On cold spells in North America and storminess in western Europe

Messori, Gabriele; Caballero, Rodrigo; Gaetani, Marco

doi:10.1002/2016gl069392

Cited by 43 publications

(76 citation statements)

References 59 publications

(85 reference statements)

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“…Before doing so, we note that the two CTPs are roughly in quadrature over the Pacific‐North American region. Since the PNA projects strongly onto the first CTP while USC events project onto the second CTP, we expect the simultaneous correlation between the PNA and USC indices to be weak (as was found by Cellitti et al [], Grotjahn et al [], and Messori et al []). Indeed, the correlation between the PNA and USC indices reaches only −0.26 (at lag 0), compared to a correlation of 0.74 between the PNA and an index similar to the CNA but based on the first, rather than the second CTP.…”

Section: Resultsmentioning

confidence: 99%

“…The dynamical drivers of cold events over North America have been studied extensively, using a diverse range of definitions for the cold events themselves [e.g., Konrad , ; Walsh et al , ; Portis et al , ; Loikith and Broccoli , ; Grotjahn et al , ; Messori et al , , and references therein]. A robust finding of these studies is the association of North American cold events with large‐scale circulation anomalies which advect very cold air equatorward, typically from the northwest.…”

Section: Introductionmentioning

confidence: 99%

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

Harnik

Messori

Caballero

et al. 2016

Geophysical Research Letters

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Extreme large‐scale North American cold events are associated with strong undulations in the tropospheric jet stream which bring cold polar air southward over the continent. Here we propose that these jet undulations are associated with the North American part of the Circumglobal Teleconnection Pattern—a pair of zonally oriented waves of zonal wave number 5 which are in zonal quadrature with each other. While the Pacific/North American pattern is associated with the first circumglobal wave pattern, North American extreme cold events are associated with the second pattern. The 300 hPa meridional wind and surface temperature anomalies associated with the Circumglobal North American wave packet are similar to those associated with the strongest eastern U.S. cold events. Both types of events are associated with a wave packet propagating all the way from Asia across the Pacific and across North America, with cold temperature anomalies spreading southeastward from Canada over the continent.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Harnik

Messori

Caballero

et al. 2016

Geophysical Research Letters

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“…This is compounded by the fact that positive correlations between the θ are generally weak, suggesting that persistent slp configurations do not necessarily match equally persistent t2m patterns. An example of this are wintertime cold spells at the mid-latitudes: while the large-scale circulation anomalies are often very persistent, the temperature can evolve rapidly with a build-up of cold t2m masses leading to a rapidly cool- ing region which then relaxes back to near-climatological values as soon as the anomalous circulation pattern weakens (Messori et al, 2016).…”

Section: Cross-analysis Of the Dynamical Propertiesmentioning

confidence: 99%

Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years

Faranda

Messori

Alvarez-Castro

et al. 2017

Nonlin. Processes Geophys.

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Abstract. Atmospheric dynamics are described by a set of partial differential equations yielding an infinite-dimensional phase space. However, the actual trajectories followed by the system appear to be constrained to a finite-dimensional phase space, i.e. a strange attractor. The dynamical properties of this attractor are difficult to determine due to the complex nature of atmospheric motions. A first step to simplify the problem is to focus on observables which affect -or are linked to phenomena which affect -human welfare and activities, such as sea-level pressure, 2 m temperature, and precipitation frequency. We make use of recent advances in dynamical systems theory to estimate two instantaneous dynamical properties of the above fields for the Northern Hemisphere: local dimension and persistence. We then use these metrics to characterize the seasonality of the different fields and their interplay. We further analyse the large-scale anomaly patterns corresponding to phase-space extremes -namely time steps at which the fields display extremes in their instantaneous dynamical properties. The analysis is based on the NCEP/NCAR reanalysis data, over the period 1948-2013. The results show that (i) despite the high dimensionality of atmospheric dynamics, the Northern Hemisphere sea-level pressure and temperature fields can on average be described by roughly 20 degrees of freedom; (ii) the precipitation field has a higher dimensionality; and (iii) the seasonal forcing modulates the variability of the dynamical indicators and affects the occurrence of phase-space extremes. We further identify a number of robust correlations between the dynamical properties of the different variables.

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“…Variations in the upper tropospheric-lower stratospheric (UTLS) jets and extratropical tropopause influence highimpact weather and climate on regional and global scales: they play key roles in circulation changes, especially in the observed widening of the tropics (e.g., Staten et al, 2016) and storm track evolution (Barnes and Screen, 2015;Messori et al, 2016;Woollings et al, 2016, and references therein). Variations in the UTLS jets influence influence surface weather patterns (e.g., see reviews by Lucas et al, 2014;Harnik et al, 2016) such as rainfall changes (e.g., Price et al, 1998;Raible et al, 2004;Karnauskas and Ummenhofer, 2014;Huang et al, 2015;Xie et al, 2015;Delworth and Zeng, 2014;Bai et al, 2016), destructive wind storms (e.g., Pinto et al, 2009Pinto et al, , 2014Gómara et al, 2014;Messori and Caballero, 2015), and extreme temperature events (e.g., Francis and Vavrus, 2012;Harnik et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Reanalysis comparisons of upper tropospheric–lower stratospheric jets and multiple tropopauses

et al. 2017

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Abstract. The representation of upper tropospheric–lower stratospheric (UTLS) jet and tropopause characteristics is compared in five modern high-resolution reanalyses for 1980 through 2014. Climatologies of upper tropospheric jet, subvortex jet (the lowermost part of the stratospheric vortex), and multiple tropopause frequency distributions in MERRA (Modern-Era Retrospective analysis for Research and Applications), ERA-I (ERA-Interim; the European Centre for Medium-Range Weather Forecasts, ECMWF, interim reanalysis), JRA-55 (the Japanese 55-year Reanalysis), and CFSR (the Climate Forecast System Reanalysis) are compared with those in MERRA-2. Differences between alternate products from individual reanalysis systems are assessed; in particular, a comparison of CFSR data on model and pressure levels highlights the importance of vertical grid spacing. Most of the differences in distributions of UTLS jets and multiple tropopauses are consistent with the differences in assimilation model grids and resolution – for example, ERA-I (with coarsest native horizontal resolution) typically shows a significant low bias in upper tropospheric jets with respect to MERRA-2, and JRA-55 (the Japanese 55-year Reanalysis) a more modest one, while CFSR (with finest native horizontal resolution) shows a high bias with respect to MERRA-2 in both upper tropospheric jets and multiple tropopauses. Vertical temperature structure and grid spacing are especially important for multiple tropopause characterizations. Substantial differences between MERRA and MERRA-2 are seen in mid- to high-latitude Southern Hemisphere (SH) winter upper tropospheric jets and multiple tropopauses as well as in the upper tropospheric jets associated with tropical circulations during the solstice seasons; some of the largest differences from the other reanalyses are seen in the same times and places. Very good qualitative agreement among the reanalyses is seen between the large-scale climatological features in UTLS jet and multiple tropopause distributions. Quantitative differences may, however, have important consequences for transport and variability studies. Our results highlight the importance of considering reanalyses differences in UTLS studies, especially in relation to resolution and model grids; this is particularly critical when using high-resolution reanalyses as an observational reference for evaluating global chemistry–climate models.

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On cold spells in North America and storminess in western Europe

Cited by 43 publications

References 59 publications

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

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

Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years

Reanalysis comparisons of upper tropospheric–lower stratospheric jets and multiple tropopauses

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