Greenland / Atlantic blocking is a strong NAO- flow regime

Woollings et al (2008, JAS; 2010, JCLIM)

Thanks to Giacomo Masato

Blocking frequency anomalies this year…

… and last year

Minor

Major

• Early December: Stratosphere leads blocking over both Greenland and Alaska?

• Early February: Blocking over Europe contributes to wave activity disturbing vortex?

Woollings et al (2008, JAS, QJ; 2010, JGR)

Nov – Dec 2009 Jan - Feb 2010

Woollings et al (2008), JAS

Similar behaviour but different phase…?

• Open solar flux – measures magnetic variations and correlates well with TSI.

• Also correlates with detrended CET.

• Lockwood et al (2010), ERL – out tomorrow!

A Solar Contribution?

Solar signal

NAO

Solar signal

This winter

MODIS 7 JAN 2010

Blocking this year also fits the solar signal

Cold temperatures in tropical lower stratosphere in December. Due to QBO (+ solar …?).

1SD of QBO in multiple regression (Crooks and Gray 2005)