1

The impact of the January 2013 Stratospheric Sudden Warming

on the TTL

Stephanie Evan & Karen Rosenlof

Warmingpoleward of 60oN

from http://www.cpc.ncep.noaa.gov/

Cooling in thetropics (25oS-25oN)

Wind deceleration =

Warming Cooling

Warming

SSW onset

- 3days

- 1 week

+ 3days

Time-seriesof wave activityin the midlatitudes

Cold Point Tropopause T & height from COSMIC

NB: Annual variation in tropopause height ~ 1km (Reid and Gage, 1981)

Dec 2012 Jan 2013

Feb 2013

Cold Point Tropopause from COSMIC

ATTREX

NOAA WV data from Troy Thornberry& Drew Rollins

8

Case for SSW in January 2009

Kodera, Eguchi, Lee, Kuroda and Yukimoto (JMSJ, 2010)

January 18th 2009

01/01/09

Changes in deep convection ?

After the SSW

Before the SSW

Changes in high clouds?

Before the SSW

After the SSW

TTL cooling

Equilibrium Level = Top of convection

Altit

ude

Level of freeconvection

Moist Adiabat

T environment

Top of convectionaffected by TTL cooling

dT/dz < dT/dzN2 < N2

(Stability is reduced)

TTL cooling and Convection?

Mean buoyancy frequency(13-17km) and OLRfor the Western Pacific(100 to 180 deg E)

January 6th

14

CoolingCooling

Warming

TTL becomes unstable -> higher convectionHigher tropopause -> higher convection

Change in convection with the SSW

15

Simplified GCM experiment (Thuburn and Craig , 2000)

Experiment with westward stratospheric force imposed =

Enhances the Brewer-Dobson circulation + stronger dynamical cooling in the tropics.

Cumulus heating

200 hPa

Westward= higher convection

Eastward= lower convection

Tropopausehigher in WSF

experiment

Control

16

Summary

• A major stratospheric sudden warming developed in Jan. 2013 and:– Warmed the pole– Cooled the TTL– Had an impact of convection and cirrus

distribution?• The TTL cooling probably resulted in additional

removal of water vapor from the lower stratosphere

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NH warming Jan 2013Easterly QBO

-1K

CHAMP/COSMIC CPT anomalies 15oS-15oN

Evolution of CPT temperature and height for different longitude bands

Tropopause TTropopause height