Effects of the North Atlantic Oscillation on precipitation-type frequency and distribution in the eastern United States

<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&#8226;s-1 for at least 1 hour or a wind gust of at least 26 m&#8226;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>

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

10.5194/wcd-2020-20 ◽

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.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-21065-2014 ◽

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.

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

Journal of Climate ◽

10.1175/jcli-d-14-00521.1 ◽

2015 ◽

Vol 28 (14) ◽

pp. 5683-5698 ◽

Cited By ~ 12

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.

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The North Atlantic Oscillation in the Atlantic-European SLP

Tellus A Dynamic Meteorology and Oceanography ◽

10.3402/tellusa.v42i5.11893 ◽

1990 ◽

Vol 42 (5) ◽

pp. 497-507 ◽

Cited By ~ 14

Author(s):

Rita Glowienka-Hense

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

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Influence of the North Atlantic oscillation on the atmospheric levels of benzo[a]pyrene over Europe

Climate Dynamics ◽

10.1007/s00382-021-05766-0 ◽

2021 ◽

Author(s):

Pedro Jiménez-Guerrero ◽

Nuno Ratola

Keyword(s):

Spatial Pattern ◽

North Atlantic Oscillation ◽

North Atlantic ◽

Transport Model ◽

Regional Scale ◽

The South ◽

Climatic Fluctuations ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

AbstractThe atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.

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