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Royal Meteorological Institute of Belgium

Validation of the method to retrieve the Aerosol Optical Depth from the Brewer Ozone measurements First preliminary results of the aerosol campaign at Uccle. Royal Meteorological Institute of Belgium.

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Royal Meteorological Institute of Belgium

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  1. Validation of the method to retrieve the Aerosol Optical Depth from the Brewer Ozone measurements • First preliminary results of the aerosol campaign at Uccle Royal Meteorological Institute of Belgium Validation of the method to retrieve the AOD and first preliminary results of the aerosol campaign. RMI December 6th 2006.

  2. Validation of the method to retrieve the Aerosol Optical Depth from the Brewer Ozone measurements Anne Cheymol, Hugo De Backer, Weine Josefsson and René Stübi anne.cheymol@oma.be Cheymol et al., jgr, 2006 Royal Meteorological Institute of Belgium Validation of the method to retrieve the AOD. RMI December 6th 2006.

  3. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Results • Measurements sites • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  4. Royal Meteorological Institute of Belgium Role of aerosol particles • Most aerosol particles’s knowledge is in VIS and IR and not in UV • Important role in climate forcing • UV-B irradiance reduction by about 5-35% • Impact on Human health Validation of the method to retrieve the AOD. RMI December 6th 2006. 3

  5. smoke Clear day on November 9th 2006 Royal Meteorological Institute of Belgium Anthropogenic origin Polluted day on January 28th 2006 Photo by A. Delcloo and A. Mangold Validation of the method to retrieve the AOD. RMI December 6th 2006. 3

  6. Royal Meteorological Institute of Belgium Natural origin of aerosol Sea salt ejected from the sea in the air Photo by Plisson Validation of the method to retrieve the AOD. RMI December 6th 2006. 3

  7. Royal Meteorological Institute of Belgium Natural origin of aerosol Pollen Clean roof Photo from the web Validation of the method to retrieve the AOD. RMI December 6th 2006. 3

  8. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Results • Measurements sites • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  9. 280-363 nm 306-320 nm Royal Meteorological Institute of Belgium 11 Validation of the method to retrieve the AOD. RMI December 6th 2006

  10. Royal Meteorological Institute of Belgium Morning Afternoon 12H Zenith angle = za sunset Rotation of the instrument during the day Validation of the method to retrieve the AOD. RMI December 6th 2006 9

  11. Royal Meteorological Institute of Belgium Summary of the Brewer measurements • 5 measurements/4mns every 30mns • Automatic rotation during the day to follow the sun • No cloud  direct sun measurement • 25° za 70 ° for one day at Uccle 10 Validation of the method to retrieve the AOD. RMI December 6th 2006

  12. Royal Meteorological Institute of Belgium Direct Sun radiation at 306, 310, 313, 316 and 320 nm Aerosol Optical Depth = attenuation of solar radiation by aerosol particles Validation of the method to retrieve the AOD. RMI December 6th 2006.

  13. Royal Meteorological Institute of Belgium Over 100 Brewer stations Validation of the method to retrieve the AOD. RMI December 6th 2006 8

  14. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Results • Measurements sites • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  15. Ozone Molecule Aerosol particles Royal Meteorological Institute of Belgium Signal received by the Brewer S() = K() Io() exp[ Do3 () + Dray () + Daer (, sec(za))] 13 Validation of the method to retrieve the AOD. RMI December 6th 2006

  16. ln[ S() ]-Do3- Dray - () sec(za) ln[ K() Io () ] Royal Meteorological Institute of Belgium Langley plot method = * + Y = A * X + B 14 Validation of the method to retrieve the AOD. RMI December 6th 2006

  17. Royal Meteorological Institute of Belgium 5 DS scans/4mn Y = ln[S()] - Do3 - Dray A = -() *X = sec(za) +B = ln[K()Io ()] Langley plot method 18/06/00 for 306.3 nm 17 Validation of the method to retrieve the AOD. RMI December 6th 2006

  18. Royal Meteorological Institute of Belgium Selection of clear days for the Langley Plot Method • ozone stdev for individual DS measurements < 2.5 DU • za per day  20° • number of good data per day  50 • Distance between each point and the regression line < 4 (Y unit) • Daily mean absolute deviation from the LP regression line < 0.055 (Y units) 16 Validation of the method to retrieve the AOD. RMI December 6th 2006

  19. Royal Meteorological Institute of Belgium Calibration factor • Calibration factor = intersect of the fitting line  B in the equation Y=AX+B • Based on the 59 best fit of the solar irradiance intensity • Average of the 59 calibration factors • error of about 0.2% • constant during the whole period at Uccle, can change in function of Brewer Validation of the method to retrieve the AOD. RMI December 6th 2006. 4

  20. Royal Meteorological Institute of Belgium Summary of the method Validation of the method to retrieve the AOD. RMI December 6th 2006. 5

  21. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Results • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  22. Royal Meteorological Institute of Belgium Where? Validation of the method to retrieve the AOD. RMI December 6th 2006.

  23. Royal Meteorological Institute of Belgium 320 nm Time difference max = 3 min sunphotometer 368 nm Validation of the method to retrieve the AOD. RMI December 6th 2006.

  24. N = 1718 Standard filters N = 1934 Real filters Errors Royal Meteorological Institute of Belgium Filters impact on AOD c = 0.87 b = 0.80 ± 0.011 a = -0.08 ± 0.004 c = 0.98 b= 0.85 ± 0.004 a= 0.02 ± 0.0014 Validation of the method to retrieve the AOD. RMI December 6th 2006.

  25. Royal Meteorological Institute of Belgium Where? Validation of the method to retrieve the AOD. RMI December 6th 2006.

  26. Royal Meteorological Institute of Belgium 320 nm Hourly mean AOD compared for 2002 sunphotometer 368 nm Validation of the method to retrieve the AOD. RMI December 6th 2006.

  27. Royal Meteorological Institute of Belgium Comparison Arosa/Davos N = 335 c = 0.62 b = 0.56 ± 0.04 a = 0.02 ± 0.0006 Validation of the method to retrieve the AOD. RMI December 6th 2006.

  28. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Physical equation • Langley plot method • Results • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  29. Royal Meteorological Institute of Belgium Where? Validation of the method to retrieve the AOD. RMI December 6th 2006.

  30. Royal Meteorological Institute of Belgium Uccle 2002-2005 N = 5781 c = 0.98 b= 1.02 ± 0.003 a= 0.06 ± 0.001 Validation of the method to retrieve the AOD. RMI December 6th 2006.

  31. N = 3169 Royal Meteorological Institute of Belgium Arosa 2004 N = 2771 c = 0.94 b= 0.98 ± 0.006 a= 0.03 ± 0.002 c = 0.98 b= 0.98 ± 0.003 a= -0.04 ± 0.001 Validation of the method to retrieve the AOD. RMI December 6th 2006.

  32. Royal Meteorological Institute of Belgium Arosa 2004 N = 5290 c = 0.99 b= 0.98 ± 0.002 a= -0.02 ± 0.0005 Validation of the method to retrieve the AOD. RMI December 6th 2006.

  33. Royal Meteorological Institute of Belgium Summary of the comparisons Validation of the method to retrieve the AOD. RMI December 6th 2006.

  34. Royal Meteorological Institute of Belgium Overview • Introduction • The Brewer instrument • Description of the method • Physical equation • Langley plot method • Results • Impact of the neutral density filter on AOD • Validation of the AOD between a Brewer and a sunphotometer • Comparisons between Brewer at the same place • Conclusions and perspectives Validation of the method to retrieve the AOD. RMI December 6th 2006.

  35. Royal Meteorological Institute of Belgium Conclusions Important role of the filter of the Brewer spectrophotometer on the accuracy of AOD High level of confidence of the method used to retrieve the AOD: correlation coefficient > 0.94 slope ~ 1 Intercept max = 0.06 Validation of the Langley plot method with a comparison between Brewer spectrophotometer and a sunphotometer Validation of the method to retrieve the AOD. RMI December 6th 2006.

  36. Royal Meteorological Institute of Belgium Perspectives Application of the method at different Brewer stations Determination of relation between different aerosol parameters: AOD, ssa, type, size and backtrajectories analysis Validation of the method to retrieve the AOD. RMI December 6th 2006.

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