East Atlantic-West Russia Pattern Research Articles

Karadeniz'de 2000-2022 Yılları Arasında Yüzey Sıcaklığının Mekansal ve Zamansal Değişimi

This study presents a comprehensive assessment of the spatio-temporal variability of Sea Surface Temperature (SST) in the Black Sea at monthly to interannual scales, with a focus on understanding its connection to major large-scale atmospheric forcing during the period 2000-2022. Monthly variations of SST in the Black Sea reveal distinct seasonal patterns. The study evaluates the potential impacts of large-scale atmospheric patterns on interannual SST variations using climate indices such as the North Atlantic Oscillation (NAO), East Atlantic/West Russia (EA-WR) and El Niño-Southern Oscillation (ENSO) during the winter months. The results indicated that these large-scale atmospheric oscillations played a substantial role in influencing SST anomalies, with the NAO and EA-WR indices particularly affecting the Black Sea's SST anomalies. The NAO index exhibited negative values during warm winters and positive values during cold winters, with extreme cold and warm winters corresponding to specific years, as observed in 2003, 2006, 2012, 2017 (cold) and 2018, 2020, 2021 (warm). Notably, the relationship between NAO and SST anomalies was not as dominant during 2000-2022. This difference might be explained by the combined influence of NAO and ENSO, which is beyond the scope of this study. The EA-WR pattern was identified as another significant large-scale atmospheric dynamic affecting the Black Sea's SST. Although it explains the cold SST anomalies in certain years, it cannot account for extreme warm SST years. While the influence of ENSO remains somewhat inconclusive for the extreme warm period, the SST pattern between 2016-2022 aligns closely with El Niño events, particularly in 2018 and 2021 when positive SOI index values coincide with warm SST years in the Black Sea.

The increase in extreme precipitation and its proportion over global land

Changes in extreme precipitation (EP) have a significant impact on the ecology and sustainable development of most regions, especially when considered against a backdrop of global warming. Using trend analysis and other methods, we analyze the changes in nine extreme precipitation indices (EPIs), looking at the proportion of EP in total precipitation from the perspectives of intensity, frequency, and duration. We also utilize a geo-detector method to investigate the impacts of 15 climate factors on EPIs. Our results indicate that although EP and their proportions show an overall increasing trend on a global scale, they had undergone a process of initial decrease followed by increase over the past approximately 70 years. And this overall global increases are charged by the significant increases happened in Northern Hemisphere and western of South America, especially EP intensity and frequency indices, and their proportion. Whereas CDD shows an opposite trend in spatial distribution, the CWD is decreasing globally. The EPIs and their proportions are all highest in the low elevation belt (≤2000 m), followed by the high elevation belt (≥4000 m), and lowest in the mid-elevation belts (2000-4000 m). Most of them have returned to or exceeded the levels of the mid-20th century in all three elevation belts. Only CWD shows a decreasing trend, which indicates that more EP amounts are occurring with less precipitation duration. In some arid areas, this makes it possible that a short period of precipitation may complete the total amount of precipitation for that year. Global temperature is proven to be the most important factor influencing the EPI globally, and followed by the temperature of each region. And the regions of high latitudes of the Northern Hemisphere and Antarctica which are greatly influenced by global temperature demonstrate the Polar amplification effect. The East Atlantic-West Russia Pattern, Atlantic Multi-Decadal Oscillation, and El Nino-Southern Oscillation indices are the secondly important factors leading to changes in the proportion of global EP. At the same time, we also find that the influence of non-monsoon factors on EP is gradually strengthening. This study clarifies changes in EP globally and in various regions, which will help provide a scientific reference for preventing disasters caused by extreme climate change.

On the connection between large-scale atmospheric circulation and winter GPCP precipitation over the Mediterranean region for the period 1980-2017

Abstract The influence of the large-scale atmospheric circulation on winter precipitation over the Mediterranean region is studied with the use of monthly 2.5° × 2.5° ERA-Interim 500 and 1000 hPa geopotential heights and GPCP-v2.3 precipitation, for the period 1980–2017. At first, Principal Component Analysis (PCA) is applied both to geopotential heights and precipitation datasets and the main modes of inter-annual variations are found. Then, these modes are investigated through Canonical Correlation Analysis (CCA) to identify the centers of action of the lower and the middle troposphere that control precipitation variability over the Mediterranean region. Three statistically significant canonical pairs are found. The first one, in the North Atlantic, controls precipitation over western Asia Minor, northern Libya and the western Iberian Peninsula. Τhe second mode corresponds to the see-saw between Greenland and central Europe and controls precipitation over the northern Mediterranean region. The third one is located north of Britain and controls precipitation over NW Africa and northern France. For each canonical pair, the mean geopotential heights and precipitation anomaly patterns for the four (10%) years with the highest and the lowest canonical scores are constructed, confirming the results of CCA. Moreover, the correlation between the canonical scores and the indices of the large-scale atmospheric oscillations, namely the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), the North Sea – Caspian Pattern (NCP) and the East Atlantic/West Russia Pattern (EA/WR), was studied.

Surface and Tropospheric Water Vapor Variability and Decadal Trends at Two Supersites of CO-PDD (Cézeaux and Puy de Dôme) in Central France

We present an analysis of decadal in situ and remote sensing observations of water vapor over the Cézeaux and puy de Dôme, located in central France (45° N, 3° E), in order to document the variability, cycles and trends of surface and tropospheric water vapor at different time scales and the geophysical processes responsible for the water vapor distributions. We use meteorological stations, GPS (Global Positioning System), and lidar datasets, supplemented with three remote sources of water vapor (COSMIC-radio-occultation, ERA-interim-ECMWF numerical model, and AIRS-satellite). The annual cycle of water vapor is clearly established for the two sites of different altitudes and for all types of measurement. Cezeaux and puy de Dôme present almost no diurnal cycle, suggesting that the variability of surface water vapor at this site is more influenced by a sporadic meteorological system than by regular diurnal variations. The lidar dataset shows a greater monthly variability of the vertical distribution than the COSMIC and AIRS satellite products. The Cézeaux site presents a positive trend for the GPS water vapor total column (0.42 ± 0.45 g·kg−1/decade during 2006–2017) and a significant negative trend for the surface water vapor mixing ratio (−0.16 ± 0.09 mm/decade during 2002–2017). The multi-linear regression analysis shows that continental forcings (East Atlantic Pattern and East Atlantic-West Russia Pattern) have a greater influence than oceanic forcing (North Atlantic Oscillation) on the water vapor variations.

The influence of the large-scale circulation patterns on temperature in Serbia

In this study, the influence of the large-scale circulation patterns on temperature in Europe and Serbia is examined. Among the large-scale circulation patterns in the Northern Hemisphere, less attention has been paid to the impact of the East Atlantic/West Russia pattern (EA/WR). The relationship between the EA/WR pattern and geopotential height at 500 hPa is investigated using reanalysis data from National Centres for Environmental Prediction – National Centre for Atmospheric Research. Temperature anomalies have been explored in relation to strong positive and negative phases of the EA/WR pattern for all months.Analyzing the correlation between the EA/WR index (EA/WRI) and geopotential height at 500 hPa, a centre with negative correlation has been found throughout the year over Russia, north of the Caspian Sea. Positive (negative) temperature anomalies prevailed over Eastern (Western) Europe for the strong negative EA/WR phase (EA/WRI < −1). The temperature anomalies associated with the strong positive phase of the EA/WR pattern (EA/WRI > 1) reflect below-average temperatures over Eastern Europe. In addition, we explored the combined effects of positive and negative phases of the North Atlantic Oscillation (NAO) or East Atlantic (EA) pattern with the EA/WR pattern on temperature variations in Europe and Serbia. We find that the effect of the EA/WR pattern on temperature changes is dependent of the EA phase but not of the NAO phase over Serbia. When the EA/WRI is negative and EA pattern or NAO are in positive phase, the positive temperature anomalies prevailed over most of Europe, including Serbia. The highest values of temperature anomalies exist over Serbia for EA/WRI < −1 and EA index > 1. It is found that this case appears more frequently in the last 20 years, contributing to the warming in Europe and Serbia.

Predicting summer monsoon of Bhutan based on SST and teleconnection indices

The paper uses a statistical method of predicting summer monsoon over Bhutan using the ocean-atmospheric circulation variables of sea surface temperature (SST), mean sea-level pressure (MSLP), and selected teleconnection indices. The predictors are selected based on the correlation. They are the SST and MSLP of the Bay of Bengal and the Arabian Sea and the MSLP of Bangladesh and northeast India. The Northern Hemisphere teleconnections of East Atlantic Pattern (EA), West Pacific Pattern (WP), Pacific/North American Pattern, and East Atlantic/West Russia Pattern (EA/WR). The rainfall station data are grouped into two regions with principal components analysis and Ward’s hierarchical clustering algorithm. A support vector machine for regression model is proposed to predict the monsoon. The model shows improved skills over traditional linear regression. The model was able to predict the summer monsoon for the test data from 2011 to 2015 with a total monthly root mean squared error of 112 mm for region A and 33 mm for region B. Model could also forecast the 2016 monsoon of the South Asia Monsoon Outlook of World Meteorological Organization (WMO) for Bhutan. The reliance on agriculture and hydropower economy makes the prediction of summer monsoon highly valuable information for farmers and various other sectors. The proposed method can predict summer monsoon for operational forecasting.

Qualitative assessment of climate-driven ecological shifts in the Caspian Sea

The worldwide occurrence of complex climate-induced ecological shifts in marine systems is one of the major challenges in sustainable bio-resources management. The occurrence of ecological environment-driven shifts was studied in the Southern Caspian Sea using the “shiftogram” method on available fisheries-related (i.e. commercially important bentho-pelagic fish stocks) ecological and climatic variables. As indicators of potential environmentally driven shift patterns we used indices for the North Atlantic Oscillation, the Southern Oscillation, the Siberian High, the East Atlantic-West Russia pattern, as well as Sea Surface Temperature and surface chlorophyll-a concentration. Given the explorative findings from the serial shift analyses, the cascading and serial order of multiple shift events in climatic-ecologic conditions of the southern Caspian Sea suggested a linkage between external forces and dynamics of ecosystem components and structures in the following order: global-scale climate forces lead to local environmental processes, which in turn lead to biological components dynamics. For the first time, this study indicates that ecological shifts are an integral component of bentho-pelagic subsystem regulatory processes and dynamics. Qualitative correspondence of biological responses of bentho-pelagic stocks to climatic events is one of the supporting evidences that overall Caspian ecosystem structures and functioning might have–at least partially–been impacted by global-scale climatic or local environmental shifts. These findings may help to foster a regional Ecosystem-based Approach to Management (EAM) as an integral part of bentho-pelagic fisheries management plans.

Impacts of Climate Modes on Air–Sea Heat Exchange in the Red Sea

Abstract The impacts of various climate modes on the Red Sea surface heat exchange are investigated using the MERRA reanalysis and the OAFlux satellite reanalysis datasets. Seasonality in the atmospheric forcing is also explored. Mode impacts peak during boreal winter [December–February (DJF)] with average anomalies of 12–18 W m−2 to be found in the northern Red Sea. The North Atlantic Oscillation (NAO), the east Atlantic–west Russia (EAWR) pattern, and the Indian monsoon index (IMI) exhibit the strongest influence on the air–sea heat exchange during the winter. In this season, the largest negative anomalies of about −30 W m−2 are associated with the EAWR pattern over the central part of the Red Sea. In other seasons, mode-related anomalies are considerably lower, especially during spring when the mode impacts are negligible. The mode impacts are strongest over the northern half of the Red Sea during winter and autumn. In summer, the southern half of the basin is strongly influenced by the multivariate ENSO index (MEI). The winter mode–related anomalies are determined mostly by the latent heat flux component, while in summer the shortwave flux is also important. The influence of the modes on the Red Sea is found to be generally weaker than on the neighboring Mediterranean basin.

Synoptic climatology of winter intense precipitation events along the Mediterranean coasts

Abstract. The link between winter (December-January-February) precipitation events at 15 Mediterranean coastal locations and synoptic features (cyclones and Northern Hemisphere teleconnection patterns) is analyzed. A list of precipitation events has been produced; q percentile thresholds (Thq) and corresponding frequency Nq (for q equal to 25, 50, 90 and 98) have been considered. A negative trend has been detected in total precipitation and N50 at many locations, while no significant trend in N25, N90 and N98 has been found. The negative phase of the North Atlantic Oscillation (NAO) and the East Atlantic/West Russia pattern (EAWR) compete for exerting the largest influence on the frequency of the 25th, 50th and 90th percentiles, with EAWR and NAO exerting their largest influence in the central and western Mediterranean areas, respectively. All percentiles show a similar behavior except for the 98th percentile, which shows no convincing link to any teleconnection pattern. The cyclone tracks that are associated with precipitation events have been selected using the ERA-40 reanalysis data, and a strong link between intense precipitation and cyclones is shown for all stations. In general, the probability of detecting a cyclone within a distance of 20° from each station increases with the intensity of the precipitation event and decreases with the duration of a dry period. The origin and track of cyclones producing intense precipitation differ among different areas. When precipitation occurs in the northwestern Mediterranean, cyclones are generally either of Atlantic origin or secondary cyclones associated with the passage of major cyclones north of the Mediterranean Basin, while they are mostly generated inside the region itself for events at the eastern Mediterranean coast. An important fraction of intense events in the southern areas is produced by cyclones that are generated over northern Africa. The analysis of sea level pressure and geopotential height at 500 hPa highlights the important role of cyclone depth, circulation strength, surrounding synoptic condition, and of slow speed of the cyclone center for producing intense precipitation events.

Large-Scale Atmospheric Circulation Favoring Deep- and Intermediate-Water Formation in the Mediterranean Sea

Abstract Atmospheric circulation patterns that are conducive to extreme ocean heat loss are investigated at four sites of special interest in the Mediterranean Sea. The Gulf of Lions, the South Adriatic Sea, the Cretan Sea, and the Levantine Sea are areas where anomalously high winter heat loss may lead to deep- or intermediate-water formation. At each of the above sites, the atmospheric circulation during such events is derived by averaging the sea level pressure (SLP) fields during the lower decile of the wintertime series of the net heat exchange. A relatively simple SLP pattern dominated by an anticyclone over northwestern Europe with a weaker cyclone to the southeast is found to be associated with strong heat loss in the selected sites with minor variations in pattern structure depending on the site. The SLP composite pattern reflects the combined effect of different atmospheric modes of variability and the authors consider the impacts on heat loss of a number of these modes (North Atlantic Oscillation, east Atlantic pattern, east Atlantic–west Russia pattern, and Scandinavian pattern), together with the North Sea–Caspian pattern and the Mediterranean index. The extremes in heat loss are strongly connected with the intensity and the positions of the poles of these patterns that modulate, through the necessary SLP gradient and associated northerlies, the transfer of cold and dry air over the areas of dense-water formation. Analysis of air–sea temperature difference, specific humidity, and evaporation anomalies indicates that the extremes of the net heat fluxes are primarily due to the latent and sensible heat flux components.

Influence of atmospheric circulation on turbulent air‐sea heat fluxes over the Mediterranean Sea during winter

The influence of the winter atmospheric circulation on the turbulent variables of the air‐sea boundary layer in the Mediterranean Sea is investigated. We examine the effects of several climatic indices and the corresponding large scale atmospheric patterns on the above variables by using a correlation analysis. The spatial characteristics and the behavior of the turbulent variables are also examined based on standard deviation and EOF analysis. Two main types of response to the index‐specified atmospheric patterns have been identified: (1) A relatively uniform response of the entire basin associated with the influence of the East Atlantic pattern and (2) opposite responses in the western and eastern sub‐basins linked mainly to the intrabasin SLP. The latter is a combined effect of the first four modes of atmospheric variability in the North Atlantic/Eurasia region, the North Atlantic Oscillation (NAO), the East Atlantic Pattern (EA), the Scandinavian Pattern (SCAND), and the East Atlantic‐West Russia Pattern (EAWR). The two identified responses of the Mediterranean Sea to the atmospheric forcing are also in accordance with the primary modes of variability of the turbulent variables that result in the EOF analysis. All of the statistically independent indices (NAO, EA, SCAND, EAWR) have to be considered in order to fully account for the modulation of the turbulent variables in the Mediterranean Sea. As an example we refer to the mechanism through which, independent modes of atmospheric variability contributed to the Eastern Mediterranean Transient event between 1987 and 1995.

Influence of atmospheric modes of variability on a deep lake south of the Alps

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 51:125-133 (2012) - DOI: https://doi.org/10.3354/cr01063 Influence of atmospheric modes of variability on a deep lake south of the Alps Nico Salmaso* IASMA Research and Innovation Centre, Istituto Agrario di S. Michele all’Adige - Fondazione E. Mach, Sustainable Agro-ecosystems and Bioresources Department, Via E. Mach 1, 38010, S. Michele all’Adige, Trento, Italy *Email: nico.salmaso@iasma.it ABSTRACT: Limnological measurements and winter air temperatures recorded in a deep lake south of the Alps (Lake Garda) have been analysed and related to temporal variations in 5 teleconnection patterns, i.e. the East Atlantic pattern (EA), the Eastern Mediterranean Pattern (EMP), the North Atlantic Oscillation (NAO), the Scandinavia pattern (SCAND) and the East Atlantic/West Russia Pattern (EA/WR). The EA and EMP played a significant role in winter in the large-scale atmospheric circulation over the Mediterranean region. Positive and negative EA, and negative and positive EMP phases were closely connected with the development of mild and harsh winters, respectively. In turn, harsh winters had a strong positive impact on the development of diatoms in spring and cyanobacteria in summer and autumn. These modifications were controlled through a linked chain of factors, which included lower winter lake water temperatures, deep lake circulation episodes, and higher replenishment of epilimnetic phosphorus at spring overturn. This work demonstrates the existence of a strong connection between large-scale climatic fluctuations over the Mediterranean area and the temporal variations in the limnological characteristics of the large lakes located between the Alps and the northern border of the Mediterranean region. Conversely, the NAO, SCAND and EA/WR did not show any relationship with the winter climate and the limnological characteristics of Lake Garda. KEY WORDS: Climatic fluctuations · Deep lakes · Lake overturn · Climate–nutrient interactions · East Atlantic pattern · Eastern Mediterranean Pattern · North Atlantic Oscillation Full text in pdf format PreviousNextCite this article as: Salmaso N (2012) Influence of atmospheric modes of variability on a deep lake south of the Alps. Clim Res 51:125-133. https://doi.org/10.3354/cr01063 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 51, No. 2. Online publication date: February 29, 2012 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2012 Inter-Research.

Examining the large‐scale spatial coherence of European drought using regional indicators of precipitation and streamflow deficit

AbstractDroughts tend to evolve slowly and affect large areas simultaneously, which suggests that improved understanding of spatial coherence of drought would enable better mitigation of drought impacts through enhanced monitoring and forecasting strategies. This study employs an up‐to‐date dataset of over 500 river flow time series from 11 European countries, along with a gridded precipitation dataset, to examine the spatial coherence of drought in Europe using regional indicators of precipitation and streamflow deficit. The drought indicators were generated for 24 homogeneous regions and, for selected regions, historical drought characteristics were corroborated with previous work. The spatial coherence of drought characteristics was then examined at a European scale. Historical droughts generally have distinctive signatures in their spatio‐temporal development, so there was limited scope for using the evolution of historical events to inform forecasting. Rather, relationships were explored in time series of drought indicators between regions. Correlations were generally low, but multivariate analyses revealed broad continental‐scale patterns, which appear to be related to large‐scale atmospheric circulation indices (in particular, the North Atlantic Oscillation and the East Atlantic–West Russia pattern). A novel methodology for forecasting was developed (and demonstrated with reference to the United Kingdom), which predicts ‘drought from drought’—i.e. uses spatial coherence of drought to facilitate early warning of drought in a target region, from drought which is developing elsewhere in Europe. Whilst the skill of the methodology is relatively modest at present, this approach presents a potential new avenue for forecasting, which offers significant advantages in that it allows prediction for all seasons, and also shows some potential for forecasting the termination of drought conditions. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Links of the significant wave height distribution in the Mediterranean sea with the Northern Hemisphere teleconnection patterns

Abstract. This study analyzes the link between the SWH (Significant Wave Height) distribution in the Mediterranean Sea during the second half of the 20th century and the Northern Hemisphere SLP (Sea Level Pressure) teleconnection patterns. The SWH distribution is computed using the WAM (WAve Model) forced by the surface wind fields provided by the ERA-40 reanalysis for the period 1958–2001. The time series of mid-latitude teleconnection patterns are downloaded from the NOAA web site. This study shows that several mid-latitude patterns are linked to the SWH field in the Mediterranean, especially in its western part during the cold season: East Atlantic Pattern (EA), Scandinavian Pattern (SCA), North Atlantic Oscillation (NAO), East Atlantic/West Russia Pattern (EA/WR) and East Pacific/ North Pacific Pattern (EP/NP). Though the East Atlantic pattern exerts the largest influence, it is not sufficient to characterize the dominant variability. NAO, though relevant, has an effect smaller than EA and comparable to other patterns. Some link results from possibly spurious structures. Patterns which have a very different global structure are associated to similar spatial features of the wave variability in the Mediterranean Sea. These two problems are, admittedly, shortcomings of this analysis, which shows the complexity of the response of the Mediterranean SWH to global scale SLP teleconnection patterns.

A study of precipitation variability in the Duero Basin (Iberian Peninsula)

AbstractSpatial and temporal average behaviour of winter precipitation in the Duero basin (DB) were analysed for 1958–1993. Monthly observed data (observed data) from 34 weather stations and a subset of daily precipitation data from the NCEP/NCAR reanalysis project (reanalysis data) were used.The spatial variability of winter precipitation was examined using principal component analysis (PCA) for both types of data. The winter precipitation fields are well represented by the first three principal components (PC), which describe 81% and 87% of the total variance for the observed and reanalysis data, respectively. The relationship between the three leading PCs and circulation patterns was also investigated. The PC1 is related to the North Atlantic Pattern (NAO), East Atlantic Pattern (EA) and Pacific North American Pattern (PNA). The PC2 is related to the East Atlantic/West Russia Pattern (EAWR), while the PC3 depends mainly on Scandinavia Pattern (SCAND) influences.The reanalysis data were used to calculate a 10‐day period to study the intra‐annual variation (S‐mode of PCA) and the spatial distribution of those precipitation amounts during the year (T‐mode of PCA). For the intra‐annual variation of precipitation, two modes statistically significant were obtained. The first mode was characterized by a broad maximum that extended from mid October to early April, and a minimum that extended from early May to September. The second mode exhibited two maxima and a minimum. The first maximum occurred in late February and the second maximum extended from early April to June. The minimum extended from mid July to early February. For the spatial distribution of precipitation, we obtained three patterns. The ‘winter’ pattern, which showed a maximum over the western area, the ‘spring’ pattern with a maximum over the eastern area, and the ‘autumn’ with a maximum over the easternmost edge of the basin. Copyright © 2006 Royal Meteorological Society.

Decadal trends in the east Atlantic-west Russia pattern and Mediterranean precipitation

Investigation of the role of the east Atlantic–west Russia (EA–WR) teleconnection pattern in determining the variability of the monthly mean Mediterranean area precipitation is performed. Space correlations between the mean monthly precipitation and the EA–WR index during 1950–2000 have been calculated. The EA–WR/precipitation correlations are statistically significant over the eastern Atlantic and southeastern Mediterranean regions. Two pairs of 10-year periods characterized by low and high EA–WR regimes have been selected. The EA–WR/precipitation correlation patterns have been calculated for each of the periods. Common features that characterize the periods with the two EA–WR regimes are determined. One of the zones with the notable differences between the correlation patterns is found located over the eastern Mediterranean (EM) region. To determine the mechanisms responsible for the differences we analyse the low and high EA–WR low-troposphere circulations characterizing periods with EM precipitation (CEMP). The differences in the correlation patterns are explained by variations in the air mass transport to the EM area during the wet December–February (DJF) months during the two EA–WR regimes. Namely, during the low EA–WR years the CEMP is characterized by mean atmospheric flow transporting the air masses from the Atlantic to the EM. On the contrary, for high EA–WR DJF months the CEMP is typically characterized by advection to the EM of the air masses from central Europe. This finding allows explanation of the observed precipitation decline over the EM during the last several decades of the past century in terms of the positive trend of the EA–WR. Copyright © 2005 Royal Meteorological Society