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Symposium on Polar Tropical Teleconnections

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  • UserLesley Gray (University of Oxford), Matt Collins (University of Exeter), Liz Thomas (British Antarctic Survey), Andrew Turner (University of Reading)
  • ClockWednesday 16 October 2019, 14:00-17:30
  • HouseSmall Lecture Theatre, Department of Geography.

If you have a question about this talk, please contact Dr Mario Krapp.

The Cambridge Centre for Climate Science kindly invites you to its symposium on polar tropical teleconnections.

Come join us for an exciting and diverse range of talks.

Schedule:

14:00 – 14:45 Lesley Gray, University of Oxford Tropical – Extratropical Teleconnections involving the Stratosphere

14:45 – 15:30 Matt Collins, University of Exeter The El Nino Southern Oscillation and its Teleconnections Under a Changing Climate

15:30 – 16:00 pm tea and coffee break

16:00 – 16:45 Liz Thomas, British Antarctic Survey, Cambridge Tropical Pacific influence on West Antarctica – evidence from ice cores

16:45 – 17:30 Andrew Turner, University of Reading BITMAP : Better understanding of Interregional Teleconections for prediction in the Monsoon and Poles

17:30 Wine reception

Abstracts:

Lesley Gray, University of Oxford: Tropical—Extratropical Teleconnections involving the Stratosphere

There is now plenty of evidence that stratospheric dynamics can impact the troposphere below. This is especially true in NH winter when we see a shift to a negative North Atlantic Oscillation (NAO) index for up to ~60 days following an extreme polar vortex event known as a Sudden Stratospheric Warming (SSW). Some winters have one, or even two, SSWs while others have none. Understanding what influences their occurrence is really interesting, and involves large-scale teleconnections within the ocean – troposphere – stratosphere system and between equatorial and high latitudes. We have a rough understanding of some of the factors that influence SSWs, such as ENSO , the QBO , the solar cycle and these can help to provide statistical predictions. But forecasting an individual SSW , especially its timing during winter – which is what is needed to be really useful – has proved a real challenge for seasonal forecasters. The talk will give an overview of the factors influencing SSWs and describe some UM experiments where we explore the timing of SSWs using a couple of case studies. The results are surprising and point to the importance of a relatively neglected region of the stratosphere where improvements could help to substantially improve SSW forecasts.

Mat Collins, University of Exeter—The El Nino Southern Oscillation and its Teleconnections Under a Changing Climate

Projections of climate change indicate an increasing frequency of extreme El Nino Southern Oscillation (ENSO) events in the future, even under low emissions scenarios. This talk will review recent literature on changes in ENSO and its teleconnections under climate change. The robustness of the physical mechanisms for the increase in frequency of extreme ENSO will be discussed. Future teleconnection changes are complex, with interactions between mean climate change and wet/dry teleconnections in both the tropics and midlatitudes. The role of vegetation in controlling those changes will be highlighted.

Liz Thomas, British Antarctic Survey, Cambridge—Tropical Pacific influence on West Antarctica – evidence from ice cores

Antarctica has experienced dramatic climate change in recent decades. Warming surface temperatures and changing wind patterns have resulted in ice shelf collapse and accelerated melting of glaciers, particularly in West Antarctica. In this talk, I present ice core records from West Antarctica and the Antarctic Peninsula, highlighting the tropical teleconnection that exists over centennial time scales. I explore the influence of the tropical pacific in driving climate change in West Antarctica and demonstrate the importance of large-scale modes of atmospheric variability on Antarctic mass balance, especially during the late 20th century.

Andrew Turner, University of Reading— BITMAP : Better understanding of Interregional Teleconections for prediction in the Monsoon and Poles In the BITMAP project (funded by JPI -Climate and the Belmont Forum), we set out to understand more about connections between high latitudes and the South Asia region. The topic is of particular interest since we expect, under Arctic ice melt and tropical tropospheric warming, the meridional temperature gradient to weaken which may have implications for the subtropical jetstream, the monsoons and the ITCZ in general. Work in BITMAP has focused in particular on Western Disturbances, a type of storm that can affect northern India and Pakistan during wintertime, supplying rainfall and sometimes extreme events. In recent years, there has been some suggestion of Western Disturbances interacting with tropical lows during the summer, leading to a rapid monsoon onset and extreme flooding. This therefore motivates us to understand how Western Disturbances have changed in the past and how they may change in the future, and to examine the basis for any change. This talk examines the structure of Western Disturbances in the ERA -Interim dataset based on a feature tracking algorithm designed at Reading, and their role in providing extreme rainfall. Next, we compare trends in Western Disturbance activity in the historical record with those in CMIP5 experiments of the 20th century, before examining projections of intensity and storm count in RCP future projections of CMIP6 . Finally, we examine the changing background state responsible for these changes.

This talk is part of the Cambridge Centre for Climate Science series.

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