Post on 16-Jul-2020
Geophysical Fluid Dynamics Laboratory
Key drivers of Western U.S. surface O3 variability during 1980-2050: From extreme transport events to background trends
Meiyun Lin
Presented at 2014 AGU Fall Meeting, A14E-01
Acknowledgements: NOAA: L.W. Horowitz, O.R. Cooper, A.O. Langford, S. J. OltmansOthers: A.M. Fiore and H. Rieder (Columbia), D. Tarasick (Environment Canada)
Mae Gustin and Rebekka Fine (Univ of Nevada)
Geophysical Fluid Dynamics Laboratory
Major challenges for Western U.S. air quality managements
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MAJOR CHALLENGES:-Frequency of stratospheric intrusions in spring [e.g. Langford et al., 2009; Lin et al., 2012b]
-Rising Asian emissions and global CH4 [e.g. Jacob et al. 1999; Cooper et al. 2010; Fiore et al. 2012]
-More frequent wildfires in summer [e.g. Westerling et al. 2006; Pfister et al. 2008; Jaffe 2011]
-High winter O3 pollution in an oil and natural gas basin [e.g. Edwards et al. 2014]
NEED PROCESS-LEVEL UNDERSTANDING ON DAILY TO MULTI-DECADAL TIME SCALES
Annual 4th Hi MDA8 O3
(2011-2013 AQS)Mean background, Apr-Jun
(NA anthrop emis off in GFDL-AM3 model)
Future NAAQS?
Current NAAQS
Sparse monitoring
Geophysical Fluid Dynamics Laboratory Lin M.Y. et al (in prep, 2014c)
Stratospheric intrusions push observed surface ozone in S. Nevada above the 75 ppbv NAAQS threshold
New Measurements: -Nevada Rural Ozone Initiative (NVROI), July 2011-present (M. Gustin & R. Fine)-Las Vegas Ozone Study, May-June 2013 (A.O. Langford)
May 25 (STT)
How do such events vary from year to year and what controls its variability?
Observed MDA8 O3 on May 25, 2013
ppb
3
Jun 2 (LA/BB)
Consistent with modeling results from Lin et al (JGR, 2012b)
NVROI Echo Peak (2286 m altitude)
Geophysical Fluid Dynamics Laboratory
Strong stratospheric influence on year-to-year variability of high-elevation Western U.S. surface O3 during April-May
Lin M.Y. et al (in review, 2014b)
75th
25th
50th
O3Strat
1990
Emissions held constantNudged to “real” winds
4
In contrast, the influences from wildfire emissions and Asian pollution are minimal (See paper) Large IAV may complicate the attribution of observed O3 trends in short records (See also Lin
et al.; Nature Geosci, 2014a)
Geophysical Fluid Dynamics Laboratory
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
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
5Lin M.Y. et al (in review, 2014b)
See my talk A51Q-07 on Friday (9:30am, Moscone West 3006) for explanations on the physical mechanisms
Changes in the high tail are statistically significant
Geophysical Fluid Dynamics Laboratory 6
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
O3Strat
BGO3
Total
Following La Niña conditions, deep STT may occur with sufficient frequency as to confound NAAQS attainment
NAAQS
BGO3
Total
MD
A8
O3
(pp
b)
MD
A8
O3
(pp
b)
O3Strat
Geophysical Fluid Dynamics Laboratory 7
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 (1.5 km altitude)
NAAQS
BGO3
Total
NAAQS
BGO3
Total
MD
A8
O3
(pp
b)
MD
A8
O3
(pp
b)
O3Strat
O3Strat
Geophysical Fluid Dynamics Laboratory 8
More frequent stratospheric intrusions expected in the following spring over WUS?
Developing seasonal predictions with a few months of lead time to aid Western U.S. AQ planning?
SST (C)
Lin M.Y. et al (in review, 2014b)
The time lag could allow regional preparations, e.g. Conducting daily forecasts for public health alerts Deploying targeted measurements aimed at identifying “exceptional events”
MD
A8
O3
(pp
b)
Gothic, Colorado
Tropical SST cooling typically peaks in winter
Geophysical Fluid Dynamics Laboratory 9
GFDL-AM3 BASE(emis+met vary over time)
Long-term U.S. surface ozone trends: Did regional NOx reductions work?
Observed
MDA8 O3 trends (ppb yr-1)
95%
50%
Larger circles indicate statistically significant trends
MAM 1988-2012
NASA Project PIs (M.Y. Lin and O.R. Cooper)The model is nudged to “real” winds, sampled at site elevation and filtered to remove local influence -- more representative of observed conditions at remote WUS sites
Geophysical Fluid Dynamics Laboratory
Must consider variability in atmospheric circulation when interpreting observed changes in baseline O3
NASA PIs (M.Y. Lin and O.R. Cooper) 10
1988 1992 1996 2000 2004 2008 2012
Me
dia
n O
3an
om
aly
in
pp
b r
ela
tive
to
20
00
Pinatubo STT+
Weaker variability in the 2000s attributed to changes in background rather than in N.A. pollution
BGO3
Nudged to real winds
Larger growth of Asian emissions in the 2000s, but weaker rate of O3
changes observed at Lassen as compared to the 1990s
Lassen Volcanic NP, Calif. (1.7 km), Mar-Apr-May
E. China NOx Emissions
No
rma
lize
d t
o 2
00
0
Model Satellites
1980 1990 2000 2010
Geophysical Fluid Dynamics Laboratory
Projections of near-term changes in WUS lower trop. ozone in spring (March-April-May)
11
Me
dia
n O
3an
om
aly
in
pp
b r
ela
tive
to
20
10
No
rmal
ize
d t
o 2
00
0
Satellites
RCP8.5
RCP4.5
RCP8.5
RCP4.5
Global CH4 (ppb)3000
2500
2000
1500
E. China NOx emissions
1980
OBS (GRB, LAV, ROM)AM3 BASE, nudged
11
Geophysical Fluid Dynamics Laboratory
Summarizing drivers of WUS O3 variability
• The frequency of deep STT affects year-to-year variability in springtime high-O3 events Linked to La Niña in the previous winter Potential for seasonal forecast
• Rising Asian emissions and global CH4 are likely the major drivers of long-term changes in mean baseline ozone, but ….
• Ozone measurements contain signatures of circulation variability: Short records may complicate the attribution of trends Must ensure an apple-to-apple comparison btw model and obs
Contact: Meiyun.Lin@noaa.gov
12
Geophysical Fluid Dynamics Laboratory
Additional slides for Q & A
Geophysical Fluid Dynamics Laboratory
The GFDL AM3 Model Hindcasts for 1978- 2012
Experiment Meteorology Forcings(radiation)
CH4
(chemistry)Aerosol and O3
precursorsFire emissions
BASE Nudged to NCEP U&V
Historical Historical Historical and RCP 8.5 beyond 2005
Historical
PRB as BASE Historical Historical Shut off over NA;
as BASE elsewhere
Historical
FIXEMIS as BASE Historical 2000 Fixed Fixed
IAVFIRE as BASE Historical 2000 Fixed Historical
IAVASIA as BASE Historical 1980 Varying in Asia only Fixed
IAV_CH4Chem
as BASE Historical Historical Fixed Fixed
Designed to isolate the role of changes in meteorology, background, STE, wildfires, methane, and Asian vs. North Americananthropogenic emissions
Model setup similar to Lin et al. [2012a, b], but at 2ºx2º resolution
Geophysical Fluid Dynamics Laboratory 15
Summarizing drivers of U.S. ozone trends In the historical period (1980-2012)
Increases in total ozone over WUS despite reductions in local emissions
GFDL AM3 (2003-2012 minus 1981-1990)
PRB
AsianIncreases from boreal fires
Total
CH4
PRB
PRBEA
Total (filtered)
Rising Asian emissions contribute ~50% of total background increases
Geophysical Fluid Dynamics Laboratory
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