The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate

Ayarzagüena, Blanca; Orsolini, Yvan; Langematz, Ulrike; Abalichin, Janna; Kubin, Anne

doi:10.1175/jcli-d-14-00210.1

Cited by 13 publications

(11 citation statements)

References 60 publications

(90 reference statements)

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“…Our results highlight the wide spectrum of behavior exhibited by the Arctic polar vortex in both time and altitude, which includes small localized weak/strong events, as well as prolonged and vertically deep ones. Distinguishing between such “major” and “minor” events has recently been highlighted by many as important for more completely describing the full variability of the stratosphere and its importance for numerous research topics including definitions of sudden warming events (e.g., Butler et al, ; Maury et al, ), polar chemical processing and ozone loss (e.g., Manney & Lawrence, ; Strahan et al, ), coupling with the troposphere (e.g., Dunn‐Sigouin & Shaw, ; Runde et al, ), understanding climate connections to, for example, the quasi‐biennial oscillation and El Niño/La Niña (e.g., Díaz‐Durán et al, ; Garfinkel et al, ; Iza et al, ), forecasting and prediction (e.g., Butler et al, ; Tripathi, Charlton‐Perez, et al, ), and defining and attributing events in climate models (e.g., Ayarzagüena et al, ; Kim et al, ).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

Lawrence

Manney

2018

JGR Atmospheres

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Computer vision techniques are used to characterize the Arctic stratospheric polar vortex in 38 years of reanalysis data. Such techniques are typically applied to analyses of digital images, but they represent powerful tools that are more widely applicable: basic techniques and considerations for geophysical applications are outlined herein. Segmentation, descriptive, and tracking algorithms are combined in the Characterization and Analysis of Vortex Evolution using Algorithms for Region Tracking (CAVE‐ART) package, which was developed to comprehensively describe dynamical and geometrical evolution of polar vortices. CAVE‐ART can characterize and track multiple vortex regions through time, providing an extensive suite of region, moments, and edge diagnostics for each. CAVE‐ART is valuable for identifying vortex‐splitting events including, but not limited to, previously cataloged vortex‐split sudden stratospheric warmings. An algorithm for identifying such events detects 52 potential events between 1980 and 2017; of these, 38 are subjectively classified as distinct “split‐like” events. The algorithm based on CAVE‐ART is also compared with moment‐based methods previously used to detect split events. Furthermore, vortex edge‐averaged wind speeds from CAVE‐ART are used to define extreme weak and strong polar vortex events over multiple vertical levels; this allows characterization of their occurrence frequencies and extents in time and altitude. Weak and strong events show distinct signatures in CAVE‐ART diagnostics: in contrast to weak events, strong vortices are more cylindrical and pole centered, and less filamented, than the climatological state. These results from CAVE‐ART exemplify the value of computer vision techniques for analysis of geophysical phenomena.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

Lawrence

Manney

2018

JGR Atmospheres

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“…Many previous studies have noted that the anomalous upward fluxes of planetary waves from the troposphere to the stratosphere are closely related to tropospheric blockings (Quiroz, ; Mukougawa and Hirooka, ; Kuroda, ; Martius et al ., ; Castanheira and Barriopedro, ; Nishii et al ., , ; Woollings et al ., ; Vial et al ., ; Ayarzaguena et al ., ). On the other hand, Marshall and Scaife () found that the predictability of stratospheric warmings and Atlantic blocking signatures can be improved when the stratosphere was better represented in a numerical model, implying a role of the stratosphere in the evolution of tropospheric blockings.…”

Section: Introductionmentioning

confidence: 97%

The connection between extreme stratospheric polar vortex events and tropospheric blockings

Huang

Tian

Zhang

et al. 2017

Quart J Royal Meteoro Soc

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The variations of tropospheric blockings and their connections with the stratospheric polar vortex during different stages of the life cycle of extreme stratospheric polar vortex events (i.e. strong vortex (SV) events and weak vortex (WV) events) are investigated. The blocking frequency decreases over the Euro-Atlantic sector and increases over the western North Pacific during the onset and maturation stages of SV events. There are more blocking days over the western North Pacific and weakened upward planetary wave fluxes in the stratosphere during the maturation stage of shorter time-scale SV events than during longer time-scale SV events and the weakening of the upward planetary wave fluxes mainly results from the linear wave interference effect. The blocking frequency is increased over the Euro-Atlantic sector during the decline stage of SV events. This increase is found to be related to the descending stratospheric zonal wind anomalies and the poleward displacement of the eddy-driven jet stream, which lasts for about 10 days and is associated with the descending positive stratospheric Northern Annular Mode (NAM) anomalies. The increased blocking frequency leads to an enhancement of the planetary wave fluxes in the stratosphere via both the linear wave interference (for shorter time-scale SV events) and nonlinear wave interference (for longer time-scale SV events) effect.The changes of the blocking frequency during the growth stage of WV events are almost opposite to those observed during the onset and maturation stages of SV events. The blocking frequency decreases over the Euro-Atlantic sector after the central dates of WV events, which are related to the descending stratospheric zonal wind anomalies and the equatorward displacement of the eddy-driven jet stream preceded by the descending negative stratospheric NAM anomalies about 10 days. We found that the nonlinear wave interference begins to make a considerable contribution to the weakening of the upward wave fluxes in the stratosphere after the central date of WV events and this is not emphasized in previous literature.

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“…In addition to influencing fields near the surface, blocking flow also impacts the winter polar stratosphere. In particular, the location, shape, and distribution of blocks are linked to planetary wave propagation and vortex displacements (Ayarzäguena et al, 2015;Martius et al, 2009;Nishii et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

et al. 2019

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The fidelity of a prerelease Energy Exascale Earth System Model (E3SM) in reproducing atmospheric blocking is evaluated with ∼100‐ and ∼25‐km horizontal resolution within ensembles of simulations with Atmospheric Modeling Intercomparison Protocol‐type active atmosphere and land surface configurations. This evaluation is conducted via a hybrid bidimensional blocking index based on geopotential height. The lower‐resolution model correctly reproduces the spatial distribution of blocking frequency maxima over the Northern Hemisphere. However, it overestimates the blocking frequency over western North America, the Pacific Northeast, and Eastern Europe regions and largely underestimates blocking frequency over the North Atlantic. The high‐resolution model significantly reduces the bias over the North Pacific region, particularly over western North America, but the biases over the North Atlantic blocking sector mostly persist. A diagnosis of the mean flow reveals that the subtropical jet is displaced poleward in the high‐resolution model with a jet core speed that is generally more realistic. A time scale analysis of eddies suggests that synoptic eddies associated with the blocking events are increased in the high‐resolution configuration. The discrepancy between the models implies that both synoptic and low‐frequency eddies play significant roles in determining North Pacific blocking, whereas North Atlantic blocking is mainly driven by low‐frequency eddies. The characteristic time scale associated with blocking events is also investigated, and it shows that both model resolutions produce events that are overly persistent. However, the bias in the high‐resolution model is reduced, which reflects more efficient energy dispersion with higher resolution.

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The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate

Cited by 13 publications

References 60 publications

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

The connection between extreme stratospheric polar vortex events and tropospheric blockings

Northern Hemisphere Blocking in ∼25‐km‐Resolution E3SM v0.3 Atmosphere‐Land Simulations

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