Exploring Combined Influences of Seasonal East Atlantic (EA) and North Atlantic Oscillation (Nao) on the Temperature-Precipitation Relationship in the Iberian Peninsula

Iberian Peninsula ◽

North Atlantic ◽

Negative Relationship ◽

East Atlantic ◽

Teleconnection Patterns ◽

The North ◽

Spatial Coverage ◽

The combined influence of the North Atlantic Oscillation (NAO) and the East Atlantic (EA) patterns on the covariability of temperatures and precipitation in 35 stations of the Iberian Peninsula during the period 1950-2019 is analysed in this work. Four EA-NAO composites were defined from teleconnection patterns positive and negative phases: EA+NAO+, EA+NAO-, EA-NAO+, and EA-NAO-. Daily data of maximum and minimum temperature were used to obtain seasonal means (TX, and TN, respectively), and the covariability of these variables with accumulated seasonal rainfall (R) was studied comparing results obtained for different NAO and EA composites. Main results indicate slight differences in the spatial coverage of correlation coefficients between R and temperature variables, except in spring when the generalized negative relationship between R and TX under EA+NAO+ and EA-NAO- disappears under EA-NAO+ and EA+NAO- composites. This result may be useful to interpret and discuss historical reconstructions of Iberian climate.

Exploring Combined Influences of Seasonal East Atlantic (EA) and North Atlantic Oscillation (NAO) on the Temperature-Precipitation Relationship in the Iberian Peninsula

Geosciences ◽

10.3390/geosciences11050211 ◽

2021 ◽

Vol 11 (5) ◽

pp. 211

Author(s):

Fernando S. Rodrigo

Keyword(s):

Iberian Peninsula ◽

North Atlantic ◽

Negative Relationship ◽

East Atlantic ◽

Teleconnection Patterns ◽

The North ◽

Spatial Coverage ◽

The combined influence of the North Atlantic Oscillation (NAO) and the East Atlantic (EA) patterns on the covariability of temperatures and precipitation in 35 stations of the Iberian Peninsula during the period 1950–2019 is analysed in this work. Four EA-NAO composites were defined from teleconnection patterns’ positive and negative phases: EA+NAO+, EA+NAO-, EA-NAO+ and EA-NAO-. Daily data of maximum and minimum temperature were used to obtain seasonal means (TX and TN, respectively), and the covariability of these variables with accumulated seasonal rainfall (R) was studied comparing results obtained for different NAO and EA composites. Main results indicate slight differences in the spatial coverage of correlation coefficients between R and temperature variables, except in spring when the generalised negative relationship between R and TX under EA+NAO+ and EA-NAO- disappears under EA-NAO+ and EA+NAO- composites. This result may be useful to interpret and discuss historical reconstructions of the Iberian climate.

Cyclones causing wind storms in the Mediterranean: characteristics, trends and links to large-scale patterns

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1379-2010 ◽

2010 ◽

Vol 10 (7) ◽

pp. 1379-1391 ◽

Cited By ~ 81

Author(s):

K. M. Nissen ◽

G. C. Leckebusch ◽

J. G. Pinto ◽

D. Renggli ◽

S. Ulbrich ◽

...

Keyword(s):

North Atlantic ◽

Positive Phase ◽

East Atlantic ◽

The North ◽

The North Atlantic ◽

Wind Storms ◽

The Mediterranean ◽

Wind Events ◽

Abstract. A climatology of cyclones with a focus on their relation to wind storm tracks in the Mediterranean region (MR) is presented. Trends in the frequency of cyclones and wind storms, as well as variations associated with the North Atlantic Oscillation (NAO), the East Atlantic/West Russian (EAWR) and the Scandinavian variability pattern (SCAND) are discussed. The study is based on the ERA40 reanalysis dataset. Wind storm tracks are identified by tracking clusters of adjacent grid boxes characterised by extremely high local wind speeds. The wind track is assigned to a cyclone track independently identified with an objective scheme. Areas with high wind activity – quantified by extreme wind tracks – are typically located south of the Golf of Genoa, south of Cyprus, southeast of Sicily and west of the Iberian Peninsula. About 69% of the wind storms are caused by cyclones located in the Mediterranean region, while the remaining 31% can be attributed to North Atlantic or Northern European cyclones. The North Atlantic Oscillation, the East Atlantic/West Russian pattern and the Scandinavian pattern all influence the amount and spatial distribution of wind inducing cyclones and wind events in the MR. The strongest signals exist for the NAO and the EAWR pattern, which are both associated with an increase in the number of organised strong wind events in the eastern MR during their positive phase. On the other hand, the storm numbers decrease over the western MR for the positive phase of the NAO and over the central MR during the positive phase of the EAWR pattern. The positive phase of the Scandinavian pattern is associated with a decrease in the number of winter wind storms over most of the MR. A third of the trends in the number of wind storms and wind producing cyclones during the winter season of the ERA40 period may be attributed to the variability of the North Atlantic Oscillation.

Impact of the North Atlantic Oscillation on Transatlantic Flight Routes and Clear-Air Turbulence

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-15-0261.1 ◽

2016 ◽

Vol 55 (3) ◽

pp. 763-771 ◽

Cited By ~ 17

Author(s):

Jung-Hoon Kim ◽

William N. Chan ◽

Banavar Sridhar ◽

Robert D. Sharman ◽

Paul D. Williams ◽

...

Keyword(s):

New York ◽

North Atlantic ◽

Large Scale ◽

Jet Streams ◽

Weather Patterns ◽

Teleconnection Patterns ◽

The North ◽

Air Turbulence ◽

AbstractThe variation of wind-optimal transatlantic flight routes and their turbulence potential is investigated to understand how upper-level winds and large-scale flow patterns can affect the efficiency and safety of long-haul flights. In this study, the wind-optimal routes (WORs) that minimize the total flight time by considering wind variations are modeled for flights between John F. Kennedy International Airport (JFK) in New York, New York, and Heathrow Airport (LHR) in London, United Kingdom, during two distinct winter periods of abnormally high and low phases of North Atlantic Oscillation (NAO) teleconnection patterns. Eastbound WORs approximate the JFK–LHR great circle (GC) route following northerly shifted jets in the +NAO period. Those WORs deviate southward following southerly shifted jets during the −NAO period, because eastbound WORs fly closely to the prevailing westerly jets to maximize tailwinds. Westbound WORs, however, spread meridionally to avoid the jets near the GC in the +NAO period to minimize headwinds. In the −NAO period, westbound WORs are north of the GC because of the southerly shifted jets. Consequently, eastbound WORs are faster but have higher probabilities of encountering clear-air turbulence than westbound ones, because eastbound WORs are close to the jet streams, especially near the cyclonic shear side of the jets in the northern (southern) part of the GC in the +NAO (−NAO) period. This study suggests how predicted teleconnection weather patterns can be used for long-haul strategic flight planning, ultimately contributing to minimizing aviation’s impact on the environment.

Impact of the North Atlantic Oscillation on river runoff in the Belarus part of the Baltic Sea basin

Hydrology Research ◽

10.2166/nh.2007.025 ◽

2007 ◽

Vol 38 (4-5) ◽

pp. 413-423 ◽

Cited By ~ 3

Author(s):

I. Danilovich ◽

D. Wrzesiński ◽

L. Nekrasova

Keyword(s):

North Atlantic ◽

River Runoff ◽

The Baltic Sea ◽

The North ◽

The North Atlantic ◽

The Baltic ◽

Baltic Sea Basin ◽

The dynamics of the North Atlantic Oscillation (NAO) and river runoff in the Belarus part of the Baltic Sea basin have been studied. Correlation coefficients between NAO indices and monthly, seasonal and annual discharges were calculated, changes in the runoff in the opposite stages of NAO and its intra-annual distribution were analysed, and runoff trends for different time series were investigated. The closest connection could be observed between NAO indices for December–March and the runoff of Belarusian rivers in the Baltic basin. The highest correlation coefficients were calculated for winter and spring months. The intra-annual runoff differs in opposite stages of the North Atlantic Oscillation. The most significant increase of monthly runoff was observed after 1961. There was a positive trend of runoff at the beginning of the year, but a negative one in the summer and autumn months.

Winter Cyclone Regimes Over The North Atlantic

10.21203/rs.3.rs-786439/v1 ◽

2021 ◽

Author(s):

Veronika N. Maslova ◽

Elena N. Voskresenskaya ◽

Alexander V. Yurovsky ◽

Mikhail Yu. Bardin

Keyword(s):

North Atlantic ◽

Reanalysis Data ◽

East Atlantic ◽

Teleconnection Patterns ◽

The Third ◽

The North ◽

Function Decomposition ◽

Spectral Peaks ◽

The North Atlantic ◽

Abstract To study regimes of winter cyclones in the North Atlantic, empirical orthogonal function decomposition was applied separately to the frequency, depth and area of cyclones obtained using 6-hourly NCEP/NCAR reanalysis data in 1952–2017 and the developed methodology. The first mode represented the opposite changes of cyclone anomalies in the northern and southern/central North Atlantic. The second mode was characterized by the greatest regional anomalies between its phases over Europe, off its coast and over the Mediterranean. The greatest changes of anomalies for the third modes were in temperate latitudes, both over the ocean and Europe. Linear trends were significant only for the first modes of cyclone parameters. The largest part of variability (74–90% of dispersion) of all cyclone modes corresponded to the periods up to 15 years and was used for spectral analysis, which identified significant spectral peaks: 2.5–3, 4.5, 6 and 8.5 years. These periods coincided with spectral peaks of the main interannual climate signals. Regression analysis allowed to identify the sets of teleconnection patterns responsible jointly for 60–85% of dispersion of the first cyclone modes. The North Atlantic Oscillation and Arctic Oscillation were the main patterns for the first modes of the cyclone parameters. For the second and third frequency modes, the East Atlantic (EA) pattern and a combination of the East Atlantic/West Russia (EA/WR) and Scandinavia patterns played the major role, respectively. As for the third depth and area modes, the association with the EA and EA/WR patterns was shown, respectively.

Monthly Rainfall Signatures of the North Atlantic Oscillation and East Atlantic Pattern in Great Britain

Atmosphere ◽

10.3390/atmos12111533 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1533

Author(s):

Harry West ◽

Nevil Quinn ◽

Michael Horswell

Keyword(s):

Great Britain ◽

North Atlantic ◽

Monthly Rainfall ◽

East Atlantic ◽

East Atlantic Pattern ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation ◽

Regional Rainfall

Atmospheric-oceanic circulations (teleconnections) have an important influence on regional climate. In Great Britain, the North Atlantic Oscillation (NAO) has long been understood as the leading mode of climate variability, and its phase and magnitude have been found to influence regional rainfall in previous research. The East Atlantic Pattern (EA) is also increasingly recognised as being a secondary influence on European climate. In this study we use high resolution gridded rainfall and Standardised Precipitation Index (SPI) time series data for Great Britain to map the monthly rainfall signatures of the NAO and EA over the period January 1950–December 2015. Our analyses show that the influence of the two teleconnections varies in space and time with distinctive monthly signatures observed in both average rainfall/SPI-1 values and incidences of wet/dry extremes. In the winter months the NAO has a strong influence on rainfall and extremes in the north-western regions. Meanwhile, in the southern and central regions stronger EA-rainfall relationships are present. In the summer months opposing positive/negative phases of the NAO and EA result in stronger wet/dry signatures which are more spatially consistent. Our findings suggest that both the NAO and EA have a prominent influence on regional rainfall distribution and volume in Great Britain, which in turn has implications for the use of teleconnection forecasts in water management Decemberision making. We conclude that accounting for both NAO and EA influences will lead to an enhanced understanding of both historic and future spatial distribution of monthly precipitation.

The response of Iberian rivers to the North Atlantic Oscillation

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-8-4459-2011 ◽

2011 ◽

Vol 8 (3) ◽

pp. 4459-4493 ◽

Cited By ~ 1

Author(s):

J. Lorenzo-Lacruz ◽

S. M. Vicente-Serrano ◽

J. I. López-Moreno ◽

J. C. González-Hidalgo ◽

E. Morán-Tejeda

Keyword(s):

Water Resources ◽

Iberian Peninsula ◽

North Atlantic ◽

The North ◽

Surface Water Resources ◽

The North Atlantic ◽

Spatio Temporal ◽

The North Atlantic Oscillation ◽

Iberian Rivers

Abstract. In this study we analyzed the influence of the North Atlantic Oscillation (NAO) on the streamflow in 187 sub-basins of the Iberian Peninsula. Monthly and one-month lagged correlations were conducted to assess the spatio-temporal extent of the NAO influence on Iberian river discharges. Analysis of the persistence of the winter NAO throughout the year was also undertaken, together with analysis of streamflow anomalies during positive and negative NAO phases. Moving-window correlation analyses were conducted to assess potential changes in the temporal evolution of the NAO influence on Iberian streamflows. The results show that the NAO has a large impact on surface water resources throughout the Iberian Peninsula during winter, and in the Atlantic watershed during autumn. We showed that water resources management and snowmelt are causing the persistent dependence of streamflows on the previous winter NAO. We found that strongly positive streamflow anomalies occurred during winter, especially in the Atlantic watershed, and provide evidence of non-stationarity and spatial variability in the NAO influence on Iberian water resources.

Alternative Indices for the Warm-Season NAO and Precipitation Variability in West Greenland

Journal of Climate ◽

10.1175/2007jcli1724.1 ◽

2008 ◽

Vol 21 (3) ◽

pp. 532-541 ◽

Cited By ~ 1

Author(s):

Frank A. Aebly ◽

Qi Hu ◽

Sherilyn C. Fritz

Keyword(s):

North Atlantic ◽

Warm Season ◽

Precipitation Variability ◽

Future Climate Change ◽

West Greenland ◽

The North ◽

The North Atlantic ◽

Abstract Observed precipitation records from Kangerlussuaq, Greenland, and atmospheric variables from the NCEP–NCAR reanalysis were used in a statistical analysis to elucidate controls on the seasonal variation of precipitation and develop indices that may be potentially useful for analyzing precipitation variability in paleoclimate and future climate change investigations. Three distinct patterns of correlation between precipitation and the 500-hPa geopotential height were found to represent three dominant atmospheric patterns that strongly influence precipitation for different times of the year. All three patterns show a relation to the North Atlantic Oscillation signature found in the first empirical orthogonal function of the 500-hPa height field. Spatially dependent indices were developed based on the 500-hPa geopotential field. The correlation coefficients between precipitation at Kangerlussuaq and these indices range from −0.38 for winter to 0.64 for the warm season (May–September). The warm-season index herein is the first index reported in the literature that correlates significantly with precipitation during the warm season. Correlations of these indices with precipitation in Oslo, Norway, are high and are of opposite sign to west Greenland indices for the winter and summer months. This indicates that they are good representations of the atmospheric patterns associated with the North Atlantic Oscillation and the west Greenland–northern Europe “seesaw.” High correlations are also found with precipitation measured at Nuuk, Qaqortoq, and Upernavik, Greenland.

Are the North Atlantic Oscillation and the Northern Annular Mode Distinguishable?

Journal of the Atmospheric Sciences ◽

10.1175/jas3798.1 ◽

2006 ◽

Vol 63 (11) ◽

pp. 2915-2930 ◽

Cited By ~ 64

Author(s):

Steven B. Feldstein ◽

Christian Franzke

Keyword(s):

North Atlantic ◽

Wave Breaking ◽

Null Hypothesis ◽

Annular Mode ◽

Northern Annular Mode ◽

Teleconnection Patterns ◽

The North ◽

The North Atlantic ◽

Abstract This study addresses the question of whether persistent events of the North Atlantic Oscillation (NAO) and the Northern Annular Mode (NAM) teleconnection patterns are distinguishable from each other. Standard daily index time series are used to specify the amplitude of the NAO and NAM patterns. The above question is examined with composites of sea level pressure, and 300- and 40-hPa streamfunction, along with tests of field significance. A null hypothesis is specified that the NAO and NAM persistent events are indistinguishable. This null hypothesis is evaluated by calculating the difference between time-averaged NAO and NAM composites. It is found that the null hypothesis cannot be rejected even at the 80% confidence level. The wave-breaking characteristics during the NAM life cycle are also examined. Both the positive and negative NAM phases yield the same wave-breaking properties as those for the NAO. The results suggest that not only are the NAO and NAM persistent events indistinguishable, but that the NAO/NAM events are neither confined to the North Atlantic, nor are they annular.