Supplement of Atmos. Chem. Phys., 23, 9669–9683, 2023
https://doi.org/10.5194/acp-23-9669-2023-supplement
© Author(s) 2023. CC BY 4.0 License.
Supplement of
Direct observations of NO
x
emissions over the San Joaquin Valley using
airborne flux measurements during RECAP-CA 2021 field campaign
Qindan Zhu et al.
Correspondence to:
Qindan Zhu (qindan_zhu@berkeley.edu) and Ronald C. Cohen (rccohen@berkeley.edu)
The copyright of individual parts of the supplement might differ from the article licence.
(a)
(b)
Figure S1: RECAP flight patch over San Joaquin Valley (a) and Los Angeles (b), consisting
of 7 flights and 9 flights, respectively.
2
Figure S2: The distribution of relative difference between PBL height from HRRR and
interpolated PBL height from the measurements.
3
(a)
(b)
-0.5
0
0.5
1
1.5
2
Fluxes calc using variable lag time
(mg N/(m
2
hr))
-1
-0.5
0
0.5
1
1.5
2
Fluxes calc using constant lag time
(mg N/(m
2
hr))
Fit: 0.9853x + -0.011
R
2
= 0.9566
1:1
-1
-0.5
0
0.5
1
(Const. lag - Var. lag)/Var. lag
0
500
1000
1500
2000
2500
3000
Count
Figure S3: a) the comparison of calculated fluxes using various and constant lag time. b)
corresponds the relative difference of fluxes.
4
-2000
-1500
-1000
-500
0
500
1000
1500
2000
Lag shift (0.2s)
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Norm. Cross Variance
휃
푁푂
!
Figure S4: The normalized covariance peak for NO
x
and potential temperature (
θ
).
5
10
-3
10
-2
10
-1
10
0
10
1
Hz
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
f x CoS
<
푤
!
휃
!
>
<
푤
!
푁푂
"
!
>
Figure S5: Normalized co-spectra of NO
x
and heat flux. The black dashed represents the
Nyquist frequency for NO
x
flux.
6
0.0
0.2
0.4
0.6
0.8
1.0
1.2
NO
x
flux (mg N/(m
2
hr))
400
600
800
1000
1200
Altitude (m)
Figure S6: Vertical distribution of observed flux during racetrack, separated by the west
patch (red) and east patch (east). The dot represents the median flux and the shade refers
to the interquantile range.
7
Figure S7: The spatial distribution of observed flux at each segment during racetrack. The
black line contours the 90% of the footprint extent.
8
0
2
4
6
8
10
12
The 90% footprint extent along wind (km)
0
500
1000
1500
2000
2500
3000
3500
Count density
Figure S8: The count density distribution of 90% footprint extent.
9
Soil
Mixed
-0.05
0
0.05
0.1
Trimethylbenzene Flux (mg/(m
2
hr))
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Trimethylbenzene Flux over soil land type (mg/(m
2
hr))
0
100
200
300
400
500
600
700
800
900
Count
(a)
(b)
Figure S9: a) the comparison of trimethylbenzene fluxes with footprints exclusively covering
soil land cover type and those with footprints covering mixed land cover types. b) The
distribution of trimethylbenzene fluxes with footprints exclusively covering soil land cover
type. The dashed line denotes a trimethylbenzene flux of 0.02 mg m
−
2
h
−
1
.
10
(a)
(b)
(
c
)
(
d
)
(
e
)
(
f
)
Figure S10: The estimated gridded emission map for each flight, aligned in the order of flight
days.
©
OpenStreetMap contributors 2022. Distributed under the Open Data Commons
Open Database License (ODbL) v1.0.
11
(a)
(b)
(
c
)
Figure S11: a) The estimated anthropogenic NO
x
emission map at 4km during weekday. b)
and c) are EMFAC and FIVE anthropogenic emission inventories matched both in time and
space, respectively.
©
OpenStreetMap contributors 2022. Distributed under the Open Data
Commons Open Database License (ODbL) v1.0.
12