GEOPHYSICAL RESEARCH LETTERS
Supporting Information for ”Impacts of Traffic
Reductions Associated with COVID-19 on Southern
California Air Quality”
H.A. Parker
1
, S. Hasheminassab
2
, J.D. Crounse
1
, C.M. Roehl
1
, P.O.
Wennberg
1
1
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
2
South Coast Air Quality Management District, Diamond Bar, CA, USA
Contents of this file
1. Text S1
2. Figures S1 to S16
3. Table S1
November 21, 2020, 2:39pm
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:
Text S1. Caltech Air Quality Station (CITAQS)
The Caltech Air Quality Station (CITAQS) contains a set of high sensitivity Teledyne air
quality sensors including continuous measurements of PM
10
and PM
2.5
(Teledyne T640); trace
gas measurements of NO and NO
y
(Teledyne T200U), CO (Teledyne M300EU2), SO
2
(Teledyne
T100U); and optical trace gas measurements of O
3
(Teledyne T400) and NO
2
(Teledyne T500U)
that reports at a one minute temporal resolution. The CITAQS was deployed outside the Linde
Robinson Building on Caltech campus in Pasadena, CA on March 20,2020 to continue measuring
indefinitely.
November 21, 2020, 2:39pm
:
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Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure S1.
Left: 7-day moving average temperature (top), relative humidity (middle), and
wind speed (bottom) in 2020 and 2015 to 2019 in the South Coast Air Basin. For 2020, mea-
surements before 19 March are in green and after 19 March are in red. The averages of the
measurements for 2015 to 2019 are in black with the associated range as grey shading. Right:
Monthly average precipitation in the South Coast Air Basin in 2020 and 2015 to 2019 in cen-
timeters per month.
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:
Air Monitoring Site
O3
NOx
PM2.5
Anaheim
ü
ü
ü
Azusa
ü
ü
û
Banning Airport
ü
ü
ü
Compton
ü
ü
û
Central LA
ü
ü
ü
Crestline
û
û
ü
Fontana
ü
ü
û
Glendora
ü
ü
ü
La Habra
ü
ü
û
Lake Elsinore
ü
ü
ü
LAX
ü
ü
û
Mira Loma
ü
ü
ü
Pasadena
ü
ü
û
Pico Rivera
ü
ü
û
Pomona
ü
ü
û
Reseda
ü
ü
ü
Rubidoux
ü
ü
ü
San Bernardino
ü
ü
û
Santa Clarita
ü
ü
ü
South Long Beach
û
û
ü
Upland
ü
ü
ü
West LA
ü
ü
û
Temecula
û
û
ü
Location of air monitoring sites
Figure S2.
Left: Breakdown of monitoring sites and the measurements included in the
analysis. Right: Map of the locations of the sites described in the table on the left.
Site Name
Latitude
Longitude
2000 - 2019 NO2 trend (%/yr)
2000 - 2019 O3 trend (%/yr)
2000 - 2019 Ox trend (%/yr)
2020 NO2 Anomaly (%, ppb)
2020 O3 Anomaly (%, ppb)
2020 Ox Anomaly (%, ppb)
Banning
33.92086
-116.85841
-9.08
-0.39
-0.91
15, 0.3 (22, 0.4)
-5, -3.3 (-1, -0.4)
-3, 2.2 (1, 0.6)
San Bernardino
34.106678
-117.274063
-6.26
0.64
-0.62
-8, -0.5 (-4, -0.3)
2, 1.4 (10, 6.4)
4, 2.8 (9, 7.8)
Lake Elsinore
33.67649
-117.33098
-7.38
-0.87
-1.28
-29, -0.5 (-10, -0.2)
-6, -3.1 (-1, -0.7)
-5, -3.0 (-1,-0.4)
Fontana
34.10002
-117.49201
-6.11
0.01
-1.22
10, 0.7 (13, 0.9)
0, -0.2 (8, 4.9)
4, 3.6 (11, 7.6)
Upland
34.10374
-117.62914
-8.09
0.45
-1.22
10, 0.6 (23, 1.2)
0, 0.3 (8, 5.6)
6, 3.88 (14, 9.71)
Pomona
34.06703
-117.7514
-6.96
0.44
-1.53
-18, -1.3 (-15, -1.1)
8, 4.7 (17, 9.9)
11, 6.9 (19, 11.7)
Glendora
34.14435
-117.85036
-6.67
0.11
-1.35
-20, -1.5 (-12, -0.9)
4, 2.7 (12, 7.8)
5, 3.3 (13, 8.9)
Azusa
34.1365
-117.92391
-5.24
0.41
-1.00
-26, -2.4 (-20, -1.8)
4, 2.1 (11, 6.7)
2, 1.5 (10, 6.6)
La Habra
33.92513
-117.95264
-7.14
0.17
-1.28
-9, -0.4 (-1, 0.0)
-1, -0.7 (4, 2.2)
2, 0.8 (7, 3.8)
Pasadena
34.1326
-118.1272
-6.56
0.11
-1.53
-16, -1.0 (-14, -0.7)
16, 8.6 (20, 12.6)
16, 9.4 (23, 13.2)
Central LA
34.06659
-118.22688
-4.90
-0.09
-1.43
-31, -2.5 (-24, -1.9)
-3, -1.4 (5, 2.4)
-6, -3.1 (2, 1.1)
West LA
34.05111
-118.45636
-6.83
-0.18
-0.93
95, 2.5 (176, 3.7)
-13, -6.5 (-10, -4.8)
-6, -3.1 (0, -0.1)
Reseda
34.19925
-118.53276
-5.70
0.46
-0.39
-33, -1.3 (-34, -1.4)
-8, -5.0 (-3, -1.8)
-7, -4.8 (-3, -2.0)
Average East of 117.75 W
-7.38
-0.03
-1.05
0, 0 (9, 0.2)
-2, -1.3 (5, 2.6)
1, 0.3 (7, 3.9)
Average West of 117.75 W
-6.35
0.18
-1.21
-7, -0.9 (7, -0.3)
-2, -0.5 (7, 4.5)
2, 1.6 (9, 5.9)
Average
-6.82
0.07
-1.13
-4, -0.6 (8, -0.2)
-2, 0.0 (6, 3.9)
2, 1.2 (8, 5.3)
Table S1.
2000 to 2019 trends and 2020 anomalies in afternoon (12:00 - 16:00 local) NO
2
,
O
3
, and O
x
concentrations for sites in the basin that have measurements of both NO
2
and O
3
for the 2000 to 2020 period. Anomalies represent the difference between values observed during
2020 COVID period afternoons and the values expected from a 2000-2019 fit of COVID period
afternoons. Values in parentheses represent the anomaly values for the 19 April to 30 June period
instead of the 19 March to 30 June period.
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Figure S3.
Plots of mean O
3
concentrations by hour of day and day of week in Pasadena for
our analysis period in 2020 and the average of 2015 to 2019. Vertical lines mark 12pm and 4pm
respectively in each plot.
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Figure S4.
Air quality index time series for daily AQI values for LA county for 2010 to 2020
generated on the EPA website (
https://www.epa.gov/outdoor-air-quality-data/air-data
-multiyear-tile-plot
).
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Figure S5.
Air quality index time series for daily AQI values for San Bernardino county for 2010
to 2020 generated on the EPA website (
https://www.epa.gov/outdoor-air-quality-data/
air-data-multiyear-tile-plot
).
November 21, 2020, 2:39pm
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:
Figure S6.
Air quality index time series for daily AQI values for Riverside county for 2010
to 2020 generated on the EPA website (
https://www.epa.gov/outdoor-air-quality-data/
air-data-multiyear-tile-plot
).
November 21, 2020, 2:39pm
:
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Figure S7.
Air quality index time series for daily AQI values for Orange county for 2010
to 2020 generated on the EPA website (
https://www.epa.gov/outdoor-air-quality-data/
air-data-multiyear-tile-plot
).
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:
Basin Average
Basin Maximum
All days included
All days included
Rainy days excluded
Rainy days excluded
Figure S8.
Sensitivity test by excluding the rainy days from the analysis (right, in red) in
comparison to including all the days (left, in black). The means are reported to the right of the
box plots with the standard deviation in parenthesis.
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Change of 8
-
hr DM O3 per site
COVID Period (2020)
–
COVID Period (2015
-
2019)
Figure S9.
Left: Box plots of 8-hr DM O
3
values during the 2015 to 2019 COVID period and
2020 COVID period. Right: Map of the difference between the 2015 to 2019 COVID period and
2020 COVID period in parts per billion (top) and percentage (bottom).
November 21, 2020, 2:39pm