baseline ozone in western north america: measurements and … · 2015. 4. 6. · ushuaia, argentina...
TRANSCRIPT
Baseline Ozone in Western North America:
Measurements and Models
David Parrish
CIRES University of Colorado
NOAA/ESRL Chemical Sciences Division
Boulder, Colorado USA
Consultant with David.D.Parrish, LLC
Acknowledgements:
Many people have provided O3 data sets
~ 575 years of data from ~ 29 sites!
Results from 3 CCMs:
J.-F. Lamarque – NCAR CAM-chem
V. Naik, L. Horowitz – NOAA GFDL-CM3
D. T. Shindell - GISS-E2-R
Used for latest IPCC Report AR5
Free running
meteorology with
similar emissions
Importance of CCMs:
Calculate “Background” O3
Is it possible to meet NAAQS through U.S. controls?
Measured daily maximum O3 (ppbv) Modele
d d
aily
maxim
um
O3 (
ppbv)
Green bars show policy-relevant background O3 for April–June 2010 at
polluted sites in Southern California, California’s Central Valley, and Las
Vegas, Nevada (minimum, 25th, 50th, 75th percentiles and maximum).
M. Lin et al.,
JGR, 2014
Proposed
NAAQS Green bars =
background
O3
Assimilated
meteorology
Today’s Approach to answers:
Quantify and compare measured and modeled:
• Long-term O3 changes
• Brief look at global emission inventories
• Seasonal cycles of O3 in the marine
troposphere
Critical Questions:
What is the magnitude of baseline ozone and how is it
changing?
How accurate are model calculations of baseline ozone?
Combine 3 Japanese
MBL data sets
Combine 5 NA Pacific
MBL data sets
Cooper et al., 2010 NA
free troposphere data
set
2 mountain sites
Approximately baseline sites: Northern mid-latitudes: Japan
and western North America – Continental Asia outflow
Guiding ideas:
O3 lifetime in free troposphere is long
enough that similar trends are expected at
all of these sites.
Continuous, slowly varying trends are
expected.
Include as many data as possible to improve
precision – seasonal means at many sites
Pay close attention to confidence limits – I
will give 95% confidence intervals
Avoid continental influence
Trinidad Head
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Long-term changes
In my opinion, this includes all
available data as of 2011
Could be updated with more
recent data and other sites
(Mt. Bachelor, Cheeka Peak)
Similar long-term changes for
all sites when normalized
(true in all seasons)
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Long-term changes
Spring
Measurements
Normalize by dividing by
year 2000 intercept
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Long-term changes
Spring
Measurements
Similar long-term changes for
all sites (in all seasons)
when normalized
Polynomial fits give Shape
Factors that define long-
term changes for all sites
(different between seasons)
(Power Series expansion with
year 2000 as origin; keep
terms with statistically
significant coefficients.)
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Long-term changes
Spring
Measurements
Similar long-term changes for
all sites (in all seasons)
when normalized
Polynomial fits give Shape
Factors that define long-
term changes for all sites
(different between seasons)
O3 = a + bt + ct2
(t = year -2000) a = 100.5 ± 1.5, b = 0.93 ±
0.16, c = -0.021 ± 0.022
Similar long-term changes for
all sites (in all seasons)
when normalized
Polynomial fits give Shape
Factors that define long-
term changes for all sites
(different between seasons)
O3 = a + bt + ct2
(t = year -2000) a = 100.5 ± 1.5, b = 0.93 ±
0.16, c = -0.021 ± 0.022
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Long-term changes
For comparing measured and
modeled trends, exact co-
location is not important!
Measurements and Models:
Normalization gives similar
long-term changes for all
sites (in all seasons).
Quantify and Compare
measurements and
models
Measurements: O3
continues to increase in
spring
Models: O3 maximum
reached, now
decreasing
Parrish et al., JGR, 2014
Long-term changes
Long-term changes
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Measurements: O3 now
decreasing in summer
Models: O3 maximum
reached earlier
We have talked about increasing
background O3. This is no
longer the case during the high
O3 season!
Long-term changes
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Measurements: O3 has
increased less in
autumn than other
seasons
Models: O3 maximum
reached earlier
Long-term changes
Quantify and Compare
measurements and
models
Parrish et al., JGR, 2014
Measurements: O3 still
increasing in winter.
Models: O3 maximum
appears to be coming
earlier
1960 1980 2000 0.01
0.10
0.50
0.05
NO
x to
CO
mo
lar
rati
o
Hassler et al., 2015, in preparation
ACCMIP
Inventories for Los Angeles Basin
MACCity
Measurements Los Angeles
[Pollack et al.,2013]
(NOx to CO ratio is proxy for NOx to VOC ratio, which controls pollution photochemistry)
Brief look at global
emission inventories
Quantify and Compare
measurements and
models
Global emission inventories
require improvement:
If Emission input is not
accurate, Model output
cannot be accurate.
Quantify and Compare measurements and models
O3 seasonal cycles in marine troposphere
Ushuaia,
Argentina Cape
Grim
Cape
Point
Samoa
Storofdi,
Iceland
Mace Head
Trinidad
Head
Approximately baseline sites
7 marine
boundary
layer sites:
3 northern
mid-latitudes
1 tropical
3 southern
mid-latitudes
Quantify and Compare measurements and models
Seasonal cycles
29 years of monthly averages
Ian Galbally - CSIRO
Detrend, Calculate Fourier Transform
Only fundamental and 2nd
harmonic significant.
Only fundamental and 2nd
harmonic significant.
Two, and only two, terms are
significant in measured and
all modeled seasonal cycles
at all 7 sites.
Quantify and Compare measurements and models
Seasonal cycles
29 years of monthly averages
Detrend, Calculate Fourier Transform
Fundamental
2nd Harmonic
Quantify and Compare measurements and models
Seasonal cycles
29 years of monthly averages
Fundamental
2nd Harmonic
Fit sine functions to fundamental and 2nd harmonic
5 parameters define average
seasonal cycle:
• Annual average (Y0),
• 2 magnitudes (A1, A2),
• 2 phases (f1, f2)
Provide basis for quantitative
comparisons
Cape Grim
Quantify and Compare measurements and models
Seasonal cycles
29 years of monthly averages
Fundamental
2nd Harmonic
Fit sine functions to fundamental and 2nd harmonic
Pacific MBL
All sites have a late winter to
early spring maximum and
a summer minimum
Quantify and Compare measurements and models
Seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
All sites have a late winter to
early spring maximum and
a summer minimum
Highest ozone at northern
mid-latitudes, lowest in
tropics
Quantify and Compare measurements and models
Seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
All sites have a late winter to
early spring maximum and
a summer minimum
Highest ozone at northern
mid-latitudes, lowest in
tropics
Models reproduce seasonal
cycles reasonably well in
the marine boundary layer
Quantify and Compare measurements and models
Seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
Trinidad Head:
• 2nd harmonic is large
relative to fundamental;
secondary maximum in
fall
• Models overestimate MBL
baseline O3 by 10-17 ppb
(30-52%)
• Relative contributions of
fundamental and second
harmonic differ widely
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
Hypothetical Picture:
Photochemical production
dominates in lower FT –
May-June seasonal max
Photochemical destruction
dominates in MBL –
summer minimum, late
winter seasonal maximum
Stratospheric influence
dominates in upper FT –
spring seasonal max
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
Hypothetical Picture:
Model results do not fit this
hypothetical picture:
No strong shift in seasonal
cycle above MBL
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
O3 sharply
reduced in MBL
Model results do not fit this
hypothetical picture:
No strong shift in seasonal
cycle above MBL
Hypothetical Picture:
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
O3 sharply
reduced in MBL
Model results do not fit this
hypothetical picture:
No strong shift in seasonal
cycle above MBL
No sharp reduction in O3
within MBL
Hypothetical Picture:
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
Model results do not fit this
hypothetical picture
No strong shift in seasonal
cycle above MBL
No sharp reduction in O3
within MBL
Hypothetical Picture:
2nd harmonic
confined to MBL
Quantify and Compare measurements and models
Altitude dependence
of seasonal cycles
Fit sine functions to fundamental and 2nd harmonic
MBL structure and
dynamics?
Hypothetical Picture:
Model results do not fit this
hypothetical picture
No strong shift in seasonal
cycle above MBL
No sharp reduction in O3
within MBL
2nd harmonic term of seasonal
cycle present throughout
troposphere
Conclusions:
Baseline O3 transported from Pacific to North America
increased rapidly before 2000, but decrease has stopped
in summer and autumn.
Models (at least these 3 CCMs) cannot quantitatively
calculate baseline O3:
• Give incorrect trends
• Overestimate magnitude by 30-50% in MBL
• Give incorrect altitude gradients
Why?
Time evolution of emission inventories are poorly defined.
Marine boundary layer dynamics appear to be poorly
described.
Others?
Note: Hess et al., ACP, 2015 find that stratosphere to
troposphere flux and methane chemistry play major roles
in tropospheric O3 trends.
Quantify and Compare measurements and models
Seasonal cycles
29 years of monthly averages
Fundamental
2nd Harmonic
Fit sine functions to fundamental and 2nd harmonic
5 parameters define
average seasonal cycle:
• Annual average (Y0),
• 2 magnitudes (A1, A2),
• 2 phases (f1, f2)
Provide basis for quanti-
tative comparisons