scholarly journals Arctic Oscillation impact on thermal regime of the Baltic region Eastern part

2016 ◽  
Vol 2 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Индре Гечайте ◽  
Indre Gecaite ◽  
Александр Погорельцев ◽  
Aleksandr Pogoreltsev ◽  
Александр Угрюмов ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Geomagnetic Activity ◽  
Large Scale ◽  
Arctic Oscillation ◽  
Polar Vortex ◽  
Weather Forecast ◽  
Time Interval ◽  
Baltic Region ◽  
Stratospheric Polar Vortex ◽  
The Baltic

Statistical estimations of Arctic Oscillation (AO) impact on air temperature regime in the Eastern part of Baltic region are presented. The region is characterized by high inter-annual and inter-seasonal variabilities. It is important to note that in the region of global warming extremely low winter temperatures can be observed on the European territory of Russia. AO is one of large-scale global structures of atmospheric circulation closely associated with weather variability in Northern Europe. AО anomalies occur in the upper atmosphere (stratosphere) and only then transferred to tropospheric lower layers. The anomalies can be preserved during long period up to two months, so they can be predictors in long-range weather forecast. In turn, changes in stratospheric polar vortex and sudden stratospheric warmings can be related to the geomagnetic activity. Perhaps, the geomagnetic activity influences the meridional temperature gradient and then changes in the structure of the stratospheric zonal wind. In turn, the changes have an impact on the tropospheric circulation. The stratosphere–troposphere connection occurs during winter months. Therefore, the paper presents the analysis of extremely cold winter anomalies in the Eastern part of Baltic Sea region. At the same time, we considered atmospheric circulation peculiarities related to AO phase change. The analyzable time interval covers 1951–2014.

scholarly journals Arctic Oscillation impact on thermal regime in the Eastern part of the Baltic region

2016 ◽  
Vol 2 (1) ◽  
pp. 89-96
Author(s):  
Индре Гечайте ◽  
Indre Gecaite ◽  
Александр Погорельцев ◽  
Aleksandr Pogoreltsev ◽  
Александр Угрюмов ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Geomagnetic Activity ◽  
Large Scale ◽  
Arctic Oscillation ◽  
Polar Vortex ◽  
Baltic Region ◽  
Stratospheric Polar Vortex ◽  
Weather Forecasts ◽  
Tropospheric Circulation ◽  
The Baltic

The paper presents statistical estimations of Arctic Oscillation (AO) impact on air temperature regime in the eastern part of the Baltic region. The region is characterized by high inter-annual and inter-seasonal variability. It is important to note that in the region of global warming extremely low winter temperatures can be observed on the European territory of Russia. AO is one of the large-scale global patterns of atmospheric circulation closely associated with weather variability in northern Europe. AО anomalies occur in the upper atmosphere (stratosphere) and only then are transferred to tropospheric lower layers. The anomalies can persist over a long period of time (up to two months); so they can serve as precursors in long-range weather forecasts. In turn, changes in stratospheric polar vortex and sudden stratospheric warmings can be related to geomagnetic activity. Perhaps geomagnetic activity influences the meridional temperature gradient and then changes the structure of the stratospheric zonal wind. These changes have an effect on the tropospheric circulation. The stratosphere–troposphere coupling takes place during winter months. Therefore, the paper deals with extremely cold winter anomalies in the eastern part of the Baltic Sea region. At the same time, we examine atmospheric circulation peculiarities associated with AO phase change. We analyze data for 1951–2014.

High vs. low latitude influence on seasonal stratospheric pathways in the atmospheric model ICON

2021 ◽  
Author(s):  
Raphael Köhler ◽  
Dörthe Handorf ◽  
Ralf Jaiser ◽  
Klaus Dethloff
Keyword(s):  
Large Scale ◽  
Arctic Oscillation ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Atmospheric Model ◽  
The Arctic ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Enso Events ◽  
Hemisphere Winter

<p>Stratospheric pathways play an important role in connecting distant anomaly patterns to each other on seasonal timescales. As long-lived stratospheric extreme events can influence the large-scale tropospheric circulation on timescales of multiple weeks, stratospheric pathways have been identified as one of the main potential sources for subseasonal to seasonal predictability in mid-latitudes. These pathways have been shown to connect Arctic anomalies to lower latitudes and vice versa. However, there is an ongoing discussion on how strong these stratospheric pathways are and how they exactly work.</p><p> </p><p>In this context, we investigate two strongly discussed stratospheric pathways by analysing a suite of seasonal experiments with the atmospheric model ICON: On the one hand, the effect of El Niño-Southern Oscillation (ENSO) on the stratospheric polar vortex, and thus the circulation in mid and high latitudes in winter. And on the other hand, the effect of a rapidly changing Arctic on lower latitudes via the stratosphere. The former effect is simulated realistically by ICON, and the results from the ensemble simulations suggest that ENSO has an effect on the large-scale Northern Hemisphere winter circulation. The ICON experiments and the reanalysis exhibit a weakened stratospheric vortex in warm ENSO years. Furthermore, in particular in winter, warm ENSO events favour the negative phase of the Arctic Oscillation, whereas cold events favour the positive phase. The ICON simulations also suggest a significant effect of ENSO on the Atlantic-European sector in late winter. Unlike the effect of ENSO, ICON simulations and the reanalysis do not agree on the stratospheric pathway for Arctic-midlatitude linkages. Whereas the reanalysis exhibits a weakening of the stratospheric vortex in midwinter and a connected tropospheric negative Arctic Oscillation circulation response to amplified Arctic warming, this is not the case in the ICON simulations. Implications and potential reasons for this discrepancy are further analysed and discussed in this work.  </p>

Flow-dependent sub-seasonal forecast skill for Atlantic-European weather regimes

2020 ◽  
Author(s):  
Dominik Büeler ◽  
Julian F. Quinting ◽  
Jan Wandel ◽  
Christian M. Grams
Keyword(s):  
Model Calibration ◽  
Large Scale ◽  
Weather Prediction ◽  
Polar Vortex ◽  
Weather Forecast ◽  
Forecast Skill ◽  
Forecast Horizon ◽  
Stratospheric Polar Vortex ◽  
Continuous Increase ◽  
Weather Regimes

<p><span><span>The continuous increase of computational power and improvement of numerical weather prediction systems in recent decades has allowed extending the operational weather forecast horizon into sub-seasonal time scales (10 – 60 days). On these scales, quasi-stationary, persistent, and recurrent large-scale flow patterns, so-called weather regimes, explain most of the regional surface weather variability and are thus of primary interest in sub-seasonal forecasting for the respective region. Here, we assess the skill of sub-seasonal reforecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) for predicting 7 year-round weather regimes in the Atlantic-European region. We primarily show that forecast skill considerably differs for different flow situations and seasons. We further elucidate the effect of model calibration on forecast skill: simply removing the model bias is shown to hardly affect and for some flow situations even reduce forecast skill, which indicates that flow-dependent model calibration techniques might be more useful for sub-seasonal weather regime forecasts. Finally, we give an outlook on how lower-frequency climate modes such as the stratospheric polar vortex as well as midlatitude synoptic-scale activity such as warm conveyor belts may enhance or dilute flow-dependent forecast skill.</span></span></p>

Improvement in Prediction of the Arctic Oscillation with a Realistic Ocean Initial Condition in a CGCM

2015 ◽  
Vol 28 (22) ◽  
pp. 8951-8967 ◽  
Author(s):  
Hae-Jeong Kim ◽  
Joong-Bae Ahn
Keyword(s):  
Arctic Oscillation ◽  
Polar Vortex ◽  
Polar Front ◽  
Forecast Skill ◽  
Sea Surface ◽  
The Arctic ◽  
Initial Condition ◽  
Stratospheric Polar Vortex ◽  
The Arctic Oscillation ◽  
Polar Front Jet

Abstract This study verifies the impact of improved ocean initial conditions on the Arctic Oscillation (AO) forecast skill by assessing the one-month lead predictability of boreal winter AO using the Pusan National University (PNU) coupled general circulation model (CGCM). Hindcast experiments were performed on two versions of the model, one does not use assimilated ocean initial data (V1.0) and one does (V1.1), and the results were comparatively analyzed. The forecast skill of V1.1 was superior to that of V1.0 in terms of the correlation coefficient between the predicted and observed AO indices. In the regression analysis, V1.1 showed more realistic spatial similarities than V1.0 did in predicted sea surface temperature and atmospheric circulation fields. The authors suggest the relative importance of the contribution of the ocean initial condition to the AO forecast skill was because the ocean data assimilation increased the predictability of the AO, to some extent, through the improved interaction between tropical forcing induced by realistic sea surface temperature (SST) and atmospheric circulation. In V1.1, as in the observation, the cold equatorial Pacific SST anomalies generated the weakened tropical convection and Hadley circulation over the Pacific, resulting in a decelerated subtropical jet and accelerated polar front jet in the extratropics. The intensified polar front jet implies a stronger stratospheric polar vortex relevant to the positive AO phase; hence, surface manifestations of the reflected positive AO phase were then induced through the downward propagation of the stratospheric polar vortex. The results suggest that properly assimilated initial ocean conditions might contribute to improve the predictability of global oscillations, such as the AO, through large-scale tropical ocean–atmosphere interaction.

scholarly journals MILITARY-POLITICAL CONFRONTATION BETWEEN THE RUSSIAN FEDERATION AND THE NATO MEMBER STATES IN THE BALTIC REGION

2019 ◽  
Vol 6 (2) ◽  
pp. 9-16
Author(s):  
IGOR TSEPENDA
Keyword(s):  
United States ◽  
Russian Federation ◽  
United States Of America ◽  
Large Scale ◽  
The United States ◽  
Baltic Region ◽  
Member States ◽  
Military Presence ◽  
The Russian Federation ◽  
The Baltic

This article analyses a range of problems faced by the NATO member states in the Baltic region in connection with Russian aggression in Ukraine. It is indicated that the Russian Federation boosts its military presence in the Kaliningrad Oblast: it deploys advanced missile systems and armored fighting vehicles to the region, increases its military contingent and rearms its Navy in the Baltic Sea. It is stressed that Russia has violated the 1987 Treaty on the Elimination of Intermediate-range and Shorter-range Missiles (the INF Treaty) and in recent years has been conducting large-scale military exercises. It is pointed out that amid the growing threat from Russia, the countries of the Baltic region have to reconsider their military strategies, to join their efforts in order to prevent any possible aggression. The NATO member states, the United States of America in particular, take part in the military drills in the region. Sweden’s military cooperation with NATO and the United States of America – a controversial issue in Swedish political circles – is discussed. The question of enhancing military interaction between the members of NATO – Germany and Norway, the Unites States and Poland – is addressed too. The advantages of building collective missile defense capability in the Baltic region and taking other steps to restrain Russia’s aggressive actions are indicated.

scholarly journals The Polar Vortex and Extreme Weather: The Beast from the East in Winter 2018

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 664 ◽  
Author(s):  
James Overland ◽  
Richard Hall ◽  
Edward Hanna ◽  
Alexey Karpechko ◽  
Timo Vihma ◽  
...  
Keyword(s):  
North America ◽  
Atmospheric Circulation ◽  
Polar Vortex ◽  
Extreme Weather ◽  
Extreme Weather Events ◽  
Late Winter ◽  
Public Attention ◽  
Cold Surface ◽  
Stratospheric Polar Vortex ◽  
Weather Events

Public attention has recently focused on high-impact extreme weather events in midlatitudes that originate in the sub-Arctic. We investigate movements of the stratospheric polar vortex (SPV) and related changes in lower atmospheric circulation during the February-March 2018 “Beast from the East” cold winter event that dramatically affected much of Europe and north-central North America. This study demonstrates that the movement of the SPV is a key linkage in late winter subarctic and northern midlatitude extreme weather events. February–March 2018 saw two types of subarctic-midlatitude weather connections. In the first type, the SPV was displaced from the pole to lower latitudes over North America in February and then was found over northern Siberia in March. Mid-February and mid-March are examples of persistent near vertically aligned geopotential height structures of the atmospheric circulation. These structures over North America and Eurasia advected cold Arctic air southward. The second type of cold surface event was associated with a weak regional SPV and a sudden stratospheric warming event over Europe during the second half of February. These late winter linkage events that arise through dynamic instabilities of the SPV are more common in the last decade, but the potential role of enhanced Arctic amplification is uncertain.

scholarly journals Windows of Opportunity for Skillful Forecasts Subseasonal to Seasonal and Beyond

2020 ◽  
Vol 101 (5) ◽  
pp. E608-E625 ◽  
Author(s):  
Annarita Mariotti ◽  
Cory Baggett ◽  
Elizabeth A. Barnes ◽  
Emily Becker ◽  
Amy Butler ◽  
...  
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Polar Vortex ◽  
Prediction Skill ◽  
High Demand ◽  
Stratospheric Polar Vortex ◽  
Weather Forecasts ◽  
Windows Of Opportunity ◽  
Process Understanding ◽  
Persistent Anomalies

Abstract There is high demand and a growing expectation for predictions of environmental conditions that go beyond 0–14-day weather forecasts with outlooks extending to one or more seasons and beyond. This is driven by the needs of the energy, water management, and agriculture sectors, to name a few. There is an increasing realization that, unlike weather forecasts, prediction skill on longer time scales can leverage specific climate phenomena or conditions for a predictable signal above the weather noise. Currently, it is understood that these conditions are intermittent in time and have spatially heterogeneous impacts on skill, hence providing strategic windows of opportunity for skillful forecasts. Research points to such windows of opportunity, including El Niño or La Niña events, active periods of the Madden–Julian oscillation, disruptions of the stratospheric polar vortex, when certain large-scale atmospheric regimes are in place, or when persistent anomalies occur in the ocean or land surface. Gains could be obtained by increasingly developing prediction tools and metrics that strategically target these specific windows of opportunity. Across the globe, reevaluating forecasts in this manner could find value in forecasts previously discarded as not skillful. Users’ expectations for prediction skill could be more adequately met, as they are better aware of when and where to expect skill and if the prediction is actionable. Given that there is still untapped potential, in terms of process understanding and prediction methodologies, it is safe to expect that in the future forecast opportunities will expand. Process research and the development of innovative methodologies will aid such progress.

Sign in / Sign up

Export Citation Format

Share Document