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Modifications and Field Testing of PSAP for Aerosol Light Absorption and Extinction Measurements

This document outlines the key modifications, calibrations, and field tests conducted on Photoacoustic Spectrometers (PSAP) for measuring aerosol light absorption and extinction. It covers optics and electronics modifications, including adjustments in wavelength settings and light sources. The goal is to characterize existing instruments, quantify measurement uncertainties, and derive methods for spectral aerosol absorption analysis based on multi-wavelength data. Collaboration among NOAA, DRI, UW, NASA, and other institutions was crucial for achieving these objectives during the June 2002 study.

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Modifications and Field Testing of PSAP for Aerosol Light Absorption and Extinction Measurements

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  1. PSAP modification, calibration and field test • PSAP modification: optics, program • OEC modification • Campaign at DRI • Field test during NEAQS

  2. PSAP modifications:Light sourceHoles Detectors

  3. Detector-weighted mean wavelengths: Blue: 471 nm, Green: 543 nm, Red: 659 nm

  4. Electronics modification

  5. Principle of the 3wl PSAP

  6. OEC L = 660 cm

  7. Effective length reduction by purge air

  8. OEC at DRI OEC at UW

  9. Reno Aerosol Optics StudyJune, 2002 John Ogren NOAA/CMDL

  10. Objectives • Characterize new and existing instruments for measuring aerosol light absorption and extinction • Quantify the uncertainty in the measurements of aerosol light absorption coefficient used by NOAA and ARM • Derive methods for determining spectral aerosol absorption from multi-wavelength measurements of absorption and (extinction - scattering)

  11. Participants • NOAA/CMDL (Ogren, Sheridan) • DRI (Arnott, Moosmüller, Varma) • U. Washington (Covert, Virkkula, Ahlquist) • NASA/Ames (Strawa, Schmid) and Picarro Networks, Inc. (Owano, Provencal) • Thermo Andersen/DLR (Schloesser, Petzold) • Portland State U. (Atkinson)

  12. Absorption Coefficient Measurements • Photoacoustic • #1 532 nm • #2 1047 nm • Filter-based • Particle/soot absorption photometer (PSAP) • #1: 565 nm • #2 460, 540, 660 nm • Aethalometer • #1 370, 470, 521, 590, 660, 880, 950 nm • #2 370, 430, 470, 521, 565, 700, 950 nm • Carusso (multi-angle) • #1: 670 nm

  13. Extinction Coefficient Measurements • Folded path extinction cell (6.6 m path) • #1 460, 540, 660 nm • Cavity-ring down (CRD) • #1: 532 nm • #2: 690, 1550 nm • #3: 532, 1064 nm

  14. Scattering Coefficient Measurements • TSI 3563 integrating nephelometer • #1 450, 550, 700 nm • Radiance M903 integrating nephelometer • #1: 530 nm • DRI integrating sphere nephelometer • #1: 532 nm • NASA/Ames CRD nephelometer • #1: 690 nm

  15. Typical scattering and extinction data

  16. EC & SC calculations 1) STP 2) Drift correction for EC 3) SC truncation correction, J.O. 4) SC interpolation to EC wavelengths: 5) Time shifts to match EC & SC data

  17. Extinction by White Aerosols (532nm)

  18. Extinction by Gray Aerosols (532nm) Notes: Data points represent kerosene soot runs with varying amounts of ammonium sulfate. Scattering measured with TSI nephelometer, absorption with DRI photoacoustic instrument.

  19. Ammonium sulfate experiments, 1-min data, nominal wls

  20. Latex experiments, 1 min data

  21. AS, varying wavelengths

  22. OEC vs Neph in white experiments

  23. EC-SC vs PSAP, 1-min data, all experimentsPSAP data corrected according to Bond et al. (1999).

  24. EC-SC vs PSAP, 1-min data, good experimentsPSAP data corrected according to Bond et al. (1999).

  25. Looking for theloading correction function f(Tr), 1 When looking for f(Tr), use

  26. Looking for theloading correction function f(Tr), 2

  27. Looking for theloading correction function f(Tr), 3

  28. Looking for theloading correction function f(Tr), 4

  29. Looking for theloading correction function f(Tr), 5 Vary interpolation wavelengths => minimizing yields different values for k0, k1 & g

  30. Using f(Tr) = k0 + k1ln(Tr) - g ssp

  31. PSAP response to white aerosol, 1

  32. PSAP response to white aerosol, 2

  33. PSAP response to white aerosol, 3

  34. PSAP response to white aerosol, 4

  35. PSAP response to white aerosol, 5 Is fit 3 worth the extra work?

  36. Field test during NEAQS, 1

  37. Field test during NEAQS, 2

  38. Field test during NEAQS, 3 Noise

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