1. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 1 How can satellites help define the history of carbonaceous aerosols in the industrial era. Acknowledgements: –Paris Workshop - September 2003 organized by Didier Tanré and Yoram Kaufman: Slides abstracted from the talks of M. Herman (POLDER), G. De Leeuw (ATSR), O. Torres (TOMS), C. Hsu (SeaWiFs), L. Remer (MODIS) and D. Diner (MISR), G. Myhre (comparison).

2. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 2 How can satellites help define the history of carbonaceous aerosols in the industrial era –Satellites do not measure optical depth (except for solar occultation for stratospheric aerosols) they measure reflectance –Assumptions are required about size, shape and refractive index in retrievals –More measurements reduces the number of assumptions –More measurements are: More wavelengths More angles More elements in the Stokes vector (polarization) All of the above

3. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 3 –VIS/NIR/SWIR single view measurements AVHRR on POESS, MODIS on Terra and Aqua, GLI and OCTS on ADEOS, SeaWiFS, CZCS. Magnitude and spectral variation of radiances used to estimate size and optical depth of aerosols. Easier over ocean where the surface has a fairly well defined contribution How can satellites help define the history of carbonaceous aerosols in the industrial era

4. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 4 –VIS/NIR/SWIR single view measurements Can estimate aerosol load over land Land surface variability is a problem particularly for bright surfaces since land is generally brighter than the atmosphere but can be solved to some extent How can satellites help define the history of carbonaceous aerosols in the industrial era

5. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 5 –VIS/NIR/SWIR single view measurements How can satellites help define the history of carbonaceous aerosols in the industrial era MODIS burn scar Aug 23, 2000 MODIS AOT Aug 23, 2000 MODIS fire/smoke Aug. 23 2000 MODIS Fire Temp. Aug 23, 2000 MOPITT CO Aug 22-27

6. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 6 Winter Spring Summer Autumn *Hsu et al. 2003, submitted –VIS/NIR/SWIR single view measurements Even over deserts blue/UV measurements can be used to estimate aerosol optical depth and single scattering albedo. How can satellites help define the history of carbonaceous aerosols in the industrial era

7. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 7 –UV measurements (340/380 nm on TOMS) TOMS, OMI on Aura, OMPS on NPOESS. Also possible using measurements from the European GOME and SCHIAMACHY instruments. Use effect of absorbing aerosols on the amount of molecular scattering that occurs. Land is less of a problem than VIS/NIR because surface is dark and atmosphere is bright. Sensitive to vertical extent of aerosols. How can satellites help define the history of carbonaceous aerosols in the industrial era

8. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 8 Sept. 4/2002 SeaWIFS RGB EP-TOMS TOMS-AERONET AOT comparison ssa= 0.97` (A. Chaikovsky Minsk, Earlinet) How can satellites help define the history of carbonaceous aerosols in the industrial era

9. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 9 –Multi-angle measurements POLDER - up to 14 view angles with polarization in some bands MISR - high spatial resolution multi-angle and multi-spectral retrievals, spectral range 440-865 nm with nine view angles ATSR, ATSR-2, AATSR on ERS satellites- broader spectral range with two view angles. Potential to identify non-spherical particles How can satellites help define the history of carbonaceous aerosols in the industrial era

10. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 10 –Multi-angle measurements Nadir 70º Stereo heightAerosol OD How can satellites help define the history of carbonaceous aerosols in the industrial era

11. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 11 –Multi-angle measurements How can satellites help define the history of carbonaceous aerosols in the industrial era –Spectral and Directional information of ATSR-2 –Shape of the BRDF independent of the wavelength –Effects of aerosols small at 1.6 µm –Bi-modal aerosol model –Data available on TEMIS website (www.temis.nl)www.temis.nl –Implementation DV&SV algorithms at KNMI: AOD over Europe, end 1995-early 2001 Veefkind et al., GRL vol 25, no. 16, 3135- 3138, 1998

12. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 12 False color images using measurements at 410, 865 and 2250 nm - left hand side is reflectance, right hand side is polarized reflectance. Strong spectral contrast and weak variation of reflectance with scattering geometry. Weak spectral contrast and large variation with scattering geometry of polarized reflectance Easier to separate surface contribution from atmospheric contribution using polarized reflectance. –Polarization measurements POLDER - polarization measurements at 440, 670 and 865 nm with 12-15 view angles RSP aircraft instrument, polarization measurements at from 410-2250 nm with 150 view angles. NASA’s Glory mission (2006/2007) and APS on NPOESS (2010?). How can satellites help define the history of carbonaceous aerosols in the industrial era

13. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 13 How can satellites help define the history of carbonaceous aerosols in the industrial era –Polarization measurements Identification of non-spherical particles more straightforward with polarization measurements, Sensitivity of polarization to refractive index of aerosols can be used to identify aerosol type, particularly differentiation of smoke from sulfates.

14. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 14 Over the oceans, product of optical thickness and Angstrom coefficient Over land, sensitive to « small aerosols » since large particles do not polarise Biomass burning Mai 1997 Bréon, François-Marie, LSCE, France How can satellites help define the history of carbonaceous aerosols in the industrial era

15. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 15 With more angles and spectral bands than POLDER retrieve a detailed aerosol model optical depth at 0.55µm of 0.102 a bimodal size distribution with modes of effective radius 0.35µm (water soluble) and 1.01µm (sea salt). The spectral optical depths measured by a MFRSR (right panel) indicate that the retrieved optical depth and size distribution are realistic. How can satellites help define the history of carbonaceous aerosols in the industrial era

16. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 16 Retrievals (and POLDERs index) work over land because the surface polarized reflectance is grey which allows the 2250 nm polarized reflectance to be used as a proxy for the surface even when the surface albedo is bright and/or variable (e.g. at 555 and 865 nm). Including over deserts and urban areas such as LA. How can satellites help define the history of carbonaceous aerosols in the industrial era

17. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 17 What sort of differences do different species show in polarization? East coast summer time haze over the Dismal swamp shows polarized reflectance increasing with frequency indicating small particles with a refractive index consistent with a hydrated salt of some kind. How can satellites help define the history of carbonaceous aerosols in the industrial era

18. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 18 West coast fires, 10-29- 03. Size and refractive index of smoke aerosols are substantially different to the haze. Still small but appear to have very high real refractive index and single scattering albedo of order 0.9. Implication is that POLDER should have particularly good sensitivity to smoke in its aerosol index. How can satellites help define the history of carbonaceous aerosols in the industrial era

19. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 19 LIDARs such as the GLAS will provide the best information on the vertical profile of aerosol opacity. How can satellites help define the history of carbonaceous aerosols in the industrial era

20. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 20 How can satellites help define the history of carbonaceous aerosols in the industrial era Retrievals use different approaches with different assumptions and biases. What does it all mean for a scientist interested in the aerosols? Following summary taken from Myhre et al. based on paper in press JAS 2003: Factor of two differences Largest uncertainty over SH high latitude ocean. Upper limit on AOD retrievals is a problem Biased low compared to AERONET at high optical depths Global land and ocean Global land Global ocean

21. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 21 How can satellites help define the history of carbonaceous aerosols in the industrial era History –TOMS and AVHRR have the longest record allowing some evaluation of inter-annual variability. A TOMS-like record will continue because of the need for ozone monitoring. –SeaWiFS and ATSR are more recent and capable than AVHRR but precede (AD) EOS satellites. ATSR data availability has been an issue but may be being resolved based on de Leeuw presentation. SeaWiFs data and reprocessing to do aerosols over bright surfaces is planned. –GLI, OCTS and POLDER are all of interest for aerosols but failures of ADEOS satellites limit temporal coverage. POLDER is only space-borne polarimeter to fly around our planet. GLI has highest spatial resolution 380 nm measurements made providing a potential improvement over information available from TOMS.

22. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 22 How can satellites help define the history of carbonaceous aerosols in the industrial era –Presently MODIS, MISR, AATSR, Schiamachy, GOME, TOMS and AVHRR are all providing aerosol products. –In future NASA’s A-train with a POLDER sensor, OMI (TOMS+), A-band on OCO, CALIPSO. VIIRS and OMPS on NPP. GOME2, other European spectrometers following on from Schiamachy? NASA’s Glory with advanced polarization measurements EarthCARE with HSRL? Japanese SGLI with polarization measurements? Advanced MISR sensor with spectral range from 380-2150 nm and polarization measurements under study.

23. NASA GISS 21-Nov-15 Carbonaceous Aerosol Workshop Page 23 How can satellites help define the history of carbonaceous aerosols in the industrial era Summary –Current sensors provide capability to estimate not only optical depth, but also size distribution and single scatter albedo (if enough aerosol present) over ocean and land. –Future sensors will provide speciation (in so far as an estimate of an aerosols refractive index is a useful tool for this) from polarization measurements and lidars will provide good constraints on the vertical profile of aerosols. –Primary difficulty in using products for the evaluation of aerosol transport models is understanding how the assumptions that are required in the estimate of aerosol properties interact with the assumptions in transport models.