Projections of Southern Hemisphere atmospheric circulation interannual variability

Grainger, Simon; Frederiksen, Carsten S.; Zheng, Xunhua

doi:10.1007/s00382-016-3135-2

Cited by 9 publications

(7 citation statements)

References 53 publications

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“…Grainger et al (2017) [81] further showed that for SWWA, the negative trend in rainfall was closely associated with the aforementioned annular pattern in Z 500hPa geopotential height, with positive height anomalies and anti-cyclonic flow at 300 hPa over the region of decreasing rainfall. Frederiksen and Grainger (2015) [58] had earlier identified this same pattern in the leading slow external geopotential height mode of covariability in multi-model ensemble CMIP3 simulations and attributed this trend to external radiative forcing, including greenhouse gases.…”

Section: Projections Of the Future Sh Climatementioning

confidence: 95%

“…They found that most models simulated the changes in zonal wind, but only about a third of the models captured the observed changes in baroclinic instability with reduced magnitude. The subset of models capable of simulating the observed spatial trends in the Phillips Criterion and the associated changes in winter rainfall over southern Australia, especially in SWWA, were used as a basis for a subsequent CMIP5 multi-model ensemble study conducted by Grainger et al (2017) [81]. They found that the externally forced austral summer (DJF) variability in the Z 500hPa geopotential height resided almost exclusively in an SAM-like teleconnection with uniform positive loading in the tropics, extending to at least 30 • S, exhibiting an annular structure with negative loadings at higher latitudes.…”

Section: Projections Of the Future Sh Climatementioning

confidence: 99%

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Beyond the First Tipping Points of Southern Hemisphere Climate

O’Kane,

Frederiksen,

Frederiksen

et al. 2024

Climate

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Analysis of observations, reanalysis, and model simulations, including those using machine learning methods specifically designed for regime identification, has revealed changes in aspects of the Southern Hemisphere (SH) circulation and Australian climate and extremes over the last half-century that indicate transitions to new states. In particular, our analysis shows a dramatic shift in the metastability of the SH climate that occurred in the late 1970s, associated with a large-scale regime transition in the SH atmospheric circulation, with systematic changes in the subtropical jet, blocking, zonal winds, and storm tracks. Analysis via nonstationary clustering reveals a regime shift coincident with a sharp transition to warmer oceanic sea surface temperatures and increased baroclinicity in the large scales of the Antarctic Circumpolar Circulation (ACC), extending across the whole hemisphere. At the same time, the background state of the tropical Pacific thermocline shoaled, leading to an increased likelihood of El Niño events. The SH climate shift in the late 1970s is the first hemispheric regime shift that can be directly attributed to anthropogenic climate change. These changes in dynamics are associated with additional regional tipping points, including reductions in mean and extreme rainfall in south-west Western Australia (SWWA) and streamflow into Perth dams, and also with increases in mean and extreme rainfall over northern Australia since the late 1970s. The drying of south-eastern Australia (SEA) occurred against a background of accelerating increases in average and extreme temperatures across the whole continent since the 1990s, implying further inflection points may have occurred. Analysis of climate model simulations capturing the essence of these observed shifts indicates that these systematic changes will continue into the late 21st century under high greenhouse gas emission scenarios. Here, we review two decades of work, revealing for the first time that tipping points characteristic of regime transitions are inferred to have already occurred in the SH climate system.

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Section: Projections Of the Future Sh Climatementioning

confidence: 95%

Section: Projections Of the Future Sh Climatementioning

confidence: 99%

Beyond the First Tipping Points of Southern Hemisphere Climate

O’Kane,

Frederiksen,

Frederiksen

et al. 2024

Climate

Self Cite

View full text Add to dashboard Cite

show abstract

“…They found that most models simulated the changes in zonal wind, but only about a third of the models captured the observed changes in baroclinic instability and with reduced magnitude. The subset of models capable of simulating the observed spatial trends in the Phillips' Criterion and the associated changes in winter rainfall over southern Australia and especially in SWWA were used as a basis for a subsequent CMIP5 multi-model ensemble study conducted by Grainger et al (2017) [76]. They found that the externally forced austral summer (DJF) variability in the Z 500hPa geopotential height resided almost exclusively in a SAM-like teleconnection with uniform positive loading in the tropics, extending to at least 30 • S with an annular structure with negative loadings exhibited at higher latitudes.…”

Section: Projections Of the Future Sh Climatementioning

confidence: 99%

Beyond the First Tipping Points of Southern Hemisphere Climate

O’Kane¹,

Frederiksen²,

Frederiksen³

et al. 2023

Preprint

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Analysis of observations, reanalysis and model simulations, including via machine learning methods specifically designed for regime identification, have revealed changes in aspects of the Southern Hemisphere (SH) circulation and Australian climate and extremes over the last half century that point to transitions to new states. In particular, our analysis shows a dramatic shift in the metastability of the SH climate occurred in the late 1970s, associated with a large scale regime transition in the SH atmospheric circulation with systematic changes to the subtropical jet, blocking, zonal winds and storm tracks. Analysis via nonstationary clustering reveals a regime shift was coincident with a sharp transition to warmer oceanic sea surface temperatures and increased baroclinicity in the large scales of the Antarctic Circumpolar Circulation (ACC), extending across the whole hemisphere. At the same time, the background state of the tropical Pacific thermocline shoaled, leading to increased likelihood of El Ni\~{n}o events. These changes in the dynamics have preceded additional regional tipping points associated with reductions in mean and extreme rainfall in South-west Western Australia (SWWA) and streamflow into Perth dams, and also with increases in mean and extreme rainfall over Northern Australia since the late 1970s. The drying of South-eastern Australia (SEA) occurred against a background of accelerating increases in average and extreme temperatures across the whole continent since the 1990s, implying further inflection points may have occurred. Through climate model simulations capturing the essence of these observed shifts our analysis indicates these systematic changes will continue into the late 21st century under high greenhouse gas emission scenarios. Here we review two decades of work, revealing for the first time, that tipping points characteristic of first and second order regime transitions are inferred to have already occurred in the SH climate system.

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“…By reducing the dimensionality of the data, the relationship between the atmospheric and surface weather may be more readily understood. Changes in atmospheric CPs have been linked with changes in atmospheric and oceanic phenomena such as the North Atlantic Oscillation (NAO; Saaroni et al ., 2019; Putniković et al ., 2018; Cherenkova and Semenov, 2017) the Arctic Oscillation (AO) via Arctic amplification (Francis et al ., 2018), the El Niño Southern Oscillation (ENSO; Grainger et al ., 2017), and the Atlantic Multidecadal Oscillation (AMO; Cherenkova and Semenov, 2017). Many of the studies that examine changes in the frequency of CPs are typically interested in better understanding how these changes are associated with extreme surface weather events.…”

Section: Introductionmentioning

confidence: 99%

Assessing trends in atmospheric circulation patterns across North America

Smith

Obarein

Sheridan

et al. 2021

Intl Journal of Climatology

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Circulation patterns (CPs) are discrete categorizations of spatial fields of atmospheric conditions, often used to examine the interaction between the overlying atmosphere and surface weather. Examining changes in the frequency of these atmospheric CPs may therefore help us better understand the relationship between a changing climate and the occurrence of extreme weather events. In this study, we use self‐organized maps to classify CPs from 500 mb geopotential heights (500z) and mean sea‐level pressure (MSLP) for five regions across North America, using two different reanalysis datasets. Trends in CPs (from 1979 to 2018) from both the North American Regional Reanalysis (NARR) and the recently released ERA5 datasets are compared using a new method in which the CPs from the ERA5 dataset are based on the principal components of the NARR data. This results in a more direct comparison between the CPs of each dataset. z500 CP trends were generally larger than the MSLP CP trends and the NARR CP trends were generally larger than the ERA5 CP trends. Furthermore, the most extreme summer‐dominant CPs were found to have increased significantly over the 40‐year study period in all five regions for both the NARR and ERA5 CPs.

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Projections of Southern Hemisphere atmospheric circulation interannual variability

Cited by 9 publications

References 53 publications

Beyond the First Tipping Points of Southern Hemisphere Climate

Beyond the First Tipping Points of Southern Hemisphere Climate

Beyond the First Tipping Points of Southern Hemisphere Climate

Assessing trends in atmospheric circulation patterns across North America

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