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1) Satellite group, Max Planck institute for Chemistry, Mainz, Germany

This study compares the SCDs and profiles of nitrous acid (HONO) obtained from MAX-DOAS observations during the MAD-CAT campaign with outputs from a chemical model simulation. The motivation lies in understanding the gas-phase distribution of NO2, high daytime HONO concentrations, heterogeneous reactions, and soil emissions. Challenges of MAX-DOAS HONO observation include low concentrations and uncertainties due to interferences. The workshop conducted sensitivity studies, intercomparisons of HONO SCDs, and presented preliminary profiles along with model comparisons.

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1) Satellite group, Max Planck institute for Chemistry, Mainz, Germany

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  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 07.07.15 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: 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 0.003. • The dominate interferences and systematical uncertainties are still unclear. 07.07.2015 - 7th 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 07.07.2015 - 7th 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 2013. 16 MAX-DOAS instruments and some assistant independent techniques from 11 DOAS groups participated in it. Seven MAX-DOAS instruments join in HONO intercomparison: Same elevation angles: 1, 2, 3, 4, 5, 6, 8, 10, 15, 30, 90 Same azimuth angles: North east, 51° 07.07.2015 - 7th 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. 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  6. Possible H2O absorption around 364 nm Calibration problem in UV found recently, publish soon 07.07.2015 - 7th 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,. 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  8. Polynomial correction measurements: Synthetic spectra • The dependence of HONO SCD on polynomial correction is much stronger in 335-361 wavelength range. • 335-373 range is most stable wavelength range 07.07.2015 - 7th 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. Synthetic spectra No noise measurements 07.07.2015 - 7th 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, 335-373 has the smallest systematic uncertainty, +-15×10^14 (typical 75%). 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  11. Baseline DOAS fitting parameters for intercomparison 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  12. Intercomparisons of HONO dSCD- 18 June sample EA=1 EA=2 EA=3 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. 07.07.2015 - 7th 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 EA=1 EA=2 EA=15 EA=30 Seq. ref: 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. 07.07.2015 - 7th 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 07.07.2015 - 7th 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. 07.07.2015 - 7th 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, O4cross sections and possible H2O absorption around 364 nm (except 335-361 nm) are the dominate systematic uncertainty sources. • 335-373 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 × 1014molecs/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. 30.04.2014 - EGU General Assembly 2014, Yang Wang

  18. Great thanks for your attention! - 18 - 30.04.2014 - EGU General Assembly 2014, Yang Wang

  19. Conclusion: Systematic uncertainties: 1) Polynomial correction (except 335-373 nm), offset correction, Ring spectrum, fitting wavelength range, O4cross sections and possible H2O absorption around 364 nm (except 335-361 nm) are the dominate systematic uncertainty source. 2) In 335-373 ~ +-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 × 1014molecs/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. 30.04.2014 - EGU General Assembly 2014, Yang Wang

  20. Model & Measurement: Model 2013.06.14-2013.06.20 • 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 07.07.2015 - 7th 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. 07.07.2015 - 7th 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: 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  25. Fitting wavelength range 335-361, 335-373 and 335-390 nm: measurements: Fitting error: • systematic difference (-5 to 20 ×10^14), much larger fitting error in 335-361 (by 50%) • Measurements different from synthetic spectra Synthetic spectra: 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  26. Dominate interferences • NO2, O4 and Ring are the important interferences. • 335-361: NO2>O4>Ring • 335-373: NO2>O4>Ring • 335-390: 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. 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

  27. Effect of nonlinear correction of offset and stray light Measurements on 16, 18 June: Stray light effect, suggest first order offset correction to avoid the effect of stray light Synthetic spectra (no offset current): Effect of nonlinear offset correction, -10 to 5 ×10^14 molecs/cm^2 07.07.2015 - 7th 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. 335-361 without the possible H2O absorption, 335-390 including one more HONO peak, the possible H2O interference could be weaker. 07.07.2015 - 7th 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, 335-373nm is good for the baseline DOAS fit settings of the intercomparison. 07.07.2015 - 7th 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=1 EA=2 EA=3 EA=10 EA=15 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 07.07.2015 - 7th DOAS Workshop 2015, Yang Wang

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