Northern Hemisphere Jet Stream Position Indices as Diagnostic Tools for Climate and Ecosystem Dynamics

Abstract The latitudinal position of the Northern Hemisphere jet stream (NHJ) modulates the occurrence and frequency of extreme weather events. Precipitation anomalies in particular are associated with NHJ variability; the resulting floods and droughts can have considerable societal and economic impacts. This study develops a new climatology of the 300-hPa NHJ using a bottom-up approach based on seasonally explicit latitudinal NHJ positions. Four seasons with coherent NHJ patterns were identified (January–February, April–May, July–August, and October–November), along with 32 longitudinal sectors where the seasonal NHJ shows strong spatial coherence. These 32 longitudinal sectors were then used as NHJ position indices to examine the influence of seasonal NHJ position on the geographical distribution of NH precipitation and temperature variability and their link to atmospheric circulation pattern. The analyses show that the NHJ indices are related to broad-scale patterns in temperature and precipitation variability, in terrestrial vegetation productivity and spring phenology, and can be used as diagnostic/prognostic tools to link ecosystem and socioeconomic dynamics to upper-level atmospheric patterns.

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Evidence linking rapid Arctic warming to mid-latitude weather patterns

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2014.0170 ◽

2015 ◽

Vol 373 (2045) ◽

pp. 20140170 ◽

Cited By ~ 62

Author(s):

Jennifer Francis ◽

Natasa Skific

Keyword(s):

Northern Hemisphere ◽

Weather Conditions ◽

Extreme Weather Events ◽

Jet Stream ◽

Self Organizing Maps ◽

Arctic Warming ◽

Scientific Debate ◽

Weather Patterns ◽

Enhanced Sensitivity ◽

Active Research

The effects of rapid Arctic warming and ice loss on weather patterns in the Northern Hemisphere is a topic of active research, lively scientific debate and high societal impact. The emergence of Arctic amplification—the enhanced sensitivity of high-latitude temperature to global warming—in only the last 10–20 years presents a challenge to identifying statistically robust atmospheric responses using observations. Several recent studies have proposed and demonstrated new mechanisms by which the changing Arctic may be affecting weather patterns in mid-latitudes, and these linkages differ fundamentally from tropics/jet-stream interactions through the transfer of wave energy. In this study, new metrics and evidence are presented that suggest disproportionate Arctic warming—and resulting weakening of the poleward temperature gradient—is causing the Northern Hemisphere circulation to assume a more meridional character (i.e. wavier), although not uniformly in space or by season, and that highly amplified jet-stream patterns are occurring more frequently. Further analysis based on self-organizing maps supports this finding. These changes in circulation are expected to lead to persistent weather patterns that are known to cause extreme weather events. As emissions of greenhouse gases continue unabated, therefore, the continued amplification of Arctic warming should favour an increased occurrence of extreme events caused by prolonged weather conditions.

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Extreme weather events on seasonal and intraseasonal timescales in the context of climate change

Hydrometeorological research and forecasting ◽

10.37162/2618-9631-2021-1-36-57 ◽

2021 ◽

pp. 36-57

Author(s):

D.B. Kiktev ◽

◽

E.N. Kruglova ◽

I.A. Kulikova ◽

A.V. Muravev ◽

...

Keyword(s):

Climate Change ◽

Long Range ◽

Northern Hemisphere ◽

Extreme Events ◽

Extreme Weather ◽

Extreme Weather Events ◽

Weather Forecasts ◽

Temperature And Precipitation ◽

Weather Events ◽

Precipitation Regimes

The automatic identification of objects associated with various extreme weather events (EWE) on seasonal and intraseasonal timescales is done based on surface air temperature and precipitation datasets (NCEP/NCAR daily reanalysis fields for the Northern Hemisphere). Some features of the spatial and temporal variability of the extreme characteristics of temperature and precipitation regimes are considered in the context of climate change. An inventory of extreme events is carried out for the Northern Hemisphere in 1981–2019 depending on the spatial extent, duration, and intensity of EWEs. The years with the most striking events are noted, and a brief description of their specific features is given. The results will be used to analyze the EWE predictability in the context of the verification of long-range weather forecasts. Keywords: extreme weather events, climate change, identification of extreme events, long-range weather forecasts

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Spatial variations in the warming trend and the transition to more severe weather in midlatitudes

Scientific Reports ◽

10.1038/s41598-020-80701-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Francisco Estrada ◽

Dukpa Kim ◽

Pierre Perron

Keyword(s):

Radiative Forcing ◽

Warming Trend ◽

Severe Weather ◽

Montreal Protocol ◽

The Arctic ◽

Extreme Weather Events ◽

Jet Stream ◽

Atmospheric Blocking ◽

Regional Warming ◽

Weather Events

AbstractDue to various feedback processes called Arctic amplification, the high-latitudes’ response to increases in radiative forcing is much larger than elsewhere in the world, with a warming more than twice the global average. Since the 1990’s, this rapid warming of the Arctic was accompanied by no-warming or cooling over midlatitudes in the Northern Hemisphere in winter (the hiatus). The decrease in the thermal contrast between Arctic and midlatitudes has been connected to extreme weather events in midlatitudes via, e.g., shifts in the jet stream towards the equator and increases in the probability of high-latitude atmospheric blocking. Here we present an observational attribution study showing the spatial structure of the response to changes in radiative forcing. The results also connect the hiatus with diminished contrast between temperatures over regions in the Arctic and midlatitudes. Recent changes in these regional warming trends are linked to international actions such as the Montreal Protocol, and illustrate how changes in radiative forcing can trigger unexpected responses from the climate system. The lesson for climate policy is that human intervention with the climate is already large enough that even if stabilization was attained, impacts from an adjusting climate are to be expected.

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Seasonal biological carryover dominates northern vegetation growth

Nature Communications ◽

10.1038/s41467-021-21223-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Xu Lian ◽

Shilong Piao ◽

Anping Chen ◽

Kai Wang ◽

Xiangyi Li ◽

...

Keyword(s):

Northern Hemisphere ◽

Growing Season ◽

Ecosystem Dynamics ◽

Environmental Drivers ◽

Subsequent Growth ◽

Ecosystem Models ◽

Carryover Effect ◽

Vegetation Growth ◽

Sequestration Potential ◽

Future Warming

AbstractThe state of ecosystems is influenced strongly by their past, and describing this carryover effect is important to accurately forecast their future behaviors. However, the strength and persistence of this carryover effect on ecosystem dynamics in comparison to that of simultaneous environmental drivers are still poorly understood. Here, we show that vegetation growth carryover (VGC), defined as the effect of present states of vegetation on subsequent growth, exerts strong positive impacts on seasonal vegetation growth over the Northern Hemisphere. In particular, this VGC of early growing-season vegetation growth is even stronger than past and co-occurring climate on determining peak-to-late season vegetation growth, and is the primary contributor to the recently observed annual greening trend. The effect of seasonal VGC persists into the subsequent year but not further. Current process-based ecosystem models greatly underestimate the VGC effect, and may therefore underestimate the CO2 sequestration potential of northern vegetation under future warming.

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Legacy effects of spring phenology on vegetation growth under preseason meteorological drought in the Northern Hemisphere

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2021.108630 ◽

2021 ◽

Vol 310 ◽

pp. 108630

Author(s):

Zhaoqi Zeng ◽

Wenxiang Wu ◽

Quansheng Ge ◽

Zhaolei Li ◽

Xiaoyue Wang ◽

...

Keyword(s):

Northern Hemisphere ◽

Meteorological Drought ◽

Legacy Effects ◽

Spring Phenology ◽

Vegetation Growth

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

Journal of Climate ◽

10.1175/jcli-d-21-0200.1 ◽

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.

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Ionospheric response to winter stratosphere/lower mesosphere jet stream in the Northern Hemisphere as derived from vertical radio sounding data

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2017.08.033 ◽

2018 ◽

Vol 180 ◽

pp. 126-136 ◽

Cited By ~ 4

Author(s):

M.A. Chernigovskaya ◽

B.G. Shpynev ◽

K.G. Ratovsky ◽

A.Yu. Belinskaya ◽

A.E. Stepanov ◽

...

Keyword(s):

Northern Hemisphere ◽

Jet Stream ◽

Ionospheric Response ◽

Radio Sounding

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Multi-model dynamic climate emulator for solar geoengineering

10.5194/acp-2016-535 ◽

2016 ◽

Author(s):

Douglas G. MacMartin ◽

Ben Kravitz

Keyword(s):

Sea Ice ◽

Northern Hemisphere ◽

General Circulation ◽

Circulation Model ◽

Nonlinear Effects ◽

Accurate Estimate ◽

Natural Variability ◽

Sea Ice Extent ◽

Temperature And Precipitation ◽

Solar Geoengineering

Abstract. Climate emulators trained on existing simulations can be used to project the climate effects that would result from different possible future pathways of anthropogenic forcing, without relying on general circulation model (GCM) simulations for every possible pathway. We extend this idea to include different amounts of solar geoengineering in addition to different pathways of green-house gas concentrations by training emulators from a multi-model ensemble of simulations from the Geoengineering Model Intercomparison Project (GeoMIP). The emulator is trained on the abrupt 4 x CO2 and a compensating solar reduction simulation (G1), and evaluated by comparing predictions against a simulated 1 % per year CO2 increase and a similarly smaller solar reduction (G2). We find reasonable agreement in most models for predicting changes in temperature and precipitation (including regional effects), and annual-mean Northern hemisphere sea ice extent, with the difference between simulation and prediction typically smaller than natural variability. This verifies that the linearity assumption used in constructing the emulator is sufficient for these variables over the range of forcing considered. Annual-minimum Northern hemisphere sea ice extent is less-well predicted, indicating the limits of the linearity assumption. For future pathways involving relatively small forcing from solar geoengineering, the errors introduced from nonlinear effects may be smaller than the uncertainty due to natural variability, and the emulator prediction may be a more accurate estimate of the forced component of the models' response than an actual simulation would be.

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Summer Westerly Jet in Northern Hemisphere during the Mid-Holocene: A Multi-Model Study

Atmosphere ◽

10.3390/atmos11111193 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1193

Author(s):

Chuchu Xu ◽

Mi Yan ◽

Liang Ning ◽

Jian Liu

Keyword(s):

Temperature Gradient ◽

Northern Hemisphere ◽

Hadley Cell ◽

Dynamic Processes ◽

Jet Stream ◽

Meridional Temperature Gradient ◽

The North ◽

Westerly Jet ◽

Poleward Shift ◽

Thermodynamic Processes

The upper-level jet stream, a narrow band of maximum wind speed in the mid-latitude westerlies, exerts a considerable influence on the global climate by modulating the transport and distribution of momentum, heat and moisture. In this study by using four high-resolution models in the Paleoclimate Modelling Intercomparison Project phase 3, the changes of position and intensity of the northern hemisphere westerly jet at 200 hPa in summer during the mid-Holocene (MH), as well as the related mechanisms, are investigated. The four models show similar performance on the westerly jet. At the hemispheric scale, the simulated westerly jet has a poleward shift during the MH compared to the preindustrial period. The warming in arctic and cooling in the tropics during the MH are caused by the orbital changes of the earth and the precipitation changes, and it could lead to the weakened meridional temperature gradient and pressure gradient, which might account for the poleward shift of the westerly jet from the thermodynamic perspective. From the dynamic perspective, two maximum centers of eddy kinetic energy are simulated over the North Pacific and North Atlantic with the north deviation, which could cause the northward movement of the westerly jet. The weakening of the jet stream is associated with the change of the Hadley cell and the meridional temperature gradient. The largest weakening is over the Pacific Ocean where both the dynamic and the thermodynamic processes have weakening effects. The smallest weakening is over the Atlantic Ocean, and it is induced by the offset effects of dynamic processes and thermodynamic processes. The weakening over the Eurasia is mainly caused by the dynamic processes.

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A Multiregion Model Evaluation and Attribution Study of Historical Changes in the Area Affected by Temperature and Precipitation Extremes

Journal of Climate ◽

10.1175/jcli-d-16-0164.1 ◽

2016 ◽

Vol 29 (23) ◽

pp. 8285-8299 ◽

Cited By ~ 9

Author(s):

Andrea J. Dittus ◽

David J. Karoly ◽

Sophie C. Lewis ◽

Lisa V. Alexander ◽

Markus G. Donat

Keyword(s):

North America ◽

Northern Hemisphere ◽

Minimum Temperature ◽

Climate Models ◽

Heavy Precipitation ◽

Precipitation Extremes ◽

Annual Precipitation ◽

Total Annual Precipitation ◽

Temperature And Precipitation ◽

Increasing Trends

Abstract The skill of eight climate models in simulating the variability and trends in the observed areal extent of daily temperature and precipitation extremes is evaluated across five large-scale regions, using the climate extremes index (CEI) framework. Focusing on Europe, North America, Asia, Australia, and the Northern Hemisphere, results show that overall the models are generally able to simulate the decadal variability and trends of the observed temperature and precipitation components over the period 1951–2005. Climate models are able to reproduce observed increasing trends in the area experiencing warm maximum and minimum temperature extremes, as well as, to a lesser extent, increasing trends in the areas experiencing an extreme contribution of heavy precipitation to total annual precipitation for the Northern Hemisphere regions. Using simulations performed under different radiative forcing scenarios, the causes of simulated and observed trends are investigated. A clear anthropogenic signal is found in the trends in the maximum and minimum temperature components for all regions. In North America, a strong anthropogenically forced trend in the maximum temperature component is simulated despite no significant trend in the gridded observations, although a trend is detected in a reanalysis product. A distinct anthropogenic influence is also found for trends in the area affected by a much-above-average contribution of heavy precipitation to annual precipitation totals for Europe in a majority of models and to varying degrees in other Northern Hemisphere regions. However, observed trends in the area experiencing extreme total annual precipitation and extreme number of wet and dry days are not reproduced by climate models under any forcing scenario.

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