An Interdisciplinary Approach to the Study of Extreme Weather Events: Large-Scale Atmospheric Controls and Insights from Dynamical Systems Theory and Statistical Mechanics

Messori, Gabriele; Caballero, Rodrigo; Bouchet, Freddy; Faranda, Davide; Grotjahn, Richard; Harnik, Nili; Jewson, Stephen; Pinto, Joaquim G.; Rivière, Gwendal; Woollings, Tim; Yiou, Pascal

doi:10.1175/bams-d-17-0296.1

Cited by 15 publications

(15 citation statements)

References 16 publications

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“…According to the Fifth Intergovernmental Panel on Climate Change report, the intensity of heat waves in Europe will increase in the future (Collins et al, 2013). Hence, forecasting and assessing the risk of heat waves is a pivotal issue (Messori et al, 2018). Also, due to the various impacts driven by different characteristics of heat waves, no uniform definition of a heat wave exists (Perkins, 2015).…”

Section: Introductionmentioning

confidence: 99%

Processes determining heat waves across different European climates

Zschenderlein

Fink

Pfahl

et al. 2019

Quart J Royal Meteoro Soc

114

128

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This study presents a comprehensive analysis of processes determining heat waves across different climates in Europe for the period 1979–2016. Heat waves are defined using a percentile‐based index and the main processes quantified along trajectories are adiabatic compression by subsidence and local and remote diabatic processes in the upper and lower troposphere. This Lagrangian analysis is complemented by an Eulerian calculation of horizontal temperature advection. During typical summers in Europe, one or two heat waves occur, with an average duration of five days. Whereas high near‐surface temperatures over Scandinavia are accompanied by omega‐like blocking structures at 500 hPa, heat waves over the Mediterranean are connected to comparably flat ridges. Tracing air masses backwards from the heat waves, we identify three trajectory clusters with coherent thermodynamic characteristics, vertical motions, and geographic origins. In all regions, horizontal temperature advection is almost negligible. In two of the three clusters, subsidence in the free atmosphere is very important in establishing high temperatures near the surface, while the air masses in the third cluster are warmed primarily due to diabatic heating near the surface. Large interregional differences occur between the British Isles and western Russia. Over the latter region, near‐surface transport and diabatic heating appear to be very important in determining the intensity of the heat waves, whereas subsidence and adiabatic warming are of first‐order importance for the British Isles. Although the large‐scale pattern is quasistationary during heat wave days, new air masses are entrained steadily into the lower troposphere during the life cycle of a heat wave. Overall, the results of the present study provide a guideline as to which processes and diagnostics weather and climate studies should focus on to understand the severity of heat waves.

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Section: Introductionmentioning

confidence: 99%

Processes determining heat waves across different European climates

Zschenderlein

Fink

Pfahl

et al. 2019

Quart J Royal Meteoro Soc

114

128

View full text Add to dashboard Cite

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“…These metrics are intuitively linked to the intrinsic predictability of the atmosphere: a highly persistent (low θ), low-dimensional (low d) state will be more predictable than a low-persistence (high θ), high-dimensional (high d) one (Messori et al 2017). Different interpretations of predictability depend on different factors or may emphasize different aspects of the atmospheric circulation, and thus show discrepancies in direct comparisons (Messori et al 2018). Indeed, while the notions of practical and intrinsic predictability are linked, there is not always a direct correspondence between the two (Scher and Messori 2019).…”

Section: Introductionmentioning

confidence: 99%

Dynamics and predictability of cold spells over the Eastern Mediterranean

et al. 2020

Self Cite

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The accurate prediction of extreme weather events is an important and challenging task, and has typically relied on numerical simulations of the atmosphere. Here, we combine insights from numerical forecasts with recent developments in dynamical systems theory, which describe atmospheric states in terms of their persistence (θ−1) and local dimension (d), and inform on how the atmosphere evolves to and from a given state of interest. These metrics are intuitively linked to the intrinsic predictability of the atmosphere: a highly persistent, low-dimensional state will be more predictable than a low-persistence, high-dimensional one. We argue that θ−1 and d, derived from reanalysis sea level pressure (SLP) and geopotential height (Z500) fields, can provide complementary predictive information for mid-latitude extreme weather events. Specifically, signatures of regional extreme weather events might be reflected in the dynamical systems metrics, even when the actual extreme is not well-simulated in numerical forecasting systems. We focus on cold spells in the Eastern Mediterranean, and particularly those associated with snow cover in Jerusalem. These rare events are systematically associated with Cyprus Lows, which are the dominant rain-bearing weather system in the region. In our analysis, we compare the ‘cold spell Cyprus Lows’ to other ‘regular’ Cyprus Low days. Significant differences are found between cold spells and ‘regular’ Cyprus Lows from a dynamical systems perspective. When considering SLP, the intrinsic predictability of cold spells is lowest hours before the onset of snow. We find that the cyclone’s location, depth and magnitude of air-sea fluxes play an important role in determining its intrinsic predictability. The dynamical systems metrics computed on Z500 display a different temporal evolution to their SLP counterparts, highlighting the different characteristics of the atmospheric flow at the different levels. We conclude that the dynamical systems approach, although sometimes challenging to interpret, can complement conventional numerical forecasts and forecast skill measures, such as model spread and absolute error. This methodology outlines an important avenue for future research, which can potentially be fruitfully applied to other regions and other types of weather extremes.

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“…Global climate change and regional Arctic feedbacks are responsible for an Arctic Amplification, that Arctic temperatures are increasing faster than in the rest of the hemisphere (Notz & Stroeve, 2016). The tropospheric jet stream is the pathway or bridge to midlatitude weather events, which in turn is also influenced by internal variability (chaotic atmosphere), tropical and midlatitude oceans, and the stratospheric polar vortex wind pattern (Messori et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Resolving Future Arctic/Midlatitude Weather Connections

Wang

2018

Earth's Future

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Given ongoing large changes in the Arctic, high-latitude forcing is a new potential driver for sub-seasonal weather impacts at midlatitudes in coming decades. Such linkage research, however, is controversial. Some metrics find supporting evidence and others report no robust correlations. Model studies reach different conclusions. Case studies from particular historical months suggest potential connections. We propose that a difficulty in resolving the science is due to the inherent complexity and intermittent character of atmospheric dynamics, which serves as a variable causal bridge between changes in the Arctic and midlatitude weather. Linkages may be more favorable in one atmospheric jet stream pattern than another. Linkages are a two-step process: thermodynamic forcing, i.e. warm Arctic temperatures and loss of sea ice, is generally favorable in the last decade, but internal atmospheric dynamics, i.e. the jet stream location and strength, must also allow for a connection. Thus, in the last decade only a few possible linkage events are noted into and out of the Arctic; for examples

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An Interdisciplinary Approach to the Study of Extreme Weather Events: Large-Scale Atmospheric Controls and Insights from Dynamical Systems Theory and Statistical Mechanics

Cited by 15 publications

References 16 publications

Processes determining heat waves across different European climates

Processes determining heat waves across different European climates

Dynamics and predictability of cold spells over the Eastern Mediterranean

Resolving Future Arctic/Midlatitude Weather Connections

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