weekday/weekend o 3 and pm differences in three cities outside california betty k. pun and christian...
DESCRIPTION
Objectives At 3 urban locations outside CA, study the day-of-the-week dependence of –diurnal profile of hourly O 3 concentrations –daily maximum 1-hour and 8-hour O 3 –PM 10 and PM 2.5 Test hypotheses for the “weekend effect” Identify changes in the weekday/weekend difference over a longer periodTRANSCRIPT
Weekday/Weekend O3 and PM Differences in Three Cities Outside California
Betty K. Pun and Christian SeigneurAER, San Ramon, CA
Warren WhiteWashington University, St. Louis, MO
“Weekend Effect” Research Workgroup Meeting13 April 2000
Introduction
CARB, NREL, CRC• Data analysis• Modeling• Field study
CRC Project A-36B is a data analysis project to study weekday/weekend differences in O3 and PM in areas outside CA
Chicago
Philadelphia
Atlanta
Objectives
• At 3 urban locations outside CA, study the day-of-the-week dependence of– diurnal profile of hourly O3 concentrations
– daily maximum 1-hour and 8-hour O3
– PM10 and PM2.5
• Test hypotheses for the “weekend effect”• Identify changes in the weekday/weekend
difference over a longer period
Technical Approach
Airshed Selection
Data Compilation
Characterization of Day-of-the-W eek Behavior (Ozone, PM)
Hypothesis 1 :Changes inVO C, NO xEm issions
Hypothesis 2 :Friday/Saturday
N ight Traffic
Hypothesis 3:Tem poral
Traffic P rofiles
Hypothesis 4:Spatia l Traffic
Profiles
Hypothesis 5:O ther Non-
m obile Sources
Hypothesis 6:PM Effect on
Photochem istry
SynthesisCA Studies
Ozone Monitoring Sites
Area No. Sites Years(1) MonthsAtlanta 8 5 Mar/Apr - Oct/Nov 3 1Chicago 21 5 Apr - Oct or
Jan - Dec 5 2/3Philadelphia 6 5 Mar - Nov or
Jan - Dec
(1) 1995 - 1999
Hour-of-the-Week Analysis
• Ozone– Atlanta, GA– Chicago, IL– Philadelphia, PA
• PM– Chicago, IL
Hourly Data Recordby Site
Group by Day of Week
Group by Hour of Day
Average Concentration of Each Hour
Atlanta, GA; 1995 - 1999
Atlanta Site No. 1513500024
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hours)
Ozo
ne C
once
ntra
tion
(ppm
)
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Friday
Monday
Chicago, IL; 1995 - 1999
Chicago Site No. 1703110034
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hours)
Ozo
ne C
once
ntra
tion
(ppm
)
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Sunday
WednesdayWednesday
Philadelphia, PA; 1995 - 1999
Philadelphia Site No. 4210100244
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hours)
Ozo
ne C
once
ntra
tion
(ppm
)
Monday Tuesday
Wednesday Thursday
Friday SaturdaySunday
Sunday
Friday
Maximum One-Hour Concentrations
0.25
0.20
0.15
0.10
0.05
0.00
Norm
alize
d Fr
eque
ncy
0.160.140.120.100.080.060.040.020.00
O3 Concentration (ppm)
weekday weekend
Atlanta Site No. 1313500024
Maximum One-Hour Concentrations Mean and Standard Deviation
Atlanta Site No. 1313500024
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
Monday
Tuesday
Wednes
day
Thursday
Friday
Saturday
Sunday
Ozo
ne C
once
ntra
tion
(ppm
)
Bootstrap Sampling
. . .
ObservedData
BootstrapSamples
Sampling with replacement
The population distribution of any statistic can be approximated by the distribution of that statistic derived from the bootstrap samples
Hypothesis Testing by the Shift MethodExample: Friday-Monday O3 Difference
Dis
tr ibu
ti on
o f th
e d i
ffere
nce
Bootstrap meandifference 5.3 ppb
Observed difference5.2 ppb
Hypothesized difference0 ppb (Null hypothesis)
Nulldistribution
Probability that the observeddifference (5.2 ppb) occurs
by chance if the true difference is 0 ppb
Bootstrapdistribution
Atlanta, GA; Maximum One-Hour O3
• Average Values: 8 out of 11 sites show statistically significant(1) differences – High O3 on Fridays (7) and Saturdays (1)
– Low O3 on Mondays (7) and Sundays (1)
• Median Values (7) and 90th Percentile (10)– High O3 on Fridays
– Low O3 on Mondays, Sundays, and Tuesdays
• Exceedances of the NAAQS occurred on Fridays (41), Thursdays (40), Saturdays (31)
(1) 10% confidence level
Maximum One-Hour Concentrations Mean and Standard Deviation
Chicago Site 1703110034
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Monday
Tuesday
Wednes
day
Thursday
Friday
Saturd
ay
Sunday
Ozo
ne C
once
ntra
tion
(ppm
)
Chicago, IL; Maximum One-Hour O3
• Average Values: 25 out of 26 sites show statistically significant differences – High O3 on Sundays (23) and Saturdays (2)
– Low O3 on Tuesdays (12), Wednesdays (10), Other Weekdays (5)
• Median Values (24)– High O3 on Sundays; Low O3 during midweek
• 90th Percentile (25) – High O3 on Saturdays and Sundays; low O3 early work
week
Maximum One-Hour Concentrations Mean and Standard Deviation
Philadelphia Site No. 4210100244
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Monday
Tuesday
Wednes
day
Thursday
Friday
Saturd
ay
Sunday
Ozo
ne C
once
ntra
tion
(ppm
)
Philadelphia, PA; Maximum One-Hour O3
• Average Values: all 6 sites show statistically significant differences– High O3 on Sundays (4) and Saturdays (2)
– Low O3 on Fridays (3), Wednesdays (2), and Thursdays
• Median Values (3)– High on Sundays; Low during late week
• 90th Percentile (6)– High on Weekends and Mondays; low on Fridays
Maximum 8-Hour O3 Concentrations
• Atlanta– Day-of-week differences in 8-hour O3 is less significant
than 1-hour O3
– High concentrations on Fridays (4 sites) and Saturdays (4)
• Chicago– Day-of-week difference in 8-hour O3 similar to 1-hour
O3; individual sites may show higher or lower differences
– High concentrations on Sundays; low during midweek
• Philadelphia– Weekly cycle more apparent in 8-hour than in
1-hour concentrations– High O3 on weekends, low late work week
Maximum 8-Hour O3 Concentrations (continued)
PM10 at Chicago, IL; 1995 - 1999
Chicago Site No. 1812700238
15
20
25
30
35
40
45
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Time (hr)
PM
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
(g/
m3 )
Chicago Site No. 1812700238
0
10
20
30
40
50
Monday
Tuesday
Wednes
day
Thursday
Friday
Saturday
Sunday
24-h
our P
M
24-Hour Average PM10
• High 24-hour averaged PM on Tuesdays and Fridays, low PM on weekends
• Statistics significant (5%) at all 5 sites
(g/
m3 )
Hour-of-week Profiles of NOx
0.14
0.12
0.10
0.08
0.06
0.04
NOx C
once
ntra
tion
(ppm
)
2220181614121086420
Time (hour)
Chicago Site No. 1703100634
Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Correlation Between O3 and NOx
0.12
0.10
0.08
0.06
0.04
0.02
0.00
O3 C
once
ntra
tion
(ppm
)
0.50.40.30.20.10.0
6 - 9 a.m. Average NOx Concentration (ppm)
Chicago Metropolitan Area
Summary
• Atlanta: O3 weekly buildup– High O3 on Fridays, low O3 on Mondays
• Chicago: O3 weekend effect– High O3 on Sundays, low O3 during midweek
• Philadelphia: O3 weekend effect– High O3 on Sundays, low O3 during late work week
• Chicago: PM high during the week, low on weekends
Future Work
• Use VOC/NOx ratio to bypass the confounding effects of meteorology
• Test hypotheses• Test historical trends• Need access to EPA’s AIRS database!!!!!!!
– VOC– PM10 for Atlanta, Philadelphia
– Availability of PM2.5