scholarly journals A regime view of future atmospheric circulation changes in Northern mid-latitudes

2020 ◽  
Author(s):  
Federico Fabiano ◽  
Virna Meccia ◽  
Paolo Davini ◽  
Paolo Ghinassi ◽  
Susanna Corti
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
The Arctic ◽  
The North ◽  
The Pacific ◽  
General Improvement ◽  
Polar Stratosphere ◽  
The North Atlantic ◽  
Different Levels ◽  
Circulation Changes

Abstract. Future wintertime atmospheric circulation changes in the Euro-Atlantic (EAT) and Pacific-North American (PNA) sectors are studied from a Weather Regimes perspective. The CMIP5 and CMIP6 historical simulations performance in reproducing the observed regimes is first evaluated, showing a general improvement of CMIP6 models, more evident for EAT. The circulation changes projected by CMIP5 and CMIP6 scenario simulations are analyzed in terms of the change in the frequency and persistence of the regimes. In the EAT sector, significant positive trends are found for the frequency and persistence of NAO+ for SSP245, SSP370 and SSP585 scenarios, with a concomitant decrease in the frequency of the Scandinavian Blocking and Atlantic Ridge regimes. For PNA, the Pacific Through regime shows a significant increase, while the Bering Ridge is predicted to decrease in all scenarios analyzed. The spread among the model responses is linked to different levels of warming in the Polar Stratosphere, the North Atlantic and the Arctic.

scholarly journals A regime view of future atmospheric circulation changes in northern mid-latitudes

2021 ◽  
Vol 2 (1) ◽  
pp. 163-180
Author(s):  
Federico Fabiano ◽  
Virna L. Meccia ◽  
Paolo Davini ◽  
Paolo Ghinassi ◽  
Susanna Corti
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Coupled Model ◽  
The Arctic ◽  
Historical Simulation ◽  
Simulation Performance ◽  
The North ◽  
The Pacific ◽  
General Improvement ◽  
Circulation Changes

Abstract. Future wintertime atmospheric circulation changes in the Euro–Atlantic (EAT) and Pacific–North American (PAC) sectors are studied from a weather regimes perspective. The Coupled Model Intercomparison Project phases 5 and 6 (CMIP5 and CMIP6) historical simulation performance in reproducing the observed regimes is first evaluated, showing a general improvement in the CMIP6 models, which is more evident for EAT. The circulation changes projected by CMIP5 and CMIP6 scenario simulations are analysed in terms of the change in the frequency and persistence of the regimes. In the EAT sector, significant positive trends are found for the frequency and persistence of NAO+ (North Atlantic Oscillation) for SSP2–4.5, SSP3–7.0 and SSP5–8.5 scenarios with a concomitant decrease in the frequency of the Scandinavian blocking and Atlantic Ridge regimes. For PAC, the Pacific Trough regime shows a significant increase, while the Bering Ridge is predicted to decrease in all scenarios analysed. The spread among the model responses is linked to different levels of warming in the polar stratosphere, the tropical upper troposphere, the North Atlantic and the Arctic.

A regime view of future atmospheric circulation changes in Northern mid-latitudes

2021 ◽  
Author(s):  
Federico Fabiano ◽  
Virna L. Meccia ◽  
Paolo Davini ◽  
Paolo Ghinassi ◽  
Susanna Corti
Keyword(s):  
Atmospheric Circulation ◽  
Winter Season ◽  
Model Performance ◽  
The Arctic ◽  
Historical Period ◽  
Weather Regimes ◽  
The North ◽  
The Pacific ◽  
General Improvement ◽  
Circulation Changes

<p>Future changes in the mid-latitude wintertime atmospheric circulation are studied from a weather regimes perspective. The analysis is based on daily geopotential height at 500 hPa during the extended winter season (NDJFM) from both CMIP5 and CMIP6 historical and scenario simulations. The model performance in reproducing the observed weather regimes during the historical period in the Euro-Atlantic (EAT) and Pacific-North American (PAC) sectors is first evaluated, showing a general improvement of CMIP6 models in terms of regime patterns, frequencies and variance ratio. The projected circulation changes in the future climate (2050-2100) under the different scenarios are analysed in terms of the change in the frequency and persistence of the regimes. Significant positive trends are found for the frequency of NAO+ and negative trends for the Scandinavian Blocking and Atlantic Ridge regimes. This confirms the tendency for the zonalization of the circulation in the EAT sector, with decreased latitudinal variability of the jet stream. For the PAC sector, significant changes are seen for the Pacific Trough regime (increase) and the Bering Ridge (decrease), while there is no agreement in the response of the two PNA regimes. The spread among the model responses in the most extreme scenarios is analysed through a multi-linear regression approach and linked to different levels of warming in the polar stratosphere, the tropical upper troposphere, the North Atlantic and the Arctic.</p>

scholarly journals Two leading modes of wintertime atmospheric circulation drive the recent warm Arctic-cold Eurasia temperature pattern

2020 ◽  
Author(s):  
kunhui Ye ◽  
Gabriele Messori
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
The North ◽  
Downward Longwave Radiation ◽  
North Asia ◽  
Arctic Sea ◽  
The North Atlantic

<p>The wintertime warm Arctic-cold Eurasia (WACE) temperature trend during 1990-2010 was characterized by accelerating warming in the Arctic region, cooling in Eurasia and accelerating autumn/winter Arctic sea ice loss. We identify two atmospheric circulation modes over the North Atlantic-Northern Eurasian sector which displayed strong upward trends over the same period and can explain a large part of the observed decadal WACE pattern. Both modes bear a close resemblance to well-known teleconnection patterns and are relatively independent from anomalies in Arctic sea-ice cover. The first mode (PC1) captures the recent negative trends in the North Atlantic Oscillation and increased Greenland blocking frequency while the second mode (PC2) is reminiscent of a Rossby wave train and reflects an increased blocking frequency over the Urals and North Asia. We find that the loss in the Arctic sea ice and the upward trends in the PC1/PC2 together account for most of the decadal Arctic warming trend (>80%). However, the decadal Eurasian cooling trends may be primarily ascribed to the two circulation modes alone: all of the cooling in Siberia is contributed to by the PC1, and 65% of the cooling in East Asia by their combination (the contribution by PC2 doubles that by PC1). Enhanced intraseasonal activity of the two circulation modes increases blocking frequencies over Greenland, the Ural region and North Asia, which drive anomalous moisture/heat flux towards the Arctic and alter the downward longwave radiation. It weakens warm advection and enhances advection of Arctic cold airmass towards Eurasia.</p>

scholarly journals Reconstructing Late Holocene North Atlantic atmospheric circulation changes using functional paleoclimate networks

2017 ◽  
Vol 13 (11) ◽  
pp. 1593-1608 ◽  
Author(s):  
Jasper G. Franke ◽  
Johannes P. Werner ◽  
Reik V. Donner
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Late Holocene ◽  
Dominant Mode ◽  
The North ◽  
The North Atlantic ◽  
Earth’S Climate ◽  
The North Atlantic Oscillation ◽  
Circulation Changes

Abstract. Obtaining reliable reconstructions of long-term atmospheric circulation changes in the North Atlantic region presents a persistent challenge to contemporary paleoclimate research, which has been addressed by a multitude of recent studies. In order to contribute a novel methodological aspect to this active field, we apply here evolving functional network analysis, a recently developed tool for studying temporal changes of the spatial co-variability structure of the Earth's climate system, to a set of Late Holocene paleoclimate proxy records covering the last two millennia. The emerging patterns obtained by our analysis are related to long-term changes in the dominant mode of atmospheric circulation in the region, the North Atlantic Oscillation (NAO). By comparing the time-dependent inter-regional linkage structures of the obtained functional paleoclimate network representations to a recent multi-centennial NAO reconstruction, we identify co-variability between southern Greenland, Svalbard, and Fennoscandia as being indicative of a positive NAO phase, while connections from Greenland and Fennoscandia to central Europe are more pronounced during negative NAO phases. By drawing upon this correspondence, we use some key parameters of the evolving network structure to obtain a qualitative reconstruction of the NAO long-term variability over the entire Common Era (last 2000 years) using a linear regression model trained upon the existing shorter reconstruction.

scholarly journals Two Leading Modes of Wintertime Atmospheric Circulation Drive the Recent Warm Arctic–Cold Eurasia Temperature Pattern

2020 ◽  
Vol 33 (13) ◽  
pp. 5565-5587 ◽  
Author(s):  
Kunhui Ye ◽  
Gabriele Messori
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
The North ◽  
Downward Longwave Radiation ◽  
North Asia ◽  
Arctic Sea ◽  
The North Atlantic

AbstractThe wintertime warm Arctic–cold Eurasia (WACE) temperature trend during 1990–2010 was characterized by accelerating warming in the Arctic region, cooling in Eurasia, and accelerating autumn/winter Arctic sea ice loss. We identify two atmospheric circulation modes over the North Atlantic–northern Eurasian sector that displayed strong upward trends over the same period and can explain a large part of the observed decadal WACE pattern. Both modes bear a close resemblance to well-known teleconnection patterns and are relatively independent from variability in Arctic sea ice cover. The first mode (PC1) captures the recent negative trends in the North Atlantic Oscillation and increased Greenland blocking frequency, while the second mode (PC2) is reminiscent of a Rossby wave train and reflects an increased blocking frequency over the Urals and north Asia. We find that the loss in the Arctic sea ice and the upward trends in PC1 and PC2 together account for most of the decadal Arctic warming trend (>80%). However, the decadal Eurasian cooling trends may be primarily ascribed to the two circulation modes alone: all of the cooling in Siberia is contributed to by PC1 and 65% of the cooling in East Asia by their combination (the contribution by PC2 doubles that by PC1). Enhanced intraseasonal activity of the two circulation modes increases blocking frequencies over Greenland, the Ural region, and north Asia, which drive anomalous moisture/heat flux toward the Arctic and alter the downward longwave radiation. This also weakens warm advection and enhances advection of cold Arctic airmasses towards Eurasia.

Why Does a Colder (Warmer) Winter Tend to Be Followed by a Warmer (Cooler) Summer over Northeast Eurasia?

2020 ◽  
Vol 33 (17) ◽  
pp. 7255-7274
Author(s):  
Shangfeng Chen ◽  
Renguang Wu ◽  
Wen Chen ◽  
Kai Li
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Wave Train ◽  
The Arctic ◽  
The North ◽  
Atmospheric Wave ◽  
Anomaly Pattern ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
Sst Anomalies

AbstractThis study reveals a pronounced out-of-phase relationship between surface air temperature (SAT) anomalies over northeast Eurasia in boreal winter and the following summer during 1980–2017. A colder (warmer) winter over northeast Eurasia tends to be followed by a warmer (cooler) summer of next year. The processes for the out-of-phase relation of winter and summer SAT involve the Arctic Oscillation (AO), the air–sea interaction in the North Atlantic Ocean, and a Eurasian anomalous atmospheric circulation pattern induced by the North Atlantic sea surface temperature (SST) anomalies. Winter negative AO/North Atlantic Oscillation (NAO)-like atmospheric circulation anomalies lead to continental cooling over Eurasia via anomalous advection and a tripolar SST anomaly pattern in the North Atlantic. The North Atlantic SST anomaly pattern switches to a dipolar pattern in the following summer via air–sea interaction processes and associated surface heat flux changes. The summer North Atlantic dipolar SST anomaly pattern induces a downstream atmospheric wave train, including large-scale positive geopotential height anomalies over northeast Eurasia, which contributes to positive SAT anomalies there via enhancement of downward surface shortwave radiation and anomalous advection. Barotropic model experiments verify the role of the summer North Atlantic SST anomalies in triggering the atmospheric wave train over Eurasia. Through the above processes, a colder winter is followed by a warmer summer over northeast Eurasia. The above processes apply to the years when warmer winters are followed by cooler summers except for opposite signs of SAT, atmospheric circulation, and SST anomalies.

scholarly journals Reconstructing past atmospheric circulation changes using oxygen isotopes in lake sediments from Sweden

2009 ◽  
Vol 5 (3) ◽  
pp. 1609-1644 ◽  
Author(s):  
C. E. Jonsson ◽  
S. Andersson ◽  
G. C. Rosqvist ◽  
M. J. Leng
Keyword(s):  
Water Balance ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Oxygen Isotopic Composition ◽  
Oceanic Circulation ◽  
The North ◽  
Oxygen Isotopic ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Circulation Changes

Abstract. Here we use lake sediment studies from Sweden to illustrate how Holocene-aged oxygen isotope records (from lakes located in different hydrological settings) can provide information about climate change. In particular changes in precipitation, atmospheric circulation and water balance. We highlight the importance of understanding the present and past lake hydrology, and the relationship between climate parameters and the oxygen isotopic composition of precipitation (δ18Op) and lake waters (δ18Olakewater) for interpretation of the oxygen isotopic record from the sediments (δ18O). Both precipitation reconstructions from northern Sweden and water balance reconstructions from south and central Sweden show that the atmospheric circulation changed from zonal to a more meridional air flow over the Holocene. Superimposed on this Holocene trend are δ18Op minima resembling intervals of the negative phase of the North Atlantic Oscillation (NAO), thus suggesting that the climate of northern Europe is strongly influenced by atmospheric and oceanic circulation changes over the North Atlantic.

scholarly journals Two types of North American droughts related to different atmospheric circulation patterns

2019 ◽  
Author(s):  
Angela-Maria Burgdorf ◽  
Stefan Brönnimann ◽  
Jörg Franke
Keyword(s):  
Atmospheric Circulation ◽  
Great Plains ◽  
North Atlantic ◽  
North American ◽  
Wave Train ◽  
Drought Indices ◽  
Dust Bowl ◽  
The North ◽  
The Pacific ◽  
The North Atlantic

Abstract. Proxy-based studies suggest that the southwestern USA is affected by two types of drought, often termed Dust Bowl-type droughts and 1950s type droughts. The spatial drought patterns of the two types are distinct. It has been suggested that they are related to different circulation characteristics, but lack of observation-based data has precluded further studies. In this paper, we analyze multi-annual droughts in North America since 1600 in tree-ring based drought reconstructions and in a global, monthly 3-dimensional reconstruction of the atmosphere. Using cluster analysis of drought indices, we confirm the two main drought types and find a similar catalog of events as previous studies. These two main types of droughts are then analyzed with respect to sea-surface temperatures (SST), sea-level pressure, and 500 hPa geopotential height (GPH) in summer. 1950s-type droughts are related to a stronger wave-train over the Pacific-North American sector than Dust Bowl-type droughts, whereas the latter show the imprint of a poleward shifted jet and establishment of a Great Plains ridge. The 500 hPa GPH patterns of the two types differ significantly not only over the contiguous United States and Canada but also over the North Atlantic and the Pacific. Dust Bowl-type droughts are associated with positive anomalies, while 1950s-type droughts exhibit strong negative anomalies. In comparison with 1950s-type droughts, the Dust Bowl-type droughts are characterized by higher SSTs in the North Atlantic. Results suggest that atmospheric circulation and SST characteristics not only over the Pacific but also over the extratropical North Atlantic affect the spatial pattern of North American droughts.

scholarly journals Reconstructing past atmospheric circulation changes using oxygen isotopes in lake sediments from Sweden

2010 ◽  
Vol 6 (1) ◽  
pp. 49-62 ◽  
Author(s):  
C. E. Jonsson ◽  
S. Andersson ◽  
G. C. Rosqvist ◽  
M. J. Leng
Keyword(s):  
Water Balance ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Oxygen Isotopic Composition ◽  
Oceanic Circulation ◽  
The North ◽  
Oxygen Isotopic ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Circulation Changes

Abstract. Here we use lake sediment studies from Sweden to illustrate how Holocene-aged oxygen isotope records from lakes located in different hydrological settings, can provide information about climate change. In particular changes in precipitation, atmospheric circulation and water balance. We highlight the importance of understanding the present lake hydrology, and the relationship between climate variables and the oxygen isotopic composition of precipitation ( δ18Op) and lake waters (δ18Olakewater) for interpretation of the oxygen isotopic record from the sediments (δ18O). Both precipitation reconstructions from Northern Sweden and water balance reconstructions from South and Central Sweden show that the atmospheric circulation changed from zonal to a more meridional airflow over the Holocene. Superimposed on this Holocene trend are δ18Op minima resembling intervals of the negative phase of the North Atlantic Oscillation (NAO), thus suggesting that the climate of Northern Europe is strongly influenced by atmospheric and oceanic circulation changes over the North Atlantic.

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