influence of mid-latitude cyclones on european background

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Influence of mid-latitude cyclones on European background surface ozone investigated in observations, MACC and MERRA-2 reanalysesK. Emma Knowland1,2, Ruth Doherty3, Kevin Hodges4 and Lesley Ott2

Global Modeling & Assimilation Office

1USRA/GESTAR;2NASAGSFC,GlobalModelingandAssimilationOffice(GMAO),Greenbelt,MD;3SchoolofGeoscience,UniversityofEdinburgh,Edinburgh,UK;4DeptartmentofMeteorology,UniversityofReaching,Reading,UK

Take Home Messages!

National Aeronautics and

Space Administration

Deeetal.,2011“TheERA-Interimreanalysis:configurationandperformanceofthedataassimilationsystem”Q.J.R.Meteorol.Soc.,137,553–597.doi:10.1002/qj.828.Gelaroetal.,2017“TheModern-EraRetrospectiveAnalysisforResearchandApplications,Version2(MERRA-2)”J.Climate,30,5419–5454,doi:10.1175/JCLI-D-16-0758.1.Hodges,K.I.1995“Featuretrackingontheunit-sphere”Mon.Wea.Rev.,123,3458-3465Hodges,K.I.1999“Adaptiveconstraintsforfeaturetracking”,Mon.Wea.Rev.,127,1362-1373Innesetal.,2013“TheMACCreanalysis:an8yrdatasetofatmosphericcomposition”,Atmos.Chem.Phys.,13,4073-4109Knowlandetal.,2017“Theinfluenceofmid-latitudecyclonesonEuropeanbackgroundsurfaceozone”,Atmos.Chem.Phys.,17,12421-12447,doi:10.5194/acp-17-12421-2017

Figure 6: N1 cyclone 24 hours later (5 March 2007 00UTC). Cold front has passed over Mace Head.

DataSurface O3 Observations

Reanalysis

Ø Met and chemical variables on 12 pressure levels from 1000 to 200 hPaØ Relative vorticity at 850 hPa (ζ850hPa), mean sea level pressure (MSLP),

temperature (T), specific humidity (q), winds (u,v), vertical velocity (⍵), equivalent potential temperature (θe), and O3.

Figure 3: Schematic of a storm track identified on 850hPa field, transferred on multiple levels. Spherical cap around storm center at time of maximum ζ850hPa is illustrated.

Storm tracks and O31. Storm tracks were identified in ERA-Interim and MACC using the objective feature tracking algorithm, TRACK (Hodges 1995, 1999). 2. O3 at Mace Head and Monte Velho were sorted each season, to remove the increasing background signal, and ranked by percentiles (pc)3. Tracks were matched to concurrent surface O3observations at Mace Head and Monte Velho.

5. All points within a 20°spherical cap over the storm centre are selected and oriented in the direction of the storm’s movement

Figure 1: Storm track density (contours) over Europe. North, Center and South regions indicated for Mace Head (blue dot). Monte Velho (red dot).

a) b)

c) d)

40oW 30oW 20oW 10oW 0 10oE 20oE30oN

40oN

50oN

60oN

70oN

MH O3 (ppbv)O3<4040<O3<4545<O3<5050<O3<5555<O3<6060<O3

MH O3 (ppbv)O3<4040<O3<4545<O3<5050<O3<5555<O3<6060<O3

40oW 30oW 20oW 10oW 0 10oE 20oE30oN

40oN

50oN

60oN

70oN

MH O3 (ppbv)O3<4040<O3<4545<O3<5050<O3<5555<O3<6060<O3

MH O3 (ppbv)O3<4040<O3<4545<O3<5050<O3<5555<O3<6060<O3

S1

N1

4 March 2007 12UTC

25 April 2012 00UTC

40oW 30oW 20oW 10oW 0 10oE 20oE

20oN

30oN

40oN

50oN

60oN

MV O3 (ppbv)O3<3030<O3<4040<O3<4545<O3<5055<O3<6060<O3

MV O3 (ppbv)O3<3030<O3<4040<O3<4545<O3<5055<O3<6060<O3

40oW 30oW 20oW 10oW 0 10oE 20oE

20oN

30oN

40oN

50oN

60oN

MV O3 (ppbv)O3<3030<O3<4040<O3<4545<O3<5055<O3<6060<O3

MV O3 (ppbv)O3<3030<O3<4040<O3<4545<O3<5055<O3<6060<O3

N2

S2

21 May 2006 06UTC

13 March 200718UTC

a)

b)

MaceHead

%tracks“high”O3O3>75thpc

#years moretrackswithhighO3(#significant)

%tracks“low”O3O3>75th pc

#years moretrackswithlowO3(#significant)

North 52% 18(15) 37 % 5(0)Center 51% 17 (6) 41% 6(1)South 45% 7(2) 53% 16(8)

N1 cyclone: North of Mace Head

25303540455055606570758085

O3(p

pbv)

1000

hP

a

975

985 995

99510051015

1025

20 m s-1

75oW 60oW 45oW 30oW 15oW 0 15oE 30oE30oN

45oN

60oN

75oN

25303540455055606570758085

O3(p

pbv)

850

hPa

20 m s-1

30oN

45oN

60oN

75oN

40485664728088

O3(p

pbv)

500

hPa

20 m s-1

30oN

45oN

60oN

75oN

4080

120160200240280

O3(p

pbv)

300

hPa

20 m s-1

30oN

45oN

60oN

75oN

N1

a)

b)

c)

d)

First study to our knowledge to quantify theinfluence extratropical cyclones have on thetemporal variability of springtime surface ozone(O3) measured on the west coast of Europe whencyclones are nearby.

We show passing cyclones have a discernibleinfluence on surface O3 concentrations.

In-depth findings from four case studies, using acombination of reanalyses and a modeled tracer,demonstrate there are several transportpathways before O3-rich air eventually reachesthe surface. (Knowland et al., 2017 ACP)

When cyclones track north of 53ºN, there is a significant relationship with high levels of surface O3 (> 75th pc). The further away a cyclone is from the main storm track, more likely associated with low O3 (< 25th pc).

4. Case study cyclones (Fig 2 below) identified for a) high O3b) Passing through North or South regionsc) Strong, top 20 % based on maximum ζ850hPad) two consecutive time steps with high O3

Strongcyclonetracks,N1andS1,associatedwithhighO3 atMaceHead(Fig.2)

2

2

4

4

4

4

6

6

6

6

8

8

8

8

8

1

0

1

0

1

2

14

30

o

W 15

o

W 0 15

o

E

20

o

N

30

o

N

40

o

N

50

o

N

60

o

N

70

o

N

ERA-Interim 1979-present ECMWFIFS O3chemistryparametrization

O3 assimilated ~0.7°60levels

Deeetal.,2011

MACC 2003-2012 ECMWF IFS Coupled toMOZART-3CTM


Innessetal.,2013

MERRA-2 1980-present GEOS-5 SimplifiedO3chemistry


Gelaroetal.,2017

MaceHead,Ireland 1988-2012 EMEP Inmain stormtrack(Fig.1)

Monte Velho,Portugal 1989-2009* EMEP Southofmain stormtrack

S1 cyclone: South of Mace Head

⬆️ Strong O3 gradient across the cold front, 1) with maritime clean air first to Mace Head 2) elevated levels of O3 behind the front.

Figure5:N1cyclone4March200700UTC

⬅️ Descent of stratospheric O3-rich air behind the strong frontal boundary in dry intrusion (DI) airstream. ⬅️ Ascent of O3-poor air in the warm converyorbelt (WCB) up to 400 hPa.

⬆️ Descent of O3-rich air in DI⬆️ Transport across North Atlantic

in strong westerly winds.⬆️ Persistent high O3 observed at

Mace Head for 1.5 days

25303540455055606570758085

O3(p

pbv)

990 995

995

1000

10001000

1005

1005

1005

1010

1010

1010

1015

1015

1015

1015

1020 102010

25

10 m s-110

10 m s-1

75oW 60oW 45oW 30oW 15oW 0 15oE 30oE30oN

45oN

60oN

75oN

N1N1

P P

a) b)

Figure4:N1cycloneisasecondarycyclonetoparentlow“P”.a)1000hPaMACCO3,SLP,winds.b)AnalysischartfromUKMetOffice.MaceHeadindicatedbypinkcircle.

4March200700UTC

Figurekey:O3 (color),tropopause(2PVU,thinkblackline),⍵ (white= descent, black=ascent), MSLP (lowest pressure level), θe (dotted lines). Mace Head (black dot)

a) b)

c) d)

Figure5: S1cyclone25April201200UTCinMACC

a) b)

c) d)

Figure5: S1cyclone25April201200UTCMERRA-2

MACC MERRA-2

⬅️ Descent of O3-rich air reaches surface

⬅️ O3-rich below tropopause is from upstream DI

⬅️ O3-rich air below tropopause

• TropopauseislevelaboveMaceHead.DIistothesouth.• O3-richairbelowtropopauseinMERRA-2->airislikelyfromthestratosphere• ResidualhighO3 fromupstreamdecayingDIairstreamentrainedintoS1

⬅️ O3-rich air not from S1’s DI

DI DI

DIDI

Figure 2: Tracks colored by MACC O3 interpolated to the Mace Head location. Max ζ850hPa indicated by cross.

5March200700UTC

influence of mid-latitude cyclones on european background

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