© Crown copyright Met Office Stratospheric Influences on the Troposphere Adam Scaife December 2010.

© Crown copyright Met Office

Stratospheric Influences on the Troposphere

Adam Scaife

December 2010


Outline

• Monthly variability:

• sudden stratospheric warmings

• predictability

• surface impacts

• Seasonal/Interannual variability

• El Nino-Southern Oscillation

• Quasi-Biennial Oscillation

• Summary


Sudden Stratospheric Warmings26th Jan 19634th Jan 1963

Figure courtesy of Colombia Uni.

Usual situation: polar cyclone, eastward flow

Sudden warming: Filling of the polar cyclone, net westward flow, ~50K rise in few days!

Wave driven (wave 2 here):

(Note that 1962-63 is the coldest UK winter of the 20th century…..)


• Early studies suggested an NAO/AO response to imposed stratospheric changes in GCMs

• Observations show downward propagation of wind anomalies from the upper stratosphere to the troposphere

• Some studies show additional predictability from the stratosphere on monthly to seasonal timescales

Monthly Variability


Dynamical forecastDynamical forecast + 70hPa stat fcast

Christiansen 2005

Downward propagating winds

Baldwin and Dunkerton 2001

See also:

Kodera et al 1990, Boville 1984

Surface wind at 60N


Cold Eurasian winter 2005/6

• Colder than 1970-2000 over much of Europe

• 2nd coldest in 10 years using area mean T

• Record snowfall in parts of central Europe • Late winter colder than early winter

• Intense sudden stratospheric warming

January 2006 February 2006December 2005

Zonal wind through the winter


Winter 2005/6 Atmospheric model

• 50/25 members• HadISST as a boundary condition

Atmospheric model + stratospheric forcing:• 25 members• HadISST as lower boundary condition• Perturbed stratosphere from 1st Jan

Zonal wind at 50hPa

Exp

CtlObs

SST only

SST + Strat forcing

Observations

Cold European signal from IMPOSED stratospheric warming

Even clearer example in winter 2008/9

Scaife and Knight, QJRMS, 2008


Sudden Stratospheric Warming 2009

E.g. Jan 2009; easterlies (in blue) descend from the upper atmosphere:

Followed by extreme snowfall in Feb 2009

Similar events in winter 2009/10

Jan 2009 zonal winds


Cold Air Outbreaks across NH

Scandinavian blocking precedes warmings

Negative Arctic Oscillation / North Atlantic Oscillation follows

Cooling across the whole of northern Eurasia and Eastern USA

Kolstad et al (2010)


Standard

model

Extended

model

40km

85km

Predictability and vertical resolution


Predictability of stratospheric warmings

Improved seasonal prediction of European winter cold spells:

StandardExtended

0.6 | 0.30.6 | 0.40.7 | 0.30.7 | 0.20.4 | 0.1Peak easterly magnitude(fraction of observed)

12 | 89 | 612 | 1215 | 1013 | 5Maximum lead time for capture (days)

EventMean

26 Feb1999

15 Dec1998

7 Dec1987

24 Feb1984

Zonal wind(10hPa,60N)

(Ext | Stand)

Marshall and Scaife, in press


• It is not only the ocean which contains a long memory - stratospheric processes have a long memory too! The QBO has a period of 2-3 yrs and is predictable for 1-2 cycles.

• Key mechanisms of interannual to decadal variability can also involve stratospheric processes.

• Two recent examples…..

Seasonal to Interannual Variability


El Nino

ENSO peaks in winter

Remarkable levels of predictability even 6 months ahead

Remote effects?

ENSO forecast skill


ENSO teleconnections

Model El Nino anomaly (50hPa geopotential height)

Observations (Hamilton, 1993)

Stratospheric component appears in models (Van Loon and Labitzke 1987, Hamilton, 1993, Manzini et al. 2006)ENSO events produce a –ve NAO-like response (e.g. Moron and Gouirand 2003, Bronniman et al. 2004) Clearly visible in 2/3 of observed El Nino events (Toniazzo and Scaife 2006)Reproduced in numerical models (Cagnazzo and Manzini 2009, Ineson and Scaife 2009)


Downward progression

Descending signals

Slower at lower altitudes

Indicative of wave-mean flow interaction from a steady (tropospheric) wave source

Temperature Zonal wind


Surface Climate ImpactModel Observations

PMSL

Temperature

Precipitation

Ineson and Scaife, Nat. Geoscience, 2009

Big enough to affect forecasts


StandardObservations Extended

Effects of vertical resolution (actually domain)

See Ineson and Scaife, Nat. Geosci., 2009


Winter 2009/10

Moderate El Nino and negative Arctic Oscillation

Not a coincidence!

El Nino N Atlantic Oscillation


Testing extended model in winter 2009/10 predictions:

Winter 2009/10New SystemOld System

• GloSea4 system showed cold signal for Europe last winter

• Also predicted –ve NAO ~5hPa

• Extended model with improved ENSO teleconnection strengthens this signal


Quasi-Biennial Oscillation

• Quasi-periodic 2-3 year period

• Nonlinear driving from small scale waves

• Propagates down with time (c.f. ENSO and SSW!)

Scaife et al, GRL 2000, JAS 2002.


QBO Forecast Skill

Standard model drifts to weak winds (c.f. Boer and Hamilton 2008)

Extended model simulates realistic QBO

Surface impacts?

QBO anomaly, 30hPa, initialised in December

DEC JAN FEB MAR APR

0

10

20

- 20

- 10

Eastward phase

Westward phase


Quasi-Biennial Oscillation

QBOE-QBOW

MODEL T

• Highly predictable for 2 years at least

• Initialised in current models but decays after few months

• Eurasian (NAO like) signal: QBO -> extratropics -> surface

• Signal comparable to year-to-year variability and therefore important

Marshall and Scaife, J. Geophys. Res., 2009.

OBS T


CLIVAR-WGSIP Stratospheric Historical Forecast Project

Extended Model Hindcasts

• Parallel to standard model WGSIP-CHFP

• Extended models

• Initialising extra atmosphere

• Integrations

• 4 month lead times (1st November and 1st May start dates)

• 2 seasons (DJF and JJA)

• Case study years: 1989 onwards

• At least 6 members for each hindcast season


Participants:

Institute Model Resolution Model top

Reference Contact

Met Office HC

HadGEM N96L85

N96L38

85km

40km

Arribas et al., Mon. Wea. Rev., 2011

[email protected]

Meteo France

Arpege 4.4 + OPA

L91

L31

0.01hPa

10hPa

Gueremy et al, 2005, Tellus, 57A, p308-319

[email protected]

[email protected]

ECMWF IFS L91

L62

0.01hPa

5hPa

? [email protected]

CCCMA CMAM T63L71

T63L41

~100km

~31km

Scinocca et al 2008, ACP, 8, 7055-7074

[email protected]

[email protected]

NCEP CFS v1 L64

?

? Saha et al, J.Clim., vol.19, no.15, p3483-3517

[email protected]

[email protected]

CPTEC CPTEC ? ? ? [email protected]

IFM-GEOMAR

ECHAM5 T63L31

T63L47

10hPa

0.01hPa

Roeckner et al 2003, MPI report No. 349, 127pp

Manzini et al 2006, J. Clim., 19, 3863-3881.

[email protected]

mailto:[email protected]











SUMMARY

• Stratospheric dynamics are important for monthly to seasonal surface variability and project onto the NAO:

• Sudden Warmings -> 30-60d anomalies –ve NAO

• ENSO -> extratropics -> stratosphere -> NAO

• Volcanoes -> stratosphere -> extratropics -> NAO

• QBO -> extratropics -> NAO

• There are also longer term influences (outside the scope of this talk)

• Necessary to include these effects to maximise prediction skill in the extratropics

• CLIVAR-WGSIP is carrying out an experiment with international groups to characterise the benefits in predictability from including these processes

© Crown copyright Met Office Stratospheric Influences on the Troposphere Adam Scaife December 2010.

Documents

Transcript of © Crown copyright Met Office Stratospheric Influences on the Troposphere Adam Scaife December 2010.