Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment

Y. J. Kaufman, P. V. Hobbs, V. W.J.H. Kirchhoff, P. Artaxo, L. A. Remer, B. N. Holben, M. D. King, D. E. Ward, E. M. Prins, K. M. Longo, L. F. Mattos, C. A. Nobre, J. D. Spinhirne, Q. Ji, A. M. Thompson, J. F. Gleason, S. A. Christopher, S. C. Tsay

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Abstract

The Smoke, Clouds, and Radiation-Brazil (SCAR-B) field project took place in the Brazilian Amazon and cerrado regions in August-September 1995 as a collaboration between Brazilian and American scientists. SCAR-B, a comprehensive experiment to study biomass burning, emphasized measurements of surface biomass, fires, smoke aerosol and trace gases, clouds, and radiation, their climatic effects, and remote sensing from aircraft and satellites. It included aircraft and ground-based in situ measurements of smoke emission factors and the compositions, sizes, and optical properties of the smoke particles; studies of the formation of ozone; the transport and evolution of smoke; and smoke interactions with water vapor and clouds. This overview paper introduces SCAR-B and summarizes some of the main results obtained so far. (1) Fires: measurements of the size distribution of fires, using the 50 m resolution MODIS Airborne Simulator, show that most of the fires are small (e.g., 0.005 km2), but the satellite sensors (e.g., AVHRR and MODIS with 1 km resolution) can detect fires in Brazil which are responsible for 60-85% of the burned biomass; (2) Aerosol: smoke particles emitted from fires increase their radius by as much as 60% during their first three days in the atmosphere due to condensation and coagulation, reaching a mass median radius of 0.13-0.17 μm; (3) Radiative forcing: estimates of the globally averaged direct radiative forcing due to smoke worldwide, based on the properties of smoke measured in SCAR-B (-0.1 to -0.3 W m-2), are smaller than previously modeled due to a lower single-scattering albedo (0.8 to 0.9), smaller scattering efficiency (3 m2 g-1 at 550 nm), and low humidification factor; and (4) Effect on clouds: a good relationship was found between cloud condensation nuclei and smoke volume concentrations, thus an increase in the smoke emission is expected to affect cloud properties. In SCAR-B, new techniques were developed for deriving the absorption and refractive index of smoke from ground-based remote sensing. Future spaceborne radiometers (e.g., MODIS on the Earth Observing System), simulated on aircraft, proved to be very useful for monitoring smoke properties, surface properties, and the impacts of smoke on radiation and climate.

Original languageEnglish (US)
Article number98JD02281
Pages (from-to)31783-31808
Number of pages26
JournalJournal of Geophysical Research Atmospheres
Volume103
Issue numberD24
DOIs
StatePublished - 1998

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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    Kaufman, Y. J., Hobbs, P. V., Kirchhoff, V. W. J. H., Artaxo, P., Remer, L. A., Holben, B. N., King, M. D., Ward, D. E., Prins, E. M., Longo, K. M., Mattos, L. F., Nobre, C. A., Spinhirne, J. D., Ji, Q., Thompson, A. M., Gleason, J. F., Christopher, S. A., & Tsay, S. C. (1998). Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment. Journal of Geophysical Research Atmospheres, 103(D24), 31783-31808. [98JD02281]. https://doi.org/10.1029/98JD02281