scholarly journals On the Meridional Structure of Annular Modes

2005 ◽  
Vol 18 (12) ◽  
pp. 2119-2122 ◽  
Author(s):  
Matthew A. H. Wittman ◽  
Andrew J. Charlton ◽  
Lorenzo M. Polvani
Keyword(s):  
Observational Studies ◽  
The Arctic ◽  
Atmospheric Models ◽  
Northern Annular Mode ◽  
Annular Modes ◽  
Orthogonal Function ◽  
The North ◽  
Wide Range ◽  
The Arctic Oscillation ◽  
Simple Stochastic Model

Abstract Using a simple stochastic model, the authors illustrate that the occurrence of a meridional dipole in the first empirical orthogonal function (EOF) of a time-dependent zonal jet is a simple consequence of the north–south excursion of the jet center, and this geometrical fact can be understood without appealing to fluid dynamical principles. From this it follows that one ought not, perhaps, be surprised at the fact that such dipoles, commonly referred to as the Arctic Oscillation (AO) or the Northern Annular Mode (NAM), have robustly been identified in many observational studies and appear to be ubiquitous in atmospheric models across a wide range of complexity.

scholarly journals Empirical Mode Reduction in a Model of Extratropical Low-Frequency Variability

2006 ◽  
Vol 63 (7) ◽  
pp. 1859-1877 ◽  
Author(s):  
D. Kondrashov ◽  
S. Kravtsov ◽  
M. Ghil
Keyword(s):  
Numerical Study ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
The Arctic ◽  
Reduced Model ◽  
The North ◽  
Low Frequency Variability ◽  
Intraseasonal Oscillations ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation

Abstract This paper constructs and analyzes a reduced nonlinear stochastic model of extratropical low-frequency variability. To do so, it applies multilevel quadratic regression to the output of a long simulation of a global baroclinic, quasigeostrophic, three-level (QG3) model with topography; the model's phase space has a dimension of O(104). The reduced model has 45 variables and captures well the non-Gaussian features of the QG3 model's probability density function (PDF). In particular, the reduced model's PDF shares with the QG3 model its four anomalously persistent flow patterns, which correspond to opposite phases of the Arctic Oscillation and the North Atlantic Oscillation, as well as the Markov chain of transitions between these regimes. In addition, multichannel singular spectrum analysis identifies intraseasonal oscillations with a period of 35–37 days and of 20 days in the data generated by both the QG3 model and its low-dimensional analog. An analytical and numerical study of the reduced model starts with the fixed points and oscillatory eigenmodes of the model's deterministic part and uses systematically an increasing noise parameter to connect these with the behavior of the full, stochastically forced model version. The results of this study point to the origin of the QG3 model's multiple regimes and intraseasonal oscillations and identify the connections between the two types of behavior.

The North Atlantic Oscillation and the Arctic Oscillation favour harmful algal blooms in SW Europe

Harmful Algae ◽  
2014 ◽  
Vol 39 ◽  
pp. 121-126 ◽  
Author(s):  
José C. Báez ◽  
Raimundo Real ◽  
Victoria López-Rodas ◽  
Eduardo Costas ◽  
A. Enrique Salvo ◽  
...  
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Arctic Oscillation ◽  
The Arctic ◽  
The North ◽  
The North Atlantic ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation

scholarly journals Interaction between the MJO and Polar Circulations

2013 ◽  
Vol 26 (11) ◽  
pp. 3562-3574 ◽  
Author(s):  
Maria Flatau ◽  
Young-Joon Kim
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Warm Season ◽  
Cold Season ◽  
The Arctic ◽  
Boreal Winter ◽  
Annular Modes ◽  
The Indian Ocean ◽  
The Arctic Oscillation ◽  
The Tropics

Abstract A tropical–polar connection and its seasonal dependence are examined using the real-time multivariate Madden–Julian oscillation (MJO) (RMM) index and daily indices for the annular modes, the Arctic Oscillation (AO) and the Antarctic Oscillation (AAO). On the intraseasonal time scale, the MJO appears to force the annular modes in both hemispheres. On this scale, during the cold season, the convection in the Indian Ocean precedes the increase of the AO/AAO. Interestingly, during the boreal winter (Southern Hemisphere warm season), strong MJOs in the Indian Ocean are related to a decrease of the AAO index, and AO/AAO tendencies are out of phase. On the longer time scales, a persistent AO/AAO anomaly appears to influence the convection in the tropical belt and impact the distribution of MJO-preferred phases. It is shown that this may be a result of the sea surface temperature (SST) changes related to a persistent AO, with cooling over the Indian Ocean and warming over Indonesia. In the Southern Hemisphere, the SST anomalies are to some extent also related to a persistent AAO pattern, but this relationship is much weaker and appears only during the Southern Hemisphere cold season. On the basis of these results, a mechanism involving the air–sea interaction in the tropics is suggested as a possible link between persistent AO and convective activity in the Indian Ocean and western Pacific.

scholarly journals The influence of Arctic air masses on climatic conditions of the snow accumulation period in the center of the European territory of Russia

2021 ◽  
pp. 16-25
Author(s):  
Julia Nikolaevna Chizhova
Keyword(s):  
North Atlantic ◽  
Arctic Oscillation ◽  
Winter Precipitation ◽  
Climatic Conditions ◽  
The Arctic ◽  
Air Masses ◽  
The North ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation ◽  
The Relationship

The subject of this article is exmination of the influence of the Arctic air flow on the climatic conditions of the winter period in the center of the European territory of Russia (Moscow). In recent years, the question of the relationship between regional climatic conditions and such global circulation patterns as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AK) has become increasingly important. Based on the data of long-term observations of temperature and precipitation, the relationship with the AK and NAO was considered. For the winter months of the period 2014-2018, the back trajectories of the movement of air masses were computed for each date of precipitation to identify the sources of precipitation. The amount of winter precipitation that forms the snow cover of Moscow has no connection with either the North Atlantic Oscillation or the Arctic Oscillation. The Moscow region is located at the intersection of the zones of influence of positive and negative phases of both cyclonic patterns (AK and NAO), which determine the weather in the Northern Hemisphere. For the winter months, a correlation between the surface air temperature and NAO (r = 0.72) and AK (r = 0.66) was established. Winter precipitation in the center of the European territory of Russiais mainly associated with the unloading of Atlantic air masses. Arctic air masses relatively rarely invade Moscow region and bring little precipitation (their contribution does not exceed 12% of the total winter precipitation).

scholarly journals Changes in extreme temperature indices over the Peripannonian region of Bosnia and Herzegovina

Geografie ◽  
2019 ◽  
Vol 124 (1) ◽  
pp. 19-40
Author(s):  
Tatjana Popov ◽  
Slobodan Gnjato ◽  
Goran Trbić
Keyword(s):  
Bosnia And Herzegovina ◽  
Extreme Temperature ◽  
The Arctic ◽  
The North ◽  
Expert Team ◽  
Temperature Indices ◽  
Maximum Temperatures ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation ◽  
Cold Extremes

The paper analyzes changes in extreme temperature indices over the Peripannonian region of Bosnia and Herzegovina. Data on daily minimum and maximum temperatures during the period 1961–2016 from four meteorological stations were used for the calculation in the RClimDex (1.0) sopware trends in 16 indices recommended by the Expert team on climate change detection and indices. The estimated significant upward tendency in indices of warm extremes and downward in cold-related indices confirm that warming is present. The highest trend values were obtained for indices TXx, TNn, TN90p, TX90p, SU25, SU30 and WSDI. The results indicate significant distributional changes in the period 1987−2016 compared to the period 1961−1990. A significant positive (negative) correlation between the East-Atlantic pattern and indices of warm (cold) extremes was determined throughout the year. In winter and spring, significant links to the North Atlantic Oscillation and the Arctic Oscillation, respectively, were also found.

scholarly journals Study of Oil in the North of Russia by the Geological Committee at the End of the 19th Century – the Beginning of the 20th Century

2021 ◽  
Vol 937 (4) ◽  
pp. 042082
Author(s):  
T P Filippova
Keyword(s):  
Field Studies ◽  
The Arctic ◽  
Russian Science ◽  
The North ◽  
New Information ◽  
Wide Range ◽  
Northern Territories ◽  
The 19Th Century ◽  
First Time

Abstract The article draws attention to the study of the historical experience of Russian science in the development of the Arctic and northern territories of Russia. Based on a wide range of archival and published sources, the role of the Geological Committee in the scientific study of the Ukhta oil-bearing region is analyzed. The chronological framework of the study covers the period of the organization’s activity from 1882 to 1929. The field studies carried out by the Geological Committee which started during this period in the Ukhta region are considered in detail. As a result of this activity, this territory was comprehensively studied for the first time, including a detailed geological survey, the search for oil deposits, and an assessment of its industrial potential. It has been determined that as a result of the surveys of the Geological Committee, new information about the features of the geological and orographic structure of the region was obtained and the oil-bearing potential was proved. It has been concluded that the research of the scientists of the committee laid a fundamental basis for the study of the Ukhta oil-bearing region and predetermined its further development history and great significance for the state.

scholarly journals Analysis and Discussion of Atmospheric Precursor of European Heat Summers

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Christine Träger-Chatterjee ◽  
Richard W. Müller ◽  
Jörg Bendix
Keyword(s):  
Time Series ◽  
False Alarm ◽  
North Sea ◽  
Southern Oscillation ◽  
The Arctic ◽  
The Novel ◽  
The North ◽  
Spring Transition ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation

The prediction of summers with notable droughts and heatwaves on the seasonal scale is challenging, especially in extratropical regions, since their development is not yet fully understood. Thus, monitoring and analysis of such summers are important tasks to close this knowledge gap. In a previous paper, the authors presented hints that extreme summers are connected with specific conditions during the winter-spring transition season. Here, these findings are further discussed and analysed in the context of the Earth’s circulation systems. No evidence for a connection between the North Atlantic Oscillation or the Arctic Oscillation during the winter-spring transition and extremely hot and dry summers is found. However, inspection of the geopotential at 850 hPa shows that a Greenland-North Sea-Dipole is connected with extreme summers in Central Europe. This motivated the introduction of the novel Greenland-North Sea-Dipole-Index, GNDI. However, using this index as predictor would lead to one false alarm and one missed event in the time series analysed (1958–2011). Hints are found that the disturbance of the “dipole-summer” connection is due to El Niño/Southern Oscillation (ENSO). To consider the ENSO effect, the novel Central European Drought Index (CEDI) has been developed, which is composed of the GNDI and the Bivariate ENSO Time Series Index. The CEDI enables a correct indication of all extremely hot and dry summers between 1958 and 2011 without any false alarm.

scholarly journals Reconsideration of the True versus Apparent Arctic Oscillation

2008 ◽  
Vol 21 (10) ◽  
pp. 2047-2062 ◽  
Author(s):  
Hisanori Itoh
Keyword(s):  
Spatial Correlation ◽  
Arctic Oscillation ◽  
Physical Reality ◽  
The Arctic ◽  
Sea Level Pressure ◽  
The North ◽  
The Pacific ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation ◽  
Almost All

Abstract The physical reality of the Arctic Oscillation (AO; or northern annular mode) is considered. The data used are mainly the monthly mean sea level pressure (SLP). A schematic figure is first presented to illustrate the relationship between the North Atlantic Oscillation (NAO)–Pacific–North American Oscillation (PNA) system and the AO–negative correlation mode between the Atlantic and the Pacific (AO–NCM) system. Although the NAO–PNA (apparent AO–NCM) and true AO–NCM systems give rise to the same EOFs, the probability density functions for the time coefficients of the two leading modes are different. Therefore, the discrimination of the two systems is possible. Several pieces of evidence indicate that, in the real world, the NAO–PNA and the AO–NCM are located on almost the same plane in phase space. This means that the NAO–PNA and AO–NCM systems have the same variations on the plane in common, implying that when the NAO–PNA system is real, the AO–NCM is unlikely to be real. Simple independent component analysis is carried out to distinguish between the true and apparent AO–NCM systems, indicating that the NAO and PNA are independent oscillations, that is, true ones. The analysis is extended to the winter mean SLP field, for which the EOF shows the NAO–PNA but not the AO–NCM. This may be due to the fact that the winter mean NAO and PNA patterns have little spatial correlation. Calculations using randomly selected samples also indicate that when the NAO and PNA patterns have little spatial correlation, the AO never appears as EOF1. All the preceding results show that almost all characteristics of the AO–NCM can be explained from those of the NAO–PNA. Hence it is concluded that the AO, which is extracted by EOF analysis from the temporarily independent but spatially overlapping variations of the NAO and PNA, is almost apparent.

ALIEN PLANT SPECIES IN THE RUSSIAN ARCTIC: SPATIAL PATTERNS, CORRIDORS AND LOCAL INVASIONS

2021 ◽  
Vol 14 (3) ◽  
pp. 50-62
Author(s):  
O. V. Morozova ◽  
A. A. Tishkov
Keyword(s):  
Alien Species ◽  
Plant Species ◽  
Human Migration ◽  
The Arctic ◽  
Alien Plant Species ◽  
Migration Activity ◽  
Alien Plant ◽  
The North ◽  
Northern Border ◽  
Wide Range

The article analyzes the diversity of alien plant species in the Russian part of the Arctic (RA) based on the generalization of different publications. Alien plant species present in all regions of the RA, but compared with more southern biomes, their share in regional floras is relatively small and unevenly distributed, from 1-2% in the north of Yakutia and in the continental part of Chukotka to 22-27% on the Kola Peninsula and in the Bolshezemelskaya tundra. In general, the low species diversity of alien species in the RA is explained by two groups of factors. The first one includes socio-economic indicators: relatively late and still focal economic development of the region and, in general, low human migration activity here. The second one unites natural factors, among which the climate is of paramount importance. It has been shown that mainly plurizonal species with the northern border of their ranges in the boreal zone are introduced into the RA, but the direct donor regions are often not known when alien species are introduced. These species are clearly better adapted to a wide range of conditions, allowing them to survive in the harsh Arctic climate. By the way of invasion into the RA, unintentionally introduced species prevail, and the main vectors are transport, migration activity, in recent years - arctic tourism, as well as introduction with contaminated materials. The distribution of alien species is locally and mostly associated with settlements and industrial centers.

Palynological evidence of Holocene climate change in the eastern Arctic: a possible shift in the Arctic oscillation at the millennial time scaleThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.

2008 ◽  
Vol 45 (11) ◽  
pp. 1363-1375 ◽  
Author(s):  
David Ledu ◽  
André Rochon ◽  
Anne de Vernal ◽  
Guillaume St-Onge
Keyword(s):  
Arctic Ocean ◽  
Arctic Oscillation ◽  
North Atlantic Ocean ◽  
Sediment Cores ◽  
Sea Surface ◽  
The Arctic ◽  
Last Deglaciation ◽  
Holocene Climate ◽  
The North ◽  
The Arctic Oscillation

Dinocyst assemblages and the physical properties of two sediment cores collected in the easternmost part of the main axis of the Northwest Passage, Canadian Arctic Ocean (cores 2004-804-009 BC and 2004-804-009 PC, 74°11.2′N, 81°11.7′W) were used to reconstruct changes in sea-surface conditions and to characterize changes in the depositional environment. Core 2004-804-009 PC spans the last 12 180 calibrated (cal) years BP, with sedimentation rates ranging from 45 to 122 cm/ka. Quantitative estimates of sea-surface parameters reveal relatively large hydrographic variability at millennial time scale. Before 11 000 cal years BP, our records suggest terrigenous inputs related to the last deglaciation. Between 11 000 and 9600 cal years BP, harsh conditions prevailed with August sea-surface temperatures <2 °C and the dominance of heterotrophic taxa. This episode was followed by a gradual increase in the relative abundance of phototrophic taxa and the establishment of milder condition with sea-surface temperature (SST) reaching ∼2 °C ∼8300 cal years BP, possibly related to increased exchange between the Arctic Ocean and the North Atlantic Ocean. From 6000 cal years BP to the late Holocene, climate variability could be the results of changes in the synoptic-scale atmospheric pattern such as the Arctic oscillation.

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