on the role of climate variability on tropospheric ozone · geophysical fluid dynamics laboratory...

Geophysical Fluid Dynamics Laboratory

On the Role of Climate Variability on Tropospheric Ozone

Meiyun Lin

Presented at 2014 AGU Fall Meeting, A51Q-07

Acknowledgements: NOAA: L.W. Horowitz, S.M. Fan, A.O. Langford, S. J. OltmansOthers: A.M. Fiore and H. Rieder (Columbia), D. Tarasick (Environment Canada)


Drivers of trop. O3 variability over the North Pacific and Western N. America in SPRING

PACIFIC SUBTROPICAL REGION: Sensitive to the subtropical jet location

[Zeng & Pyle 2005; Koumoutsaris et al 2008; Neu et al 2014]

Greater Asian than stratospheric influence on variability [Lin et al., Nature Geosci, 2014a]

1990-2012 mean background O3 at 500 hPa in Apr-May

WESTERN U.S.- Sensitive to the eddy-driven jet- Highly variable on synoptic time scales

- Prone to deep strat. Intrusions

Langford et al. 2009; Lin et al. 2012ab

1979-2011, MAM

Skerlak et al. [2014]

NEED PROCESS-LEVEL UNDERSTANDING ON DAILY TO MULTI-DECADAL TIME SCALES

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

Spring

Fall

Tracer of East Asian Pollution E. China NOx Emissions

Norm

aliz

ed

to

20

00

Model Satellites

1980 1990 2000 2010

Mauna Loa Observatory (3.4 km altitude)

Lin M.Y. et al (2014)

Tropospheric ozone trends at Mauna Loa Observatory tied to decadal climate variability

The puzzle: Little change in spring Increase in fall

almost tripled!


Increasing ozone at Mauna Loa in FALL tied to a shift in circulation patterns since the mid-1990s

Lin M.Y. et al (Nature GeoSci., 2014)

Changes in NCEP 500hPa height (1995-2011 minus 1980-1994)

Must consider decadal climate variability as well as emission changes for

attribution of pollutant trends

OBS: 11% decade-1 (p<0.05) FIXEMIS (Nudged): 7% decade-1 (p<0.05)

BASE (Nudged): 13% decade-1 (p<0.05)

[m]

Sep

-O

ct

4


Decreasing ozone at Mauna Loa in SPRING tied to recent La-Niña-like decadal cooling + weakening airflow from Asia

ElNiño


AMIP (fixed emissions)

El Niño La Niña

(ppb)

40

50

70

60

80

Me

an b

ackgrou

nd

50

0 h

Pa, A

pr-M

ay

5

Ozo

ne

An

om

aly

, pp

b(2

5th

pe

rce

nti

le)

LaNiña-like decadal cooling [Chavez2003; Meehl2013; Kosaka2013]

P<0.01

20N

40N

60N


Decreasing ozone at Mauna Loa in SPRING tied to recent La-Niña-like decadal cooling + weakening airflow from Asia

Decreasing Rn (Bq/m3) Weakening airflow

from Eurasia

ElNiñoLaNiña-like decadal cooling

[Chavez2003; Meehl2013; Kosaka2013]


AMIP (fixed emissions)

El Niño La Niña

(ppb)

40

50

70

60

80

Even higher?

Me

an b

ackgrou

nd

50

0 h

Pa, A

pr-M

ay

6

Ozo

ne

An

om

aly

, pp

b(2

5th

pe

rce

nti

le)

P<0.01

20N

40N

60N


Strong stratospheric influence on year-to-year variability of high-elevation Western U.S. surface O3 during Apr-May

Lin M.Y. et al (in review, 2014b)

75th

25th

50th

O3Strat

1990

7

In contrast, the influence of wildfire emissions and Asian pollution are minimal (see paper) Large IAV may complicate the attribution of observed O3 trends in short records.

Emissions held constantNudged to “real” winds

Geophysical Fluid Dynamics Laboratory 8

1999 (La Niña)

1992 (Pinatubo)

Frequent deep STT events

Weaker events, lower mean values

Gothic in the Colorado Rocky Mtn (2.9 km altitude)

NAAQS

O3S

BGO3

Total

Following La Niña conditions, deep STT may occur with sufficient frequency as to confound NAAQS attainment

NAAQS

O3S

BGO3

Total

MD

A8

O3

(pp

b)

MD

A8

O3

(pp

b)


The high tail of the observed daily surface O3 distribution over Western U.S. increases during La Niña springs

Observed daily max 8-h average (MDA8) ozone

Changes in the high tail are statistically significant

Neutral, µ = 56.5,σ = 7.5El Niño, µ = 56.9,σ = 7.3La Niña, µ = 58.5,σ = 7.9Pinatubo, µ = 54.3,σ = 6.5

9Lin M.Y. et al (in review, 2014b)

Little change in WUS surface O3 during El Niño despite increased UTLS O3

burdens reported previously [e.g. Langford1998; Bronnimann2004; Neu2014].


Western US surface O3 variability correlates poorly with O3

burdens in the UTLS but strongly with that in the Free Trop

Niño 3.4 Index

Apr-May 1995

Apr-May 2000

Apr-May 2005

Apr-May 2010

12-mon running mean UTLS O3

anomaly (%) r2(UTLS, Surface) = 0.07

98/99 07/08 10/11

Jan 1990

Jan 1995

Jan 2000

Jan 2005

Jan 2010

Jan 1990

Jan 1995

Jan 2000

Jan 2005

Jan 2010

Trinidad

-20

0

20

40

10

5

0

-5

Apr-May mean FreeTrop & SurfaceO3 anomaly (ppb)r2(FreeTrop, Surface) =0.74

Apr-May 1990 10


Late winter storm-track shifts towards U.S. Pacific Northwest during La Niña, facilitating deep tropopause folds

GFDL CM3 (2000 yrs)

NCEP (1948-2008)

Figure from Li & Lau (J. Climate, 2012); See also discussions in Trenberth et al, 1998; Seager2010

Anomalies in rms of 2-10-day bandpassed filtered 500mb heights

El Niño La Niña

Contours: 250mb Heights

11

Geophysical Fluid Dynamics Laboratory Lin M.Y. et al (in review, 2014b)

Winter

Late Spring

El Niño (NCEP1948-2013) La Niña (NCEP1948-2013)

The enhanced storm-track activity over the central western U.S. persists in late spring for strong La Niña episodes

Anomalies in rms of 2-10-day bandpassed filtered 500mb heights

12

Geophysical Fluid Dynamics Laboratory Lin M.Y. et al (in review, 2014b)

Variance in daily O3Strat at 500hPa

Summarizing sources in daily to interannual variability of lower trop. ozone during spring related to ENSO

La Niña

El Niño

El Niño

La Niña

(ppb2)

Lin M.Y. et al (Nature GeoSci., 2014a); 13


Take-Home Messages

Contact: [email protected]

La NiñaWinter

More frequent deep STT events in the following spring over Western US;Potential for seasonal prediction

El NiñoWinter

Little influence on Western US surface O3

despite increased UTLS O3 burdens

Must consider climate variability when interpreting observed trends in tropospheric ozone levels.

SST

GFDL AM3

14


Additional slides for Q & A


GFDL model indicates influence from circulation shifts that modulate Asian pollution reaching Hawaii

O3S

trat

Tra

cer

% C

han

ge i

n E

AC

Ot

BASE

- Varying emissions

- Nudged to “real winds”

FIXEMIS

- Constant emissions

- Nudged to “real winds”

[Lin

et

al.,

2012b]

1980-1995

1996-2011

J F M A M J J A S O N D

(1996-2

011)

–(1

980-1

995)



Following El Niño conditions, stronger airflow from Asia towards Hawaii in SPRING

Me

an O

3A

no

mal

y (p

pb

)

East

Asi

an C

Ot

(pp

b)

Year


Geophysical Fluid Dynamics Laboratory 18

Following La Niña conditions, deep STT may occur with sufficient frequency as to confound NAAQS attainment

2011 (La Niña)

2007 (Neutral)

Chiricahua NM in Arizona (1570 m)

NAAQS

O3S

BGO3

Total

NAAQS

O3S

BGO3

Total


Role of dynamical variability on free tropospheric ozone over Western U.S. during spring

Meiyun Lin et al., in prep

O3Strat

• Observations as in Cooper et al. [2010; 2012].• Sparse sampling and short records may complicate the unambiguous attribution of

observed trends

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