1

Understanding Relationships Between Changes in Ambient Ozone and

Precursor Concentrations and Changes in VOC and NOx Emissions

from 1990 to 2004 in Central California

Envair – C. Blanchard and S. Tanenbaum

DRI – E. Fujita and D. Campbell

Alpine Geophysics – J. Wilkinson

December 19, 2007

2

Today’s Topics

I. Project overview

II. Phase I: summary of results

III. Phase II: objectives and schedule

IV. Phase II: summary of results

3

I. Project Overview

• Phase I (completed)– Databases and methods– Ozone and precursor trends by site and by

subregion – Precursor trends compared to county-level

emission trends– Meteorological classifications – Ozone trends for all high-ozone days and by

meteorological class

4

I. Project Overview (continued)

• Phase II (in progress) – Grid emission inventories, 1990-2004 – Relate ambient primary-pollutant trends to

zone-of-influence emission trends– Relate ozone trends to ambient and emission

trends of precursors, and to meteorological conditions

– Submit final report

5

II. Phase I: Summary of Results

6

Sub-Region

N orthern S ierra Footh ills

Southern S ierra Footh ills

Sacram ento Valley

N orthern SF Bay A rea

Eastern SF Bay A reaSouthern SF Bay A reaN orthern San Joaquin

C entra l San Joaquin

Southern San Joaquin

AQ Sites and Subregions

7

1990 – 2004 AQ Trends Summary

• No trends significantly upward*• NOx sig* down at 22 of 28 sites**• CO sig* down at 21 of 25 sites**• NMOC sig* down at 5 of 7 sites***• Ozone sig* down at 7 of 42 sites**• Annual mean top-60 ozone trends similar

to trends in annual 4th-highest 8-hour max

* p < 0.05** At least 10 years data. One or both metrics.*** 7 - 10 years data

8

Phase I Findings: Precursor Trends

• On average, ambient precursor decreases are comparable to county-level emissions decreases

• There is a possibility that emission decreases are overestimated or underestimated for some counties

• Confirmation requires comparison of site trends to spatially-resolved emission trends (Phase II)

9

Ambient and Emissions Decreases for NOx

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Fremont-Chapel W

ay

Livermore

Jackson-Clinton Road

San Andreas-Gold Strike

Pittsburg-10th Street

Bethel Island Road

Concord-2975 Treat Blvd

Placerville-Gold Nugget

Fresno-Drumm

ond Street

Parlier

Fresno-Sierra Skypark #2

Fresno-1st Street

Clovis-N Villa Avenue

Edison

Oildale-3311 Manor Stree

Arvin-Bear Mountain Blvd

Bakersfield-Golden State

Bakersfield-5558 Califor

Merced-S Coffee Avenue

Roseville-N Sunrise Blvd

North Highlands-Blackfoo

Sacramento-Del Paso M

ano

Elk Grove-Bruceville Roa

Sacramento-T Street

Folsom

Stockton-Hazelton Street

Gilroy-9th Street

San Jose-4th Street

Vallejo-304 Tuolumne Str

Modesto-14th Street

Turlock-S Minaret Street

Visalia-N Church Street

Sonora-Barretta Street

Site

Dec

reas

e (N

orm

aliz

ed V

alu

es)

Ambient NOx Decrease at Sites Emissions NOx Decrease in County

(Artifact due to site relocation)X

10

Ambient and Emissions Decreases for CO

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Fremont-Chapel W

ay

Livermore

Jackson-Clinton Road

San Andreas-Gold Strike

Pittsburg-10th Street

Bethel Island Road

Concord-2975 Treat Blvd

Placerville-Gold Nugget

Fresno-Drumm

ond Street

Parlier

Fresno-Sierra Skypark #2

Fresno-1st Street

Clovis-N Villa Avenue

Edison

Oildale-3311 Manor Stree

Arvin-Bear Mountain Blvd

Bakersfield-Golden State

Bakersfield-5558 Califor

Merced-S Coffee Avenue

Roseville-N Sunrise Blvd

North Highlands-Blackfoo

Sacramento-Del Paso M

ano

Elk Grove-Bruceville Roa

Sacramento-T Street

Folsom

Stockton-Hazelton Street

Gilroy-9th Street

San Jose-4th Street

Vallejo-304 Tuolumne Str

Modesto-14th Street

Turlock-S Minaret Street

Visalia-N Church Street

Sonora-Barretta Street

Site

Dec

reas

e (N

orm

aliz

ed V

alu

es)

Ambient CO Decrease at Sites Emissions CO Decrease in County

11

Phase I Findings: Ozone Trends

• Phase I analyses demonstrate spatial variations of ozone concentrations and trends but do not explain them

• Site-to-site variations and directional variations of mean concentrations suggest importance of local ozone formation

• More detailed analyses in Phase II

• Potential limitation is signal-to-noise

12* Eastern SFB is Livermore Old 1st St 1990-2000 only

Ozone Trends in Subregions - Medians of Site Trends

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

EasternSFB*

NorthernSFB

SouthernSFB

NorthernSJV

Central SJV

SouthernSJV

Sacra- mentoValley

NorthernSierra

Foothills

SouthernSierra

Foothills

Subregion

Ozo

ne

Tre

nd

(p

pb

v p

er y

ear)

4th Highest 8-hour maximum Top 60 8-hour maximum

13

Meteorological Classification

1. Principal component analysis (PCA) of regional-scale met variables

2. K-means clustering of PCs

PCA applied to all days of all years from 1990 to 2004(n = 5480** days)

Clustering applied to all ozone-season days(n = 2790 days)

** 5441 with pressure gradient data; 4202 with 850 mb data

14

Clusters separate days into groups with different 850 mb wind directions

15

Number of Days in Each Cluster, By Month

0

50

100

150

200

250

300

350

400

May June July August Sep Oct

Month

Nu

mb

er o

f D

ays

1 2 3 4Cluster

16

Characteristics of Met Clusters• Cluster 1: N and E 850 mb winds, lower surface

pressure at San Francisco than elsewhere, and low surface wind speeds. Mean ozone and precursor concentrations are high due to generally poor ventilation.

• Cluster 2: SW 850 mb winds and higher surface wind speeds than in cluster 1.

• Cluster 3: more W 850 mb winds and higher surface wind speeds. Mean ozone ~ 5 to 15 ppbv lower than in cluster 1.

• Cluster 4: similar to cluster 1, but with better ventilation and 850 mb winds that are on average more N than for days in cluster 1.

17

18

Mean peak 8-hour ozone concentrations varied among sites, subregions, and met types – these days are all top-60 peak 8-hour days

19

Change in Mean Peak Daily 8-Hour Ozone, 1995-99 to 2000-04(by Meteorological Class and Subregion)

-15

-10

-5

0

5

10

15

Ozo

ne

Ch

ang

e (p

pb

v)

Type 1 Type 2 Type 3 Type 4

Change in Mean Peak Daily 8-Hour Ozone, 1995-99 to 2000-04(by Meteorological Class and Subregion)

-15

-10

-5

0

5

10

15

Ozo

ne

Ch

ang

e (p

pb

v)

Type 1 Type 2 Type 3 Type 4Type 1 Type 2 Type 3 Type 4

(Order is SBA, NBA, EBA, NSJ, SAC, NSF, CSJ, SSJ)

20

III. Phase II: Objectives and Schedule

• Objectives– More accurate comparison of sites’ AQ trends

with “zone-of-influence” emission trends– Better understanding of ozone trends at sites

within each subregion and the relation of ozone to precursor trends and meteorological variation

• Schedule – Complete by end of December

21

Phase II Tasks• Task 5: Prepare gridded emission inventories,

1990 – 2004• Task 6:

– (a) Compare “zone-of-influence” emission trends to ambient primary-pollutant trends.

– (b) Relate ozone changes to precursor trends and meteorology.

• Task 7: Prepare final report and draft manuscript. • Task 8: Provide data, documentation, and software• Task 9: Present findings at meetings

22

Task 5 Approach

• Generate gridded inventories from county-level inventories, 1990 - 2004

• Develop monitor-specific “zone-of-influence” emission trends using 3x3 5x5, and 7x7 arrays of grid cells around each long-term monitor

23

Task 5 Status

• Gridded inventories were generated from county-level inventories and year 2000 surrogate files prepared by STI

• Discrepancies identified and revisions made• We created month and year “zone-of-

influence” CO, NOx, and NMOC emissions using 3x3, 5x5, and 7x7 arrays of grid cells around each long-term monitor

• We are examining current and historical site photos for evidence of changes in land use

24

Potential Biases in Gridded Emissions(Due to Not Using Historical Surrogates)

• Sites located in nonurban settings in 1990 becoming urban by 2000– Not problematic if site is still nonurban– Not too problematic for trends from 1994-

2004 (year 2000 is approximate midpoint)

• Relocated sites – must match emissions– Livermore– Folsom– Madera

25

Candidate Sites: Possible 1990-2004 New Urbanization Within 5 – 10 km

• Bethel Island 1990-2004• Grass Valley 1994-2004• Cool 1996-2004• Auburn 1990-2004• Fresno Sierra Skypark 1992-2004• Edison 1990-2004

Options: Limit trend comparisons to 1994-2004 and/or adjust gridded emissions on site-specific basis

26

Task 6 Status

• In progress: comparisons of “zone-of-influence” emission trends to ambient primary-pollutant trends

• Also in progress: analyses of ozone changes in relation to precursor trends

• Completed: analyses of met classes

• Completed: analyses of ozone trends at detailed temporal and spatial resolution

27

IV. Phase II: Summary of Results

28

Ambient and Emissions Trends for Ozone Precursors

• Ambient and emissions trends show discrepancies for NOx when emissions are quantified at county and regional scales

• Work in progress: comparisons at smaller spatial scales

29

Precursor Trends: Regional Scale

• We compared ambient precursor decreases to regional emissions decreases

• Combined subregions (2 to 6 counties): - Sacramento + N Sierra Foothills - East Bay + South Bay + SF (central Bay area)- N San Joaquin + S Sierra Foothills - Central San Joaquin + S San Joaquin

30

Ambient and Emissions Decreases for NOx

-0.2

0

0.2

0.4

0.6

0.8

1

Pittsbu

rg-1

0th

Street

Bethe

l Islan

d Roa

d

Conco

rd-2

975

Treat

Blvd

Vallejo

-304

Tuo

lumne

Str

Frem

ont-C

hape

l Way

Liver

mor

e

Gilroy-

9th

Street

San Jo

se-4

th S

treet

Placer

ville-

Gold N

ugge

t

Rosev

ille-N

Sun

rise

Blvd

North

High

lands

-Blac

kfoo

Sacra

men

to-D

el Pas

o M

ano

Elk Gro

ve-B

ruce

ville

Roa

Sacra

men

to-T

Stre

et

Jack

son-

Clinto

n Roa

d

San A

ndre

as-G

old S

trike

Mer

ced-

S Cof

fee

Avenu

e

Stock

ton-

Hazelt

on S

treet

Mod

esto

-14t

h Stre

et

Turloc

k-S M

inare

t Stre

et

Sonor

a-Bar

retta

Stre

et

Fresn

o-Dru

mm

ond

Parlie

r

Fresn

o-Sier

ra S

kypa

rk #

2

Fresn

o-1s

t Stre

et

Clovis-

N Villa

Ave

nue

Edison

Oildale

-331

1 M

anor

Stre

e

Arvin-

Bear M

ount

ain B

lvd

Baker

sfield

-Gold

en S

tate

Baker

sfield

-555

8 Cali

for

Visalia

-N C

hurc

h Stre

etDec

reas

es (

No

rmal

ized

Val

ues

)

Ambient NOx Decreases at Site Emissions NOx Decreases by Area

Ambient-emissions NOx discrepancy exists for central Bay and Sacramento areas

31

Ambient and Emissions Decreases for CO

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Pittsbu

rg-1

0th

Street

Bethe

l Islan

d Roa

d

Conco

rd-2

975

Treat

Blvd

Vallejo

-304

Tuo

lumne

Str

Frem

ont-C

hape

l Way

Liver

mor

e

Gilroy-

9th

Street

San Jo

se-4

th S

treet

Placer

ville-

Gold N

ugge

t

Rosev

ille-N

Sun

rise

Blvd

North

High

lands

-Blac

kfoo

Sacra

men

to-D

el Pas

o M

ano

Elk Gro

ve-B

ruce

ville

Roa

Sacra

men

to-T

Stre

et

Jack

son-

Clinto

n Roa

d

San A

ndre

as-G

old S

trike

Mer

ced-

S Cof

fee

Avenu

e

Stock

ton-

Hazelt

on S

treet

Mod

esto

-14t

h Stre

et

Turloc

k-S M

inare

t Stre

et

Sonor

a-Bar

retta

Stre

et

Fresn

o-Dru

mm

ond

Parlie

r

Fresn

o-Sier

ra S

kypa

rk #

2

Fresn

o-1s

t Stre

et

Clovis-

N Villa

Ave

nue

Edison

Oildale

-331

1 M

anor

Stre

e

Arvin-

Bear M

ount

ain B

lvd

Baker

sfield

-Gold

en S

tate

Baker

sfield

-555

8 Cali

for

Visalia

-N C

hurc

h Stre

etDec

reas

es (

No

rmal

ized

Val

ue)

Ambient CO Decreases at Site Emissions CO Decreases by Area

32

Working hypothesis: Diesel NOx emissions have not decreased

To be determined: are there discrepancies between ambient and near-site emissions

trends?

Why aren’t the ambient NOx trends at some sites

as large as expected from the emission trends?

33

Ozone Trends: Spatial and Temporal Patterns of

Changes

34

Ozone concentration surfaces show changes in frequencies of high-ozone days over time – but some sites show more high-ozone days in lateryears

35

1-Jan

31-Jan

1-Mar

31-Mar

30-Apr

30-May 29-

Jun 29-Jul 28-

Aug 27-Sep 27-

Oct 26-Nov 26-

Dec

1990

1992

1994

1996

1998

2000

2002

2004

40

80

120

Pea

k 8-

ho

ur

Ozo

ne

(pp

bv)North Highlands Ozone

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

36

1-Jan

31-Jan

1-Mar

31-Mar

30-Apr

30-May 29-

Jun 29-Jul 28-

Aug 27-Sep 27-

Oct 26-Nov 26-

Dec

1990

1992

1994

1996

1998

2000

2002

2004

40

80

120

Pea

k 8

-ho

ur

Ozo

ne

(pp

bv)

Sacramento-Del Paso Ozone

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

37

1-May

22-May

15-Jun

12-Jul

9-Aug

28-Aug

14-Sep

29-Sep 14-

Oct 29-Oct

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

40

80

120

Pea

k 8-

ho

ur

Ozo

ne

(pp

bv)

Sacramento-Del Paso Ozone - Cluster 1

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

38

1-M

ay

16-M

ay

31-M

ay

15-J

un

30-J

un

17-J

ul

4-A

ug

22-A

ug

10-S

ep

29-S

ep

19-O

ct1990

1991

1992

1993

1994

1995

1996

1997

1998

19992000

20012002

20032004

40

80

120

Pea

k 8

-h

ou

r O

zon

e (p

pb

v)

Sacramento-Del Paso Ozone - Cluster 3

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

39

1-Jan

31-Jan

1-Mar

31-Mar

30-Apr

30-May 29-

Jun 29-Jul 28-

Aug 27-Sep 27-

Oct 26-Nov 26-

Dec

1990

1992

1994

1996

1998

2000

2002

2004

40

80

120

Pea

k 8-

ho

ur

Ozo

ne

(pp

bv)

Fresno 1st Street Ozone

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

40

1-Jan

31-Jan

1-Mar

31-Mar

30-Apr

30-May 29-

Jun 29-Jul 28-

Aug 27-Sep 27-

Oct 26-Nov 26-

Dec

1990

1992

1994

1996

1998

2000

2002

2004

40

80

120

Pea

k 8-

ho

ur

Ozo

ne

(pp

bv)

Parlier Ozone

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

41

1-Jan31-Jan

1-Mar31-Mar

30-Apr

30-May

29-Jun

29-Jul

28-Aug

27-Sep

27-Oct

26-Nov

26-Dec

1990

1992

1994

1996

1998

2000

2002

2004

40

80

120

Pea

k 8-

ho

ur

Ozo

ne

(pp

bv)

Parlier Ozone

80-120 ppbv

40-80 ppbv

Peak 8-Hour Ozone

42

From Tracy to Yosemite …..

Tracy

M odesto

Turlock

M erced

Jerseydale

Yosem iteSan FranciscoBay

M onterey Bay

Tuolum ne

A lam eda

C ontra C osta

San Joaquin

S tanislaus

M erced

M ariposa

M adera

C alaveras

Santa C lara

…..a transect analysis

43

Means by hour, determined from top 60 peak ozone days

Peak ozone increases from Tracy to Merced, then declines …

Jerseydale and Yosemite are less influenced by fresh emissions

44

Tracy

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne

(pp

bv)

Tracy 1995-99 Tracy 2000-04

Mean ozone at Tracy declines between 1995-99 and2000-2004 during almost all hours

45

Modesto

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne (p

pb

v)

Modesto 1995-99 Modesto 2000-04

Also, mean ozone at Modesto declines between 1995-99 and2000-2004 from 8 am through 7 pm

46

Modesto - Tracy

-25

-20

-15

-10

-5

0

5

10

15

20

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne

Dif

fere

nce

(p

pb

v)

Modesto-Tracy 1995-99 Modesto-Tracy 2000-04

And … Modesto-Tracy differences similar between 1995-99 and 2000-2004 (except from 6 am through 11 pm)

47

Turlock - Modesto

-6

-4

-2

0

2

4

6

8

10

12

14

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne D

iffe

ren

ce (p

pb

v)

Turlock-Modesto 1995-99 Turlock-Modest 2000-04

But … the Turlock-Modesto difference increases between 1995-99 and 2000-2004 during all hours

48

Merced - Turlock

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne D

iffe

ren

ce (p

pb

v)

Merced-Turlock 1995-99 Merced-Turlock 2000-04

And … the Merced-Turlock difference increases between 1995-99 and 2000-2004 during almost all hours

49

Jerseydale - Merced

-20

-10

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Hour

Ozo

ne D

iffe

ren

ce (p

pb

v)

Jerseydale-Merced 1995-99 Jerseydale-Merced 2000-04

Yet … the Jerseydale-Merced difference declines between 1995-99 and 2000-2004 during all hours

50

How Does Northern SJV Ozone FormationIn 2000-04 Compare With1995-99?

• Lower at western boundary – ozone declined at Tracy and Modesto

• Decreased overall – indicated by declines at Jerseydale - reflect outflow and probably also aloft concentrations

• Increased within parts of the northern SJV – as shown by intersite differences that are larger in later years

51

Decreasing

Increasing

Average M axim um 8-hour O zone

Mean Peak Ozone In 2000-04 and 1990-94

Sites WithIncreasing Ozone

(from north to south)North Highlands

PittsburgConcordTurlockMerced

Fresno SkyparkClovis

Fresno DrummondParlierOildaleArvin

Maricopa

52

Decreasing

Increasing

Average D ifference between S ite and Upw ind S iteM axim um 8-hour O zone

Sites With Increasing Ozone Differential

(from north to south)Concord

Modesto 14th

TurlockMerced

Fresno SkyparkFresno Drummond

ParlierArvin

A Double Difference: Mean Peak Ozone In2000-04 and 1990-94 at Site and at Nearest Site

53

Changes in Mean Diurnal Ozone Concentrations

54

2000 - 2004 Compared With 1990 - 1994

55

2000 - 2004 Compared With 1995 - 1999

56

Despite localized effects, there is a subregional coherence of ozone trends

57

Temporal Changes in Ozone

• Higher ozone concentrations at night during most recent years

• Higher daytime ozone concentrations at some sites interspersed between sites having lower daytime ozone

• Implies localized effects – but subregional coherence also exists

58

Meteorological Variations

• Characterized ozone and precursor means by met cluster and subcluster

• Ozone trends are not explained by changes in meteorological conditions

59

Differences Between Parlier and Madera Mean Ozone, By Time Period (Hourly Means, Top 60 Days)

-15

-5

5

15

25

35

Par

lier-

Mad

era,

clu

ster

1

0 2 4 6 8 10 12 14 16 18 20 22 24HOUR

2000_04

1995_99

1990_94

-15

-5

5

15

25

35

Par

lier-

Mad

era,

clu

ster

2

0 2 4 6 8 10 12 14 16 18 20 22 24HOUR

2000_04

1995_99

1990_94

-15

-5

5

15

25

35

Par

lier-

Mad

era,

clu

ster

3

0 2 4 6 8 10 12 14 16 18 20 22 24HOUR

2000_04

1995_99

1990_94

-15

-5

5

15

25

35

Par

lier-

Mad

era,

clu

ster

4

0 2 4 6 8 10 12 14 16 18 20 22 24HOUR

2000_04

1995_99

1990_94

Cluster 1 Cluster 2

Cluster 3 Cluster 4

Period Period

Period Period

60

Ozone Trends – Preliminary Conclusions

• Overall ozone levels decreased

• Ozone formation increased in some portions of the Sacramento and central San Joaquin valleys

• These areas have experienced high growth and development

• To be continued ….

61

If you are looking at this slide, you’ve seen too many slides