Seasonal forecasts of northern hemisphere winter 2009/10

Northern hemisphere winter 2009/10 was exceptional for atmospheric circulation: the North Atlantic Oscillation (NAO) index was the lowest on record for over a century. This contributed to cold conditions over large areas of Eurasia and North America. Here we use two versions of the Met Office GloSea...

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Bibliographic Details
Published in:Environmental Research Letters
Main Authors: D R Fereday, A Maidens, A Arribas, A A Scaife, J R Knight
Format: Article in Journal/Newspaper
Language:English
Published: IOP Publishing 2012
Subjects:
92.60.Xg
92.70.Gt
92.60.Cc
seasonal forecasting
northern hemisphere
stratosphere/troposphere interactions
Environmental technology. Sanitary engineering
TD1-1066
Environmental sciences
GE1-350
Science
Q
Physics
QC1-999
North Atlantic
North Atlantic oscillation
Online Access:https://doi.org/10.1088/1748-9326/7/3/034031
https://doaj.org/article/3a8096af675147d7ba6fe4c679c18320
Description
Summary:Northern hemisphere winter 2009/10 was exceptional for atmospheric circulation: the North Atlantic Oscillation (NAO) index was the lowest on record for over a century. This contributed to cold conditions over large areas of Eurasia and North America. Here we use two versions of the Met Office GloSea4 seasonal forecast system to investigate the predictability of this exceptional winter. The first is the then operational version of GloSea4, which uses a low top model and successfully predicted a negative NAO in forecasts produced in September, October and November 2009. The second uses a new high top model, which better simulates sudden stratospheric warmings (SSWs). This is particularly relevant for 2009/10 due to its unusual combination of a strong El Niño and an easterly quasi-biennial oscillation (QBO) phase, favouring SSW development. SSWs are shown to play an influential role in surface conditions, producing a stronger sea level pressure signal and improving predictions of the 2009/10 winter.

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