The influence of mid-latitude cyclones on European background surface ozone

K. Emma Knowland(USRA/GESTAR NASA/GMAO)

In collaboration with: Ruth Doherty (U. Edinburgh)Kevin Hodges (U. Reading)Lesley Ott (NASA/GMAO)

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The influence of mid-latitude cyclones on European background surface ozone

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The special issue is open to all publications that inform about the aspects of intercontinental transport of air pollution and provide answers to the HTAP scientific questions:

What fraction of air pollution concentrations or deposition can be attributed to sources of contemporary anthropogenic emissions within the region as compared to extra-regional, non-anthropogenic or legacy sources of pollution?

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Catto et al., 2010, J. Climate (modified from Browning, 1997, Meteorol. Appl.)

heightCold front

Warm front

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

heightCold front

Warm front

1. Storms ventilate the lower atmosphere of pollutants

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WCB

Catto et al., 2010, J. Climate

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

heightCold front

Warm frontCatto et al., 2010, J. Climate

1. Storms ventilate the lower atmosphere of pollutants

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SI

WCB

2. Introduce stratospheric air into the troposphere SI

H

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

Questions• Do passing cyclones have a detectable

impact on surface O3 concentrations?

• What are the key synoptic features associated with cyclones that impact surface O3 concentrations?

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

Two EMEP remote coastal monitoring stations

• Mace Head, Ireland

• 53°N, 10°W

• Hourly observations available from 1 April 1988 until 31 December 2014

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

Two EMEP remote coastal monitoring stations

• Monte Velho, Portugal

• 38°N, 9°W

• Hourly observations available from 1 January 1988 until 31 December 2009

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

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ERA-Interim ReanalysisEuropean Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis product• Available:

• January 1979 – July 2015 (3 months prior to present)

• 6 hourly resolution• Spring (MAM) 1979 – 2012

• Construct cyclone tracks using the objective feature tracking algorithm, TRACK (Hodges 1995, 1999):• TRACK identifies cyclones by maxima in 850-hPa

relative vorticity (ζ850)

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

TRACK

Relationship between O3 at Mace Head and cyclone tracks

Mean percent of tracks in a seasonassociated with high O3

Mean percent of tracks in a seasonassociated with low O3

Mean number of tracks in a season

North 51.8% 36.6% 32

Center 51.0% 40.8% 30

South 44.9% 52.7% 25

Number of years with more tracks associated with high O3

Number of years with more tracks associated with low O3

North 18 (15) 5 (0)

Center 17 (6) 6 (1)

South 7 (2) 16 (8)

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.) 10

MACC ReanalysisMonitoring Atmospheric Composition and Climate

Modern Era Retrospective analysis for Research and Applications version 2

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• O3 assimilated into an extended version of the ECMWF Integrated Forecast System (IFS)

• IFS coupled to a Mozart-3 Chemistry Transport Model (CTM)

(Inness et al., 2013, ACP)

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

MERRA-2 Reanalysis

• O3 assimilated from OMI and MLS since 2004• GEOS-5 model includes simplified O3 chemistry

scheme for both the stratosphere and troposphere based on monthly-dependent production/loss rates

(Gelaro et al., 2017, J.Clim.)

N1 cyclone 4 March 2007 00UTC

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.)

N1 cyclone 4 March 2007 00UTC 13

Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.)

N1 cyclone 5 March 2007 00UTC

N1

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.)

N1 cyclone 4 March 2007 00UTC (Knowland et al., in prep.) 15

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N1 cyclone 4 March 2007 00UTC (Knowland et al., in prep.)

MERRA-2 Reanalysis

S1 cyclone 25 April 2012 00UTC

At time of maximum vorticity

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.)

S1 cyclone 25 April 2012 00UTC 18

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S1 cyclone 25 April 2012 00UTC (Knowland et al., in prep.)

MERRA-2 Reanalysis

S1 cyclone 25 April 2012 18UTC 20

Summary▫ O3 measurements at Mace Head and Monte Velho are

influenced by cyclone tracks passing in the vicinity of the observation sites

▫ The relationship between O3 observed and cyclone tracks is dependent on the region, which demonstrates the importance of the associated fronts and conveyor belts

▫ The case studies demonstrate The importance of the passage of a cyclone’s cold front to

surface O3 measurements The ability of cyclones to bring down O3 from the

stratosphere Nearby surface high pressure systems also play an

important role in the temporal variability of surface O3

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Background | Question | Data & Methods | Results | Summary | k.e.knowland@nasa.gov

(Knowland et al., in prep.)

Thank you!

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