climate Change, </em>in press (2019)</p>

Impact of Antarctic Ozone Depletion and Recovery on Southern Hemisphere Precipitation, Evaporation, and Extreme Changes

2012 ◽  
Vol 25 (9) ◽  
pp. 3145-3154 ◽  
Author(s):  
Ariaan Purich ◽  
Seok-Woo Son
Keyword(s):  
Twentieth Century ◽  
Southern Hemisphere ◽  
Ozone Depletion ◽  
Extreme Precipitation ◽  
Extreme Precipitation Events ◽  
Climate Simulations ◽  
Antarctic Ozone ◽  
Precipitation Changes ◽  
The Impact ◽  
Light Precipitation

The possible impact of Antarctic ozone depletion and recovery on Southern Hemisphere (SH) mean and extreme precipitation and evaporation is examined using multimodel output from the Climate Model Intercomparison Project 3 (CMIP3). By grouping models into four sets, those with and without ozone depletion in twentieth-century climate simulations and those with and without ozone recovery in twenty-first-century climate simulations, and comparing their multimodel-mean trends, it is shown that Antarctic ozone forcings significantly modulate extratropical precipitation changes in austral summer. The impact on evaporation trends is however minimal, especially in twentieth-century climate simulations. In general, ozone depletion has increased (decreased) precipitation in high latitudes (midlatitudes), in agreement with the poleward displacement of the westerly jet and associated storm tracks by Antarctic ozone depletion. Although weaker, the opposite is also true for ozone recovery. These precipitation changes are primarily associated with changes in light precipitation (1–10 mm day−1). Contributions by very light precipitation (0.1–1 mm day−1) and moderate-to-heavy precipitation (>10 mm day−1) are minor. Likewise, no systematic changes are found in extreme precipitation events, although extreme surface wind events are highly sensitive to ozone forcings. This result indicates that, while extratropical mean precipitation trends are significantly modulated by ozone-induced large-scale circulation changes, extreme precipitation changes are likely more sensitive to thermodynamic processes near the surface than to dynamical processes in the free atmosphere.

Some Polish Composers of To-Day

Tempo ◽  
1948 ◽  
pp. 25-28
Author(s):  
Andrzej Panufnik
Keyword(s):  
Twentieth Century ◽  
Fertile Soil ◽  
Early Twentieth Century ◽  
Progressive Group ◽  
Karol Szymanowski

It is ten years since KAROL SZYMANOWSKI died at fifty-four. He was the most prominent representative of the “radical progressive” group of early twentieth century composers, which we call “Young Poland.” In their manysided and pioneering efforts they prepared the fertile soil on which Poland's present day's music thrives.

V1214: Edward Loughborough Keyes: An Early Twentieth Century Leader In Urology

2004 ◽  
Vol 171 (4S) ◽  
pp. 320-320
Author(s):  
Peter J. Stahl ◽  
E. Darracott Vaughan ◽  
Edward S. Belt ◽  
David A. Bloom ◽  
Ann Arbor
Keyword(s):  
Twentieth Century ◽  
Early Twentieth Century

Twentieth Century Classics

2009 ◽  
Author(s):  
Rajiva Wijesinha
Keyword(s):  
Twentieth Century
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