Changes in the Extratropical Storm Tracks in Response to Changes in SST in an AGCM

Graff, Lise Seland; LaCasce, J. H.

doi:10.1175/jcli-d-11-00174.1

Cited by 55 publications

(60 citation statements)

References 63 publications

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“…Investigating the sensitivity of the NH extratropical storm tracks to SST in a regional atmospheric model, Woollings et al (2010) highlighted the importance of sufficient horizontal resolution for resolving gradients in SST, such as those associated with the Gulf Stream, to realistically represent the position of storm tracks. Similarly, in idealized AGCM experiments, several studies raised the importance of the latitudinal position of meridional SST (gradients) for midlatitude storm tracks (Graff and LaCasce 2012;Ogawa et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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Characteristics of atmospheric blocking in the Southern Hemisphere (SH) are explored in atmospheric general circulation model (AGCM) simulations with the Community Atmosphere Model, version 3, with a particular focus on the Australia-New Zealand sector. Preferred locations of blocking in SH observations and the associated seasonal cycle are well represented in the AGCM simulations, but the observed magnitude of blocking is underestimated throughout the year, particularly in late winter and spring. This is related to overly zonal flow due to an enhanced meridional pressure gradient in the model, which results in a decreased amplitude of the longwave trough/ridge pattern. A range of AGCM sensitivity experiments explores the effect on SH blocking of tropical heating, midlatitude sea surface temperatures, and land-sea temperature gradients created over the Australian continent during austral winter. The combined effects of tropical heating and extratropical temperature gradients are further explored in a configuration that is favorable for blocking in the Australia-New Zealand sector with warm SST anomalies to the north of Australia, cold to the southwest of Australia, warm to the southeast, and cool Australian land temperatures. The blockingfavorable configuration indicates a significant strengthening of the subtropical jet and a reduction in midlatitude flow, which results from changes in the thermal wind. While these overall changes in mean climate, predominantly forced by the tropical heating, enhance blocking activity, the magnitude of atmospheric blocking compared to observations is still underestimated. The blocking-unfavorable configuration with surface forcing anomalies of opposite sign results in a weakening subtropical jet, enhanced midlatitude flow, and significantly reduced blocking.

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Section: Introductionmentioning

confidence: 99%

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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“…The increased storm activity level temperature gradient and pushes the jet/storm track equatorward (e.g., Bengtsson and Hodges,230 2006; Brayshaw et al, 2008;Butler et al, 2010;Lu et al, 2010;Graff and LaCasce, 2012;Shaw et al, 2016), with various possibilities for the precise mechanism (Lorenz and DeWeaver, 2007;Chen et al, 2008;Kidston et al, 2011;Michel and Rivière, 2014). The idea that the low-level gradient ∆T 850 has greater leverage in the 1.5…”

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confidence: 99%

Midlatitude atmospheric circulation responses under 1.5 °C and 2.0 °C warming and implications for regional impacts

Li¹,

Michel²,

Graff³

et al. 2017

Preprint

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Abstract.This study investigates the global response of the midlatitude atmospheric circulation to 1.5• C and 2.0 • C of warming using the HAPPI "Half a degree Additional warming, Projections, Prognosis and Impacts" ensemble, with a focus on the winter season. Characterizing and understanding 5 this response is critical for accurately assessing the near-term regional impacts of climate change and the benefits of limiting warming to the 1.5• C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the circulation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model 10

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“…This is not due to chance, as already shown for extratropical storms through AGCM model (Graff and LaCasce, 2012). We managed to distinguish four situations, even if configurations are less obvious than those recorded above the tropical ocean (Figure 7).…”

Section: Synoptic Scheme Of Storm Formation In Different Contextsmentioning

confidence: 80%

Middle- to late-Holocene storminess in Brittany (NW France): Part II – The chronology of events and climate forcing

Vliët-Lanoé¹,

Penaud²,

Hénaff³

et al. 2014

The Holocene

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This study focuses on the recurring climate conditions required for the largest storms occurring in NW France (Brittany). It is based on the analysed records of storm events along Western Brittany coast (see Part I). In this manuscript (Part II), storm recurrence is explored along with forcing mechanisms. Periods of more frequent storm events over the two last centuries are analysed first in order to link these events with possible forcing mechanisms (North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) modes) triggering the most destructive storms. Then, palaeostorm events are discussed at the Holocene scale, from 6000 yr BP to present, to verify the forcing mechanisms. Most recorded events appear to be linked with cooling episodes, mostly in winter, a transition to or from a negative winter NAO mode, a positive AMO mode. Extreme storms occur immediately prior to the 'Medieval Warm Period' (MWP). Maximum effects are reached prior to the onset of the MWP and during the Maunder and Dalton solar minima. Low storm activity occurred during the Spörer Minimum linked to an acceleration of the Atlantic Meridional Overturning Circulation (AMOC). Main storm triggers seem to correspond to a positive AMO mode with an unstable jetstream configuration driving a negative NAO. In this study, four specific weather configurations were defined to explain each type of recorded storminess. The strongest storms correspond to low AMO and decennial-negative NAO modes (e.g. 'Little Ice Age'), or high AMO in association with dominant low NAO modes, as during the early Middle Age and present-day period. Fresh or warm oceans in association with a positive NAO mode are stormy but with very low sting storms frequency. Although in agreement with the orbital forcing and the Holocene glacial history, increasing storm frequency and intensity is most probably partly biased by continuous sea-level rise and resulting erosion.

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Changes in the Extratropical Storm Tracks in Response to Changes in SST in an AGCM

Cited by 55 publications

References 63 publications

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Midlatitude atmospheric circulation responses under 1.5 °C and 2.0 °C warming and implications for regional impacts

Middle- to late-Holocene storminess in Brittany (NW France): Part II – The chronology of events and climate forcing

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