E-mail: [email protected] | Web: gmao.gsfc.nasa.gov
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
O3 assimilated ~0.7°60levels
Innessetal.,2013
MERRA-2 1980-present GEOS-5 SimplifiedO3chemistry
O3 assimilated ~0.5°72levels
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
