Highlights fromHighlights from

An EU project funded in An EU project funded in

Framework Programme VFramework Programme V

1. Techn. Univ. Munich, Germany (TUM)

2. Karlsruhe Res. Center, Germany (IFU)

3. Max-Planck-Institute for Meteorology, Hamburg, Germany (MPI)

4. University of Agricultural Sciences, Vienna, Austria (BOKU)

5. U.K. Meteorological Office, U.K. (UKMO)

6. Utrecht University, Netherlands (IMAU)

7. Meteorological Institute, Netherlands (KNMI)

8. Consiglio Nazionale dell Ricerche, Bologna, Italy (CNR)

9. Aristotelian University of Thessaloniki, Greece (AUTH)

10. National Technical University of Athens, Greece (NTUA)

11. University of Berne, Switzerland (LRU)

12. Vienna Environmental Research Accelerator, Vienna, Austria (VERA)

13. ETH Zurich, Switzerland (ETHZ)

Partnership

develop a 3-D Lagrangian perspective of STE, with a focus on „deep“ exchange events

investigate the mixing of stratospheric and tropospheric air

do measurements to estimate the impact of STE on tropospheric chemistry

intercompare and validate methods and models used to calculate STE

examine variability and trends of STE during the past few decades and under scenarios of climate change

study the relative impact of STE on the oxidation capacity of the troposphere

Objectives

Use STE as a general term, referring to stratosphere-troposphere exchange in both directions

Use STT specifically for one-way stratosphere-to-troposphere transport

Use TST specifically for one-way troposphere-to-stratosphere transport

New Nomenclature

Observations of STT at mountain peak stations: What is the influence on ozone?

Seasonal variation of ozone contribution of stratospherically influenced air to the observed ozone mixing ratio at the Zugspitze peak (IFU)(IFU)

0

5

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45

50

1 2 3 4 5 6 7 8 9 10 11 12

% c

ontr

ibut

ion

Obtained from monthly statistics (1990-2000) based on data filtering using 7Be and relative humidity.

Total stratospheric contribution may be larger, due to unidentified „aged“ stratospheric air.

Identification of stratospheric intrusions atIdentification of stratospheric intrusions atMt. Cimone based on different observation criteria Mt. Cimone based on different observation criteria

((77Be, humidity, etc.) Be, humidity, etc.) (CNR)(CNR)

Daily average ozone increase on days with anintrusion is 5-7% relative to the monthly average

Seasonal variation of 7Be, a „stratospheric“ tracer (LRU, AUTH)

3

4

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7

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Jan

Fe

b

Ma

r

Ap

r

Ma

y

Jun

Jul

Au

g

Se

p

Oct

No

v

De

c

Be

-7 [

mB

q m

-3]

Jungfraujoch

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7

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9

10

11

Jan

Fe

b

Ma

r

Ap

r

Ma

y

Jun

Jul

Au

g

Se

p

Oct

No

v

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c

Be

-7 [

mB

q m

-3]

Sonnblick

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7

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11

Jan

Fe

b

Ma

r

Ap

r

Ma

y

Jun

Jul

Au

g

Se

p

Oct

No

v

De

c

Be

-7 [

mB

q m

-3]

Zugspitze

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4

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7

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11

Jan

Fe

b

Ma

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Ap

r

Ma

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Jun

Jul

Au

g

Se

p

Oct

No

v

De

c

Be

-7 [

mB

q m

-3]

Mt. Cimone

Little seasonal variation, summer maximum:Reflects minimum in washout and higher tropopause in summer

10Be / 7Be climatology (LRU, VERA, AUTH)First time ever 10Be monitoring in EuropeWorldwide available atmospheric 10Be data multiplied

0

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

stra

tosp

her

ic o

zon

e co

ntr

ibu

tio

n a

t su

rfac

e (%

)

1st quartile

median

3rd quartile

mean

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

stra

tosp

her

ic o

zon

e co

ntr

ibu

tio

n a

t su

rfac

e (%

)

1st quartile

median

3rd quartile

mean

7Be, 10Be have same sources and sinks, but different radioactive decay times.Thus, their ratio is not affected by washout (Raisbeck et al., 1981)

Making certain assumptions, Dibb et al. (1994) derived surface ozonefrom the stratosphere using the 10Be / 7Be ratio.

Monte Carlo simulation: quantification is very sensitive to assumptions applied.

Jungfraujoch Zugspitze

Upper troposphereUpper troposphere

Middle troposphere Middle troposphere

Lower troposphereLower troposphere

1-year Climatology of Ozone in the Troposphere Obtained by Combining MOZAIC Measurements with Back Trajectories (TUM)

Model validation and intercomparison

A deep STT event

Water vapor satellite imageplus isentropic PV (20/6/01)(courtesy of Owen Cooper, NOAA)

FLEXPART stratospheric ozone tracer column between 5.5 and 11 km altitude (TUM)

Ozone lidar measurementsat Garmisch-Partenkirchen(IFU)

ECHAM full chemistry simulation (IMAU)

FLEXPART stratosphericozone tracer (TUM) ECMWF O3

10

30

50

70

90

110

130

06.18.01 06.20.01 06.22.01 06.24.01 06.26.01Date

Re

l.H

um

. (%

), O

zon

e ( g

/m3)

1

1,5

2

2,5

3

3,5

4

10

Be

/ 7

Be

(a

t /

at)

Rel. Humid. (%) Ozone (ug/m^3) 10Be / 7Be (at / at)

Deep STT event, as seen at Jungfraujoch(LRU, VERA and AUTH)7Be and 10Be both decrease (washout), but their ratio increases

Model intercomparison exerciseModel intercomparison exercise (KNMI)(KNMI)

Lagrangian models without turbulence underestimate the extension of the intrusion

Eulerian climate (-chemistry) models suffer from numerical diffusion and coarse resolution and overestimate the extent of the intrusion

7 models were requested to simulate the same stratospheric intrusion event

Stratospheric tracer with a lifetime of 2 days in the troposphere

Trajectory models

Lagrangian models with turbulence and convection

Eulerian models

Eulerian models

Model intercomparison exerciseModel intercomparison exercise (KNMI)(KNMI)

Large differences are found among the models for theLarge differences are found among the models for the

concentrations of the stratospheric tracer at 700 hPaconcentrations of the stratospheric tracer at 700 hPa

A new concept and new STE properties

A New Concept ofA New Concept ofStratosphere-Troposphere ExchangeStratosphere-Troposphere Exchange

Troposphere

Stratosphere

LowermostStratosphere

Boundary layer

A deep TST event, delivering possibly polluted A deep TST event, delivering possibly polluted boundary-layer air to the lowermost stratosphereboundary-layer air to the lowermost stratosphere

(ETHZ)(ETHZ)

Lagrangian Tools to Study „Deep STE“Lagrangian Tools to Study „Deep STE“(ETHZ and TUM)(ETHZ and TUM)

LAGRANTO (ETHZ): Trajectory model

Focus on timescales of a few days

FLEXPART (TUM): Lagrangian particle dispersion model

Extend the timescales

Parameterizations of turbulenceand convection

Comparison of FLEXPART extratropical net Comparison of FLEXPART extratropical net STE with Appenzeller et al. (1996) budget STE with Appenzeller et al. (1996) budget

study using „downward control“study using „downward control“ (TUM)(TUM)

Northern Hemisphere Southern Hemisphere

Broken line: Appenzeller et al.Solid line: FLEXPART Lagrangian method

Stronger seasonal cycle, butannual mean net mass flux ingood agreement

How long has air spent in the troposphere How long has air spent in the troposphere when it (re-)enters the stratosphere?when it (re-)enters the stratosphere? (TUM)(TUM)

all ¼ ½ 1 2 3 4 6 8 10 20 40 90 365 days

More than 90% of the flux into thestratosphere is less than 6 hours „old“

Fresh „return fluxes“are highly sensitiveto parameterizations(equivalent to thecancellation of termsin the Wei formula),

BUT:THEY ARE NOTVERY RELEVANT!

FLEXPART concentration of STT air in the FLEXPART concentration of STT air in the troposphere, in dependence of the „age“troposphere, in dependence of the „age“

(TUM)(TUM)

0-1 days 1-4 days 4-10 days

20-90 days >90 days10-20 days

Fraction of total tropospheric mass

The seasonality of deep STE using The seasonality of deep STE using FLEXPARTFLEXPART (TUM) (TUM)

Net STE

Stratospheric air that arrives at the surface

Within 1 dayWithin 4 days

STT

Take seasonal variation of ozone at the tropopause and assume 1-month lifetime in troposphereWithin 40 daysWithin 40 days

Winter Climatology (1979-1993) of Winter Climatology (1979-1993) of Deep STTDeep STT Events Using LAGRANTOEvents Using LAGRANTO (ETHZ)(ETHZ)

Frequency (%) of Frequency (%) of „destinations“ of STT „destinations“ of STT particles that arrive below particles that arrive below 700 hPa within 4 days700 hPa within 4 days

Maxima at the Maxima at the ENDEND of the of the Pacific stormtrack and at Pacific stormtrack and at the the STARTSTART of the Atlantic of the Atlantic stormtrackstormtrack

Almost no deep intrusions Almost no deep intrusions over large parts of Asiaover large parts of Asia

Winter Climatology (1979-1993) of Winter Climatology (1979-1993) of Deep TSTDeep TST Events Using LAGRANTOEvents Using LAGRANTO (ETHZ)(ETHZ)

Frequency of „sources“ below 700 hPa of TST particles within 4 days

Maxima at the start of the stormtracks downwind of North America and Japan.Emissions from these regions may reach the lowermost stratosphere within short timescales.

Simulated chemical effects of STT

Influence of STT on the oxidizing capacity of the Influence of STT on the oxidizing capacity of the troposphere, according to ECHAMtroposphere, according to ECHAM (IMAU)(IMAU)

Seasonal cycle of the calculated tropospheric OH budgets for the NH

Photolysis of Tropospheric O3

Photolysis of Stratospheric O3

Influence of mixing of stratospheric andInfluence of mixing of stratospheric andtropospheric air on OH concentrationstropospheric air on OH concentrations (BOKU)(BOKU)

OH radicals are enhanced byup to a factor 25 relative tothe no-mixing case

There is a slight speed-up ofozone destruction, due tomixing

STE interannual variability and possible future changes

NAO+ minus NAO-NAO+ minus NAO- (TUM)

During NAO+ STTDuring NAO+ STTis shifted towards higher is shifted towards higher latitudes and altitudes in latitudes and altitudes in the middle latitudesthe middle latitudes

STT variability based on re-analysis data:Influence of the North Atlantic Oscillation on STT

NAO+ (winter) NAO-

Location of STTevents + measure ofstorm track (in green)(ETHZ)

Difference in Difference in stratospheric tracerstratospheric tracerconcentration for El concentration for El Nino minus La NinaNino minus La Ninain the eastern Pacificin the eastern Pacific

During El Nino STE During El Nino STE in the tropical in the tropical eastern Pacific is eastern Pacific is shifted towards shifted towards higher altitudeshigher altitudes

Climate variability based on re-analysis data:Influence of El Nino/Southern Oscillation on STE (TUM)

MAECHAM simulation of MAECHAM simulation of 1010Be, Be, 77Be Be transporttransport (MPI) (MPI)

Annual mean residual meridional mass flux 10Be / 7Be

Annual mean residual circulationamplifies from 1860 to 2000 to 2100, leading to enhanced STE

Cyclonic activity intensifies inSH, but decreases in NH! Asymmetry in 10Be/7Bechanges!

A glance into a future ozone scenario (A1FI) A glance into a future ozone scenario (A1FI) with STOCHEMwith STOCHEM (UKMO) (UKMO)

Difference (ppbv) between stratospheric ozone at the surface for the years 2091-94 and 1991-1994

A glance into a future scenario with STOCHEMA glance into a future scenario with STOCHEM (UKMO)(UKMO)

Total surface ozone at Mace Head decreases (due to enhanced water vapor in the future climate) if precursor emissions remain unchanged, but the contribution of ozone from the stratosphere increases