1. Intercomparison of HONO SCDs and profiles from MAX-DOAS observations during the MAD-CAT campaign and comparison to chemical model simulations
Yang Wang, Thomas Wagner, Pinhua Xie, Julia Remmers, Ang Li, Johannes Lampel, Udo Friess, Enno.Peters, Folkard Wittrock, Andreas Richter, Andreas Hilboll, Rainer Volkamer, Ivan.Ortega, Francois Hendrick, Michel Van Roozendael, Jin Junli, Jianzhong Ma, Olga Puentedura, Junli Jin, Hang Su, Yafang Cheng, MAD-CAT Team
1) Satellite group, Max Planck institute for Chemistry, Mainz, Germany
2) Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China
3) Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
4) Institute of Environmental Physics, University of Bremen, Bremen, Germany
5) Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
6) BIRA-IASB – Belgian Institute for Space Aeronomy, Brussels, Belgium
7) Chinese Academy of Meteorological Sciences, Beijing, China
8) Multiphase Chemistry, Max Planck institute for Chemistry, Mainz, Germany

2. Motivation: MAX-DOAS Gas-phase of NO2 Vertical distribution
Daytime high HONO cons
Heterogeneous reaction
Soil emission
MAX-DOAS
Challenges of MAX-DOAS HONO observation:
Low concentration (5 ppt to 500 ppt) => the optical depth below
The dominate interferences and systematical uncertainties are still unclear.
th DOAS Workshop 2015, Yang Wang

3. Overview: Motivation Sensitivity studies for the baseline fit settings
Intercomparisons of HONO SCD
Preliminary results of HONO profiles and compared with Chemical model
Conclusion
th DOAS Workshop 2015, Yang Wang

4. MAD-CAT campaign and HONO intercomparison
MAD-CAT: Multi Axis DOAS – Comparison Campaign for Aerosols and Trace Gases at the Max Planck Institute for Chemistry in Mainz from June to October MAX-DOAS instruments and some assistant independent techniques from 11 DOAS groups participated in it.
Seven MAX-DOAS instruments join in HONO intercomparison:
Instrument
Group
Type of Spectrometer / Camera
Types of instrument
Envimes MAX-DOAS
IUP, Heidelberg
Avantes ULS
Scientific grade
MAXDOAS
BIRA-IASB
Oriel MS260i / Roper 1340x400
BreDOM MAX-DOAS
IUP, Bremen
Shamrock 303I/Roper 1300x400
2D-MAX-DOAS
Hefei, CAS
Action SP2500i
CU-Boulder
Acton SP2150/PIXIS 400
4azimuth-MAX-DOAS
MPIC
Andor
mini-MAX-DOAS
Beijing, CMA
ocean optics usb 2000
Mini DOAS
Same elevation angles:
1, 2, 3, 4, 5, 6, 8, 10, 15, 30, 90
Same azimuth angles:
North east, 51°
th DOAS Workshop 2015, Yang Wang

5. Sensitivity studies for the baseline HONO fit settings
Interferences of HONO SCD in 3 wavelength ranges :
NO2 (AMF wavelength dependence), Ring
(temperature, up to 30%), O4 cross sections
2) Possible H2O absorption around 364 nm
3) Polynomial correction
4) Nonlinear offset correction of fitting (up to 50%)
5) Fraunhofer reference spectrum, dailynoon and sequential, considering ozone interference (typical 0.5%) and instrument property variations (slit function and stray light?)
Two procedures to characterize the dependences of HONO on the up items:
Measurements from Chinese Hefei MAX-DOAS instrument, two clear days with low and high HONO concentration
Synthetic spectra from Bremen using SCIATRAN
Synthetic spectra: Same 11 EAs with measurements, 18 combination of SZA and SAA according to measurement location and time period, one assumed HONO profile, with and without random noise.
th DOAS Workshop 2015, Yang Wang

6. Possible H2O absorption around 364 nm
Calibration problem in UV found recently, publish soon
th DOAS Workshop 2015, Yang Wang

7. Possible H2O absorption around 364 nm
HONO dSCD
On 18 June
Changes of HONO SCD including H2O have good linear correlation with H2O SCD.
Not including H2O, underestimation is up to 10×10^14 (mean SCD ~ 20 ×10^14), 50%
In the next months, a new H2O can be acquired,.
th DOAS Workshop 2015, Yang Wang

8. Polynomial correction
measurements:
Synthetic spectra
The dependence of HONO SCD on polynomial correction is much stronger in wavelength range.
range is most stable wavelength range
th DOAS Workshop 2015, Yang Wang

9. Dependence on O4 cross section
Thalman, Hermans and Greenblatt (calibration problem) O4 cross sections
Large difference between two O4 cross sections
HONO SCD changes between using different O4 cross sections are up to 4*10^14, (20%)
Similar HONO SCD difference for measurements with synthetic spectra indicate Thalman cross section could be close to true O4 absorption structure.
measurements
Synthetic spectra
No noise
th DOAS Workshop 2015, Yang Wang

10. Total systematic uncertainties
Syst. Unc.
polynomial
Random. Unc
Scientific MAX-DOAS
offset correction> ring > O4
H2O
For scientific MAX-DOAS, systematic uncertainties are much larger than random uncertainties
Including new H2O cross section, has the smallest systematic uncertainty, +-15×10^14 (typical 75%).
th DOAS Workshop 2015, Yang Wang

11. Baseline DOAS fitting parameters for intercomparison
Specification
Fitting interval
Wavelength calibration
Calibration based on reference solar NDSC (air)
HONO
Stutz et al. (2000), 296 K
NO2
Vandaele et al. (1998), 220 K and 298 K convolved with I0 correction (1*10^17 molecules/cm2)
Taylor series approach: correct the wavelength dependence of NO2 AMF O3
Bogumil et al., (2003), 223 K and 243 K convolved with I0 correction (1*10^20 molecules/cm2)
BrO
Fleischmann et al. (2004), 223 K O4
Thalman_volkamer, 293k
HCHO
Meller and Moortgat (1992), 297 K
Ring effect
Ring from NDSC and additional multi scattering compensation
Intensity offset
first order offset (two terms)
Polynomial term
Polynomial of order 5
Wavelength adjustment
All spectra shifted and stretched against reference spectrum
Reference spectrum
daily reference at 11:30
The mean spectrum in zenith view before and after the off-axis spectrum
th DOAS Workshop 2015, Yang Wang

12. Intercomparisons of HONO dSCD - 18 June sample
EA= EA= EA= EA=4
10^15
Molecs/cm^2
Seq. ref:
HONO dSCD
Daily ref:
UTC time (local time -1 hour)
In general the results from fits with seq. ref. agree well, comparably the difference between the results from fits with daily ref. is larger in the afternoon.
th DOAS Workshop 2015, Yang Wang

13. Intercomparisons of HONO SCD - Statistic histograms of the absolute HONO dSCD deviations from the reference (Heidelberg, BIRA and Hefei) in the whole comparison period
Seq. ref:
EA= EA= EA= EA=30
Number of observations
HONO dSCD deviation/ 10^15 molecs/cm^2
all the instruments have a symmetric and quasi-Gaussian shape statistic histogram. SDs and mean deviation mostly less than ± 0.4 × 1015 molecs/cm2 close to the DOAS fitting error.
th DOAS Workshop 2015, Yang Wang

14. Intercomparisons of HONO SCD - mean deviation and standard deviation of the HONO dSCDs from the reference for the fits with seq. and noon Ref
10^15 molecs/cm^2
for sequential Ref, Mean and SD for all EAs are quite similar and close to zero.
In general the mean and SD for daily noon Ref are larger than those for sequential Ref.
For daily noon Ref, Mean and SD for low EA are smaller than those for high EA
th DOAS Workshop 2015, Yang Wang

15. Intercomparisons of HONO SCD - linear regressions of the HONO dSCD against the reference to show the consistency of diurnal variation
for eight days with high HONO dSCD
R and slope are much better for low EA than high EA because of low SCD for high EA.
for daily noon Ref, for some instruments, the offset is much larger than that for sequential Ref.
th DOAS Workshop 2015, Yang Wang

16. Preliminary results of HONO profiles from Hefei and BIRA and compared with Chemical model
VMR / ppt:
BIRA:
1.0
0.5
0.0
Hefei:
1.0
0.5
0.0
noon
noon
BIRA<=> Hefei HONO profiles
Shape is similar, but Hefei value > BIRA
AK =>profile inversion sensitive to layer below 1km
WRFCHEM model (including heterogeneous reaction of NO2 on aerosol, 6*6km) shows similar profile shape with MAX-DOAS but much higher value.
WRFCHEM :
UTC time

17. Conclusion: Systematic uncertainties:
Polynomial correction , offset correction, Ring spectrum, O4 cross sections and possible H2O absorption around 364 nm (except nm) are the dominate systematic uncertainty sources.
has the smallest uncertainty.
Intercomparion:
For the fits with sequential Ref, the consistencies between the instruments are quite well for all EAs. Their deviations are less than ± 4 × 1014 molecs/cm2 close to the random uncertainty.
For the fits with daily noon Ref, the consistencies are worse for some instruments especially for high EA, due to the variation of instrument properties (e.t. stray light and slit function)
Future:
Compare HONO profiles from different groups and try to understand the dominate HONO daytime source by the combination of model and lab measurements.
EGU General Assembly 2014, Yang Wang

18. Great thanks for your attention!
- 18 -
EGU General Assembly 2014, Yang Wang

19. Conclusion: Systematic uncertainties:
1) Polynomial correction (except nm), offset correction, Ring spectrum, fitting wavelength range, O4 cross sections and possible H2O absorption around 364 nm (except nm) are the dominate systematic uncertainty source.
2) In ~ +-15 ×10^14 molecs/cm^2, much larger than random uncertainty of scientific grade MAX-DOAS
Intercomparion:
For the fits with sequential Ref, the consistencies between the instruments are quite well for all EAs. Their deviations are less than ± 4 × 1014 molecs/cm2 close to the random uncertainty.
For the fits with daily noon Ref, the consistencies are worse for some instruments especially for high EA, due to the variation of instrument properties (e.t. stray light and slit function) and stronger interferences (Ring, O4, H2O and ozone)
Future:
HONO profile inversion to understand the dominate HONO daytime source by the combination research with model and lab measurements of soil emission flux.
EGU General Assembly 2014, Yang Wang

20. Model & Measurement: Model
2 domains
d01 18*18km
d02 6*6km
49 layers from ground to 50 hPa
12 layers --- below 2000m
CBMZ (Zaveri 1999)
with HONO hetero. Reaction:
NO2  HONO + HNO3
Aerosol uptake coefficient:
(Jacob, 2000)
MOSAIC 8-bins (Zaveri 2008)
Aerosol: 40-10,000 nm
TNO emission inventory (7km)
NOx, NH3, CO, PM, NMVOC,
EC, and OC

21. NO2 AMF wavelength dependence:
NO2 fitting
HONO is retrieved in a large wavelength interval. AMF is smaller at low wavelength than at high wavelength. However the AMF is assumed as independent values on wavelength by the classic DOAS algorithm. So the difference between measured and fitted OD induce a systematical structure
th DOAS Workshop 2015, Yang Wang

22. NO2 AMF wavelength dependence:
Pukite, Janis, Atmos. Meas. Tech., 3, 2010
Taylor approach:
Taylor approach can well correct the wavelength dependence of NO2 AMF and improve the fitting. Although this phenomenon only influence the HONO SCD by -2 to 2 ×10^13 molecs/cm^2, we still prefer to include the Taylor items into the fitting because its effect is already clearly known.
th DOAS Workshop 2015, Yang Wang

23. 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

24. MAD-CAT campaign and HONO intercomparison
Comparison time period from 12 June to 5 July, 2013:
th DOAS Workshop 2015, Yang Wang

25. Fitting wavelength range
, and nm:
measurements:
Fitting error:
systematic difference (-5 to 20 ×10^14), much larger fitting error in (by 50%)
Measurements different from synthetic spectra
Synthetic spectra:
th DOAS Workshop 2015, Yang Wang

26. Dominate interferences
NO2, O4 and Ring are the important interferences.
: NO2>O4>Ring
: NO2>O4>Ring
: O4>Ring>NO2
NO2 AMF wavelength dependence induces some residual structure, we suggest use Taylor approach to compensate this effect. But it change HONO dSCD only up to 2 ×10^13 molecs/cm^2.
th DOAS Workshop 2015, Yang Wang

27. Effect of nonlinear correction of offset and stray light
Synthetic spectra (no offset current):
Effect of nonlinear offset correction,
-10 to 5 ×10^14 molecs/cm^2
Measurements on 16, 18 June:
Stray light effect, suggest first order offset correction to avoid the effect of stray light
th DOAS Workshop 2015, Yang Wang

28. Possible H2O absorption around 364 nm
June 18, 2013
1) Changes of HONO SCD including assumed H2O have good linear correlation with H2O SCD.
2) The time series of HONO SCD changes are similar with those in different wavelength ranges.
without the possible H2O absorption,
including one more HONO peak, the possible H2O interference could be weaker.
th DOAS Workshop 2015, Yang Wang

29. Systematic uncertainties from DOAS fit and instrument
Same estimation in three wavelength ranges:
Daily noon FRS
Total sys. unc.
H2O
polynomial
Considering the systematic uncertainties, fitting errors and wavelength coverage of the spectrometers, nm is good for the baseline DOAS fit settings of the intercomparison.
th DOAS Workshop 2015, Yang Wang

30. Intercomparisons of HONO SCD - comparison of the HONO delta dSCDs from the fits with daily noon FRS and those with sequential FRS for each intruments
For daily noon FRS: Delta dSCD = dSCDoffzenith-dSCDzenith in same sequence
For sequential FRS: Delta dSCD = dSCD
EA= EA= EA= EA= EA= EA=30
Number of observations
The mean deviation indicates the monodirectional systematic bias probably caused by the symmetrical variation of the instrument properties and some stronger interferences of the DOAS fit in the morning and afternoon.
The SD of their difference indicate the random noise and bidirectional systematic bias
th DOAS Workshop 2015, Yang Wang