Did we expect a disturbed stratosphere in 2009-10?

QBO-EAST ? (Holton & Tan 1980) EL NINO ? (Ineson and Scaife, 2009; Bell et al 2009) SOLAR MINIMUM ? (Labitzke & Van Loon 1988; Kodera and Kuroda 2002) TREND ? (Chartlon et al 2008; Bell et al 2010) ... all fit with a weaker-than-average polar vortex

QBO

90N

30h

Pa T

empe

ratu

re

QBO- east

Key features of stratospheric flow:

Minor warming – early DecemberStrong vortex until mid-January – major stratospheric sudden warming (SSW)Weak, disturbed vortex late winter – persistent easterlies over polar cap

North Pole temperature at 10hPa ZMZW at 60N 10hPa

Courtesy Andrew Charlton-Perez http://www.met.reading.ac.uk/research/stratclim/current/

Minor Major

ZMZW 60-90N

Pres

sure

Pres

sure

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

NAM index

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

NAO

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

ERA-

40 o

pera

tiona

l ana

lysi

s

- 08-12-2009 - lower stratospheric

split

Strong mid-winter (Dec – Jan)

- 01-02-2010 - displacement SSW

event

Courtesy Andrew Charlton-Perez

ZMZW 60-90N

Pres

sure

Pres

sure

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

NAM index

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

NAO

Dec-01 Jan-01 Feb-01 Mar-01Dec-15 Jan-15 Feb-15

ERA-

40 o

pera

tiona

l ana

lysi

s

•growth in vertical EP-flux is pre-blocking •Was it driven by PNA-type pattern?

•Wave-2 confined to lower stratosphere

• January blocking precedes SSW•Also strong PNA-like pattern, no NAO •Low EP flux (10hPa) in late winter due to persistence of easterly anomalies in

lower stratosphere

16 NOV 16 DEC 16 JAN 16 FEB 16 MAR 16 APR

EP-flux vector (10hPa, 60N)

16 NOV 16 DEC 16 JAN 16 FEB 16 MAR 16 APR

Vertical EP-flux (100hPa)

EQ

90N

Tropospheric precursors?

NOV 500hPa Z’