CGD Seminar Series - Adam Scaife, UK Met Office, Predictability of the North Atlantic Oscillation

Title: Predictability of the North Atlantic Oscillation

Speaker: Adam Scaife, UK Met Office

Date: Tuesday, 19 November 2019

Time: 11 am - 12 pm

*Refreshments at 10:45*

Location: Mesa Lab, Main Seminar Room, ML - 132

Abstract:This seminar reviews the latest evidence for long range predictability of the winter North Atlantic Oscillation (NAO) and hence European and North American winters.  Retrospective hindcasts and recent real time predictions suggest that the winter NAO is predictable at seasonal and longer lead times.  In this seminar I show that much of this predictability originates in the tropics and the stratosphere.  High predictability of tropical rainfall is first demonstrated for current prediction systems and this is shown to lead to clear stationary Rossby waves that propagate into the extratropics, into the Atlantic sector and project onto the NAO.  We estimate that this mechanism can explain around half of the forecast variance in the NAO.  Secondly, we show that initial atmospheric conditions are also important for seasonal prediction of the NAO.  Initial anomalies in stratospheric winds at the start of winter propagate downwards into the troposphere on subseasonal timescales where they lead to anomalies in the winter mean sea level pressure.  Together, these mechanisms potentially explain the majority of forecast variance in the winter NAO.  I also show some of the remaining errors in seasonal forecasts of tropical rainfall and discuss the unresolved signal-to-noise paradox, whereby ensemble forecasts are better at predicting the real observed NAO than the they are at predicting their own simulations of the NAO.

For more information contact Tracy Baker, tbaker@ucar.edu, 303-497-1366

Building:

Room Number: 
ML-132

Type of event:

Will this event be webcast to the public by NCAR|UCAR?: 
Yes - ML-Main Seminar Room - https://www.ucar.edu/live
Announcement Timing: 
Monday, November 18, 2019 to Tuesday, November 19, 2019
Calendar Timing: 
Tuesday, November 19, 2019 - 11:00am to 12:00pm

Posted by Tracy Baker at ext. 1366, tbaker@ucar.edu

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