Supporting Information:
100
0.6
80
60
RH (%)
0.4
2
ClNO (ppbv)
0.5
0.3
40
0.2
20
0.1
0
0
0.2
0.4
0.6
0.8
N O (ppbv)
2
1
1.2
0
5
Figure S-1. ClNO2 mixing ratios vs. N2O5 mixing ratios scattered by the relative humidty for
the NACHTT study period.
12
0.5
10
0.4
8
0.3
6
0.2
4
0.1
2
0
0
0.2
0.4
0.6
0.8
N O (ppbv)
2
1
1.2
Time Since Sunset (hours)
0.6
2
ClNO (ppbv)
14
0
5
Figure S-2. ClNO2 mixing ratios vs. N2O5 mixing ratios scattered by the time since sunset for
the NACHTT study period.
70
0.6
60
0.4
40
x
0.3
30
0.2
20
0.1
10
0
NO (ppbv)
50
2
ClNO (ppbv)
0.5
0
0.2
0.4
0.6
0.8
N O (ppbv)
2
1
1.2
0
5
Figure S-3. ClNO2 mixing ratios vs. N2O5 mixing ratios scattered by NOx mixing ratios for the
NACHTT study period.
0.6
50
0.4
30
3
O (ppbv)
40
2
ClNO (ppbv)
0.5
0.3
20
0.2
10
0.1
0
0
0.2
0.4
0.6
0.8
N O (ppbv)
2
1
1.2
0
5
Figure S-4. ClNO2 mixing ratios vs. N2O5 mixing ratios scattered by ozone mixing ratios for the
NACHTT study period.
450
0.6
400
350
300
0.4
250
2
ClNO (ppbv)
0.5
0.3
200
150
0.2
100
0.1
Aerosol Surface Area (  m2/cm3)
500
50
0
0
0.2
0.4
0.6
0.8
N O (ppbv)
2
1
1.2
5
Figure S-5. ClNO2 mixing ratios vs. N2O5 mixing ratios scattered by aerosol surface area for the
NACHTT study period.
70
250
50
250
200
40
200
30
100
200
35
Cl2 (pptv)
150
40
Height (m)
100
Cl2 (pptv)
Cl2 (pptv)
150
Height (m)
50
100
250
45
60
30
150
25
20
100
Height (m)
150
50
15
20
50
50
0
12:00
18:00
00:00
06:00
0
12:00
0
5
15:00
Feb. 18-19 Local Time
18:00
21:00
00:00
03:00
0
06:00
0
15:00 18:00 21:00 00:00 03:00 06:00 09:00 12:00
Feb. 19-20 Local Time
Feb. 21-22 Local Time
50
250
50
50
10
10
180
250
250
160
20
100
Cl2 (pptv)
150
200
140
120
150
100
80
100
Height (m)
200
30
Height (m)
100
20
Cl2 (pptv)
150
30
Height (m)
200
40
Cl2 (pptv)
40
60
50
10
40
50
10
50
20
0
15:00 18:00 21:00 00:00 03:00 06:00 09:00 12:00
0
0
15:00 18:00 21:00 00:00 03:00 06:00 09:00 12:00
Feb. 22-23 Local Time
0
250
45
06:00
70
250
0
12:00
250
60
200
200
100
30
50
Cl2 (pptv)
100
150
40
Height (m)
20
Cl2 (pptv)
150
25
Height (m)
30
50
15
50
100
50
50
10
10
5
0
15:00 18:00 21:00 00:00 03:00 06:00 09:00 12:00
0
12:00
Feb. 27-28 Local Time
160
30
20
20
10
150
40
18:00
00:00
06:00
0
12:00
0
12:00
Feb. 28 - Mar. 01 Local Time
35
250
Height (m)
60
200
35
18:00
00:00
06:00
0
12:00
Mar. 01-02 Local Time
250
250
100
140
30
150
20
15
100
Cl2 (pptv)
100
60
200
80
Height (m)
150
80
200
25
Cl2 (pptv)
100
Height (m)
200
120
150
60
100
40
Height (m)
Cl2 (pptv)
00:00
Feb. 25-26 Local Time
70
40
Cl2 (pptv)
18:00
80
50
10
40
50
50
12:00
18:00
00:00
06:00
0
12:00
0
12:00
Mar. 02-03 Local Time
18:00
00:00
06:00
50
20
5
20
0
12:00
Feb. 23-24 Local Time
0
12:00
0
Mar. 03-04 Local Time
12:00
18:00
00:00
06:00
0
12:00
Mar. 04-05 Local Time
40
250
30
60
250
250
35
100
Cl2 (pptv)
150
15
Height (m)
100
15
Cl2 (pptv)
150
20
50
200
20
200
40
150
30
100
Height (m)
25
200
25
Height (m)
Cl2 (pptv)
30
20
10
10
50
50
12:00
18:00
00:00
06:00
Mar. 05-06 Local Time
0
12:00
0
50
10
5
5
12:00
15:00
18:00
21:00
00:00
Mar. 06-07 Local Time
0
03:00
0
0
12:00 15:00 18:00 21:00 00:00 03:00 06:00 09:00
Mar. 10-11 Local Time
Figure S-6. A summary of Cl2 observations over 15 days during the NACHTT study. Vertical
Cl2 profiles versus time of day. Cl2 mixing ratios are shown as colored squares. Black areas
indicate no available measurements. Note the color scales vary between panels.
8
250
200
6
5
150
4
100
Height (m)
total NO-3 (ppbv)
7
3
2
50
1
0
21:00
00:00
03:00
06:00
Feb. 25-26, Local Time
Figure S-7. Vertical profiles versus time of day for total nitrate (aerosol NO3- + HNO3(g))
mixing ratios proximal to the plume 1 intercept. Mixing ratios are shown as colored squares.
Black areas indicate no available measurements.
8
250
200
6
5
150
4
100
3
2
Height (m)
total NO-3 (ppbv)
7
50
1
0
00:00
03:00
06:00
March 4-5, Local Time
Figure S-8. Vertical profiles versus time of day for total nitrate (aerosol NO3- + HNO3(g))
mixing ratios proximal to the plume 2 intercept. Mixing ratios are shown as colored squares.
Black areas indicate no available measurements.
CO (ppm)
RH (% )
2
380
400
60
70
80
90
-
ClNO
aerosol Cl x 20
Cl x 5
aerosol NO
N O
HNO
2
3
2
2
390
5
250
3
150
Height (m)
200
100
50
0
200
400
(pptv)
600
0
2
4
(ppbv)
6
0
10
20
NO , O3 (ppbv)
2
30
280
285
0
290
 (K)
Figure S-9. Observations taken during a vertical profile (04:24 – 04:33) prior to plume 1. ClNO2
(blue dashed line), Cl2 x 5 (green solid line), and N2O5 (red dotted line) mixing ratios. Aerosol
phase Cl- x 20 (pink solid line) NO3- (blue solid line), and gas phase HNO3 (grey dashed line).
CO2 (cyan solid line, top x-axis), NO2 (orange solid line, bottom x-axis), and O3 (black solid
line, bottom x-axis) mixing ratios. Relative humidity (RH (%), purple solid line) and potential
temperature (θ (K), olive solid line).
CO (ppm)
RH (% )
2
380
400
410
60
70
80
90
-
ClNO
aerosol Cl x 20
Cl x 5
aerosol NO
N O
HNO
2
3
2
2
390
5
250
3
150
Height (m)
200
100
50
0
500
(pptv)
1000
0
2
4
(ppbv)
6
0
10
20
NO , O3 (ppbv)
2
30
280
285
 (K)
290
0
Figure S-10. Observations taken during a vertical profile (04:55 – 05:03) subsequent to plume
1. ClNO2 (blue dashed line), Cl2 x 5 (green solid line), and N2O5 (red dotted line) mixing ratios.
Aerosol phase Cl- x 20 (pink solid line) NO3- (blue solid line), and gas phase HNO3 (grey dashed
line). CO2 (cyan solid line, top x-axis), NO2 (orange solid line, bottom x-axis), and O3 (black
solid line, bottom x-axis) mixing ratios. Relative humidity (RH (%), purple solid line) and
potential temperature (θ (K), olive solid line).
CO (ppm)
RH (% )
2
370
390
400
410
40
60
80
-
ClNO
aerosol Cl x 20
Cl x 5
aerosol NO
N O
HNO
2
3
2
2
380
5
250
3
150
Height (m)
200
100
50
0
500
1000
(pptv)
1500
0
5
(ppbv)
10
0
10
20
30
NO , O3 (ppbv)
2
40
50
282
284
286
288
0
 (K)
Figure S-11. Observations taken during a vertical profile (04:04 – 04:12) prior to plume 2.
ClNO2 (blue dashed line), Cl2 x 5 (green solid line), and N2O5 (red dotted line) mixing ratios.
Aerosol phase Cl- x 20 (pink solid line) NO3- (blue solid line), and gas phase HNO3 (grey dashed
line). CO2 (cyan solid line, top x-axis), NO2 (orange solid line, bottom x-axis), and O3 (black
solid line, bottom x-axis) mixing ratios. Relative humidity (RH (%), purple solid line) and
potential temperature (θ (K), olive solid line).
3
a)
b)
total NO (ppbv)
0
2
4
6
8
0.6
200
0.5
150
0.4
200
0.3
100
Height (m)
ɸ=0.24
2
ClNO (ppbv)
250
0.2
50
150
ɸ=0.57
Height (m)
0.1
0
2
3
4
5
6
7
8
3
total NO (ppbv)
c)
250
100
200
150
50
Height (m)
ɸ=0.55
100
50
0
0.2
0.4
0.6
ClNO (ppbv)
2
0
0
0.2
0.4

0.6
0.8
0
1
ClNO2
Figure S-12. Additional data taken from a vertical profile (04:24 – 04:33) prior to plume 1. a)
Vertical profile of ClNO2 mixing ratios and total nitrate mixing ratios. In estimating the given
ClNO2 yield for the plume, the dotted lines are used as background values to determine the inplume (shaded region) enhancements of ClNO2 and total nitrate. b) ClNO2 mixing ratios are
plotted versus total nitrate (HNO3(g) + aerosol phase NO3-) mixing ratios for the single transect.
Each point is colored by the height at which the measurement was taken. The slope of the solid
black lines, which are least squares linear fits to data in the plumes (data below 135 m are
omitted from the fit), together with Eq. 3 (main text) are used to estimate the in-plume ClNO2
yield shown next to the line. c) Height versus estimated ClNO2 yields obtained from aerosol
composition data and aerosol thermodynamic modeling. The stated yield represents the average
of the yields over the shaded region.
3
total NO (ppbv)
a)
0
2
4
6
b)
8
0.6
200
250
ɸ=0.16
200
0.3
100
Height (m)
150
0.4
2
ClNO (ppbv)
0.5
0.2
50
150
Height (m)
0.1
0
0
2
4
6
8
3
total NO (ppbv)
c)
250
100
ɸ=0.53
150
ɸ=0.63
50
Height (m)
200
100
50
0
0.2
0.4
ClNO (ppbv)
2
0
0.6
0
0.2
0.4

0.6
0.8
0
1
ClNO2
Figure S-13. Additional data taken from a vertical profile (04:55 – 05:03) subsequent to plume
1. a) Vertical profile of ClNO2 mixing ratios and total nitrate mixing ratios. In estimating the
given ClNO2 yield for the plume, the dotted lines are used as background values to determine the
in-plume (shaded region) enhancements of ClNO2 and total nitrate. b) ClNO2 mixing ratios are
plotted versus total nitrate (HNO3(g) + aerosol phase NO3-) mixing ratios for the single transect.
Each point is colored by the height at which the measurement was taken. The slope of the solid
black lines, which are least squares linear fits to data in the plumes (data below 100 m are
omitted from the fit), together with Eq. 3 (main text) are used to estimate the in-plume ClNO2
yield shown next to the line. c) Height versus estimated ClNO2 yields obtained from aerosol
composition data and aerosol thermodynamic modeling. The stated yield represents the average
of the yields over the shaded region.
0
2
4
b)
6
8
250
1
200
0.8
150
0.6
ɸ=0.70
2
ClNO (ppbv)
250
150
Height (m)
200
0.4
100
0.2
50
0
0
2
4
6
Height (m)
3
total NO (ppbv)
a)
8
3
total NO (ppbv)
c)
ɸ=0.86
250
100
150
50
ɸ=0.94
Height (m)
200
100
50
0
0.5
ClNO (ppbv)
2
1
0
0
0.2
0.4

0.6
0.8
0
1
ClNO2
Figure S-14. Additional data taken from a vertical profile (04:04 – 04:12) prior to plume 2. a)
Vertical profile of ClNO2 mixing ratios and total nitrate mixing ratios. In estimating the given
ClNO2 yield for the plume, the dotted lines are used as background values to determine the inplume (shaded region) enhancements of ClNO2 and total nitrate. b) ClNO2 mixing ratios are
plotted versus total nitrate (HNO3(g) + aerosol phase NO3-) mixing ratios for the single transect.
Each point is colored by the height at which the measurement was taken. The slope of the solid
black lines, which are least squares linear fits to data in the plumes (data below 90 m are omitted
from the fit), together with Eq. 3 (main text) are used to estimate the in-plume ClNO2 yield
shown next to the line. c) Height versus estimated ClNO2 yields obtained from aerosol
composition data and aerosol thermodynamic modeling. The stated yield represents the average
of the yields over the shaded region.
a)
-
Cl
NH
+
4
250
3
NO
Organics 200
24
150
Height (m)
SO
100
50
0
2
4
6
8
10
0
14
12
3
Aerosol Loading ( g/m )
b)
-
Cl
NH
+
4
250
3
NO
Organics 200
24
150
Height (m)
SO
100
50
0
2
4
6
8
10
12
3
14
16
0
18
Aerosol Loading ( g/m )
Figure S-15. AMS-measured particle composition loadings for a) plume 1 and b) plume 2.
Reaction
NO + O3 → NO2 + O2
NO2 + O3 → NO3 + O2
NO2 + NO3 + M → N2O5 + M
NO + NO3 → 2NO2
N2O5 → NO2 + NO3
NO3 → “products”
N2O5 + HCl → ϕClNO2 + (2 - ϕ)HNO3
ClNO2 + HCl → Cl2 + HONO
k (cm3 molec-1 s-1)
1.2e-14
1.5e-17
1.4e-12
2.8e-11
1.5e-3
5.0e-4
SA / [2e-3 + 4/(ωN2O5γN2O5)]
SA / [2e-3 + 4/(ωClNO2γClNO2)]
Table S-1. Reactions and rate constants used in the chemical box model. SA is the aerosol
surface area in a volume of air (cm2/cm3). ωN2O5 and ωClNO2 are the mean molecular speeds
(cm/s) of an N2O5 molecule and ClNO2 molecule, respectively. γN2O5 and γClNO2 are the
heterogeneous reaction probabilities of N2O5 and ClNO2, respectively.