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 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.

scholarly journals Impacts of large-scale atmospheric circulation changes due to winter sea-ice retreat on Black Carbon transport and deposition to the Arctic

2016 ◽  
Author(s):  
Luca Pozzoli ◽  
Srdan Dobricic ◽  
Simone Russo ◽  
Elisabetta Vignati
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Southern Oscillation ◽  
The Arctic ◽  
The North ◽  
Ice Retreat ◽  
The North Atlantic Oscillation ◽  
Sea Ice Retreat

Abstract. Winter warming and sea ice retreat observed in the Arctic in the last decades determine changes of large scale atmospheric circulation pattern that may impact as well the transport of black carbon (BC) to the Arctic and its deposition on the sea ice, with possible feedbacks on the regional and global climate forcing. In this study we developed and applied a new statistical algorithm, based on the Maximum Likelihood Estimate approach, to determine how the changes of three large scale weather patterns (the North Atlantic Oscillation, the Scandinavian Blocking, and the El Nino-Southern Oscillation), associated with winter increasing temperatures and sea ice retreat in the Arctic, impact the transport of BC to the Arctic and its deposition. We found that the three atmospheric patterns together determine a decreasing winter deposition trend of BC between 1980 and 2015 in the Eastern Arctic while they increase BC deposition in the Western Arctic. The increasing trend is mainly due to the more frequent occurrences of stable high pressure systems (atmospheric blocking) near Scandinavia favouring the transport in the lower troposphere of BC from Europe and North Atlantic directly into to the Arctic. The North Atlantic Oscillation has a smaller impact on BC deposition in the Arctic, but determines an increasing BC atmospheric load over the entire Arctic Ocean with increasing BC concentrations in the upper troposphere. The El Nino-Southern Oscillation does not influence significantly the transport and deposition of BC to the Arctic. The results show that changes in atmospheric circulation due to polar atmospheric warming and reduced winter sea ice significantly impacted BC transport and deposition. The anthropogenic emission reductions applied in the last decades were, therefore, crucial to counterbalance the most likely trend of increasing BC pollution in the Arctic.

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 Sub-decadal- to decadal-scale climate cyclicity during the Holsteinian interglacial (MIS 11) evidenced in annually laminated sediments

2011 ◽  
Vol 7 (3) ◽  
pp. 987-999 ◽  
Author(s):  
A. Koutsodendris ◽  
A. Brauer ◽  
H. Pälike ◽  
U. C. Müller ◽  
P. Dulski ◽  
...  
Keyword(s):  
Time Series ◽  
Southern Oscillation ◽  
Laminated Sediments ◽  
Solar Cycles ◽  
The North ◽  
Decadal Scale ◽  
Time Series Analyses ◽  
Diatom Blooms ◽  
Winter Time ◽  
The North Atlantic Oscillation

Abstract. To unravel the short-term climate variability during Marine Isotope Stage (MIS) 11, which represents a close analogue to the Holocene with regard to orbital boundary conditions, we performed microfacies and time series analyses on a ~3200-yr-long record of annually laminated Holsteinian lake sediments from Dethlingen, northern Germany. These biogenic varves comprise two sub-layers: a light sub-layer, which is controlled by spring/summer diatom blooms, and a dark sub-layer consisting mainly of amorphous organic matter and fragmented diatom frustules deposited during autumn/winter. Time series analyses were performed on the thickness of the light and dark sub-layers. Signals exceeding the 95% and 99% confidence levels occur at periods that are near-identical to those known from modern instrumental data and Holocene palaeoclimatic records. Spectral peaks at periods of 90, 25, and 10.5 yr are likely associated with the 88-, 22- and 11-yr solar cycles, respectively. This variability is mainly expressed in the light sub-layer spectra, suggesting solar influence on the palaeoproductivity of the lake. Significant signals at periods between 3 and 5 yr and at ∼6 yr are strongest expressed in the dark sub-layer spectra and may reflect an influence of the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) during autumn/winter. Our results suggest that solar forcing and ENSO/NAO-like variability influenced central European climate during MIS 11 similarly to the present interglacial, thus demonstrating the comparability of the two interglacial periods at sub-decadal to decadal timescales.

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 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.

scholarly journals Maximum temperatures over Slovenia and their relationship with atmospheric circulation patterns

Geografie ◽  
2017 ◽  
Vol 122 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Dragan D. Milošević ◽  
Stevan M. Savić ◽  
Uglješa Stankov ◽  
Igor Žiberna ◽  
Milana M. Pantelić ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Southern Oscillation ◽  
The Arctic ◽  
Maximum Temperature ◽  
East Atlantic ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
Maximum Temperatures ◽  
The North Atlantic Oscillation

This paper examines temporal and spatial patterns of annual and seasonal maximum temperatures (Tmax) in Slovenia and their relationship with atmospheric circulation patterns. A significant increase in maximum temperature (Tmax; from 0.3°C to 0.5°C·decade-1) was observed throughout the country at the annual scale in the period 1963–2014. Significant positive trends are observed on all stations in summer (from 0.4°C to 0.7°C·decade-1) and spring (from 0.4°C to 0.6°C·decade-1). The results indicate significant correlations between the mean annual maximum temperature (Tmax) and the East Atlantic Oscillation (EA) (from 0.5 to 0.7), the Arctic Oscillation (AO) (from 0.4 to 0.7) and the Scandinavian Oscillation (SCAND) (from −0.3 to −0.4) throughout the country. A significant EA influence is observed in all seasons, while the AO influence is noticed in winter and spring, SCAND in spring and summer, the North Atlantic Oscillation (NAO) and the Mediterranean Oscillation (MO) in winter, the East Atlantic/Western Russia Oscillation (EA/WR) in summer and the El Nino Southern Oscillation (ENSO) in autumn.

scholarly journals Predictability Associated with Nonlinear Regimes in an Atmospheric Model

2012 ◽  
Vol 69 (3) ◽  
pp. 1137-1154 ◽  
Author(s):  
John M. Peters ◽  
Sergey Kravtsov ◽  
Nicholas T. Schwartz
Keyword(s):  
Phase Space ◽  
Atmospheric Model ◽  
Flow Patterns ◽  
The Arctic ◽  
The North ◽  
Spreading Rates ◽  
The Arctic Oscillation ◽  
Non Gaussian ◽  
The North Atlantic Oscillation ◽  
The Relationship

Abstract Atmospheric regimes are midlatitude flow patterns that persist for periods of time exceeding a few days. Here, the authors analyzed the output of an idealized atmospheric model (QG3) to examine the relationship between regimes and predictability. The regimes were defined as the regions of the QG3 phase subspace characterized by excess persistence probability relative to a benchmark linear empirical model (EMR) for geographically two-dimensional and then zonally averaged flow patterns. The regimes identified correspond to the opposite phases of the Arctic Oscillation (AO+ and AO−) and to a more regional pattern reflecting the positive phase of the North Atlantic Oscillation (NAO+). For all of these phase-space regime regions, the leading modes of the QG3 state vector decay to climatology at a slower rate than predicted by the EMR, which contributes to the maintenance of non-Gaussian regime anomalies. Predictable regimes are connected to “regime precursor” regions of the phase space, from which trajectories flow into regime regions following mean phase-space velocities. Packets of trajectories originating from these regions are characterized by anomalously low spreading rates due to a combination of low local stochastic diffusivity and convergence of the nonlinear component of mean phase-space velocities along the trajectory pathways. While unpredictable regimes do have precursor regions, trajectories emanating from these regions are characterized by relatively high spreading rates. The predictable regimes AO+ and AO− are insensitive to the metric used to identify the regimes; however, the unpredictable regime NAO+ in the 2D space is not directly associated with its zonal-metric counterpart.

A breakdown of the link between the Arctic and North Atlantic Oscillations in warm climate projections

2020 ◽  
Author(s):  
Mostafa Hamouda ◽  
Claudia Pasquero ◽  
Eli Tziperman
Keyword(s):  
North Atlantic ◽  
Climate Scenario ◽  
Reanalysis Data ◽  
The Arctic ◽  
Climate Projections ◽  
Modes Of Variability ◽  
The North ◽  
Temperature And Precipitation ◽  
The Arctic Oscillation ◽  
The North Atlantic Oscillation

<table><tbody><tr><td>The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) are climate variability modes significantly affecting temperature and precipitation variability in the mid-latitudes of the Northern hemisphere. In this study, we use both reanalysis data and model historical and warmer climate simulations to show that the relation between the two oscillations may change dramatically in a different climate. In the current climate, these two climate modes are highly correlated, as they are both strongly influenced by downward propagation of stratospheric anomalies into the troposphere. When considering a warmer climate scenario (RCP8.5 in the XXIII century), the correlation between NAO and AO drops significantly, revealing that they become two separate modes of variability. The stratosphere remains an important precursor for NAO, while the AO consistently precede stratospheric anomalies. The analysis suggests that these changes are owed to land-sea thermal contrast intensification in the Pacific region, which becomes more favorable for storm variability.</td> </tr></tbody></table>

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