cluster analysis of air quality data for ccos study domain scott beaver ahmet palazoglu, p.i....

Cluster Analysis of Air Quality Data for CCOS Study Domain

Scott BeaverAhmet Palazoglu, P.I.

University of California, Davis

Dept. Chemical Engineering & Materials Science

CCOS Technical Committee MeetingCal/EPA Building, 1001 I St., Sacramento, CA

Thursday 31 March 2007

Department of Chemical Engineering and Materials Science

Overview• Project: Cluster Analysis for CCOS Domain

I. Intra-basin analyses: wind patterns & synoptic regimes

II. Inter-basin meteorological response of O3 levels

• Intra-basin analyses:– Completed Bay Area analysis

• Strong synoptic influence; seabreeze cycles

– Preliminary North SJV wind field clustering• Synoptic & ventilation effects

– Preliminary Central SJV wind field clustering• Synoptic & mesoscale (Fresno eddy) effects

– Preliminary South SJV wind field clustering• Synoptic effects; mesoscale variability difficult to capture

– Initial Sacramento Valley & Mountain Counties analysis

• Future work and recommendations


Cluster Analysis for CCOS• Scope of 2-year project

I. Intra-basin wind field cluster analyses– Requires continuous, hourly surface wind data– Days grouped by diurnal wind field patterns– Reveals synoptic and mesoscale flow regimes

II. Inter-basin analysis

• Study Domain– 6 CCOS air basins

• San Francisco Bay Area• SJV: split into North, Central, & South• Sacramento Valley• Mountain Counties

– 1996-2004 ozone seasons (1 May – 31 October)



San Francisco Bay Area

SFBA: 4 clusters for 976 days1996

1997

1998

1999

2000

2001

2002

Jun 01 Jun 15 Jul 01 Jul 15 Aug 01 Aug 15 Sep 01 Sep 15 Sep 30

2003


*Beaver and Palazoglu, 2006: Cluster analysis of hourly wind measurements to reveal synoptic regimes affecting air quality. Journal of Applied Meteorology and Climatology, 45, 1710—26.

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SFBA clusters = synoptic regimes


H

R

V2V1

Onshore High: 353 d, 13% episodes Offshore High: 86 d, 13% episodes

Weaker Trough: 309 d, 0% episodes Deeper Trough: 309 d, 0% episodes

*Beaver, Palazoglu and Tanrikulu, 2007: Cluster sequencing to analyze synoptic transitions affecting regional ozone. Journal of Applied Meteorology and Climatology, in press.

Synoptic Transition Probabilities• R transitions rapidly to H

– Severe, multi-day episodes– Reverse HR does not occur– Polar low may “save” SFBA from episode

• Persistence of H indicates stability– Displaced by sufficiently deep trough (e.g. V2)– Bulk of episodes during persistent H

• Transitions from V1 & V2 driven by global met.– Troughs may persist for long periods; low O3 levels– Transition to H or R will occur unless O3 season ends


SJV SLAMS network


SLAMS, CIMIS, RAWS & NCDC


North SJV Wind Monitors


Wind Speed Errors at Tracy


1996—1999 are similar to 2001—2004.

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Tracy-Patterson Rd. -- Wind Speed

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Tracy-Patterson Rd. -- Wind Direction Hourly Distribution

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Hour of Day

2004

Wind Direction Errors at Tracy


1996—1999 are similar to 2001—2003.

Gantt chart for N-SJV


Yellow = 1 Nov—30 Apr winter data (not clustered)Blue = clustered stations (included in Total)Red = non-clustered stations (excluded from Total)

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H: 179 days, 42%

H H

R

V2V1

V

R: 264 days, 19%H/V: 212 days, 25%

V2: 108 days, 6%V1: 299 days, 12%

N-SJV 0900 PST Wind Field


Magenta: Carquinez Strait— Ft. Funston, Pt. San Pablo, Suisun, Bethel Is.

Blue: Altamont Pass— Kregor Peak, Tracy

Red: Pacheco Pass— Los Banos

Black: SJV floor

H H/VR V1 V2Increasing marine ventilation: R < H < H/V < V1 < V2

N-SJV Seasonal Distribution


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Black: Probability a Cluster is Realized Within 5 Days of Any Day of YearRed: Probability a Cluster is Realized as Exceedance Within 5 Days of Any Day of Year

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N-SJV Ventilation


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50Tracy Stockton Merced

1500 PST Temperature (oC)

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1000 PST Westerly Speed (m/s)

Bethel Island Tracy Los Banos

H H/V V1

V2 R H H/V V1

V2 R H H/V V1

V2 R

Altamont Pass Wind Distribution


0800PST Wind Distribution

H (164 d)

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H/V (189 d) V1 (281 d) V2 (89 d) R (245 d)

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N-SJV Synoptic Sequencing

• = 0.05– R H/V disfavored– Clusters occur in different seasons (trivial result)

• = 0.15– R H favored

– H H/V favored

– H/ V V favored

– V R favored

• Compare to Bay Area– Transitions significant at < 0.02– Stronger synoptic influence than N-SJV

Central SJV Wind Monitors


Annual Biases in Wind Direction


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180270360

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Dir

Clovis-N Villa Wind Direction

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2000—02 are ~15o more westerly than other years.

Upslope/Downslope Cycle

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Dir


Wind direction at SLAMS Sequoia monitor for 20 days during 2003.

Flow switches from easterly to westerly.

Daytime upslope flows; nighttime drainage flows

Diurnal cycle largely captures local effects.

Signal is not well modeled by clustering algorithm.

Gantt chart for C-SJV


Magenta: stations with annual biases

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H: 203 days

H H R

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R: 341 daysH/V: 169 days

V/I: 378 daysV: 279 days

IV?

C-SJV 8-hr O3 Exceedances


H RH/VV/IV

Ventilated regime episodes favor Sequoia.

Anti-cyclonic regime episodes favor SJV floor.

Percentage of days in each cluster that are 8-hr O3 exceedances

279 d 378 d 169 d 203 d 341 d

Total 40% 32% 64% 92% 59%SJV floor 29% 17% 34% 84% 52% Parlier 20% 15% 28% 73% 43% Clovis 18% 6% 12% 62% 33%

Sequoia 25% 25% 57% 64% 33%SJV floor & Sequoia 14% 10% 27% 56% 26%

C-SJV Seasonal Distribution

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C-SJV Synoptic Sequencing

• Direct transitions between H, R, and V occur infrequently

• H/V and V/I are “intermediate” states– C-SJV is buffered from synoptic effects

– Synoptic transitions have less effect on O3 levels than for N-SJV (than for Bay Area)

• Mesoscale effects important for C-SJV


The Fresno Eddy


Magenta: Carquinez Strait— Ft. Funston, Pt. San Pablo, Suisun

Blue: Altamont Pass— Kregor Peak, Tracy

Red: Pacheco Pass— Los Banos

Cyan: Parkfield (west) & Sequoia (east)

Yellow: Carrizo Plain

R H/VH V V/IDecreasing eddy strength: H > R > H/V > V > V/I

Eddy Strength and O3 Levels


Strong eddyNo/weak eddy

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Parlier southerly wind component at 0900 PST (m/s)

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Eddy (207 d)

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Stagnant (19 d) Stagnant (15 d) Stagnant (43 d)

No eddy (14 d) No eddy (60 d) No eddy (118 d)

Eddy (193 d) Eddy (296 d)R H/V V V/IH

Eddy Strength & Marine Ventilation

Within each regime, enhanced marine ventilation can suppress eddy formation

South SJV Wind Monitors


Gantt chart for S-SJV


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H/V: 206 days, 64%

H H R

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R: 373 days, 62%H: 354 days, 58%

V/I: 317 days, 22%V: 160 days, 36%

I?V


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S-SJV Seasonal Distribution

Progress


Non-contracted quality assurance is a critical but time consuming step which has delayed Phase I progress.

Obta

in d

ata

Qualit

y ass

ura

nce

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eport

Syn

optic

sequenci

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ind a

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ozo

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ynoptic

analy

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l analy

sis

San Francisco Bay Area X X X X X X XSJV North X X X \ \ XSJV Central X X X \ \ XSJV South X X \ \Sacramento Valley XMountain Counties X

Phase I Phase II

Recommendations• Transport analysis for identified met regimes using a (back-

trajectory) transport model.– Transport through gaps in Coastal Range– Transport patterns from major source areas

• NOx/VOC ratio and O3 sensitivity– Role of meteorology

• El Nino effects• Wild fire analysis• Vertical analysis

– Visalia profiler– Limited soundings?

• AQM performance evaluation• … and others from project work plan ???


cluster analysis of air quality data for ccos study domain scott beaver ahmet palazoglu, p.i....

Documents

wind direction errors

pst wind fieldmagenta

synoptic transitions

hourly surface wind

episodepersistence of

cluster sequencing

r hv disfavored clusters

v r favoredcompare