Interaction of North Atlantic baroclinic wave packets and the Mediterranean storm track

2013 ◽  
Vol 140 (680) ◽  
pp. 754-765 ◽  
Author(s):  
F. Ahmadi-Givi ◽  
M. Nasr-Esfahany ◽  
A. R. Mohebalhojeh
Keyword(s):  
North Atlantic ◽  
Wave Packets ◽  
Storm Track ◽  
Baroclinic Wave ◽  
The Mediterranean

scholarly journals Midlatitude atmospheric circulation responses under 1.5 °C and 2.0 °C warming and implications for regional impacts

2017 ◽  
Author(s):  
Camille Li ◽  
Clio Michel ◽  
Lise Seland Graff ◽  
Ingo Bethke ◽  
Giuseppe Zappa ◽  
...  
Keyword(s):  
Climate Change ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
North American ◽  
Storm Track ◽  
Internal Variability ◽  
The North ◽  
Regional Impacts ◽  
The North Atlantic ◽  
The Mediterranean

Abstract. This study investigates the global response of the midlatitude atmospheric circulation to 1.5 °C and 2.0 °C of warming using the HAPPI Half a degree Additional warming, Projections, Prognosis and Impacts ensemble, with a focus on the winter season. Characterizing and understanding this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to the 1.5 °C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5 °C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equatorward intensification of the South Pacific jet. Signals that emerge under an additional 0.5 °C of warming include a poleward shift of the North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, western Europe and the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2.0 °C world, though the ensemble spread still allows for both wetting and drying responses.

Some physical drivers of changes in the winter storm tracks over the North Atlantic and Mediterranean during the Holocene

2010 ◽  
Vol 368 (1931) ◽  
pp. 5185-5223 ◽  
Author(s):  
David James Brayshaw ◽  
Brian Hoskins ◽  
Emily Black
Keyword(s):  
North Atlantic ◽  
General Circulation ◽  
Storm Track ◽  
Storm Tracks ◽  
The Holocene ◽  
The North ◽  
The North Atlantic ◽  
The Mediterranean ◽  
The Impact ◽  
Holocene Period

The winter climate of Europe and the Mediterranean is dominated by the weather systems of the mid-latitude storm tracks. The behaviour of the storm tracks is highly variable, particularly in the eastern North Atlantic, and has a profound impact on the hydroclimate of the Mediterranean region. A deeper understanding of the storm tracks and the factors that drive them is therefore crucial for interpreting past changes in Mediterranean climate and the civilizations it has supported over the last 12 000 years (broadly the Holocene period). This paper presents a discussion of how changes in climate forcing (e.g. orbital variations, greenhouse gases, ice sheet cover) may have impacted on the ‘basic ingredients’ controlling the mid-latitude storm tracks over the North Atlantic and the Mediterranean on intermillennial time scales. Idealized simulations using the HadAM3 atmospheric general circulation model (GCM) are used to explore the basic processes, while a series of timeslice simulations from a similar atmospheric GCM coupled to a thermodynamic slab ocean (HadSM3) are examined to identify the impact these drivers have on the storm track during the Holocene. The results suggest that the North Atlantic storm track has moved northward and strengthened with time since the Early to Mid-Holocene. In contrast, the Mediterranean storm track may have weakened over the same period. It is, however, emphasized that much remains still to be understood about the evolution of the North Atlantic and Mediterranean storm tracks during the Holocene period.

scholarly journals Midlatitude atmospheric circulation responses under 1.5 and 2.0 °C warming and implications for regional impacts

2018 ◽  
Vol 9 (2) ◽  
pp. 359-382 ◽  
Author(s):  
Camille Li ◽  
Clio Michel ◽  
Lise Seland Graff ◽  
Ingo Bethke ◽  
Giuseppe Zappa ◽  
...  
Keyword(s):  
Climate Change ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
North American ◽  
Storm Track ◽  
Internal Variability ◽  
The North ◽  
Regional Impacts ◽  
The North Atlantic ◽  
The Mediterranean

Abstract. This study investigates the global response of the midlatitude atmospheric circulation to 1.5 and 2.0 °C of warming using the HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) ensemble, with a focus on the winter season. Characterising and understanding this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to 1.5 °C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks, and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5 °C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equatorward intensification of the South Pacific jet. Signals that emerge under an additional 0.5 °C of warming include a poleward shift of the North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, in western Europe, and on the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2 °C warmer world, with exceptionally dry decades becoming 5 times more likely.

The impact of southward propagation of the upper-tropospheric Rossby wave activity on the Red Sea trough

2020 ◽  
Author(s):  
Zakieh Alizadeh ◽  
Alireza Mohebalhojeh ◽  
Farhang Ahmadi-Givi ◽  
Mohammad Mirzaei ◽  
Sakineh Khansalari
Keyword(s):  
Red Sea ◽  
Rossby Wave ◽  
North Atlantic ◽  
Storm Track ◽  
Wave Activity ◽  
The Mediterranean ◽  
Northeast Africa ◽  
Upper Level ◽  
Critical Phases ◽  
Wave Activity Flux

<p>The Red Sea Trough (RST) is an inverted trough of low-pressure system at lower tropospheric levels over the northeast Africa and the Red Sea. The previous research conducted on the RST suggests that when this system is activated, heavy rainfall occurs in large parts of the eastern Mediterranean and southwest Asia. The main aim of this article is to investigate the way Rossby wave activity at the upper level troposphere and its interaction with the lower tropospheric circulation activate the RST.</p><p>This study was carried out in three stages: first, the climatological behavior of RST in winter (December to February) was studied and then, cyclones were identified and tracked in the northeast Africa and the Red Sea using a cyclone tracking scheme. In the second stage, the Rossby wave activity flux at the 300 hPa level was considered in the region. Finally, the interaction between the wave activity flux and the RST was investigated. Two critical phases for the wave flux entering the region were considered. The positive (negative) critical phase corresponds to the period when the highest (lowest) values of the wave activity flux enter the northeast Africa and Red Sea regions. The results show that, during the positive critical phase, the RST strengthens and extends to the northeast of the Mediterranean Sea and cyclogenesis is increased in the northeast of Africa and especially in the northeast of the Red Sea. The main reasons for this phenomenon can be deduced as follows:</p><p>With regard to the divergence of wave activity flux and its southward flux, the source of energy and activity needed for cyclogenesis and reinforcement of the RST is provided by the flux convergence core of the North Atlantic storm track. The results of the wave activity time series show that part of the activity from the northeast is integrated with the convergence core of the Mediterranean storm track, leading to enhancement of the cyclones in the northeast of the Red Sea and the extension of the RST to the northeast. But most of the activity joins the flux divergence core of the Mediterranean storm track in the west of the region and results in amplification of Sudan’s cyclones and activation of the RST along both the meridional and zonal directions; the important point to consider is that the wave activity flux entering the region is greater in the zonal direction. In addition to the southward propagation of the wave activity, the packets of flux convergence and divergence in the central North Atlantic are tilted in the northeast–southwest direction, indicating the dominance of anticyclonic Rossby wave breaking. Associated with the upper-level wave activity fluxes entering the region, there is jet enhancement and low-level cold advection from higher latitudes to the tropical and subtropical regions. The difference of RST between the positive and negative critical phases is turned out to be statistically significant with confidence levels of greater than or equal to 90%.</p>

Downstream Suppression of Baroclinic Waves

2021 ◽  
Vol 34 (3) ◽  
pp. 919-930
Author(s):  
Lina Boljka ◽  
David W. J. Thompson ◽  
Ying Li
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
General Circulation ◽  
Wave Packets ◽  
Storm Track ◽  
Eddy Activity ◽  
Baroclinic Waves ◽  
The North ◽  
The North Pacific ◽  
Downstream Development

AbstractBaroclinic waves drive both regional variations in weather and large-scale variability in the extratropical general circulation. They generally do not exist in isolation, but rather often form into coherent wave packets that propagate to the east via a mechanism called downstream development. Downstream development has been widely documented and explored. Here we document a novel but also key aspect of baroclinic waves: the downstream suppression of baroclinic activity that occurs in the wake of eastward propagating disturbances. Downstream suppression is apparent not only in the Southern Hemisphere storm track as shown in previous work, but also in the North Pacific and North Atlantic storm tracks. It plays an essential role in driving subseasonal periodicity in extratropical eddy activity in both hemispheres, and gives rise to the observed quiescence of the North Atlantic storm track 1–2 weeks following pronounced eddy activity in the North Pacific sector. It is argued that downstream suppression results from the anomalously low baroclinicity that arises as eastward propagating wave packets convert potential to kinetic energy. In contrast to baroclinic wave packets, which propagate to the east at roughly the group velocity in the upper troposphere, the suppression of baroclinic activity propagates eastward at a slower rate that is comparable to that of the lower to midtropospheric flow. The results have implications for understanding subseasonal variability in the extratropical troposphere of both hemispheres.

scholarly journals Mitogenomics of the endangered Mediterranean monk seal (Monachus monachus) reveals dramatic loss of diversity and supports historical gene-flow between Atlantic and eastern Mediterranean populations

2020 ◽  
Author(s):  
Alba Rey-Iglesia ◽  
Philippe Gaubert ◽  
Gonçalo Espregueira Themudo ◽  
Rosa Pires ◽  
Constanza De La Fuente ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
North Atlantic ◽  
Marine Mammals ◽  
Eastern Mediterranean ◽  
The Black Sea ◽  
Mediterranean Populations ◽  
Geographic Ranges ◽  
Western Sahara ◽  
The Mediterranean

Abstract The Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals, with only 600–700 individuals restricted to three populations off the coast of Western Sahara and Madeira (North Atlantic) and between Greece and Turkey (eastern Mediterranean). Its original range was from the Black Sea (eastern Mediterranean) to Gambia (western African coast), but was drastically reduced by commercial hunting and human persecution since the early stages of marine exploitation. We here analyse 42 mitogenomes of Mediterranean monk seals, from across their present and historical geographic ranges to assess the species population dynamics over time. Our data show a decrease in genetic diversity in the last 200 years. Extant individuals presented an almost four-fold reduction in genetic diversity when compared to historical specimens. We also detect, for the first time, a clear segregation between the two North Atlantic populations, Madeira and Cabo Blanco, regardless of their geographical proximity. Moreover, we show the presence of historical gene-flow between the two water basins, the Atlantic Ocean and the Mediterranean Sea, and the presence of at least one extinct maternal lineage in the Mediterranean. Our work demonstrates the advantages of using full mitogenomes in phylogeographic and conservation genomic studies of threatened species.

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