baseline ozone in western north america: measurements and … · 2015. 4. 6. · ushuaia, argentina...

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)


measurements and

models


Long-term changes

Spring

Measurements

Normalize by dividing by

year 2000 intercept


measurements and

models


Long-term changes

Spring

Measurements


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.)


measurements and

models


Long-term changes

Spring

Measurements



when normalized





O3 = a + bt + ct2

(t = year -2000) a = 100.5 ± 1.5, b = 0.93 ±

0.16, c = -0.021 ± 0.022



when normalized





O3 = a + bt + ct2

(t = year -2000) a = 100.5 ± 1.5, b = 0.93 ±

0.16, c = -0.021 ± 0.022


measurements and

models


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).


measurements and

models

Measurements: O3

continues to increase in

spring

Models: O3 maximum

reached, now

decreasing


Long-term changes

Long-term changes


measurements and

models


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


measurements and

models


Measurements: O3 has

increased less in

autumn than other

seasons

Models: O3 maximum

reached earlier

Long-term changes


measurements and

models


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


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


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.


Seasonal cycles


Detrend, Calculate Fourier Transform

Fundamental

2nd Harmonic


Seasonal cycles


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


Seasonal cycles


Fundamental

2nd Harmonic


Pacific MBL

All sites have a late winter to

early spring maximum and

a summer minimum


Seasonal cycles




a summer minimum

Highest ozone at northern

mid-latitudes, lowest in

tropics


Seasonal cycles




a summer minimum

Highest ozone at northern

mid-latitudes, lowest in

tropics

Models reproduce seasonal

cycles reasonably well in

the marine boundary layer


Seasonal cycles


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


Altitude dependence

of seasonal cycles


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


Altitude dependence

of seasonal cycles



Model results do not fit this

hypothetical picture:

No strong shift in seasonal

cycle above MBL


Altitude dependence

of seasonal cycles


O3 sharply

reduced in MBL




cycle above MBL



Altitude dependence

of seasonal cycles


O3 sharply

reduced in MBL




cycle above MBL

No sharp reduction in O3

within MBL



Altitude dependence

of seasonal cycles



hypothetical picture


cycle above MBL


within MBL


2nd harmonic

confined to MBL


Altitude dependence

of seasonal cycles


MBL structure and

dynamics?



hypothetical picture


cycle above MBL


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.


Seasonal cycles


Fundamental

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

baseline ozone in western north america: measurements and … · 2015. 4. 6. · ushuaia, argentina...

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