scholarly journals On the Relationship between the North Atlantic Oscillation and Early Warm Season Temperatures in the Southwestern United States

2015 ◽  
Vol 28 (14) ◽  
pp. 5683-5698 ◽  
Author(s):  
Boksoon Myoung ◽  
Seung Hee Kim ◽  
Jinwon Kim ◽  
Menas C. Kafatos
Keyword(s):  
United States ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Warm Season ◽  
Western United States ◽  
Daily Maximum ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract It is reported herein that the North Atlantic Oscillation (NAO), which has been known to directly affect winter weather conditions in western Europe and the eastern United States, is also linked to surface air temperature over the broad southwestern U.S. (SWUS) region, encompassing California, Nevada, Arizona, New Mexico, Utah, and Colorado, in the early warm season. The authors have performed monthly time-scale correlations and composite analyses using three different multidecadal temperature datasets. Results from these analyses reveal that NAO-related upstream circulation positively affects not only the means, but also the extremes, of the daily maximum and minimum temperatures in the SWUS. This NAO effect is primarily linked with the positioning of upper-tropospheric anticyclones over the western United States that are associated with development of the positive NAO phase through changes in lower-tropospheric wind directions as well as suppression of precipitation and enhanced shortwave radiation at the surface. The effect is observed in the SWUS only during the March–June period because the monthly migration of anticyclones over the western United States follows the migration of the NAO center over the subtropical Atlantic Ocean. The link between the SWUS temperatures and NAO has been strengthened in the last 30-yr period (1980–2009), compared to the previous 30-yr period (1950–79). In contrast to the NAO–SWUS temperature relationship, El Niño–Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO) show only marginal correlation strengths in several limited regions for the same 60-yr period.

scholarly journals The influence of the North Atlantic Oscillation and El Niño–Southern Oscillation on mean and extreme values of column ozone over the United States

2014 ◽  
Vol 14 (14) ◽  
pp. 21065-21099
Author(s):  
I. Petropavlovskikh ◽  
R. Evans ◽  
G. McConville ◽  
G. L. Manney ◽  
H. E. Rieder
Keyword(s):  
United States ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Total Ozone ◽  
Southern Oscillation ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Column Ozone

Abstract. Continuous measurements of total ozone (by Dobson spectrophotometers) across the contiguous United States (US) began in the early 1960s. Here, we analyze temporal and spatial variability and trends in total ozone from the five US sites with long-term records. While similar long-term ozone changes are detected at all five sites, we find differences in the patterns of ozone variability on shorter time scales. In addition to standard evaluation techniques, STL-decomposition methods (Seasonal Trend decomposition of time series based on LOcally wEighted Scatterplot Smoothing, LOESS) are used to address temporal variability and trends in the Dobson data. The LOESS-smoothed trend components show a decline of total ozone between the 1970s and 2000s and a "stabilization" at lower levels in recent years, which is also confirmed by linear trend analysis. Methods from statistical extreme value theory (EVT) are used to characterize days with high and low total ozone (termed EHOs and ELOs, respectively) at each station and to analyze temporal changes in the frequency of ozone extremes and their relationship to dynamical features such as the North Atlantic Oscillation and El Niño Southern Oscillation. A comparison of the "fingerprints" detected in the frequency distribution of the extremes with those for standard metrics (i.e., the mean) shows that more "fingerprints" are found for the extremes, particularly for the positive phase of the NAO, at all five US monitoring sites. Results from the STL-decomposition support the findings of the EVT analysis. Finally, we analyze the relative influence of low and high ozone events on seasonal mean column ozone at each station. The results show that the influence of ELOs and EHOs on seasonal mean column ozone can be as much as ±5%, or about twice as large as the overall long-term decadal ozone trends.

Rainfall Variability and Trend Analysis of Multiannual Rainfall in Romanian Plain

2017 ◽  
Vol 17 (2) ◽  
pp. 124-144 ◽  
Author(s):  
Zeineddine Nouaceur ◽  
Ovidiu Murărescu ◽  
George Murătoreanu
Keyword(s):  
North Atlantic Oscillation ◽  
Central Europe ◽  
North Atlantic ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
El Nino Southern Oscillation ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe IPCC climate models predict, for the Central Europe, are for climate changes, being seen variability of temperature, with a growing trend of 1-2,5° C (with 1° C for alpine zone – Carpathians and 2-2,5° C for plains). Current observations in the Romanian plain are not consistent, with an existence of a multiannual variability of temperature and precipitations depending on cyclonal and anti-ciclonal activity. The research is based on calculation of reduced centered index, also the graphical chronological method in information processing (MGCTI) of „Bertin Matrix” type, to show current trends of the spatio-temporal variability of precipitation in the context of global climate change. These are in line with the movement of air masses in Europe in general, and implicitly in Romania, with particular regard to the southern region of the country where the Romanian Plain. The variability of short-term global climate is generally associated with coupling phases of oceanic and atmospheric phenomena including El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). While El Niño Southern Oscillation (ENSO) affects climate variability in the world, the North Atlantic Oscillation (NAO) is the climate model dominant in the North Atlantic region. The latter cyclic oscillation whose role is still under debate could explain the variability of rainfall in much of the, central Europe area, and support the hypothesis of a return of the rains marking the end of years of drought in Romanian plain. Faced with such great changes that today affect the central Europe region and given the complexity of spatial and temporal dimensions of the climatic signal, a more thorough research of causes and retroactions would allow for a better understanding of the mechanisms behind this new trend.

scholarly journals Impacts of the North Atlantic Oscillation on Winter Precipitations and Storm Track Variability in Southeast Canada and Northeast US

2020 ◽  
Author(s):  
Julien Chartrand ◽  
Francesco Salvatore Rocco Pausata
Keyword(s):  
United States ◽  
North America ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Storm Track ◽  
The United States ◽  
Eastern North America ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. The North Atlantic Oscillation (NAO) affects atmospheric variability from eastern North America to Europe. Although the link between the NAO and winter precipitations in the eastern North America have been the focus of previous work, only few studies have hitherto provided clear physical explanations on these relationships. In this study we revisit and extend the analysis of the effect of the NAO on winter precipitations over a large domain covering southeast Canada and the northeastern United States. Furthermore, here we use the recent ERA5 reanalysis dataset (1979–2018), which currently has the highest available horizontal resolution for a global reanalysis (0.25°), to track extratropical cyclones to delve into the physical processes behind the relationship between NAO and precipitation, snowfall, snowfall-to-precipitation ratio (S/P), and snow cover depth anomalies in the region. In particular, our results show that positive NAO phases are associated with less snowfall over a wide region covering Nova Scotia, New England and the Mid-Atlantic of the United States relative to negative NAO phases. Henceforth, a significant negative correlation is also seen between S/P and the NAO over this region. This is due to a decrease (increase) in cyclogenesis of coastal storms near the United States east coast during positive (negative) NAO phases, as well as a northward (southward) displacement of the mean storm track over North America.

The Relationship between the North Atlantic Oscillation and High-Wind Observations Across the Eastern United States 

2021 ◽  
Author(s):  
Sylvia Stinnett ◽  
Joshua Durkee ◽  
Joshua Gilliland ◽  
Victoria Murley ◽  
Alan Black ◽  
...  
Keyword(s):  
United States ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Eastern United States ◽  
High Wind ◽  
The North ◽  
The North Atlantic ◽  
Wind Events ◽  
The North Atlantic Oscillation ◽  
The Relationship

<p>The North Atlantic Oscillation (NAO) is a high-frequency oscillation that has known influences on the climatology of weather patterns across the eastern United States. This study explores the relationship between the daily North Atlantic Oscillation index with observed high-wind events from 391 first-order weather stations across the eastern U.S. from 1973-2015. These events were determined following typical National Weather Service high-wind criteria: sustained winds of at least 18 m•s-1 for at least 1 hour or a wind gust of at least 26 m•s-1 for any duration. Since research literature shows high-wind events are often connected to parent mid-latitude cyclone tracks, and since the NAO has been shown to influence these storm tracks, it is hypothesized that changes in NAO phases are connected to spatial shifts and frequencies in high-wind observations. Initial results show a preferred southwesterly direction during each NAO phase. Variance in high-wind directions appears to increase (decrease) during negative (positive) NAO phases. Further, the greatest spatial difference in the mean center of high-wind observations was between positive and negative NAO phases. Overall, these preliminary findings indicate changes in high-wind observations may be linked to NAO phases.</p>

scholarly journals Letter to the editor: Are the North Atlantic Oscillation and the Southern Oscillation related in any time-scale?

2000 ◽  
Vol 18 (2) ◽  
pp. 247-251 ◽  
Author(s):  
R. García ◽  
P. Ribera ◽  
L. Gimenoo ◽  
E. Hernández
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Singular Spectrum Analysis ◽  
Atmospheric Dynamics ◽  
Meteorology And Atmospheric Dynamics ◽  
The North ◽  
Ocean Atmosphere ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. The North Atlantic Oscillation (NAO) and the Southern Oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years' that represents about 20% of the SO variance and about 25% of the NAO variance.Key words: Meteorology and atmospheric dynamics (climatology; ocean-atmosphere interactions)

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

2008 ◽  
Vol 21 (3) ◽  
pp. 532-541 ◽  
Author(s):  
Frank A. Aebly ◽  
Qi Hu ◽  
Sherilyn C. Fritz
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Warm Season ◽  
Correlation Coefficients ◽  
Precipitation Variability ◽  
Future Climate Change ◽  
West Greenland ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

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.

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