Sensitivity of the Latitude of the Westerly Jet Stream to Climate Forcing

Chen, Gang; Zhang, Pengfei; Lu, Jian

doi:10.1029/2019gl086563

Cited by 16 publications

(10 citation statements)

References 34 publications

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“…With increasing greenhouse gas concentrations, there is a tendency toward a more zonal flow in boreal summer and autumn, while in winter and spring, there is no robust change. This is consistent with the proposed tugof-war (e.g., Barnes & Polvani, 2015;Blackport & Kushner, 2017;Chen et al, 2020): the upper tropospheric warming in the tropics leads to an increased meridional temperature gradient, stronger mean westerly flow, and decreased waviness. In contrast, in boreal winter, the effect of Arctic amplification leads to a reduced meridional temperature gradient, weaker mean westerly flow, and increased waviness offsetting the impact of upper tropospheric warming in the tropics.…”

Section: Journal Of Advances In Modeling Earth Systemssupporting

confidence: 89%

“…There is an ongoing discussion on how the waviness of the atmospheric flow in middle latitudes will change in the future as a result of changes in the Arctic, through Arctic amplification, and in the tropics, through upper tropospheric warming. The contrasting driving from the Arctic versus the tropics has been termed a tug of war in the middle latitudes (e.g., Barnes & Polvani, 2015; Blackport & Kushner, 2017; Chen et al, 2020) Will there be a more zonal flow with a decrease in the intensity of atmospheric waves implying less extreme warm and cold events or will the meridionality of the flow get stronger implying more extreme warm and cold events in the middle latitudes or will there be no change? To answer this question, various different objective indices have been defined.…”

Section: Climate Responsementioning

confidence: 99%

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Simulations for CMIP6 With the AWI Climate Model AWI‐CM‐1‐1

Semmler

Danilov

Gierz

et al. 2020

J Adv Model Earth Syst

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The Alfred Wegener Institute Climate Model (AWI‐CM) participates for the first time in the Coupled Model Intercomparison Project (CMIP), CMIP6. The sea ice‐ocean component, FESOM, runs on an unstructured mesh with horizontal resolutions ranging from 8 to 80 km. FESOM is coupled to the Max Planck Institute atmospheric model ECHAM 6.3 at a horizontal resolution of about 100 km. Using objective performance indices, it is shown that AWI‐CM performs better than the average of CMIP5 models. AWI‐CM shows an equilibrium climate sensitivity of 3.2°C, which is similar to the CMIP5 average, and a transient climate response of 2.1°C which is slightly higher than the CMIP5 average. The negative trend of Arctic sea‐ice extent in September over the past 30 years is 20–30% weaker in our simulations compared to observations. With the strongest emission scenario, the AMOC decreases by 25% until the end of the century which is less than the CMIP5 average of 40%. Patterns and even magnitude of simulated temperature and precipitation changes at the end of this century compared to present‐day climate under the strong emission scenario SSP585 are similar to the multi‐model CMIP5 mean. The simulations show a 11°C warming north of the Barents Sea and around 2°C to 3°C over most parts of the ocean as well as a wetting of the Arctic, subpolar, tropical, and Southern Ocean. Furthermore, in the northern middle latitudes in boreal summer and autumn as well as in the southern middle latitudes, a more zonal atmospheric flow is projected throughout the year.

show abstract

Section: Journal Of Advances In Modeling Earth Systemssupporting

confidence: 89%

Section: Climate Responsementioning

confidence: 99%

Simulations for CMIP6 With the AWI Climate Model AWI‐CM‐1‐1

Semmler

Danilov

Gierz

et al. 2020

J Adv Model Earth Syst

View full text Add to dashboard Cite

show abstract

“…4c ) reveals that in the northern hemisphere mid-latitudes there is a statistically significant increase in westerly wind speed poleward of the climatological maximum, and a decrease to the south. From a purely thermodynamic standpoint, in response to climate change there is a tug of war between the contrasting effects on the jet of Arctic amplification and tropical upper troposphere heating 39 , 60 , 61 . While Arctic amplification would, on its own, push the mid-latitude jet closer to the equator, the tropical heating together with the expansion of the Hadley cell would push the jet poleward 62 .…”

Section: Resultsmentioning

confidence: 99%

Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response

et al. 2021

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In climate model simulations of future climate change, the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. However, the impacts of this decline, relative to other changes, remain to be identified. Here we address this problem by analyzing 30 idealized abrupt-4xCO2 climate model simulations. We find that in models with larger AMOC decline, there is a minimum warming in the North Atlantic, a southward displacement of the Inter-tropical Convergence Zone, and a poleward shift of the mid-latitude jet. The changes in the models with smaller AMOC decline are drastically different: there is a relatively larger warming in the North Atlantic, the precipitation response exhibits a wet-get-wetter, dry-get-drier pattern, and there are smaller displacements of the mid-latitude jet. Our study indicates that the AMOC is a major source of inter-model uncertainty, and continued observational efforts are needed to constrain the AMOC response in future climate change.

show abstract

“…There is an ongoing discussion on how the waviness of the atmospheric flow in middle latitudes will change in the future as a result of changes in the Arctic, through Arctic amplification, and in the tropics, through upper tropospheric warming. The contrasting driving from the Arctic versus the tropics has been termed a tug of war in the middle latitudes (e.g., Barnes & Polvani, 2015;Blackport & Kushner, 2017;Chen et al, 2020) Will there be a more zonal flow with a decrease in the intensity of atmospheric waves implying less extreme warm and cold events or will the meridionality of the flow get stronger implying more extreme warm and cold events in the middle latitudes or will there be no change? To answer this question, various different objective indices have been defined.…”

Section: Journal Of Advances In Modeling Earth Systemsmentioning

confidence: 99%

Simulations for CMIP6 with the AWI climate model AWI-CM-1-1

Semmler

Danilov

Gierz

et al. 2020

Preprint

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The Alfred Wegener Institute Climate Model (AWI-CM) participates for the first time in the Coupled Model Intercomparison Project (CMIP), CMIP6. The sea ice-ocean component, FESOM, runs on an unstructured mesh with horizontal resolutions ranging from 8 to 80 km. FESOM is coupled to the Max Planck Institute atmospheric model ECHAM 6.3 at a horizontal resolution of about 100 km. Using objective performance indices, it is shown that AWI-CM performs better than the average of CMIP5 models. AWI-CM shows an equilibrium climate sensitivity of 3.2°C, which is similar to the CMIP5 average, and a transient climate response of 2.1°C which is slightly higher than the CMIP5 average. The negative trend of Arctic sea-ice extent in September over the past 30 years is 20-30% weaker in our simulations compared to observations. With the strongest emission scenario, the AMOC decreases by 25% until the end of the century which is less than the CMIP5 average of 40%. Patterns and even magnitude of simulated temperature and precipitation changes at the end of this century compared to present-day climate under the strong emission scenario SSP585 are similar to the multi-model CMIP5 mean. The simulations show a 11°C warming north of the Barents Sea and around 2°C to 3°C over most parts of the ocean as well as a wetting of the Arctic, subpolar, tropical, and Southern Ocean. Furthermore, in the northern middle latitudes in boreal summer and autumn as well as in the southern middle latitudes, a more zonal atmospheric flow is projected throughout the year.Plain Language Summary The Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) participates for the first time with a global climate model in the Coupled Model Intercomparison Project 6 (CMIP6). The results of CMIP6 and previous model comparison projects feed into the next assessment report of the Intergovernmental Panel on Climate Change (IPCC). The IPCC assessment reports include information on past and expected climate change in the future and is written for policy-and decision-makers as well as for the general public. The main characteristics of the AWI climate model are described and compared to models from previous intercomparison projects. The projected global warming in AWI-CM is similar to the average warming predicted by climate models in the previous intercomparison project. However, the Arctic sea-ice extent declines faster than typical previous estimates. Areas that are wet in present-day climate become wetter, and areas that are dry in present-day climate become drier in the future-consistent with previous climate model simulations. The ocean currents remain rather stable in the AWI climate projections, which leads to a continued warm Gulf stream and therefore an only slightly reduced warming of the North Atlantic and parts of Europe compared to other middle-latitude regions.

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Sensitivity of the Latitude of the Westerly Jet Stream to Climate Forcing

Cited by 16 publications

References 34 publications

Simulations for CMIP6 With the AWI Climate Model AWI‐CM‐1‐1

Simulations for CMIP6 With the AWI Climate Model AWI‐CM‐1‐1

Future climate change shaped by inter-model differences in Atlantic meridional overturning circulation response

Simulations for CMIP6 with the AWI climate model AWI-CM-1-1

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