Radiative and Dynamical Influences on Polar Stratospheric Temperature Trends

Ivy, Diane J.; Solomon, Susan; Rieder, Harald E.

doi:10.1175/jcli-d-15-0503.1

Cited by 33 publications

(34 citation statements)

References 46 publications

(65 reference statements)

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“…Schneider et al (2015) concluded that the tropical SSTs were the main drivers via teleconnections of the autumn trends, based on the ensemble mean of all of the CAM4 simulations with ozone depletion not showing a strong forced response. However, unlike the sonde data shown here, the ozone depletion in the SPARC dataset shows negligible trends in the fall (Ivy et al 2016) and thus would not be expected to show a forced response.…”

Section: Discussioncontrasting

confidence: 69%

“…PORT utilizes the radiation code from NCAR's Community Atmosphere Model, version 4 (CAM4; Gent et al 2011), and calculates the changes in radiatively adjusted temperatures in a seasonally evolving fixed dynamical heating calculation above a defined masked level (typically defined as the tropopause, but here set to 500 hPa to allow the temperatures to adjust into the upper troposphere); the methodology is similar to that in Ivy et al (2016). For the PORT calculation, a full three-dimensional ozone climatology was used to prescribe a predepletion background distribution.…”

Section: B Port Simulationsmentioning

confidence: 99%

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Observed Changes in the Southern Hemispheric Circulation in May

et al. 2017

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Much research has focused on trends in the Southern Hemispheric circulation in austral summer (December-February) in the troposphere and stratosphere, whereas changes in other seasons have received less attention. Here the seasonality and structure of observed changes in tropospheric and stratospheric winds, temperature, and ozone over the Southern Hemisphere are examined. It is found that statistically significant trends similar to those of the Antarctic summer season are also observed since 1979 in austral fall, particularly May, and are strongest over the Pacific sector of the hemisphere. Evidence is provided for a significant shift in the position of the jet in May over the Pacific, and it is shown that the strengthening and shifting of the jet has rendered the latitudinal distribution of upper-tropospheric zonal wind more bimodal. The Antarctic ozone hole has cooled the lower stratosphere and strengthened the polar vortex. While the mechanism and timing are not fully understood, the ozone hole has been identified as a key driver of the summer season tropospheric circulation changes in several previous observational and modeling studies. It is found here that significant ozone depletion and associated polar cooling also occur in the lowermost stratosphere and tropopause region through austral fall, with spatial patterns that are coincident with the observed changes in stratospheric circulation. It is also shown that radiatively driven temperature changes associated with the observed ozone depletion in May represent a substantial portion of the observed May cooling in the lowermost stratosphere, suggesting a potential for contribution to the circulation changes.

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Section: Discussioncontrasting

confidence: 69%

Section: B Port Simulationsmentioning

confidence: 99%

Observed Changes in the Southern Hemispheric Circulation in May

et al. 2017

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“…It is interesting that the magnitude of model Antarctic temperature trends is similar for the ozone decline and partial recovery periods, although the corresponding ozone changes are much larger for 1979–1997. Relatively weaker cooling for 1979–1997 may reflect compensation from increased downwelling over the polar cap, as suggested in (Calvo et al, , Fu et al, , Ivy et al, , & Lin et al, ). We note that the Arctic lower stratosphere shows marginally significant cooling in the model during this 1998–2014 period, although ozone changes are not significant.…”

Section: Resultsmentioning

confidence: 82%

Troposphere‐Stratosphere Temperature Trends Derived From Satellite Data Compared With Ensemble Simulations From WACCM

Randel

Polvani

et al. 2017

JGR Atmospheres

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Decadal‐scale trends in tropospheric and stratospheric temperatures derived from satellite measurements over 1979–2014 are compared with ensemble simulations from the Whole Atmosphere Community Climate Model (WACCM). The model is forced with observed sea surface temperatures, changes in greenhouse gases, and ozone‐depleting substances, plus solar and volcanic effects, and results from five WACCM realizations (with slightly different initial conditions) are analyzed. We focus on the vertical structure of tropospheric warming and stratospheric cooling increasing with height, the latitudinal and seasonal dependence of trends, and on the temporal evolution of stratospheric temperatures in response to stratospheric ozone depletion and partial recovery. The model captures the observed trend structure in most respects, and the ensemble of simulations provides quantitative estimates of the impact of internal variability on trend estimates. In regions of low variability (e.g., over low latitudes) the ensemble mean trends agree with the observations, while in regions of high variability (e.g., the polar stratosphere) the observations mostly fall within the range of realizations. Temperature response to evolving stratospheric ozone is evaluated by computing separate trends over 1979–1997 (ozone depletion) and 1998–2014 (partial recovery). Robust changes in temperature trends between these periods occur in the global upper stratosphere and in the Antarctic spring lower stratosphere, with consistent behavior between model and observations. Observed lower stratospheric temperatures in the Antarctic show statistically significant warming after 1998, reflecting recently reported healing of the ozone hole.

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“…Ivy et al . [] showed that GHG‐induced cooling using PORT were smaller than 0.5 K/decade and had little seasonal structure; these changes are relatively small compared to the features of interest (see below). The SD‐WACCM simulations provide two estimates of ozone changes post‐2000: using time‐evolving chemistry plus dynamics/temperature driven by MERRA reanalysis data (chem‐dyn‐vol) and using time‐evolving chemistry alone (chem‐only).…”

Section: Resultsmentioning

confidence: 99%

“…Studies suggest that the Antarctic ozone hole has affected stratospheric dynamics, although greenhouse gas increases during the same period also have contributed to the dynamical changes [e.g., Thompson and Solomon , ; Manzini et al ., ; Cai , ; Son et al ., ; Butchart et al ., ; McLandress et al ., ; Lin and Fu , ; Oberländer‐Hayn et al ., ]. During the last several decades of the 20th century, Antarctic lower stratospheric temperatures were influenced not only by cooling linked to ozone losses but also by dynamical warming via increased downwelling [ Lin et al ., ; Calvo et al ., ; Ivy et al ., ]. The Antarctic ozone loss is extremely sensitive to temperature, and a difference of a degree or so in the spring season substantially influences chemical loss rates [ Rex et al ., ; Sinnhuber et al ., ; Solomon et al ., ].…”

Section: Introductionmentioning

confidence: 98%

Mirrored changes in Antarctic ozone and stratospheric temperature in the late 20th versus early 21st centuries

et al. 2017

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Observed and modeled patterns of lower stratospheric seasonal trends in Antarctic ozone and temperature in the late 20th (1979–2000) and the early 21st (2000–2014) centuries are compared. Patterns of pre‐2000 observed Antarctic ozone decreases and stratospheric cooling as a function of month and pressure are followed by opposite‐signed (i.e., “mirrored”) patterns of ozone increases and warming post‐2000. An interactive chemistry‐climate model forced by changes in anthropogenic ozone depleting substances produces broadly similar mirrored features. Statistical analysis of unforced model simulations (from long‐term model control simulations of a few centuries up to 1000 years) suggests that internal and solar natural variability alone is unable to account for the pattern of observed ozone trend mirroring, implying that forcing is the dominant driver of this behavior. Radiative calculations indicate that ozone increases have contributed to Antarctic warming of the lower stratosphere over 2000–2014, but dynamical changes that are likely due to internal variability over this relatively short period also appear to be important. Overall, the results support the recent finding that the healing of the Antarctic ozone hole is underway and that coupling between dynamics, chemistry, and radiation is important for a full understanding of the causes of observed stratospheric temperature and ozone changes.

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Radiative and Dynamical Influences on Polar Stratospheric Temperature Trends

Cited by 33 publications

References 46 publications

Observed Changes in the Southern Hemispheric Circulation in May

Observed Changes in the Southern Hemispheric Circulation in May

Troposphere‐Stratosphere Temperature Trends Derived From Satellite Data Compared With Ensemble Simulations From WACCM

Mirrored changes in Antarctic ozone and stratospheric temperature in the late 20th versus early 21st centuries

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