Simulation and Projection of the Southern Hemisphere Annular Mode in CMIP5 Models

2013 ◽  
Vol 26 (24) ◽  
pp. 9860-9879 ◽  
Author(s):  
Fei Zheng ◽  
Jianping Li ◽  
Robin T. Clark ◽  
Hyacinth C. Nnamchi
Keyword(s):  
Southern Hemisphere ◽  
Coupled Model ◽  
Austral Summer ◽  
Cmip5 Models ◽  
Spatial And Temporal Variability ◽  
Positive Trend ◽  
Annular Mode ◽  
Future Evolution ◽  
Asymmetric Component ◽  
The Future

Abstract Climate variability in the Southern Hemisphere (SH) extratropical regions is dominated by the SH annular mode (SAM). Future changes in the SAM could have a large influence on the climate over broad regions. In this paper, the authors utilized model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to examine projected future changes in the SAM during the austral summer [December–February (DJF)]. To start off, first, the ability of the models in reproducing the recently observed spatial and temporal variability was assessed. The 12 CMIP5 models examined were found to reproduce the SAM's spatial pattern reasonably well in terms of both the symmetrical and the asymmetric component. The CMIP5 models show an improvement over phase 3 of CMIP (CMIP3) in simulating the seesaw structure of the SAM and also give improvements in the recently observed positive SAM trend. However, only half the models appeared to be able to capture two major recent decadal SAM phases. Then, the future SAM trends and its sensitivity to greenhouse gas (GHG) concentrations using simulations based on the representative concentration pathways 4.5 (RCP4.5) and 8.5 (RCP8.5) were explored. With RCP4.5, a very weak negative trend for this century is found. Conversely, with RCP8.5, a significant positive trend was projected, with a magnitude similar to the recently observed trend. Finally, model uncertainty in the future SAM projections was quantified by comparing projections from the individual CMIP5 models. The results imply the response of SH polar region stratospheric temperature to GHGs could be a significant controlling factor on the future evolution of the SAM.

scholarly journals Simulating Southern Hemisphere extra-tropical climate variability with an idealised coupled atmosphere-ocean model

2012 ◽  
Vol 5 (5) ◽  
pp. 1161-1175 ◽  
Author(s):  
H. Kurzke ◽  
M. V. Kurgansky ◽  
K. Dethloff ◽  
D. Handorf ◽  
S. Erxleben ◽  
...  
Keyword(s):  
Climate Variability ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Global Ocean ◽  
Simplified Model ◽  
Cmip5 Models ◽  
Decadal Climate Variability

Abstract. A quasi-geostrophic model of Southern Hemisphere's wintertime atmospheric circulation with horizontal resolution T21 has been coupled to a global ocean circulation model with a resolution of 2° × 2° and simplified physics. This simplified coupled model reproduces qualitatively some features of the first and the second EOF of atmospheric 833 hPa geopotential height in accordance with NCEP data. The variability patterns of the simplified coupled model have been compared with variability patterns simulated by four complex state-of-the-art coupled CMIP5 models. The first EOF of the simplified model is too zonal and does not reproduce the right position of the centre of action over the Pacific Ocean and its extension to the tropics. The agreement in the second EOF between the simplified and the CMIP5 models is better. The total variance of the simplified model is weaker than the observational variance and those of the CMIP5 models. The transport properties of the Southern Ocean circulation are in qualitative accord with observations. The simplified model exhibits skill in reproducing essential features of decadal and multi-decadal climate variability in the extratropical Southern Hemisphere. Notably, 800 yr long coupled model simulations reveal sea surface temperature fluctuations on the timescale of several decades in the Antarctic Circumpolar Current region.

scholarly journals Interactions between Antarctic sea ice and large-scale atmospheric modes in CMIP5 models

2016 ◽  
Author(s):  
Serena Schroeter ◽  
Will Hobbs ◽  
Nathaniel L. Bindoff
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Coupled Model ◽  
Southern Annular Mode ◽  
Cmip5 Models ◽  
Atmospheric Variability ◽  
Annular Mode ◽  
Antarctic Sea Ice ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract. The response of Antarctic sea ice to large-scale patterns of atmospheric variability varies according to sea ice sector and season. In this study, interannual atmosphere-sea ice interactions were explored using observation-based data and compared with simulated interactions by models in the Coupled Model Intercomparison Project Phase 5. Simulated relationships between atmospheric variability and sea ice variability generally reproduced the observed relationships, though more closely during the season of sea ice advance than the season of sea ice retreat. Atmospheric influence on sea ice is known to be strongest during its advance, with the ocean emerging as a dominant driver of sea ice retreat; therefore, while it appears that models are able to capture the dominance of the atmosphere during advance, simulations of ocean-atmosphere-sea ice interactions during retreat require further investigation. A large proportion of model ensemble members overestimated the relative importance of the Southern Annular Mode compared with other modes on high southern latitude climate, while the influence of tropical forcing was underestimated. This result emerged particularly strongly during the season of sea ice retreat. The amplified zonal patterns of the Southern Annular Mode in many models and its exaggerated influence on sea ice overwhelm the comparatively underestimated meridional influence, suggesting that simulated sea ice variability would become more zonally symmetric as a result. Across the seasons of sea ice advance and retreat, 3 of the 5 sectors did not reveal a strong relationship with a pattern of large-scale atmospheric variability in one or both seasons, indicating that sea ice in these sectors may be influenced more strongly by atmospheric variability unexplained by the major atmospheric modes, or by heat exchange in the ocean.

scholarly journals Tropical cyclone formation regions in CMIP5 models: a global performance assessment and projected changes

2020 ◽  
Vol 55 (11-12) ◽  
pp. 3213-3237
Author(s):  
K. J. Tory ◽  
H. Ye ◽  
G. Brunet
Keyword(s):  
Tropical Cyclone ◽  
Performance Assessment ◽  
Southern Hemisphere ◽  
North Pacific ◽  
South Pacific ◽  
Cmip5 Models ◽  
The North ◽  
South Indian ◽  
The Future ◽  
Warming World

Abstract Tropical Cyclone (TC) formation regions are analysed in twelve CMIP5 models using a recently developed diagnostic that provides a model-performance summary in a single image for the mid-summer TC season. A subjective assessment provides an indication of how well the models perform in each TC basin throughout the globe, and which basins can be used to determine possible changes in TC formation regions in a warmer climate. The analysis is necessarily succinct so that seven basins in twelve models can be examined. Consequently, basin performance was reduced to an assessment of two common problems specific to each basin. Basins that were not too adversely affected were included in the projection exercise. The North Indian basin was excluded because the mid-summer analysis period covers a lull in TC activity. Surprisingly, the North Atlantic basin also had to be excluded, because all twelve models failed the performance assessment. A slight poleward expansion in the western North Pacific and an expansion towards the Hawaiian Islands in the eastern North Pacific is plausible in the future, while a contraction in the TC formation regions in the eastern South Indian and western South Pacific basins would reduce the Australian region TC formation area. More than half the models were too active in the eastern South Pacific and South Atlantic basins. However, projections based on the remaining models suggest these basins will remain hostile for TC formation in the future. These southern hemisphere changes are consistent with existing projections of fewer southern hemisphere TCs in a future warming world

scholarly journals ENSO Teleconnection Pattern Changes over the Southeastern United States under a Climate Change Scenario in CMIP5 Models

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Ji-Hyun Oh ◽  
D. W. Shin ◽  
Steven D. Cocke ◽  
Guillermo A. Baigorria
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Coupled Model ◽  
Winter Precipitation ◽  
Teleconnection Pattern ◽  
Cmip5 Models ◽  
Change Scenario ◽  
Historical Simulation ◽  
The Future ◽  
Precipitation Anomalies

A strong teleconnection exists between the sea surface temperature (SST) over the tropical Pacific and the winter precipitation in the southeastern United States (SE US). This feature is adopted to validate the fidelity of Coupled Model Intercomparison Project Phase 5 (CMIP5) in this study. In addition, the authors examine whether the teleconnection pattern persists in the future under a global warming scenario. Generally, most of the eight selected models show a positive correlation between November SST over Niño 3 region and December–February (DJF) mean daily precipitation anomalies over the SE US, consistent with the observation. However, the models with poor realization of skewness of Niño indices fail to simulate the realistic teleconnection pattern in the historical simulation. In the Representative Concentration Pathways 8.5 (RCP8.5) run, all of the models maintain positive and slightly increased correlation patterns. It is noteworthy that the region with strong teleconnection pattern shifts northward in the future. Increased variance of winter precipitation due to the SST teleconnection is shown over Alabama and Georgia rather than over Florida under the RCP8.5 scenario in most of the models, differing from the historical run in which the precipitation in Florida is the most attributable to the eastern Pacific SST.

Extratropical Southern Hemisphere Synchronous Pressure Variability in the Early 20th Century

2021 ◽  
pp. 1-41
Author(s):  
Ryan L. Fogt ◽  
Charlotte J. Connolly
Keyword(s):  
Southern Hemisphere ◽  
Historical Data ◽  
Austral Summer ◽  
Southern Annular Mode ◽  
Early 20Th Century ◽  
Annular Mode ◽  
Tropical Variability ◽  
Zonal Wavenumber ◽  
Meteorological Observations ◽  
Statistical Relationships

AbstractBecause continuous meteorological observations across Antarctica did not start until the middle of the 20th century, little is known about the full spatial pattern of pressure variability across the extratropical Southern Hemisphere (SH) in the early 20th century, defined here as the period from 1905-1956. To fill this gap, this study analyzes pressure observations across the SH in conjunction with seasonal pressure reconstructions across Antarctica, which are based on observed station-to-station statistical relationships between pressure over Antarctica and the southern midlatitudes. Using this newly generated dataset, it is found that the early 20th century is characterized by synchronous, but opposite signed pressure relationships between Antarctica and the SH midlatitudes, especially in austral summer and autumn. The synchronous pressure relationships are consistent with the Southern Annular Mode, extending its well-known influence on SH extratropical pressure since 1957 into the early 20th century. Apart from connections with the Southern Annular Mode, regional and shorter-duration pressure trends are found to be associated with influences from tropical variability and potentially the zonal wavenumber three pattern. Although the reduced network of SH observations and Antarctic reconstruction capture the Southern Annular Mode in the early 20th century, reanalyses products show varying skill in reproducing trends and variability, especially over the oceans and high southern latitudes prior to 1957, which stresses the importance of continual efforts of historical data rescue in data sparse regions to improve their quality.

Revisiting the relationship between dynamical sensitivity and climate sensitivity in the Southern hemisphere

2020 ◽  
Author(s):  
Thomas Wood ◽  
Amanda Maycock ◽  
Christine McKenna ◽  
Andreas Chrysanthou ◽  
John Fyfe ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Climate Sensitivity ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Storm Track ◽  
Temperature Gradients ◽  
Cmip5 Models ◽  
Positive Trend ◽  
Equilibrium Climate Sensitivity ◽  
The Relationship

<p>The Southern Annular Mode (SAM) is the dominant mode of midlatitude atmospheric circulation variability in the Southern hemisphere. In the future, the SAM trend is expected to be the net result of opposing effects from increasing greenhouse gases (GHG) and ozone recovery. Different greenhouse gas scenarios, which induce different rates of surface and atmospheric temperature change, are therefore associated with different future SAM trends (Barnes et al., 2014). Since the magnitude of warming due to GHGs is an important component of this response, one might expect to find a relationship between equilibrium climate sensitivity (ECS) and future Southern hemisphere circulation trends. In CMIP5, the relationship between the SAM and the level of tropospheric warming across models was found to be strongest in the summer and autumn and could explain around 20% of the intermodel spread (Grise and Polvani, 2014). The spread is more strongly correlated with differences in meridional temperature gradients (Harvey et al., 2014).</p><p>Many of the latest CMIP6 models show a larger equilibrium climate sensitivity (ECS) of up to ~5.5 K (Forster et al., 2019) compared to a maximum of ~4.7 K in CMIP5. This raises the important question of how a higher level of warming affects projections of the SH midlatitude circulation. In this study, we examine the response of the SAM in CMIP6 models and quantify its relationship to ECS and temperature gradients. Our starting hypothesis is that stronger surface warming will induce a larger increase in tropical free tropospheric temperatures, and hence all being equal, a larger tropics-to-pole temperature gradient and a more positive SAM trend. However, results show that despite the higher level of warming in the CMIP6 models, there is a smaller positive trend in SAM index than in CMIP5 indicating a different relationship between warming and midlatitude circulation trends in CMIP6. We attempt to explain potential reasons for these differences.</p><p><strong>References:</strong></p><p>Barnes, E.A., N.W. Barnes, and L.M. Polvani, 2014: Delayed Southern Hemisphere Climate Change Induced by Stratospheric Ozone Recovery, as Projected by the CMIP5 Models. J. Climate, 27, 852–867, https://doi.org/10.1175/JCLI-D-13-00246.1</p><p>Forster, P.M., Maycock, A.C., McKenna, C.M. et al. (2019), Latest climate models confirm need for urgent mitigation. Nat. Clim. Chang. (2019) doi:10.1038/s41558-019-0660-0</p><p>Grise, K. M., and Polvani, L. M. (2014), Is climate sensitivity related to dynamical sensitivity? A Southern Hemisphere perspective, Geophys. Res. Lett., 41, 534– 540, doi:10.1002/2013GL058466.</p><p>Harvey, B.J., Shaffrey, L.C. & Woollings, T.J. (2014) Equator­-to-­pole temperature differences and the extra­tropical storm track responses of the CMIP5 climate models, Clim Dyn, 43: 1171. https://doi.org/10.1007/s00382-013-1883-9</p>

Sixty Years of Widespread Warming in the Southern Middle and High Latitudes (1957–2016)

2019 ◽  
Vol 32 (20) ◽  
pp. 6875-6898 ◽  
Author(s):  
Megan E. Jones ◽  
David H. Bromwich ◽  
Julien P. Nicolas ◽  
Jorge Carrasco ◽  
Eva Plavcová ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Southern Hemisphere ◽  
Climate Models ◽  
Coupled Model ◽  
Southern Annular Mode ◽  
Cmip5 Models ◽  
High Latitudes ◽  
West Antarctica ◽  
Temporal Perspective ◽  
Temperature Trends

Abstract Temperature trends across Antarctica over the last few decades reveal strong and statistically significant warming in West Antarctica and the Antarctic Peninsula (AP) contrasting with no significant change overall in East Antarctica. However, recent studies have documented cooling in the AP since the late 1990s. This study aims to place temperature changes in the AP and West Antarctica into a larger spatial and temporal perspective by analyzing monthly station-based surface temperature observations since 1957 across the extratropical Southern Hemisphere, along with sea surface temperature (SST) data and mean sea level pressure reanalysis data. The results confirm statistically significant cooling in station observations and SST trends throughout the AP region since 1999. However, the full 60-yr period shows statistically significant, widespread warming across most of the Southern Hemisphere middle and high latitudes. Positive SST trends broadly reflect these warming trends, especially in the midlatitudes. After confirming the importance of the southern annular mode (SAM) on southern high-latitude climate variability, the influence is removed from the station temperature records, revealing statistically significant background warming across all of the extratropical Southern Hemisphere. Antarctic temperature trends in a suite of climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are then investigated. Consistent with previous work the CMIP5 models warm Antarctica at the background temperature rate that is 2 times faster than that observed. However, removing the SAM influence from both CMIP5 and observed temperatures results in Antarctic trends that differ only modestly, perhaps due to natural multidecadal variability remaining in the observations.

scholarly journals Assessment of Modes of Interannual Variability of Southern Hemisphere Atmospheric Circulation in CMIP5 Models

2014 ◽  
Vol 27 (21) ◽  
pp. 8107-8125 ◽  
Author(s):  
Simon Grainger ◽  
Carsten S. Frederiksen ◽  
Xiaogu Zheng
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Southern Oscillation ◽  
Slow Component ◽  
Coupled Model ◽  
Reanalysis Data ◽  
Cmip5 Models ◽  
Noise Component ◽  
Modes Of Variability ◽  
Multimodel Ensembles

Abstract An assessment is made of the modes of interannual variability in the seasonal mean summer and winter Southern Hemisphere (SH) 500-hPa geopotential height in the twentieth century in models from the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) dataset. Modes of variability of both the slow (signal) and intraseasonal (noise) components in the CMIP5 models are evaluated against those estimated from reanalysis data. There is general improvement in the leading modes of the slow (signal) component in CMIP5 models compared with the CMIP phase 3 (CMIP3) dataset. The largest improvement is in the spatial structures of the modes related to El Niño–Southern Oscillation variability in SH summer. An overall score metric is significantly higher for CMIP5 over CMIP3 in both seasons. The leading modes in the intraseasonal noise component are generally well reproduced in CMIP5 models, and there are few differences from CMIP3. A new total overall score metric is used to rank the CMIP5 models over both seasons. Weighting the seasons by the relative spread of overall scores is shown to be suitable for generating multimodel ensembles for further analysis of interannual variability. In multimodel ensembles, it is found that an ensemble of size 5 or 6 is sufficient in SH summer to reproduce well the dominant modes. In contrast, about 13 models are typically are required in SH winter. It is shown that it is necessary that the selected models individually reproduce well the leading modes of the slow component.

scholarly journals Sensitivity of the CMIP5 models to precipitation in Tropical Brazil

2020 ◽  
Vol 12 (1) ◽  
pp. 180-191
Author(s):  
Naurinete De Jesus da Costa Barreto ◽  
David Mendes ◽  
Paulo Sérgio Lucio
Keyword(s):  
Principal Component Analysis ◽  
Coupled Model ◽  
Austral Summer ◽  
Principal Component ◽  
Component Analysis ◽  
Cmip5 Models ◽  
Precipitation Regime ◽  
Temporal Space ◽  
Dominant Pattern ◽  
Intercomparison Project

The main objective of this study is to evaluate the ability of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) models to simulate weekly rainfall over Tropical Brazil. Twenty-four years of the historical experiment of sixteen models for the austral summer and fall seasons were evaluated. In the analyzes performed in this study, frequency distribution and correlation were used to evaluate temporal variability. Principal Component Analysis to ascertain the characteristics of the dominant pattern of each model. The results suggest that some models have difficulty in simulating the spatial pattern of regional precipitation, especially related to the frequency of events and temporal variation, however, the dominant pattern found by the Principal Component Analysis showed that at least six models (ACCESS1-0, CanESM2, EC-EARTH, GFDL-CM3, MIROC5 and MRI-CGCM3) reasonably represented the temporal-space precipitation regime over Tropical Brazil.

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