The Circumglobal North American wave pattern and its relation to cold events in eastern North America

Harnik, Nili; Messori, Gabriele; Caballero, Rodrigo; Feldstein, Steven B.

doi:10.1002/2016gl070760

Cited by 56 publications

(58 citation statements)

References 41 publications

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“…The overall warming, which is to be expected from the increased amount of greenhouse gas loading in the atmosphere, contributed to the trend, but the spatially non‐uniform, somewhat wave‐like temperature trend pattern suggests that a large‐scale atmospheric Rossby wave train could have played an important role as well. In fact, the relevance of atmospheric Rossby waves in producing teleconnections that cause extreme heatwaves has long been recognized (Trenberth and Branstator, ; Lyon and Dole, ; Dole et al ., ; Lau and Kim, ; Petoukhov et al ., ; Teng et al ., ; Coumou et al ., ; Harnik et al ., ).…”

Section: Introductionmentioning

confidence: 97%

“…Prior to plotting, two iterations of nine-point local smoothing were performed on (a) and the zonal mean was removed from (b). Stippling indicates statistical significance at the 95% confidence level, as derived from a Monte Carlo simulation with 1,000 random samples 1992; Lyon and Dole, 1995;Dole et al, 2011;Lau and Kim, 2012;Petoukhov et al, 2013;Teng et al, 2013;Coumou et al, 2014;Harnik et al, 2016).…”

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confidence: 99%

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Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland

Baggett

Lee

2019

Quart J Royal Meteoro Soc

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The summer of 2010 was characterized by weather and climate extremes such as the western Russia heatwave and the Pakistan floods. A recent study found that summer was dominated by a particular 200 hPa geopotential height pattern featuring an anomalous Rossby wave train with ridges centred over Greenland, Europe and Russia. The daily frequency of this pattern has dramatically increased recently and closely resembles the mean‐state difference in 200 hPa geopotential height fields between 1998–2014 (P2) and 1979–1997 (P1). Because anomalous wave trains are often driven by localized diabatic heating, it is tested in this study whether the P2 minus P1 pattern is caused by diabatic heating anomalies near Greenland. While it is found that sea ice concentrations declined and sea‐surface temperatures rose over Baffin Bay to the west of Greenland during P2, surface latent heat fluxes actually increased downward, indicating that surface processes were likely not the source of diabatic heating. Rather, an increase in vertically integrated horizontal latent‐heat flux convergence over Baffin Bay was observed in P2, which led to the condensation of water vapour and latent heating. Thus, the mid‐tropospheric circulation established the diabatic heating. A set of initial‐value calculations with idealized heating over Baffin Bay show solutions that remarkably resemble the P2 minus P1 pattern and provide a plausible explanation as to why the pattern has been occurring more frequently. This study demonstrates that changes in the Arctic can arise from moisture transport from the midlatitudes, and, in turn, these changes can induce weather and climate extremes in distant midlatitude regions.

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Section: Introductionmentioning

confidence: 97%

mentioning

confidence: 99%

Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland

Baggett

Lee

2019

Quart J Royal Meteoro Soc

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“…Pinto et al, 2013;van Oldenborgh et al, 2015;Huntingford et al, 2014;Wild et al, 2015) and cold spells in North America (e.g. Trenary et al, 2015;Lee et al, 2015;Messori et al, 2016;Harnik et al, 2016) have attracted in recent years. The analysis in Section 5.1 primarily aims to relate the information provided by our metrics to known features of the atmospheric variability over the Euro-Atlantic region, and can be viewed as a test of the robustness of the metrics we propose.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Systems Theory Sheds New Light on Compound Climate Extremes in Europe and Eastern North America

Luca¹,

Messori²,

Pons³

et al. 2019

Preprint

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We propose a novel approach to the study of compound extremes, grounded in dynamical systems theory. Specifically, we present the co-recurrence ratio (α), which elucidates the dependence structure between variables by quantifying their joint recurrences. This approach is applied to daily climate extremes, derived from the ERA-Interim reanalysis over the 1979-2018 period. The analysis focuses on concurrent (i.e. same-day) wet (total precipitation) and windy (10m wind gusts) extremes in Europe and concurrent cold (2m temperature) extremes in Eastern North America and wet extremes in Europe. Results for wet and windy extremes in Europe, which we use as a test-bed for our methodology, show that α peaks during boreal winter. High α values correspond to wet and windy extremes in north-western Europe, and to large-scale conditions resembling the positive phase of the North Atlantic Oscillation (NAO). This confirms earlier findings which link the positive NAO to a heightened frequency of extra-tropical cyclones impacting north-western Europe. For the Eastern North America-Europe case, α extremes once again reflect concurrent climate extremes - in this case cold extremes over North America and wet extremes over Europe. Our analysis provides detailed spatial information on regional hotspots for these compound extreme occurrences, and encapsulates information on their spatial footprint which is typically not included in a conventional co-occurrence analysis. We conclude that α successfully characterises compound extremes by reflecting the evolution of the associated meteorological maps. This approach is entirely general, and may be applied to different types of compound extremes and geographical regions.

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“…Baxter and Nigam (2015) demonstrated that, during the winter of 2013/2014, the North Pacific Oscillation-WP teleconnection provided a major contribution to the North American circulation anomaly. Harnik et al (2016) discovered that a large number of extreme North American cold events are related to jet stream undulations similar to the circumglobal North America pattern (Branstator 2002). Although the statistical significance between planetary climate modes and seasonal ECW behavior is well established, little information exists regarding the intraseasonal links between planetary climate modes and ECWs or the underlying physics behind these relationships.…”

Section: Introductionmentioning

confidence: 99%

Planetary and synoptic-scale dynamic control of extreme cold wave patterns over the United States

2019

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The roles of planetary and synoptic-scale waves in extreme cold wave (ECW) events over the southeastern (SE) and northwestern (NW) United States (US) are studied using a spherical harmonic decomposition in conjunction with piecewise tendency diagnosis (PTD). Planetary waves and synoptic waves jointly work together to initiate ECW events. Notably, the planetary waves not only provide a direct contribution to circulation field enacting ECW events but also alter the background circulation field in such a manner that promotes synoptic waves growth via increases in regional barotropic deformation. The SE-ECW events, concurrent with the Northern Hemisphere annular mode (NAM) negative phase, feature high latitude intensification and subsequent southeastward movement of cold surface air temperature (SAT) anomalies. The planetary-scale pattern provides a sizable contribution to the total wave pattern on both sea level pressure (SLP) and upper level. Moreover, the negative NAM planetary anomaly acts to displace the jet equatorward and thereby increases the barotropic deformation of the synoptic-scale anomaly over southeastern US. PTD confirms that the planetary-scale barotropic deformation plays a key role in deepening the negative height anomaly with a secondary contribution from baroclinic growth. In contrast, NW-ECW events feature a regional SAT cold anomaly that intensified in situ in association with a quasi-stationary positive SLP anomaly with a substantial planetary-scale wave component. The upper level circulation is characterized by a pronounced anomalous ridge over the Gulf of Alaska and a northeast-southwest tilted negative height anomaly to its east. The negative height anomaly axis is orthogonal to the planetary-scale dilatation, result in a stronger planetary barotropic deformation of the incipient negative height anomaly.

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The Circumglobal North American wave pattern and its relation to cold events in eastern North America

Cited by 56 publications

References 41 publications

Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland

Summertime midlatitude weather and climate extremes induced by moisture intrusions to the west of Greenland

Dynamical Systems Theory Sheds New Light on Compound Climate Extremes in Europe and Eastern North America

Planetary and synoptic-scale dynamic control of extreme cold wave patterns over the United States

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