On the operational predictability of blocking

Tibaldi, S.; Molteni, Franco

doi:10.3402/tellusa.v42i3.11882

Cited by 476 publications

(256 citation statements)

References 29 publications

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“…In recent years, many two-dimensional (2D) blocking indices have been proposed to identify the spatial and temporal variations of blocking events (Barriopedro et al, 2006(Barriopedro et al, , 2010Diao et al, 2006;Scherrer et al, 2006;Davini et al, 2012aDavini et al, , 2012b based upon the extension of one-dimensional blocking indices (Lejenäs and Økland, 1983;Tibaldi and Molteni, 1990;Pelly and Hoskins, 2003). The recent 2D blocking index developed by Davini et al (2012a) has the advantage of differentiating high-latitude and low-latitude events of blocking flows in the Euro-Atlantic sector compared to other 2D indices (Diao et al, 2006).…”

Section: Two-dimensional Blocking Indexmentioning

confidence: 98%

Do European blocking events precede North Atlantic Oscillation events?

Yao

Luo

2015

Adv. Atmos. Sci.

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Using a two-dimensional blocking index, the cause and effect relationship between European blocking (EB) events and North Atlantic Oscillation (NAO) events is investigated. It is shown that the EB event frequency is enhanced over Northern (Southern) Europe for negative (positive) phases of the NAO. Enhanced EB events over Northern Europe precede the establishment of negative phase NAO (NAO − ) events, while the enhanced frequency of EB events over Southern Europe lags positive phase NAO (NAO + ) events.The physical explanation for why enhanced EB events over Northern (Southern) Europe lead (lag) NAO − (NAO + ) events is also provided. It is found that the lead-lag relationship between EB events in different regions and the phase of NAO events can be explained in terms of the different latitudinal distribution of zonal wind associated with the different phases of NAO events. For NAO + events, the self-maintained eastward displacement of intensified midlatitude positive height anomalies owing to the intensified zonal wind can enhance the frequency of EB events over Southern Europe, thus supporting a standpoint that EB events over Southern Europe lag NAO + events. Over Northern Europe, EB events lead NAO − events because NAO − events arise from the self-maintained westward migration of intensified blocking anticyclones due to the weakened zonal wind in higher latitudes.

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Section: Two-dimensional Blocking Indexmentioning

confidence: 98%

Do European blocking events precede North Atlantic Oscillation events?

Yao

Luo

2015

Adv. Atmos. Sci.

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“…This definition allows a blocking structure to shift longitudinally, and other studies invoke this criteria with a reduced window width of 45° (Tyrlis and Hoskins 2008a;Hinton et al 2009). Although there is no universally accepted minimum block duration, blocking studies tend to use thresholds of 4 days (PH) or 5 days (Barriopedro et al 2008;D'Andrea et al 1998;Tibaldi and Molteni 1990), where an individual longitude must pass the blocking criteria for the minimum number of days. It is important to note that this temporal criteria is generally applied longitude by longitude, and not to the large-scale structure as a whole.…”

Section: Previous Spatial and Temporal Criteriamentioning

confidence: 99%

“…This index was modified by Tibaldi and Molteni (1990) (TM) to require a minimum westerly flow north of the reversal in order to ensure that the jet stream was indeed being split around the block. TM also allowed a small latitudinal shifting of the block by additionally searching 4°north and south of a constant latitude / c .…”

Section: Geopotential Height Indicesmentioning

confidence: 99%

“…All fields show a reversal in their meridional gradients, a characterstic of overturning and blocking of the westerlies. While some studies identify blocking events by searching for the large anticyclonic anomalies (Dole and Gordon 1983;Schwierz et al 2004;Ioannidou and Yau 2008;Croci-Maspoli et al 2007), others use a reversal of the mean flow to signify a block (Tibaldi and Molteni 1990;Pelly and Hoskins 2003;Barriopedro et al 2006;Scaife et al 2010). Barriopedro et al (2010a, b) made a recent attempt to combine the two approaches and Barriopedro et al (2010a) contains a useful review of previous blocking indices.…”

Section: Introductionmentioning

confidence: 97%

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A methodology for the comparison of blocking climatologies across indices, models and climate scenarios

2011

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There is urgent need for a consistent blocking identification method that can be used and compared across reanalyses, models and climate scenarios. We present such a method and diagnose daily blocking frequency in 43 years of ERA-40 Reanalysis for indices defined on both the commonly used geopotential height and potential temperature fields as well as a zonal wind index. Applications of various blocking indices to the same data highlights the importance of a consistent methodology for comparison and a method that identifies blocks along a path that varies with the latitude of the storm track. Since the method accommodates blocking detection using 500 mb zonal-wind which is readily available in climate model output, we diagnose blocking in 14 CMIP3 models under two different greenhouse gas scenarios. Blocking duration remains nearly constant among the scenarios, but a robust reduction in blocking frequency with global warming is demonstrated.

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“…Atmosphere 2018, 9, 331 3 of 16 The blocking index used here is the one-dimensional index based on examining the meridional gradient reversal of the 500-hPa HGT designed by Tibaldi and Molteni [26] (hereafter TM index). The calculation of the TM index can be described as follows:…”

Section: Methodsmentioning

confidence: 99%

Effects of Northern Hemisphere Atmospheric Blocking on Arctic Sea Ice Decline in Winter at Weekly Time Scales

2018

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Abstract:In this study, the effects of the Northern Hemisphere atmospheric blocking circulation on Arctic sea ice decline at weekly time scales are examined by defining four key regions based on observational data analysis. Given the regression analysis, the frequently occurring atmospheric patterns related to the sea ice decline in four key sea regions (Baffin Bay, Barents-Kara Seas, Okhotsk Sea and Bering Sea) are found to be Greenland blocking (GB), Ural blocking (UB), western Pacific blocking (PB-W) and eastern Pacific blocking (PB-E), respectively. The results show that the regional blocking frequency is higher (lower) in lower (higher) sea ice winters for each key region. Moreover, composite analysis indicates that blocking evolution is usually accompanied by significant sea ice decline at weekly time scales during the blocking life cycle for each key region. In addition, the intensified surface downward infrared radiation (IR) anomaly and the precipitable water for the entire atmosphere (PWA) in each key region are found to make significant contributions to the positive surface air temperature (SAT) anomaly, which is beneficial for the reduction in sea ice. The approximate quantitative analysis of different surface energy fluxes induced by blocking is also applied. Further analysis shows that the blocking event and the associated changes in SAT and radiation anomalies for each key region lead the sea ice decline by approximately 3~6 days. This result indicates that regional blocking can contribute to regional sea ice decline at weekly time scales through surface warming associated with enhanced water vapor and associated IR variations. Further quantitative estimates indicate that regional blocking can reduce regional sea ice cover (SIC) by 49.6%, 49.4%, 52.2% and 49.5% for Baffin Bay, Barents-Kara Seas, Okhotsk Sea and Bering Sea, respectively, during the blocking life cycle. Finally, a physical process diagrammatic sketch is given to illustrate how blocking affects SIC decline.

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On the operational predictability of blocking

Cited by 476 publications

References 29 publications

Do European blocking events precede North Atlantic Oscillation events?

Do European blocking events precede North Atlantic Oscillation events?

A methodology for the comparison of blocking climatologies across indices, models and climate scenarios

Effects of Northern Hemisphere Atmospheric Blocking on Arctic Sea Ice Decline in Winter at Weekly Time Scales

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