epp contribution to (stratospheric and)

EPP contribution to (stratospheric and) tropospheric variationsAnnika SeppäläFinnish Meteorological InstituteAcademy of Finland

A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012

So far...

• Energetic Particle Precipitation (EPP) initial effects on middle atmosphere chemistry relatively well known. We have also learned more about indirect effects on stratospheric chemistry, thanks to satellite observations.

• EPP effects on dynamics and lower altitudes less clear.

• Mesospheric dynamical changes from SPE. Jackman et al., 2007.

• What about the stratosphere and troposphere?


SH: High EPP - Low EPPNH: High EPP - Low EPP

Seppälä et al., 2009.

EPP and tropospheric temperatures (Surface Air Temperature)

>40 years of re-analysis data

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Local polar effect during winter season, not a global effect. Links to Northern Annular Mode in NH?


So far...

• Energetic Particle Precipitation (EPP) initial effects on middle atmosphere chemistry relatively well known. We have also learned more about indirect effects on stratospheric chemistry, thanks to satellite observations.

• EPP effects on dynamics and lower altitudes less clear.

• Mesospheric dynamical changes from SPE. Jackman et al., 2007.

• What about the stratosphere and troposphere?

• Connection between solar wind/geomagnetic activity/EPP and the NAM/NAO/AO? Boberg and Lundstedt, 2002, Thejll et al., 2003, Lu et al., 2008, Seppälä et al., 2009, Baumgaertner et al., 2011.

• How does the signal propagate from ~mesospheric altitudes to the troposphere? What happens in the stratosphere?

• I will try to put some of these pieces together.


EPP and chemistry

Altit

ude

[km

]

2002−2003

Oct NovDec Jan Feb

30

40

50

60

70

2003−2004

Oct NovDec Jan Feb

2004−2005

Oct NovDec Jan Feb

Altit

ude

[km

]

Oct NovDec Jan Feb30

40

50

60

Oct NovDec Jan Feb Oct NovDec Jan Feb

2005−2006

OctNovDecJanFeb

024681012141618202224262830

NO

2 Mix

ing

ratio

[ppb

v]

OctNovDecJanFeb0.51 1.52 2.53 3.54 4.55 5.56

O3 M

ixin

g ra

tio [p

pmv]

O3

NO

xLong lived changes during winter and progressing into

spring.

Seppälä et al., 2007.

Randall et al., 2005.

Chemical changes limited to the mesosphere and stratosphere, above

about 30km. How is the troposphere influenced?

If the NOx reaches the stratosphere before spring, effects on stratospheric ozone significant.

Possibility for effects until summer? Is this the pathway to

influencing troposphere?


Middle atmosphere dynamics

Strong windsacting as a

transport barrier. Isolates polar air forming the Polar vortex. Maintains NOx in the polar region, transport

downward.

Active dynamics and atmospheric coupling taking

place in the winter pole.

Poles - access regions for EPP.

Location of chemical changes.


EPP and dynamics

• Assumption: EPP leads to reduction on stratospheric ozone in the SPRING.

• From chemistry: Less O3, less long wave heating from O3 → Cooling.

• Statistical study by Lu et al: Opposite.

London, 1980.

Lu et al., 2008.

SPRING

Similar spring time zonal mean zonal wind results from WACCM presented by Kvissel et al., 2012.


London, 1980.

EPP and dynamics

• Assumption: EPP leads to reduction on stratospheric ozone in the SPRING.

• From chemistry: Less O3, less long wave heating from O3 → Cooling.

• Statistical study by Lu et al.: Opposite seen.

Lu et al., 2008.

SPRING


EPP influence on stratosphere and troposphere dynamics, probably not from an in situ chemical

effect.Back to the drawing board!

Similar spring time zonal mean zonal wind results from WACCM presented by Kvissel et al., 2012.

EPP and dynamicsWhat have we learned from models?

Mean DJF Change

Less ozone

Less cooling from O3

= heating

Decreased circulation = cooling

• ✓ EPP impact on chemistry understood.

• Model experiments: Chemistry-General Circulation Models forced with EPP-NOx source. (Rozanov et al., 2005, Baumgaertner et al., 2011)

• Both show similar surface temperature results to re-analysis data during WINTER.

• Baumgaertner et al. (2011): Ozone loss → Reduction in long wave radiative cooling in WINTER polar upper stratosphere-mesosphere → Positive WINTER temperature anomaly.

‣ Decreased mean meridional circulation → Cooling the polar stratosphere.

• Chemistry coupling to dynamics already during winter? What is the pathway? What about HOx?

WINTER

A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012 Baumgaertner et al., 2011

Recap

• EPP can reduce polar O3 in mesosphere and stratosphere.

• O3 heating effects:

• Heating in short wave (UV from Sun). SPRING

• Cooling in long wave (Terrestrial outgoing radiation). WINTER

• LESS O3 would lead to a warm anomaly if less long wave cooling, and cold anomaly if less short wave heating.

• WINTER ✓

• SPRING ✗

• → Springtime dynamical effect NOT directly from ozone.


EPP and dynamics: A closer look

• 50 years of ERA re-analysis data

• Monthly means of zonal mean zonal wind, temperature and Eliassen-Palm flux.

• All data divided into High EPP and low EPP based on the Ap index.

• Looking at deviations from the dataset mean.

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

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123

T HAp EP LAp

5 ·105 m 3s − 2

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Alt[km]

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#15

U LAp 21

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T LAp

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#16

DECP [hPa]

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2

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#15

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45678

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JANP [hPa]

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1 23456

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2345678

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FEBP [hPa]

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321

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1234

Latitude 20 40 60 80

1 11

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Latitude

MARP [hPa]

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0

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Latitude20 40 60 80

Seppälä et al., in review, 2012.A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012

50km

0km

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

1

10

100

1000

1

123

T HAp EP LAp

5 ·105 m 3s − 2

0

15

30

50

Alt[km]

11

11

#15

U LAp 21

1

T LAp

1

1

2

34

#16

DECP [hPa]

1

10

100

1000

1

11

2

0

15

30

50

Alt[km]

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#15

1

1

1

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45678

#17

JANP [hPa]

1

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1000

32

1

1 23456

0

15

30

50

Alt[km]

1

2345678

#15

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21

1

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#17

FEBP [hPa]

1

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100

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321

1

1

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0

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1

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1234


1 11

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Latitude

MARP [hPa]

20 40 60 80

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1234

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0

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Latitude20 40 60 80

DJF mean change

The results agree fairly well with previous studies for

the polar region.

Baumgaertner et al., 2011

Lu et al., 2008.

A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012Seppälä et al., in review, 2012.

50km

0km

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

1

10

100

1000

1

123

T HAp EP LAp

5 ·105 m 3s − 2

0

15

30

50

Alt[km]

11

11

#15

U LAp 21

1

T LAp

1

1

2

34

#16

DECP [hPa]

1

10

100

1000

1

11

2

0

15

30

50

Alt[km]

11

#15

1

1

1

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45678

#17

JANP [hPa]

1

10

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1000

32

1

1 23456

0

15

30

50

Alt[km]

1

2345678

#15

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FEBP [hPa]

1

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1000

321

1

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1 11

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Latitude

MARP [hPa]

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Latitude20 40 60 80

EPP and dynamicsWave forcing

• Eliassen-Palm flux (EP flux), a measure of wave activity (energy transfer).

• Arrows: Direction of wave propagation

• Contours: Zonal flow acceleration or deceleration from wave breaking.

A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012 Seppälä et al., in review, 2012.

50km

0km

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

1

10

100

1000

1

123

T HAp EP LAp

5 ·105 m 3s − 2

0

15

30

50

Alt[km]

11

11

#15

U LAp 21

1

T LAp

1

1

2

34

#16

DECP [hPa]

1

10

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1000

1

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2

0

15

30

50

Alt[km]

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#15

1

1

1

2

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45678

#17

JANP [hPa]

1

10

100

1000

32

1

1 23456

0

15

30

50

Alt[km]

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2345678

#15

43

21

1

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FEBP [hPa]

1

10

100

1000

321

1

1

2345

0

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Alt[km]

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#15

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1234


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Latitude

MARP [hPa]

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1234

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Latitude20 40 60 80

EPP and dynamicsU, T, EP

• Dec-Feb: More waves are reflected towards the equator and away from the polar region under high EPP.

• Less waves disturbing the polar vortex → stronger vortex, until Mar.

• Winds and temperatures show downward movement with time. Waves play a significant role in transferring the EPP signal from the stratosphere to the troposphere.

• Coupling through wave-mean flow interaction important just like for solar irradiance influences.

A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 2012 Seppälä et al., in review, 2012.

50km

0km

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!01234

How are the surface level temperatures modulated?

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

1

10

100

1000

1

123

T HAp EP LAp

5 ·105 m 3s − 2

0

15

30

50

Alt[km]

11

11

#15

U LAp 21

1

T LAp

1

1

2

34

#16

DECP [hPa]

1

10

100

1000

1

11

2

0

15

30

50

Alt[km]

11

#15

1

1

1

2

3

45678

#17

JANP [hPa]

1

10

100

1000

32

1

1 23456

0

15

30

50

Alt[km]

1

2345678

#15

43

21

1

1

23456

#17

FEBP [hPa]

1

10

100

1000

321

1

1

2345

0

15

30

50

Alt[km]

32

1

12

#15

1

1234


1 11

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Latitude

MARP [hPa]

20 40 60 80

1

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1000

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1234

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0

15

30

50

Alt[km]

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Latitude20 40 60 80

From Here To Here?


How are the surface level temperatures modulated?

EP HAp

5 ·105 m 3s − 2

11 2

#16

U HAp

NOVP [hPa]

1

10

100

1000

1

123

T HAp EP LAp

5 ·105 m 3s − 2

0

15

30

50

Alt[km]

11

11

#15

U LAp 21

1

T LAp

1

1

2

34

#16

DECP [hPa]

1

10

100

1000

1

11

2

0

15

30

50

Alt[km]

11

#15

1

1

1

2

3

45678

#17

JANP [hPa]

1

10

100

1000

32

1

1 23456

0

15

30

50

Alt[km]

1

2345678

#15

43

21

1

1

23456

#17

FEBP [hPa]

1

10

100

1000

321

1

1

2345

0

15

30

50

Alt[km]

32

1

12

#15

1

1234


1 11

#17

Latitude

MARP [hPa]

20 40 60 80

1

10

100

1000

1

1234

5



0

15

30

50

Alt[km]

2

1

1

#15


12

Latitude20 40 60 80

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!01234

Stronger Polar Vortex Northern Annular Mode (NAM/NAO/AO)


The Northern Annular Mode (NAM) is an internal mode of variability in the atmosphere, which reflects the strength of the

polar vortex. Stronger polar vortex drives positive NAM anomalies. The high EPP temperature pattern is typical to

positive NAM.

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!01234

Interhemispheric differences. NH vs. SH

• Focus on the NH. What about the SH?

• More stable polar vortex in SH.

• Better conditions for descent from mesosphere.

• Dynamics more difficult to influence?

• Shorter timeseries of observations, only since 1979.

• Nevertheless, SH tropospheric temperatures show variations, both in model simulations and re-analysis!

• Effects show up earlier than in NH.

• Same mechanism or different mechanism?


Conclusions

• EPP effects middle atmosphere chemistry during winter (both HOx and NOx).

• Transition from chemical control to dynamical control in the stratosphere.

• From December to March anomalously strong polar vortex and more planetary wave reflection towards the equator.

• Also, for those interested: EPP effect on wave propagation more likely during high solar irradiance periods or westerly QBO. More details in the paper.

• Strong polar vortex leads to positive NAM anomalies, reflecting on surface temperatures.

• We are still working towards fully understanding the EPP coupling to dynamics, there are lots of connections to SOLARIS work.


Thank you for your attention pre-ice breaker!

epp contribution to (stratospheric and)

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