Effect Of North Atlantic Oscillation Research Articles

The combined effects of North Atlantic Oscillation and Western Pacific teleconnection on winter temperature in Eastern Asia during 1980–2021

The combined effects of North Atlantic Oscillation and Western Pacific teleconnection on winter temperature in Eastern Asia during 1980–2021

Spatiotemporal Heterogeneity in Precipitation over China and Its Connections with Large-Scale Climate Oscillations—A Moisture Budget Perspective

Abstract Climate change can lead to variations in the probability distribution of precipitation. In this study, quantile regression (QR) is undertaken to identify the quantile trends in precipitation over China and to examine the quantile effects of various climate oscillations on precipitation. The results show that the quantile trends show apparent seasonal variations, with a greater number of stations showing trends in winter (especially at quantile levels ≥ 0.5), and larger average magnitudes of trends at nearly all quantile levels in summer. The effects of El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Pacific decadal oscillation (PDO) exhibit evident variations with respect to the quantile level. Spatial clusters are subsequently identified based on the quantile trends, and the individual and combined effects from the teleconnection patterns are further investigated from the perspective of moisture budget. Seven spatial clusters with distinct seasonal quantile trends can be identified; three of them are located in southeastern China and are characterized by increasing trends in summer and winter precipitation. Summer precipitation over this region is positively influenced by ENSO and negatively influenced by NAO, with the former affecting both the dynamic and thermodynamic components of vertically integrated moisture divergence and the latter affecting only the dynamic component. The interaction effect of ENSO and NAO on summer precipitation anomalies in months that are extremely wetter than normal is statistically significant. In comparison, winter precipitation in this region is under the positive influence of ENSO and NAO and the negative influence of PDO; the effect of ENSO on moisture convergence can be mainly attributed to its dynamic component.

An objective approach to predict the spatial property of anomalous rain-belt of Meiyu

The Meiyu 2020 with record-breaking amount of precipitation, widespread area coverage and anomalous northern location brought about great social and economic impacts in China. However, the spatial property of anomalous rain-belt for such a catastrophic Meiyu is not well predicted. In this study, high-resolution in-situ observation and reanalysis data are used to explore key signals and possible prediction method. Results show that anomalous rain-belt of Meiyu 2020 is mainly influenced by the westward extended western North Pacific subtropical high (WNPSH) in the low-latitude and enhanced meridional circulation in mid-high latitudes. However, the distribution of composite anomalous circulation, especially in the mid-high latitude, cannot be revealed for 2020 if only considering the influence from the tropical Indo-Pacific thermal conditions. Through additional consideration of North Atlantic Oscillation (NAO), which has great contribution to circulation in the Northern Hemisphere mid-high latitudes, the anomalous key circulation features in 2020 can be appropriately captured. Also, the spatial property of anomalous rain-belt like 2020 could be accurately simulated by the established prediction model including combined effects of tropical Indo-Pacific thermal conditions and NAO. Specifically, quantified analyses prove that the warmed Indian Ocean plays a dominant role and anomalous NAO also has great importance for record-breaking area coverage and anomalous northern location of Meiyu 2020. Thus, for a more accurate prediction for anomalous rain-belt such as Meiyu 2020, the combined effects of both low- and mid-high-latitudes should be comprehensively considered.

Permeable frontiers in the open sea: The case of Swordfish in the Atlantic Ocean

There is a vivid debate about the border location between North and South Atlantic swordfish stocks. Climate oscillations, East Atlantic (EA) and North Atlantic Oscillation (NAO), have a major impact on the Northern Hemisphere climate and weather conditions. The initial hypothesis of present study is that if it is considering the southern frontier, each stock will be differentially affected by both climatic oscillations, which would imply the existence of a strong border. However, a similar effect on both sides of the border would result in a permeable barrier. The results suggest that the combined effects of EA and NAO affect both the North and the South Atlantic swordfish stocks in similar ways, and consequently, the location of the border may reside farther north than the current management boundary at 5ºN.

The Effects of Atmospheric Oscillations on Crop (Olive, Grape and Cotton) Yield in the Eastern Part of the Mediterranean Region, Turkey

In the last century climate change has been a major threat to biodiversity, ecosystem services, and human well‐being. Atmospheric oscillations that occur at the regional oceanic flow pattern may affect significantly the climate of the Earth. In this study, we investigate the effects of ENSO (El Nino Southern Oscillation) and NAO (North Atlantic Oscillation) on the Mediterranean crop yield using the Nino 3, Nino3.4, Nino 4, ONI and NAO indices. Olive, which is a bioindicator type in the Mediterranean, and cotton and grapes with high yield and economic value crops were examined. According to the average production amounts in the Mediterranean Region between 1991 and 2020, 39% of cotton production is in Adana (205319 tone), 43% of grape production is in Mersin (228471 tone) and 37% of olive production is in Hatay (103854 tone). As a method, firstly, Mann Kendall rank correlation test was applied to the yield values of the crops. After the 2000s, it has been determined that the trend of yield has changed and was obtained an increasing trend. Secondly, the correlation between the yields and Nino 3, Nino3.4, Nino 4, and NAO indices were determined with the Spearman correlation coefficient. Accordingly, a high correlation of 50% and 80% was found at the p ≤ 0.05 and p ≤ 0.00 significance level in the phenological periods of the crops. The highest correlations were determined especially during the flowering period (April, May, June) for olive and grape yield with El Nino indices. The frequency of the correlation detected with the NAO index is weak. The effect on the efficiency of the phases when El Nino indices are strong was examined graphically. Accordingly, in the 1997 and 2015-2016 periods, when the El Nino phenomen was very strong, there were sharp decreases in the crop yields. This variability affects the countries whose economic activity is based on agriculture in the Mediterranean Basin, and it is likely to affect the food industry in the future.

Spatial and temporal shift in the factors affecting the population dynamics of Calanus copepods in the North Sea.

The swap in abundance between two Calanus species in the North Sea during the 1980s constitutes a quintessential example of regime shift, with important ecosystemic and economic repercussions because these copepods constitute a major component of the diet of larval and juvenile cods. It is hypothesized that this transition was driven by gradual changes in primary productivity, the North Atlantic Oscillation (NAO) and sea surface temperatures (SST), and yet how these factors contribute to the population dynamics of these two species and the overall regime shift remains unclear. Here, we combine a highly resolved and spatially structured longitudinal dataset with population dynamics theory-based models to obtain a thorough and more detailed description of populations' responses to the regime shift observed in the North Sea. Our analyses highlight that this transition exhibits a clear spatial structure and involved a decoupling between the dynamics of Calanus finmarchicus and the NAO in western regions and between Calanus helgolandicus and SST in the eastern regions of the North Sea. Consequently, the observed switch in abundance between these species reflects the interaction between species-specific attributes, a well-defined spatial structure with a marked east-west axis and a decoupling between the ecological drivers and Calanus population dynamics following the shift. Succinctly, we suspect that higher water temperatures have favored C. helgolandicus and resulted in restrictive conditions for C. finmarchicus, eventually overshadowing the effects of NAO detected in historical records. Overall, our study illustrates how population dynamics theory can be successfully employed to disentangle the complex and multifactorial nature of a regime shift in response to gradually changing environmental conditions.

The delayed effect of cooling reinforced the NAO-plague connection in pre-industrial Europe

Previous studies on the connection between climate and plague were mostly conducted without considering the influence of large-scale atmospheric circulations and long-term historical observations. The current study seeks to reveal the sophisticated role of climatic control on plague by investigating the combined effect of North Atlantic Oscillation (NAO) and temperature on plague outbreaks in Europe from 1347 to 1760 CE. Moving correlation analysis is applied to explore the non-linear relationship between NAO and plague transmission over time. Also, we apply the cross-correlation function to identify the role of temperature in mediating the NAO-plague connection and the lead-lag relationship in between. Our statistical results show that the pathway from climate change to plague incidence is distinctive in its spatial, temporal, and non-linear patterns. The multi-decadal temperature change exerted a 15–22 years lagged impact on the NAO-plague correlation in different European regions. The NAO-plague correlation in Atlantic-Central Europe primarily remained positive, while the correlation in Mediterranean Europe switched between positive and negative alternately. The modulating effect of temperature over the NAO-plague correlation increases exponentially with the magnitude of the temperature anomaly, but the effect is negligible between 0.3 and −0.3 °C anomaly. Our findings show that a lagged influence from the temperature extremes dominantly controls the correlation between NAO and plague incidence. A forecast from our study suggests that large-scale plague outbreaks are unlikely to happen in Europe if NAO remains at its current positive phase during the earth's future warming.

Forest stocks control long‐term climatic mortality risks in Scots pine dry‐edge forests

AbstractForest research has addressed the importance of an improved understanding of drought–stocks interactions in the dry edge of tree species range. Nonetheless, more efforts are still critically needed to link up the multiple ways by which climatic stressors can trigger tree mortality, including population‐level determinants and management. Here, we analyze the interactive effects of North Atlantic Oscillation (NAO), a surrogate of climatic variability in southwestern Europe, and forest stocks on tree mortality in dry‐edge populations of the most widespread Eurasian tree species, Pinus sylvestris L., in the forest of Valsaín (central Spain). Specifically, we use tree mortality data gathered since 1941 in six multiannual periods. Results suggest that the main mortality risks in these forests can occur either in positive or negative NAO phases, but that their relative impacts are critically mediated by forest structure. In NAO+ periods, commonly associated with warm–dry conditions in the Iberian Peninsula, a peak of mortality was found in closed forest sections, whereas the second peak, found in open forest sections, was related to NAO‐ periods, correlated with temperate‐rainy weather conditions. This finding reinforces the key role of management—through its control on forest structure—as a driver of forest vulnerability to climate. Accounting for the multiple ways in which stocks modulate tree responses to different risks emerges as a critical element when it comes to the design of efficient adaptation measures in managed dry‐edge forests.

North Atlantic Oscillation Effect on Interannual Variability in Winter Precipitation over the Gulf Stream

AbstractIn winter, the warm water of the Gulf Stream anchors a salient precipitation band. Previous studies suggested a close relationship between the sea surface temperature (SST) front and the precipitation band through sea level pressure (SLP) adjustment. This study uses 17 years of high-resolution precipitation observations to reveal that the variation in wintertime precipitation over the Gulf Stream is related to the North Atlantic Oscillation (NAO) at the interannual time scale. The moisture budget analysis shows that the climatological precipitation band is supported by the large evaporation from the Florida Current, mean flow, and synoptic moisture convergence within the boundary layer, with a negative contribution from mean-flow moisture advection by the prevailing northwesterlies. For interannual variability, by contrast, the negative contribution of mean-flow moisture advection significantly decreases due to anomalous southeasterlies west of the intensified Azores high at the positive NAO phase. The contributions from mean-flow moisture advection and mean and synoptic convergence vary greatly along the Gulf Stream. In addition, mean-flow and synoptic moisture convergences positively contribute to the precipitation band both in climatology and at the interannual time scale, indicative of a positive feedback between precipitation and boundary layer convergence. Our analysis suggests that the SLP adjustment mechanism across the SST front is still at work in interannual variability, and the variation of synoptic activities over the Gulf Stream plays an important role in modulating the frontal precipitation. By relating the frontal precipitation to the NAO, this study bridges small-scale air–sea interaction and large-scale atmospheric circulation.

Influence of Global Weather Conditions on Timing of the Spring Migration of Birds in the Kaniv Nature Reserve (Central Ukraine)

Abstract I studied the effect of North Atlantic Oscillation (NAO) on the phenology of spring migration of birds in Central Ukraine. Data for arrival and departure of 92 species collected in 1987 to 2018 were used. The statistically significant correlation was found for 33 (35.9 %) bird species. 50 coefficients were negative (82.0 %) and 11 ones — positive (18.0 %). The majority of relationships have been shown in February (12) and March (22). In April, they became more rarely (5). There was only one significant value for January and May. For 20 species correlations were found with averaged indices including three months (January to March). The relationships with NAO indices were much commoner for the short-distance migrants (63.3 % of studied species) than for birds wintering in tropical and Southern Africa (20.5 %) and the intermediate group (18.8 %). Wintering birds showed 8 significant coefficients in 3 species (42.9 %). Statistically significant coefficients of correlation ranged in absolute values from 0.35 to 0.80. The average absolute values were very close for different groups of species. The overall mean made 0.50 ± 0.01 (n = 61).

North Atlantic Oscillation Effect on the Water Levels of the Turkish Lakeland with Regard to Meteorological Indicators

The impact of the global climate change and the North Atlantic Oscillation (NAO) on water resources in the geography of Turkey have been revealed as a result of the investigations in recent years. Big climate events have not only a direct effect on the temperature and rainfall but also have an indirect effect on the evaporation, runoff, underground storage, and sea-lake level changes depending on these meteorological parameters. In this study, it has been investigated how the level variations of the three biggest Turkish lakes (Egirdir, Beysehir and Burdur in Turkish Lakeland) are effected from the global climate change and NAO. This process will be evaluated not only with climate indicators but also with the time variations of the meteorological data. According to the results it is revealed that the meteorological parameters of Turkish Lakeland are not affected strongly from North Atlantic Oscillation. However it is found that the lake levels are affected inversely from North Atlantic Oscillation and evaporation data. Turning points were also determined by using paired t test in the early 1990s for lake level data sets. By analyzing the dimensionless data it is found that lake levels and precipitations start to decrease after the year 1985.

Influence of the North Atlantic Oscillation at local and regional scales: a case study of the Belgian coast

Together, large‐scale atmospheric circulation and local winds determine the occurrence of storm surges that may result in disastrous erosion. This study investigates the interrelationships between large‐scale atmospheric flow and local wind regimes as driving factors of erosion at the Belgian coast. The large‐scale atmospheric circulation is examined in terms of the winter North Atlantic Oscillation (NAO) index, and it is analysed and compared with regional‐scale circulation patterns (i.e. circulation weather types) and local wind regimes, on both annual and seasonal timescales. The results indicate that a strengthening of the positive winter NAO phase can result in an increase in the frequencies of west (W), southwest (SW) and northwest (NW) directional weather types, leading to local wind speeds in excess of 8ms−1, propagating towards the coast. These conditions are likely to lead to erosive events at the coast. By contrast, a weakening of the winter NAO phase can favour the development of northeast (NE), north (N), east (E) and southeast (SE) weather types. The NE and E types generate particularly strong winds, which potentially worsen erosion at the coast. The E and SE types do not, however, affect wind at a local scale. Thus, the extent to which the wind regime at the Belgian coast is sensitive to the winter NAO is a function of the equilibrium between the NAO effects and the regional atmospheric flow direction. In this study, a downscaling conceptual model is developed which relates climate to large‐scale and local‐scale coastal erosion forcing factors. A better understanding of the variability of, and the interrelationships between, climate, meteorology and erosion can help us to adapt to the changes in coastal evolution driven by climate change, improving the prospects of long‐term coastal resilience.

The Effects of North Atlantic Oscillation on the atmospheric middle level Anomaly and precipitation of Iran.Case study: west of Iran.

The Effects of North Atlantic Oscillation on the atmospheric middle level Anomaly and precipitation of Iran.Case study: west of Iran.

Factors behind the variability of phosphorus accumulation in Finnish lakes

Phosphorus retention (TPacc) is one of the major water quality regulators in lakes. The current study aimed at ascertaining the specific lake characteristics regulating TPacc. Moreover, we were interested whether NAO (North Atlantic Oscillation), a proxy of climatic forcing, can explain variability in TPacc, additionally to that ascribed to lake characteristics. Sediment cores were obtained from 21 Finnish lakes, subject to radiometric dating and measurements of TP concentrations. Principal components (PCs) were generated using lake characteristics that are usually included into the modelling of TPacc (e.g. lake area, lake depth, catchment area, P inflow) but also the parameters that the classical models usually missed (e.g. anoxic factor). We used significant principal components (PCs), specific combinations of lake characteristics and monthly NAO values as predictors of TPacc. Lake characteristics explained the bulk of TPacc variability. The most influential factors (positive drivers) behind TPacc included PC1 (representing mainly deep lakes), PC2 (small lakes with high levels of anoxia and water column stability), PC3 (productive lakes with large catchment area and short water residence time), PC4 (lakes with high water column stability, low anoxic factor and relatively high sediment focusing) and PC5 (lakes with high levels of P inflow, anoxia and long water residence time). Additionally, we found a potential negative effect of NAO in October on the annual TPacc. This NAO was significantly positively related to temperatures in surface and near-bottom water layer (also their difference) in autumn, suggesting the possible implications for the internal P dynamics. Increased mineralization of organic matter is the most likely explanation for the reduced TPacc associated with NAO-driven water temperature increase. The analysis presented here contributes to the knowledge of the factors controlling P retention. Moreover, this spatially and temporally comprehensive sediment data can potentially be a valuable source for modelling climate change implications.

Effect of the north Atlantic oscillation on water level fluctuations in lakes of northern Poland

The paper presents an analysis of correlations between water levels in Polish lakes and the rate of the North Atlantic Oscillation (NAO) in the years 1976-2010. The detailed analysis of the spatial variability of the effect of NAO on water levels in lakes concerned 19 lakes with statistically uniform hydrometric material. Two matrices were obtained for each of the lakes, composed of 156 coefficients of correlation calculated between monthly water stages and monthly and seasonal NAO indices. They provided the basis for performing two variants of classification of lakes by Ward’s method. Four typological classes were distinguished for each variant. It was determined that stronger correlations occur in the case of water stages in lakes with seasonal than those with monthly NAO indices. The strongest effect of NAO on water stages is observed in the winter-spring period. Spatial variability of the effect has been recorded, resulting from the climatic conditions of a given region. Lakes located in the south-western part of the studied area constitute an evidently separate group. In the negative phase of NAO, they are distinguished by higher water stages in the winter-spring period. This may be associated with more frequent thaws during winters, and increased supply to lakes in the period.

Seasonal prediction of summer monsoon rainfall over cluster regions of India

Shared nearest neighbour (SNN) cluster algorithm has been applied to seasonal (June–September) rainfall departures over 30 sub-divisions of India to identify the contiguous homogeneous cluster regions over India. Five cluster regions are identified. Rainfall departure series for these cluster regions are prepared by area weighted average rainfall departures over respective sub-divisions in each cluster. The interannual and decadal variability in rainfall departures over five cluster regions is discussed. In order to consider the combined effect of North Atlantic Oscillation (NAO) and Southern Oscillation (SO), an index called effective strength index (ESI) has been defined. It has been observed that the circulation is drastically different in positive and negative phases of ESI-tendency from January to April. Hence, for each phase of ESI-tendency (positive and negative), separate prediction models have been developed for predicting summer monsoon rainfall over identified clusters. The performance of these models have been tested and found to be encouraging.

Effects of NAO on the climatic water budget at the Polish southern Baltic coast

Abstract: Effects of the North Atlantic Oscillation (NAO) on the Standardized Precipitation-Evaporation Index (SPEI), a metric of the climate-dependent water budget, in the Polish part of the southern Baltic coastal areas were analysed. The analyses were based on monthly NAO index values calculated by P.D. Jones, T. Jonsson, and D. Wheeler for 1951-2010 and on monthly temperatures and sums of precipitation in Szczecin, Ustka, and Elbląg used to calculate SPEI. No strong effects of NAO on the water budget could be demonstrated. Intensified air mass advection from the west was found to slightly reduce SPEI in the Polish coastal zone. In winter (particularly in February), the reduction was caused by the temperature increase during air mass advection from the west, which increases evaporation. In summer (mainly in August), the effect was due to the decreased sum of precipitation, the reduction, however, not being significant. Therefore, NAO effects on the water budget are considered weak and irregular.

Projection of North Atlantic Oscillation and its effect on tracer transport

Abstract. The North Atlantic Oscillation (NAO) plays an important role in the climate variability of the Northern Hemisphere, with significant consequences on long-range pollutant transport. We investigate the evolution of pollutant transport in the 21st century influenced by the NAO under a global climate change scenario. We use a free-running simulation performed by the ECHAM/MESSy Atmospheric Chemistry (EMAC) model coupled with the ocean general circulation model MPIOM, covering the period from 1950 until 2100. Similarly to other works, the model shows a future northeastward shift of the NAO centres of action and a weak positive trend of the NAO index (over 150 years). Moreover, we find that NAO trends (computed over periods shorter than 30 years) will continue to oscillate between positive and negative values in the future. To investigate the NAO effects on transport we consider carbon monoxide tracers with exponential decay and constant interannual emissions. We find that at the end of the century, the south-western Mediterranean and northern Africa will, during positive NAO phases, see higher pollutant concentrations with respect to the past, while a wider part of northern Europe will, during positive NAO phases, see lower pollutant concentrations. Such results are confirmed by the changes observed in the future for tracer concentration and vertically integrated tracer transport, differentiating the cases of “high NAO” and “low NAO” events.

Effects of NAO on the climatic water budget at the Polish southern Baltic coast

Abstract Effects of the North Atlantic Oscillation (NAO) on the Standardized Precipitation-Evaporation Index (SPEI), a metric of the climate-dependent water budget, in the Polish part of the southern Baltic coastal areas were analysed. The analyses were based on monthly NAO index values calculated by P.D. Jones, T. Jonsson, and D. Wheeler for 1951-2010 and on monthly temperatures and sums of precipitation in Szczecin, Ustka, and Elbląg used to calculate SPEI. No strong effects of NAO on the water budget could be demonstrated. Intensified air mass advection from the west was found to slightly reduce SPEI in the Polish coastal zone. In winter (particularly in February), the reduction was caused by the temperature increase during air mass advection from the west, which increases evaporation. In summer (mainly in August), the effect was due to the decreased sum of precipitation, the reduction, however, not being significant. Therefore, NAO effects on the water budget are considered weak and irregular.

Non-stationary analysis of the frequency and intensity of heavy precipitation over Canada and their relations to large-scale climate patterns

In recent years, because the frequency and severity of floods have increased across Canada, it is important to understand the characteristics of Canadian heavy precipitation. Long-term precipitation data of 463 gauging stations of Canada were analyzed using non-stationary generalized extreme value distribution (GEV), Poisson distribution and generalized Pareto (GP) distribution. Time-varying covariates that represent large-scale climate patterns such as El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific decadal oscillation (PDO) and North Pacific Oscillation (NP) were incorporated to parameters of GEV, Poisson and GP distributions. Results show that GEV distributions tend to under-estimate annual maximum daily precipitation (AMP) of western and eastern coastal regions of Canada, compared to GP distributions. Poisson regressions show that temporal clusters of heavy precipitation events in Canada are related to large-scale climate patterns. By modeling AMP time series with non-stationary GEV and heavy precipitation with non-stationary GP distributions, it is evident that AMP and heavy precipitation of Canada show strong non-stationarities (abrupt and slowly varying changes) likely because of the influence of large-scale climate patterns. AMP in southwestern coastal regions, southern Canadian Prairies and the Great Lakes tend to be higher in El Nino than in La Nina years, while AMP of other regions of Canada tends to be lower in El Nino than in La Nina years. The influence of ENSO on heavy precipitation was spatially consistent but stronger than on AMP. The effect of PDO, NAO and NP on extreme precipitation is also statistically significant at some stations across Canada.