Six-fold increase in historical Northern Hemisphere concurrent large heatwaves driven by warming and changing atmospheric circulations

2021 ◽  
pp. 1-39
Author(s):  
Cassandra D.W. Rogers ◽  
Kai Kornhuber ◽  
Sarah E. Perkins-Kirkpatrick ◽  
Paul C. Loikith ◽  
Deepti Singh
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Warm Season ◽  
Fold Increase ◽  
Circulation Pattern ◽  
Positive Influence ◽  
Climate Risks ◽  
Circulation Patterns ◽  
Multiple Regions ◽  
Barents And Kara Seas

AbstractSimultaneous heatwaves affecting multiple regions (referred to as concurrent heatwaves), pose compounding threats to various natural and societal systems, including global food chains, emergency response systems, and reinsurance industries. While anthropogenic climate change is increasing heatwave risks across most regions, the interactions between warming and circulation changes that yield concurrent heatwaves remain understudied. Here, we quantify historical (1979-2019) trends in concurrent heatwaves during the warm-season (May-September, MJJAS) across the Northern Hemisphere mid- to high-latitudes. We find a significant increase of ~46% in the mean spatial extent of concurrent heatwaves, ~17% increase in their maximum intensity, and ~6-fold increase in their frequency. Using Self-Organising Maps, we identify large-scale circulation patterns (300 hPa) associated with specific concurrent heatwave configurations across Northern Hemisphere regions. We show that observed changes in the frequency of specific circulation patterns preferentially increase the risk of concurrent heatwaves across particular regions. Patterns linking concurrent heatwaves across eastern North America, eastern and northern Europe, parts of Asia, and the Barents and Kara Seas, show the largest increases in frequency (~5.9 additional days per decade). We also quantify the relative contributions of circulation pattern changes and warming to overall observed concurrent heatwave day frequency trends. While warming has a predominant and positive influence on increasing concurrent heatwaves, circulation pattern changes have a varying influence and account for up to 0.8 additional concurrent heatwave days per decade. Identifying regions with an elevated risk of concurrent heatwaves and understanding their drivers is indispensable for evaluating projected climate risks on interconnected societal systems and fostering regional preparedness in a changing climate.

scholarly journals Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleo-climate simulations

2013 ◽  
Vol 9 (4) ◽  
pp. 3825-3870
Author(s):  
N. Merz ◽  
C. C. Raible ◽  
H. Fischer ◽  
V. Varma ◽  
M. Prange ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Circulation Pattern ◽  
Local Flow ◽  
Large Scale Circulation ◽  
Circulation Patterns ◽  
Local Accumulation

Abstract. Accumulation and aerosol chemistry records from Greenland ice cores offer the potential to reconstruct variability in Northern Hemisphere atmospheric circulation over the last millennia. However, an important prerequisite for a reconstruction is the stable relationship between local accumulation at the ice core site with the respective circulation pattern throughout the reconstruction period. We address this stability issue by using a comprehensive climate model and performing time-slice simulations for the present, the pre-industrial, the early Holocene and the last glacial maximum (LGM). The relationships between accumulation, precipitation and atmospheric circulation are investigated on on various time-scales. The analysis shows that the relationship between local accumulation on the Greenland ice sheet and the large-scale circulation undergoes a significant seasonal cycle. As the weights of the individual seasons change, annual mean accumulation variability is not necessarily related to the same atmospheric circulation patterns during the different climate states. Within a season, local Greenland accumulation variability is indeed linked to a consistent circulation pattern, which is observed for all studied climate periods, even for the LGM, however these circulation patterns are specific for different regions on the Greenland ice sheet. The simulated impact of orbital forcing and changes in the ice-sheet topography on accumulation exhibits strong spatial variability emphasizing that accumulation records from different ice core sites cannot be expected to look alike since they include a distinct local signature. Accumulation changes between different climate periods are dominated by changes in the amount of snowfall and are driven by both thermodynamic and dynamic factors. The thermodynamic impact determines the strength of the hydrological cycle, and warmer temperatures are generally accompanied by an increase in Greenland precipitation. Dynamical drivers of accumulation changes are the large-scale circulation and the local orography having a distinct influence on the local flow characteristic and hence the amount of precipitation deposited in any Greenland region.

scholarly journals Storylines of the 2018 Northern Hemisphere heat wave at pre-industrial and higher global warming levels

2020 ◽  
Author(s):  
Kathrin Wehrli ◽  
Mathias Hauser ◽  
Sonia I. Seneviratne
Keyword(s):  
Global Warming ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Heat Waves ◽  
Circulation Pattern ◽  
Community Earth System Model ◽  
Anomalous Atmospheric Circulation ◽  
Simultaneous Heat ◽  
Different Levels

<p>The 2018 summer was unusually hot in large areas of the Northern Hemisphere and simultaneous heat waves on three continents led to major impacts to agriculture and society. The event was driven by the anomalous atmospheric circulation pattern during that summer and it was only possible in a climate with global warming. There are indications that in a future, warmer climate similar events might occur regularly, affecting major ‘breadbasket’ regions of the Northern Hemisphere.</p><p>This study aims to understand the role of climate change for driving the intensity of the 2018 summer and to explore the sensitivity to changing warming levels. Model simulations are performed using the Community Earth System Model to investigate storylines for the extreme 2018 summer given the observed atmospheric large-scale circulation but different levels of background global warming: no human imprint, the 2018 conditions, and different mean global warming levels (1.5°C, 2°C, 3°C, and 4°C). The storylines explore the consequences of the event in an alternative warmer or colder world and thus help to increase our understanding of the drivers involved. The results reveal a strong contribution by the present-day level of global warming and provide an outlook to similar events in a possible future climate.</p>

scholarly journals Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain

2005 ◽  
Vol 18 (13) ◽  
pp. 2308-2329 ◽  
Author(s):  
S. Rutherford ◽  
M. E. Mann ◽  
T. J. Osborn ◽  
K. R. Briffa ◽  
P D. Jones ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Warm Season ◽  
Cold Season ◽  
Target Domain ◽  
Proxy Data ◽  
Mean Temperature ◽  
Reconstructed Temperature ◽  
Temperature Reconstructions ◽  
Methodological Considerations

Abstract Results are presented from a set of experiments designed to investigate factors that may influence proxy-based reconstructions of large-scale temperature patterns in past centuries. The factors investigated include 1) the method used to assimilate proxy data into a climate reconstruction, 2) the proxy data network used, 3) the target season, and 4) the spatial domain of the reconstruction. Estimates of hemispheric-mean temperature are formed through spatial averaging of reconstructed temperature patterns that are based on either the local calibration of proxy and instrumental data or a more elaborate multivariate climate field reconstruction approach. The experiments compare results based on the global multiproxy dataset used by Mann and coworkers, with results obtained using the extratropical Northern Hemisphere (NH) maximum latewood tree-ring density set used by Briffa and coworkers. Mean temperature reconstructions are compared for the full NH (Tropics and extratropics, land and ocean) and extratropical continents only, withvarying target seasons (cold-season half year, warm-season half year, and annual mean). The comparisons demonstrate dependence of reconstructions on seasonal, spatial, and methodological considerations, emphasizing the primary importance of the target region and seasonal window of the reconstruction. The comparisons support the generally robust nature of several previously published estimates of NH mean temperature changes in past centuries and suggest that further improvements in reconstructive skill are most likely to arise from an emphasis on the quality, rather than quantity, of available proxy data.

A 300-year high resolution Greenland ice record of large-scale atmospheric pollution by arsenic in the Northern Hemisphere

2020 ◽  
Author(s):  
Khanghyun Lee ◽  
Changhee Han ◽  
Seong-Joon Jun ◽  
Jong Ik Lee ◽  
Sungmin Hong
Keyword(s):  
High Resolution ◽  
Northern Hemisphere ◽  
Atmospheric Pollution ◽  
Large Scale ◽  
18Th Century ◽  
Fold Increase ◽  
Mean Value ◽  
Subsequent Increase ◽  
The Great Depression ◽  
The First World War

<p>We report the first high-resolution record of arsenic (As) observed in Greenland snow and ice for the periods 1711 to 1970 and 2003 to 2009 AD. The results show well-defined large-scale atmospheric pollution by this toxic element in the Northern Hemisphere, beginning as early as the 18th century. The most striking feature is an abrupt, unprecedented enrichment factor (EF) peak in the late 1890s, with a ~30-fold increase in the mean value above the Holocene natural level. Highly enriched As was evident until the late 1910s; a sharp decline was observed after the First World War, reaching a minimum in the early 1930s during the Great Depression. A subsequent increase lasted until the mid-1950s, before decreasing again. Comparisons between the observed variations and Cu smelting data indicate that Cu smelting in Europe and North America was the likely source of early anthropogenic As in Greenland. Despite a significant reduction of ~80% in concentration and ~60% in EF from the 1950s to the 2000s, more than 80% of present-day As in Greenland is of anthropogenic origin, probably due to increasing As emissions from coal combustion in China. This highlights the demand for the implementation of national and international environmental regulations to further reduce As emissions.</p>

scholarly journals Linking large-scale circulation patterns to low-cloud properties

2020 ◽  
Vol 20 (12) ◽  
pp. 7125-7138
Author(s):  
Timothy W. Juliano ◽  
Zachary J. Lebo
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Marine Boundary Layer ◽  
Warm Season ◽  
Cloud Droplet ◽  
Synoptic Scale ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Circulation Patterns ◽  
Satellite Retrievals

Abstract. The North Pacific High (NPH) is a fundamental meteorological feature present during the boreal warm season. Marine boundary layer (MBL) clouds, which are persistent in this oceanic region, are influenced directly by the NPH. In this study, we combine 11 years of reanalysis and an unsupervised machine learning technique to examine the gamut of 850 hPa synoptic-scale circulation patterns. This approach reveals two distinguishable regimes – a dominant NPH setup and a land-falling cyclone – and in between a spectrum of large-scale patterns. We then use satellite retrievals to elucidate for the first time the explicit dependence of MBL cloud properties (namely cloud droplet number concentration, liquid water path, and shortwave cloud radiative effect – CRESW) on 850 hPa circulation patterns over the northeast Pacific Ocean. We find that CRESW spans from −146.8 to −115.5 W m−2, indicating that the range of observed MBL cloud properties must be accounted for in global and regional climate models. Our results demonstrate the value of combining reanalysis and satellite retrievals to help clarify the relationship between synoptic-scale dynamics and cloud physics.

scholarly journals Impact of Climate Variability on Climate Beach-Based Tourism Aptitude: A Case Study in the Atlantic Coast of SW Europe

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1328
Author(s):  
Domingo F. Rasilla
Keyword(s):  
Large Scale ◽  
Atlantic Coast ◽  
Circulation Pattern ◽  
Spatial And Temporal Variability ◽  
Western Coast ◽  
English Channel ◽  
Pca Analysis ◽  
Pattern Approach ◽  
Circulation Patterns

The spatial and temporal variability of the summer (July–August) climate beach-based tourism aptitude along the Atlantic coast of SW Europe from 1973 to 2017 and its links with the atmospheric circulation has been analyzed, combining an empirical index and a circulation pattern approach. Three different coastal sectors were defined from a PCA analysis: Galicia-N of Portugal, the Gulf of Biscay, and the western coast of France and the English Channel. Each region experienced a contrasted evolution due to geographical factors such as latitude, orography and exposure to the prevailing circulation patterns. No significant increase in aptitude was found because the background warming has not been balanced by trends in cloudiness or precipitation. Several possible causes are discussed, from local to large-scale, such as the recent evolution of the summer NAO pattern impacting the northernmost region.

scholarly journals Linking large-scale circulation patterns to low-cloud properties

2019 ◽  
Author(s):  
Timothy W. Juliano ◽  
Zachary J. Lebo
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Climate Models ◽  
Marine Boundary Layer ◽  
Warm Season ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Synoptic Scale ◽  
Cloud Properties ◽  
Circulation Patterns

Abstract. The North Pacific High (NPH) is a fundamental meteorological feature present during the boreal warm season. Marine boundary layer (MBL) clouds, which are persistent in this oceanic region, are influenced directly by the NPH. In this study, we combine 11 years of reanalysis and an unsupervised machine learning technique to examine the gamut of 850-hPa synoptic-scale circulation patterns. This approach, which yields the frequency at which these regimes occur, reveals two distinguishable patterns – a dominant NPH setup and a land-falling cyclone – and in between a spectrum of regimes. We then use satellite retrievals to elucidate for the first time the explicit dependence of MBL cloud properties (namely cloud droplet number concentration and cloud droplet effective radius) on 850-hPa circulation patterns over the northeast Pacific Ocean. Moreover, we find that shortwave cloud radiative forcing ranges from − 144.0 to − 117.5 W/m2, indicating that the range of MBL cloud properties must be accounted for in global and regional climate models. Our results demonstrate the value of combining reanalysis and satellite observations to help clarify the relationship between synoptic-scale dynamics and cloud microphysics.

scholarly journals Effect of the El Niño Decaying Pace on the East Asian Summer Monsoon Circulation Pattern during Post-El Niño Summers

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 140
Author(s):  
Wenping Jiang ◽  
Gen Li ◽  
Gongjie Wang
Keyword(s):  
El Niño ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
El Nino ◽  
East Asian ◽  
Circulation Pattern ◽  
Northwest Pacific ◽  
Monsoon Circulation ◽  
Circulation Patterns ◽  
Sst Anomalies

El Niño events vary from case to case with different decaying paces. In this study, we demonstrate that the different El Niño decaying paces have distinct impacts on the East Asian monsoon circulation pattern during post-El Niño summers. For fast decaying (FD) El Niño summers, a large-scale anomalous anticyclone dominates over East Asia and the North Pacific from subtropical to mid-latitude; whereas, the East Asian monsoon circulation display a dipole pattern with anomalous northern cyclone and southern anticyclone for slow decaying (SD) El Niño summers. The difference in anomalous East Asian monsoon circulation patterns was closely associated with the sea surface temperature (SST) anomaly patterns in the tropics. In FD El Niño summers, the cold SST anomalies in the tropical central-eastern Pacific and warm SST anomalies in the Maritime Continent induce the anticyclone anomalies over the Northwest Pacific. In contrast, the warm Kelvin wave anchored over the tropical Indian Ocean during SD El Niño summers plays a crucial role in sustaining the anticyclone anomalies over the Northwest Pacific. In particular, the opposite atmospheric circulation anomaly patterns over Northeast Asia and the mid-latitude North Pacific are mainly modulated by the stationary Rossby wave trains triggered by the opposite SST anomalies in the tropical eastern Pacific during FD and SD El Niño summers. Finally, the effect of distinct summer monsoon circulation patterns associated with the El Niño decay pace on the summer climate over East Asia are also discussed.

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