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 2009Jan - 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)