A Robust Intensification of Wintertime Jet Stream Extremes in Future Climates

2021 ◽  
Author(s):  
Ben Harvey
Keyword(s):  
North America ◽  
North Atlantic ◽  
Western Europe ◽  
Subsequent Development ◽  
Jet Stream ◽  
Wind Speeds ◽  
The North ◽  
Sequence Of Events ◽  
The North Atlantic ◽  
Jet Streak

<p>The east coast of North America experienced a record-breaking jet stream event on 20 Feb 2019, with peak wind speeds exceeding 110 m/s observed by weather balloons over Nova Scotia. At the time this was the strongest wind speed ever recorded over North America. The extreme `jet streak' propagated out over the North Atlantic where it played a key role in the subsequent development of a large and rapidly deepening cyclone on 22 Feb 2019. The cyclone had little societal impact because it did not make landfall. It did however act to amplify a large scale Rossby wave, producing a strong poleward advection of warm air towards western Europe, and leading to record-breaking February warmth in several European countries on 27 Feb 2019. The whole sequence of events took just over a week to complete.</p><p>This case provides an illustration of how climate extremes (here the record warmth in western Europe) are often the result of complex and chaotic nonlinear interactions of the atmosphere on weather timescales. The particular sequence of events is not uncommon, but both the strength of the initial jet streak over North America and the resulting temperatures in Europe were. Given the observed trend in surface temperatures, it seems likely that the temperatures were at least partly enhanced in a passive way by the warming climate. A more difficult question to answer is whether climate change is also impacting the frequency or amplitude of the preceding sequence of weather events. As a first step to answering this question, this study asks the question: do we expect extreme jet streak events to intensify in future?</p><p>Based on an analysis of CMIP simulations over the North Atlantic, we find a robust intensification of wintertime jet extremes in future climates, with the strongest instantaneous wind speeds increasing in every model. This contrasts with the strength of the time mean jet streams, which do not exhibit a robust change across the ensemble. Possible reasons for the differing behaviour of the mean winds and the extreme winds are discussed and a hypothesis is suggested to explain the robust increase in the latter.</p>

Seasonal Predictability of Wintertime mid-latitude Cyclonic Activity over the North Atlantic and Europe

2021 ◽  
Author(s):  
Alvise Aranyossy ◽  
Sebastian Brune ◽  
Lara Hellmich ◽  
Johanna Baehr
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Jet Stream ◽  
Cyclonic Activity ◽  
Max Planck ◽  
Pressure System ◽  
Wind Speeds ◽  
Average Lifespan ◽  
The North ◽  
The North Atlantic

<p>We analyse the connections between the wintertime North Atlantic Oscillation (NAO), the eddy-driven jet stream with the mid-latitude cyclonic activity over the North Atlantic and Europe. We investigate, through the comparison against ECMWF ERA5 and hindcast simulations from the Max Planck Institute Earth System Model (MPI-ESM), the potential for enhancement of the seasonal prediction skill of the Eddy Kinetic Energy (EKE) by accounting for the connections between large-scale climate and the regional cyclonic activity. Our analysis focuses on the wintertime months (December-March) in the 1979-2019 period, with seasonal predictions initialized every November 1st. We calculate EKE from wind speeds at 250 hPa, which we use as a proxy for cyclonic activity. The zonal and meridional wind speeds are bandpass filtered with a cut-off at 3-10 days to fit with the average lifespan of mid-latitude cyclones. </p><p>Preliminary results suggest that in ERA5, major positive anomalies in EKE, both in quantity and duration, are correlated with a northern position of the jet stream and a positive phase of the NAO. Apparently, a deepened Icelandic low-pressure system offers favourable conditions for mid-latitude cyclones in terms of growth and average lifespan. In contrast, negative anomalies in EKE over the North Atlantic and Central Europe are associated with a more equatorward jet stream, these are also linked to a negative phase of the NAO.  Thus, in ERA5, the eddy-driven jet stream and the NAO play a significant role in the spatial and temporal distribution of wintertime mid-latitude cyclonic activity over the North Atlantic and Europe. We extend this connection to the MPI-ESM hindcast simulations and present an analysis of their predictive skill of EKE for wintertime months.</p>

scholarly journals The Antecedent Large-Scale Conditions of the “Perfect Storms” of Late October and Early November 1991

2010 ◽  
Vol 138 (7) ◽  
pp. 2546-2569 ◽  
Author(s):  
Jason M. Cordeira ◽  
Lance F. Bosart
Keyword(s):  
North America ◽  
Kinetic Energy ◽  
North Atlantic ◽  
North Pacific ◽  
Large Scale ◽  
Baroclinic Instability ◽  
Subsequent Development ◽  
Eddy Kinetic Energy ◽  
The North ◽  
The North Atlantic

Abstract The “Perfect Storms” (PSs) were a series of three high-impact extratropical cyclones (ECs) that impacted North America and the North Atlantic in late October and early November 1991. The PSs included the Perfect Storm in the northwest Atlantic, a second EC over the North Atlantic that developed from the interaction of the PS with Hurricane Grace, and a third EC over North America commonly known as the “1991 Halloween Blizzard.” The PSs greatly impacted the North Atlantic and North America with large waves, coastal flooding, heavy snow, and accumulating ice, and they also provided an opportunity to investigate the physical processes that contributed to a downstream baroclinic development (DBD) episode across North America that culminated in the ECs. Downstream baroclinic development resulted from an amplification of the large-scale flow over the North Pacific that was influenced by anomalous tropical convection, the recurvature and extratropical transition of western North Pacific Tropical Cyclones Orchid, Pat, and Ruth, and the subsequent evolution of the extratropical flow. The progression of DBD occurred following the development of a negative PNA regime and the generation of baroclinic instability over North America associated with equatorward-displaced potential vorticity anomalies and poleward-displaced corridors of high moisture content. An analysis of the eddy kinetic energy tendency equation demonstrated that the resulting baroclinic conversion of eddy available potential energy into eddy kinetic energy during the cyclogenesis process facilitated the progression of DBD across North America and the subsequent development of the ECs.

NATO and Its Commentators: The First Five Years

1954 ◽  
Vol 8 (4) ◽  
pp. 447-467 ◽  
Author(s):  
Lawrence S. Kaplan
Keyword(s):  
World War Ii ◽  
North America ◽  
United Nations ◽  
North Atlantic ◽  
Western Europe ◽  
North Atlantic Treaty Organization ◽  
World War ◽  
Armed Attack ◽  
The North ◽  
The North Atlantic

The signing of the North Atlantic Treaty on April 4, 1949, gave rise to a number of books and articles on the North Atlantic Treaty Organization (NATO) the volume of which will probably continue for some time. The treaty and the organization that it created represent the clearest challenge to Soviet expansionism since the end of World War II. Through this action twelve nations of North America and western Europe resolved to consider an armed attack against one member an attack against them all, and to create sufficient stiength within the alliance to deter potential aggressors. But NATO's continuing interest to commentators stems from reasons other than its value as a weapon against the spread of communism. To some writers NATO appears to be a stimulant that would revive a moribund United Nations, to others it is the beginning of a new kind of alliance unprecedented in history, to still others, it is a symbol of America's rejection of isolationism. So vague are some of the treaty's articles and so rapid has been the evolution of the organization that almost any observer could derive whatever meaning he wishes out of NATO's development.

scholarly journals The North Atlantic Waveguide and Downstream Impact Experiment

2018 ◽  
Vol 99 (8) ◽  
pp. 1607-1637 ◽  
Author(s):  
Andreas Schäfler ◽  
George Craig ◽  
Heini Wernli ◽  
Philippe Arbogast ◽  
James D. Doyle ◽  
...  
Keyword(s):  
North Atlantic ◽  
Subsequent Development ◽  
Jet Stream ◽  
Atmospheric Measurements ◽  
Weather Impact ◽  
The North ◽  
Impact Experiment ◽  
Research Aircraft ◽  
The North Atlantic ◽  
The Impact

AbstractThe North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.

scholarly journals The Impact of Land-Ocean Contrast on The Seasonal To Decadal Variability of The Northern Hemisphere Jet Stream

2021 ◽  
Author(s):  
Samantha Hallam ◽  
Simon Josey ◽  
Gerard McCarthy ◽  
Joel Hirschi
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Jet Stream ◽  
Latitude Range ◽  
The North ◽  
Regional Basis ◽  
The North Atlantic ◽  
The North Pacific

Abstract Seasonal to decadal variations in Northern Hemisphere jet stream latitude and speed over land (Eurasia, North America) and oceanic (North Atlantic, North Pacific) regions are presented for the period 1871 – 2011 from the Twentieth Century Reanalysis dataset. Significant regional differences are seen on seasonal to decadal timescales. The ocean acts to reduce the seasonal jet latitude range from 20° over Eurasia to 10° over the North Atlantic where the ocean meridional heat transport is greatest. The mean jet latitude range is at a minimum in winter (DJF), along the western boundary of the North Pacific and North Atlantic, where the land-sea contrast and SST gradients are strongest. The 141-year trends in jet latitude and speed show differences on a regional basis. The North Atlantic has significant increasing jet latitude trends in all seasons, up to 3° in winter. Eurasia has significant increasing trends in winter and summer, however, no increase is seen across the North Pacific or North America. Jet speed shows significant increases evident in winter (up to 4.7ms -1 ), spring and autumn over the North Atlantic, Eurasia and North America however, over the North Pacific no increase is observed. Long term trends are generally overlaid by multidecadal variability, particularly evident in the North Pacific, where 20-year variability in jet latitude and jet speed are seen, associated with the Pacific Decadal Oscillation which explains 50% of the winter variance in jet latitude since 1940. Northern hemisphere jet variability and trends differ on a regional basis (North Atlantic, North Pacific, Eurasia and America) on seasonal to decadal timescales, indicating different mechanisms are influencing the jet latitude and speed. It is important that the differing regional trends and mechanisms are incorporated into climate models and predictions.

Notes on Power Operated Controls for Large Aircraft

1945 ◽  
Vol 49 (410) ◽  
pp. 51-54
Author(s):  
A. Gouge
Keyword(s):  
North America ◽  
North Atlantic ◽  
The North ◽  
The World ◽  
The North Atlantic ◽  
Large Aircraft

A Study of the air routes of the world brings out almost at once the fact that some of the most difficult route are also the most attractive. For instance, the North Atlantic route which couples North America with Europe is certainly one of the most difficult in the world, but also by the fact that it couples two of the most densely populated, as well as the most wealthy groups of people in the world, one of the most attractive.

Edges and interactions beyond Europe

2018 ◽  
Author(s):  
Peter S. Wells ◽  
Naoise Mac Sweeney
Keyword(s):  
North America ◽  
Iron Age ◽  
North Atlantic ◽  
Cultural Practices ◽  
Raw Materials ◽  
Long Distance ◽  
The North ◽  
First Millennium ◽  
Temperate Europe ◽  
The North Atlantic

Iron Age Europe, once studied as a relatively closed, coherent continent, is being seen increasingly as a dynamic part of the much larger, interconnected world. Interactions, direct and indirect, with communities in Asia, Africa, and, by the end of the first millennium AD, North America, had significant effects on the peoples of Iron Age Europe. In the Near East and Egypt, and much later in the North Atlantic, the interactions can be linked directly to historically documented peoples and their rulers, while in temperate Europe the evidence is exclusively archaeological until the very end of the prehistoric Iron Age. The evidence attests to often long-distance interactions and their effects in regard to the movement of peoples, and the introduction into Europe of raw materials, crafted objects, styles, motifs, and cultural practices, as well as the ideas that accompanied them.

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