1 / 33

Ground-based measurements of tropospheric NO 2

Ground-based measurements of tropospheric NO 2 - Comparison of MAX-DOAS results to other instruments for DANDELIONS-. Folkard Wittrock, Hilke Oetjen, Anja Schönhardt, Andreas Richter, John P. Burrows - IUP Bremen Hester Volten, Daan Swart - RIVM Ellen Brinksma - KNMI. Outline.

fala
Download Presentation

Ground-based measurements of tropospheric NO 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ground-based measurements of tropospheric NO2 - Comparison of MAX-DOAS results to other instruments for DANDELIONS- Folkard Wittrock, Hilke Oetjen, Anja Schönhardt, Andreas Richter, John P. Burrows - IUP Bremen Hester Volten, Daan Swart - RIVM Ellen Brinksma - KNMI

  2. Outline • DANDELIONS campaign • MAX-DOAS • Profile Retrieval Algorithm „BREAM“ • Results – focusing on 2nd campaign in 2006 • BREAM / geometric approach • BREAM / in situ • BREAM / LIDAR • BREAM / satellite • Conclusions and Outlook

  3. DANDELIONS “Dutch Aerosol and Nitrogen Dioxide Experiments for vaLIdation of OMI and SCIAMACHY“ CESAR site (Cabauw) located at 51.971°N, 4.927°E 0.70 m below ASL Dandelions Objectives: Validation of satellite measurements Intercomparison of instruments (NO2, O3, aerosols) NO2: ground in situ, lower tropospheric profile (lidar), total columns MAX-DOAS intercomparison -> ideal for evaluation of MAX-DOAScapabilities for profile retrieval

  4. MAX-DOAS Detection: • UV/vis measurement of scattered sunlight measured for different lines of sight • Method: Differential Optical Absorption Spectroscopy - DOAS • Result: averaged absorption along all contributing light paths -> Slant Column Retrieval: • Correction for vertical sensitivity (airmass factors) depending on several meteorological parameters (e.g. albedo, aerosol) • Optimal Estimation for profile retrieval from ground (BREAM) Results: • VC and profile information for the lower troposphere

  5. Multi Axis (MAX)-DOAS Zenith: Stratosphere O3 NO2 BrO IO OClO IO NO2 H2O BrO HCHO O3 CHOCHO Horizon: Troposphere

  6. MAX-DOAS during Dandelions 2006 – Some Technical Details • The Bremen DOAS instruments: • Spectrometer (f=275mm) for visible Wavelength range: 399.5 – 715.0 nm • Spectrometer (f=500mm) for UV Wavelength range: 324.0 – 409.0 nm • One fixed azimuthal viewing direction: N The telescope on the roof of the portocabin E W • 11 Lines of sight: • Zenith • Scan from 0° to 16° in 2° steps • 30° elevation • Integration time: 1 min • Full scan duration: 12 min or5 scans per hour 54° S

  7. MAX-DOAS during Dandelions 2006

  8. MAX-DOAS during Dandelions 2006

  9. - problems with instruments Dandelions 2006 – NO2 sequence Sat Sun

  10. Dandelions 2006 – NO2 sequence Sat Sun

  11. Bremian Advanced MAX-DOAS Retrieval Algorithm - BREAM Flowchart for BREAM

  12. Bremian Advanced MAX-DOAS Retrieval Algorithm - BREAM • Example of input data and results for BREAM • usually 1 hour temporal steps comprising 3 to 5 scans • retrieval grid 50 m • for NO2 two wavelength regions are used to benefit from different effective light paths

  13. Dandelions 2006 – NO2 in the UV and vis Zenith • Scans show smaller NO2 values for the UV • due to different air mass factors (effective light paths) -> valuable information for profile retrieval scans Wavelength ranges: Vis: 450-497 nm UV: 345-365 nm

  14. Bremian Advanced MAX-DOAS Retrieval Algorithm - BREAM • Averaging Kernel Matrix: • Only one scan • for SZA about 35° • trace of A (number of pieces of independent information): 2.8 • illustrates the high sensitivity to the lowermost layers while for altitudes more than one kilometre there is only very little height information

  15. Bremian Advanced MAX-DOAS Retrieval Algorithm - BREAM Influence of some important input parameters on the retrieved profile (sensitivity study for one day) <-> small effect on derived tropospheric column, reflecting the fact that some parameter errors have different effects at different altitudes (e.g. aerosol)

  16. Bremian Advanced MAX-DOAS Retrieval Algorithm - BREAM

  17. Results

  18. Results

  19. Results

  20. Results

  21. Results

  22. Results

  23. Results

  24. Results

  25. Results

  26. Results

  27. Results

  28. Results

  29. Results

  30. Results

  31. Results

  32. Conclusions and Outlook • MAX-DOAS NO2 profile and tropospheric column data for almost all golden days • Tropospheric vertical column agrees well with pure geometric approach <-> in agreement with previous studies:VC is not very sensitive to retrieval parameters • Comparison to in situ measurements contradictory: general variation captured well, in particular for polluted days in situ much higher <-> interference problem?? • Comparison with NO2-LIDAR much better in terms of absolute values, but profile shape of the LIDAR is different • All in all not very surprising: NO2 is very variable in time, in space (and in experiment) <-> in particular more profile measurements needed

  33. Results

More Related