North Atlantic Jet position induces latitudinal decouplings in forest productivity in Europe

2020 ◽  
Author(s):  
Isabel Dorado-Liñán ◽  
Valerie Trouet ◽  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
European Beech ◽  
Forest Productivity ◽  
Atmospheric Circulation Patterns ◽  
Summer Climate ◽  
The North ◽  
Circulation Patterns ◽  
Latitudinal Position ◽  
The North Atlantic

<p>Dynamically-driven extreme weather events have large ecological, social and economic consequences including large tree-growth reductions and forest mortality. These events are likely to become globally more frequent and intense in the near future with increased anthropogenic forcing and associated changes in couple atmosphere-ocean circulation. The European continent is under the control of different atmospheric circulation patterns leading to geographical climatic gradients caused by their eventual position and strength, being the North Atlantic Oscillation (NAO) and the East Atlantic Pattern (EA) the main modes of North Atlantic climate variability (Barnston and Levezey 1987; Folland et al. 2009). Both, NAO and EA reflect jet stream changes as a consequence of variations in the eddy forcing, being the North Atlantic Jet (NAJ) the pattern connecting the large-scale atmospheric variability over the North Atlantic basin (Woollings, Hannachi, and Hoskins 2010). Thus, the identification and characterization of the links between forest productivity and the precursors of large-scale dynamics inducing extreme events may boost our capacity of assessing their predictability and enhancing forecasting skills.<br>Here, we scale forest response to climate to higher atmospheric levels by establishing the connection between extreme positive and negative anomalies in productivity of European forests to the latitudinal position of the NAJ. For that, we use a network of 344 European beech tree-ring chronologies extending from the Iberian Peninsula to the Carpathians and from Greece to northern UK.<br>Our results show a geographical gradient on tree growth across Europe explained either by the asymmetric forest response to homogeneous summer climate over Europe or to a distinct summer climate dipole leading to diverging climatic conditions in northeaster and southwestern Europe. In both cases, the continental-scale European-beech growth patterns are linked to the NAJ latitudinal position and its determinant influence on summer climate over Europe. The projected increase in the frequency of northward migrations of the NAJ for the next century may enhance the differences in forest productivity across Europe by inducing subcontinental-wide beech forest growth reduction.</p><p><br>Barnston, Anthony Gaston, and Robert E. Levezey. 1987. "Classification, seasonality and persistence of low-frequency atmospheric circulation patterns" Mon. Weather Rev. 115: 1083-1126.<br>Folland, Chris K, Jeff Knight, Hans W Linderholm, David Fereday, Sarah Ineson, and James W Hurrell. 2009. “The Summer North Atlantic Oscillation: Past, Present, and Future.” Journal of Climate 22 (5): 1082–1103. https://doi.org/10.1175/2008JCLI2459.1.<br>Woollings, Tim, Abdel Hannachi, and Brian Hoskins. 2010. “Variability of the North Atlantic Eddy-Driven Jet Stream.” Quarterly Journal of the Royal Meteorological Society 136 (649): 856–68. https://doi.org/10.1002/qj.625.</p><p> </p>

scholarly journals The sensitivity of snowfall to weather states over Sweden

2017 ◽  
Author(s):  
Lars Norin ◽  
Abhay Devasthale ◽  
Tristan S. L'Ecuyer
Keyword(s):  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Cyclonic Circulation ◽  
Satellite Observations ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. For a high latitude country like Sweden snowfall is an important contributor to the regional water cycle. Furthermore, snowfall impacts surface properties, affects atmospheric thermodynamics, has implications for traffic and logistics management, disaster preparedness, and also impacts climate through changes in surface albedo and turbulent heat fluxes. For Sweden it has been shown that large-scale atmospheric circulation patterns, or weather states, are important for precipitation variability. Although the link between atmospheric circulation patterns and precipitation has been investigated for rainfall there are no studied focused on the sensitivity of snowfall to weather states over Sweden. In this work we investigate the response of snowfall to eight selected weather states. These weather states consist of four dominant wind directions together with cyclonic and anti-cyclonic circulation patterns and enhanced positive and negative phases of the North Atlantic oscillation. The presented analysis is based on multiple data sources, such as ground-based radar measurements, satellite observations, spatially-interpolated in situ observations, and reanalysis data. The data from these sources converge to underline the sensitivity of falling snow over Sweden to the different weather states. In this paper we examine both average snowfall intensities and snowfall accumulations associated with the different weather states. It is shown that even though the heaviest snowfall intensities occur during conditions with winds from the southwest, the largest contribution to snowfall accumulation arrives from winds from the southeast. Large differences in snowfall due to variations in the North Atlantic oscillation are shown as well as a strong effect of cyclonic and anti-cyclonic circulation patterns. Satellite observations are used to reveal the vertical structures of snowfall during the different weather states.

scholarly journals Can preferred atmospheric circulation patterns over the North-Atlantic-Eurasian region be associated with arctic sea ice loss?

Polar Science ◽  
2017 ◽  
Vol 14 ◽  
pp. 9-20 ◽  
Author(s):  
Berit Crasemann ◽  
Dörthe Handorf ◽  
Ralf Jaiser ◽  
Klaus Dethloff ◽  
Tetsu Nakamura ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Arctic Sea Ice ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
Arctic Sea ◽  
The North Atlantic ◽  
Arctic Sea Ice Loss ◽  
Eurasian Region

scholarly journals Decadal Variability in a Central Greenland High-Resolution Deuterium Isotope Record and Its Relationship to the Frequency of Daily Atmospheric Circulation Patterns from the North Atlantic Region

2010 ◽  
Vol 23 (17) ◽  
pp. 4608-4618 ◽  
Author(s):  
Norel Rimbu ◽  
Gerrit Lohmann
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Decadal Variability ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
Isotope Record ◽  
The North Atlantic

Abstract The variability of an annual resolution deuterium time series from central Greenland is investigated in connection with the variability in the frequency of daily atmospheric circulation patterns in the North Atlantic region. Statistical analysis reveals that a large part of the decadal variability of the deuterium isotope record is related to decadal variability in the frequency of several identified daily circulation patterns. The study shows that these circulation patterns induce variations in the deuterium record by altering where isotopic fractionation occurs, mainly during the passage of the associated air masses over continental areas. The study identifies three significant periodic components in the deuterium isotope record at ∼12, ∼20, and ∼30 yr. It also shows that the ∼20-yr signal in the deuterium isotope record is related to the variability in the frequency of a winter circulation type. An analysis of six oxygen isotope records from central Greenland reveals decadal variations similar to the deuterium isotope record. The authors argue that high-resolution stable isotope records from Greenland ice cores can be used to obtain information about the frequency of certain daily circulation patterns during past periods.

scholarly journals The sensitivity of snowfall to weather states over Sweden

2017 ◽  
Vol 10 (9) ◽  
pp. 3249-3263 ◽  
Author(s):  
Lars Norin ◽  
Abhay Devasthale ◽  
Tristan S. L'Ecuyer
Keyword(s):  
North Atlantic Oscillation ◽  
Atmospheric Circulation ◽  
North Atlantic ◽  
Satellite Observations ◽  
Anticyclonic Circulation ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. For a high-latitude country like Sweden snowfall is an important contributor to the regional water cycle. Furthermore, snowfall impacts surface properties, affects atmospheric thermodynamics, has implications for traffic and logistics management, disaster preparedness, and also impacts climate through changes in surface albedo and turbulent heat fluxes. For Sweden it has been shown that large-scale atmospheric circulation patterns, or weather states, are important for precipitation variability. Although the link between atmospheric circulation patterns and precipitation has been investigated for rainfall there are no studies focused on the sensitivity of snowfall to weather states over Sweden.In this work we investigate the response of snowfall to eight selected weather states. These weather states consist of four dominant wind directions together with cyclonic and anticyclonic circulation patterns and enhanced positive and negative phases of the North Atlantic Oscillation. The presented analysis is based on multiple data sources, such as ground-based radar measurements, satellite observations, spatially interpolated in situ observations, and reanalysis data. The data from these sources converge to underline the sensitivity of falling snow over Sweden to the different weather states.In this paper we examine both average snowfall intensities and snowfall accumulations associated with the different weather states. It is shown that, even though the heaviest snowfall intensities occur during conditions with winds from the south-west, the largest contribution to snowfall accumulation arrives with winds from the south-east. Large differences in snowfall due to variations in the North Atlantic Oscillation are shown as well as a strong effect of cyclonic and anticyclonic circulation patterns. Satellite observations are used to reveal the vertical structures of snowfall during the different weather states.

Neural interpretation of European summer climate ensemble predictions

2020 ◽  
Author(s):  
Julianna Carvalho Oliveira ◽  
Eduardo Zorita ◽  
Johanna Baehr ◽  
Thomas Ludwig
Keyword(s):  
Neural Network ◽  
North Atlantic ◽  
Seasonal Prediction ◽  
Physical Processes ◽  
Summer Climate ◽  
The North ◽  
Predictive Skill ◽  
Circulation Patterns ◽  
Skill Analysis ◽  
The North Atlantic

<p>Current state-of-the-art dynamical seasonal prediction systems still show limited skill, particularly over Europe in summer. To circumvent this, we propose a neural network-based classification of individual ensemble members at the initialisation of summer climate predictions, prior to performing a skill analysis. Different from European winter climate, largely dominated by the North Atlantic Oscillation, predictability of European summer climate has been associated with several physical mechanisms, including teleconnections with the tropics. Recent studies have shown that predictive skill improves when the dominant physical processes in a given season are identified at the initialisation of a prediction. Each of these dominant physical processes is associated with large-scale circulation patterns, often depicted by modes of Empirical Orthogonal Functions (EOF). We argue that Self-Organising Maps (SOM), a type of neural network classifier, can provide further insight on interpreting the predictive skill of mixed resolution hindcast ensemble simulations generated by MPI-ESM. This is achieved by identifying which circulation patterns over the North Atlantic-European sector (NAE) at the initialisation of hindcasts lead to more predictable states than others, their preferable transition states, and whether the spatial structure of each SOM mode play a role in shaping climate over Europe. We train SOM networks on sea level pressure fields of ERA-20C reanalysis at the initialisation of the seasonal prediction system (every May) for the period of 1900-2010, covering NAE. We compare the SOM-derived modes with circulation patterns derived from EOF analysis, and characterise each class of circulation regime. This analysis is used to distinguish classes of predictions with two different sets of MPI-ESM initialised simulations with 10 and 30 members, covering the period of 1902-2008 and 1982-2016, respectively. We then discuss the differences and advantages of performing a neural interpretation of the skill of an ensemble prediction, over traditional skill analysis.</p><p><br><br></p>

scholarly journals Evidence for strong relations between the upper Tagus loess formation (central Iberia) and the marine atmosphere off the Iberian margin during the last glacial period

2021 ◽  
pp. 1-30
Author(s):  
Daniel Wolf ◽  
Thomas Kolb ◽  
Karolin Ryborz ◽  
Susann Heinrich ◽  
Imke Schäfer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Moisture Transfer ◽  
Sea Temperature ◽  
Last Glacial ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Terrestrial Environments ◽  
The North Atlantic ◽  
Iberian Margin ◽  
The Last Glacial

Abstract During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

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