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  • 11
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    Correction to “Black carbon (soot) aerosol in the lower stratosphere and upper troposphere” by R. F. Pueschel, D. F. Black, K. G. Snetsinger, A. D. A. Hansen, S. Verna, and K. Kato (1992)
    American Geophysical Union
    Details
    Publication Date: 1992-10-23
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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    PAPER CURRENT
  • 12
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    Diminished effects of El Chichon on stratospheric aerosols, early 1984 to late 1986 (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Stratospheric aerosol collections by wire impactors, taken mainly over the western U.S. from early 1984 to late 1986, show the diminishing effects of El Chichon's 1982 eruption, and provide a set of data for judging subsequent volcanic effects. Decrease in sulfate burden during the study time is due to preferential gravitational settling-out of large (above 0.5-micron diameter) sulfate aerosol droplets. As a result of settling from higher levels, lower altitude (12.2-15.2 km) air early in 1984 tends to contain more sulfate than higher level (19.8-21.3 km) air. As of late 1986, however, high- and low-altitude sulfate contents have decreased and are similar, suggesting large-particle settling has been completed. The later sulfate collection size distributions resemble unimodal background spectra, whereas earlier ones are bimodal. Average sulfate load for all altitudes decreases during the period of study from 0.4 to 0.08 microgram/cu m. The latter value is somewhat higher than a volcanically unenriched pre-El Chichon level, suggesting that even as of 1987, stratospheric background had not been obtained.
    Keywords: GEOPHYSICS
    Type: Atmospheric Environment (ISSN 0004-6981); 26A; 16; p. 2947-2951.
    Format: text
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    NASA TECHNICAL REPORTS
  • 13
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    Evolution of Pinatubo aerosol near 19 km altitude over western North America (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Stratospheric aerosols, collected near 19 km altitude on wire impactors over western North America from August 20, 1991 to May 11, 1993, show strong influence of the June 1991 Mt. Pinatubo eruption. Lognormal size distributions are bimodal; each of the mode radii increases and reaches maximum value at about 15 months after eruption. The second (large particle) mode becomes well developed then, and about 40% of the droplets are larger than 0.4 micron radius. The eruption of Mt. Spurr (Alaska) may also have contributed to this. Sulfate mass loading decays exponentially (e-folding 216 days), similar to El Chichon. Silicates are present in samples only immediately after eruption. Two years after eruption, sulfate mass loading is about 0.4 micrograms/cu m, about an order of magnitude higher than background pre-volcanic values. Aerosol size distributions are still bimodal with a very well-defined large droplet mode.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 12; p. 1129-1132
    Format: text
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  • 14
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    Physical and optical properties of the Pinatubo volcanic aerosol: Aircraft observations with impactors and a Sun-tracking photometer (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: As determined in situ by impactor samplers flown on an ER-2 at 16.5- to 20.7-km pressure altitude and on a DC-8 at 9.5- to 12.6-km pressure altitudes, the 1991 Pinatubo volcanic eruption increased the particle surface area of stratospheric aerosols up to 50-fold and the particle volume up to 2 orders of magnitude. Particle composition was typical of a sulfuric acid-water mixture at ER-2 altitudes. Ash particles coated with sulfuric acid comprised a significant fraction of aerosol at DC-8 altitudes. Mie-computed light extinction increased up to 20-fold at midvisible and greater than 100-fold at near-IR wavelengths. The optical thickness measured through the aerosol layer by an autotracking Sun photometer aboard a DC-8 aircraft at 10.7- to 11.3-km pressure altitudes shows a spectral shape that is similar to the Mie-calculated spectral extinction at ER-2 altitudes. Surface area distributions calculated by inversion of spectral optical depth measurements show characteristics that are similar to the mean surface area distribution resulting from 35 in situ measurements.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D6; p. 12,915-12,922
    Format: text
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    NASA TECHNICAL REPORTS
  • 15
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    Black carbon (soot) aerosol in the lower stratosphere and upper troposphere (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: As determined by impactor samplers flown on ER-2 and DC-8 aircraft, black carbon aerosol (BCA) mass loadings in the stratosphere average 0.6 nanograms per standard cubic meter, or 0.01 percent of the total aerosol. Upper tropospheric BCA increases to 0.3 percent. Low stratospheric concentration is commensurate with present commercial air traffic fuel consumption, given the following assumptions: the BCA emissions are 0.1 grams per kilogram of fuel consumed, 10 percent of route mileage is above the tropopause, and average BCA stratospheric residence time is about one year. Taking BCA into account, the stratospheric single scatter albedo is about 0.99. Using parameters for planned supersonic commercial aircraft, whose emissions will be predominantly in the stratosphere, it is shown that such traffic will double stratospheric BCA concentration. This would reduce the aerosol single scattering albedo by one percent, and double the BCA surface area that is available for heterogeneous chemistry.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 16, A
    Format: text
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  • 16
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    Time variations of aerosols in the stratosphere following Mount St. Helens eruptions (1982)
    In:  CASI
    Details
    Publication Date: 2006-04-12
    Description: Samples of stratospheric aerosols collected with U-2 aircraft for several months following the first three major eruptions of Mount St. Helens were analyzed for ash and liquid acid content. Ash grain sizes and compositions vary depending on collection altitude, location within the drifting cloud, and days following their injection. s computers Size distributions of ash particles vary with altitude. Generally small particles are depleted more rapidly at low altitudes (12 km) than at higher altitudes (17-18 km). Although samples collected 1 day after the first eruption of May 18, 1980, were dry, flow marks on the aircraft indicated parts of the cloud contained heavy acid concentrations. Indeed, all other samples obtained within 1 to 4 days after later eruptions (May 25 and June 12, 1980) were covered with copious amounts of liquid acid. Proportions of liquid to ash varied considerably depending on sampling location and cloud age. Because the acid-coated ash globules were large, they rapidly fell from the stratosphere until, by late June 1980, only a residue of acid droplets remained. Size distributions and concentrations of these droplets varied considerably.
    Keywords: GEOPHYSICS
    Type: Atmospheric Effects and Potential Climatic Impact of the 1980 Eruptions of Mt. St. Helens; p 55-64
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    NASA TECHNICAL REPORTS
  • 17
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    Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.
    Keywords: GEOPHYSICS
    Type: Aerosol Science and Technology (ISSN 0278-6826); 12; 992-1002
    Format: text
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    NASA TECHNICAL REPORTS
  • 18
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    Effects of El Chichon on stratospheric aerosols late 1982 to early 1984 (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Stratospheric aerosols collected over the western U.S. from late 1982 to early 1984 show the strong effects of El Chichon's eruption. Although mineral particles disappeared during this period, large acid droplets were still common. Because these have never been seen in prevolcanic, background-level collections, they apparently result from increased droplet growth made possible by the unusual abundance of sulfate. Aerosol size distributions show a wide variety of multimodal curves due to mixing of air masses containing aerosols of various ages or histories. Toward the end of the study time there are fewer large aerosols because of gravitational settling and poleward transport. The result is a steady reduction in sulfate, as most aerosol mass is concentrated in a small number of large droplets. Even the later sulfate levels are, however, five times typical prevolcanic background contents. Thus the influence of El Chichon on high-altitude was still considerable 22 months after eruption.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 14761-14
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  • 19
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    Condensed nitrate, sulfate, and chloride in Antarctic stratospheric aerosols (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The 1987 Airborne Antarctic Ozone Experiment, in which the NO3, Cl, and SO4 contents of stratospheric aerosols were estimated, is discussed. The aerosol size and chemical composition measurements were carried out on samples collected during August 17 to September 4, 1987. The data indicate that condensed nitrate is found below a threshold temperature of 193.6 + or - 3.0 K, which is generally found at latitudes exceeding 64 deg S. A negative correlation exists between condensed nitrate and ozone correlation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 11271-11
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  • 20
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    Erlichmanite /OsS sub 2/, a new mineral. (1971)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Natural osmium disulfide (termed erlichmanite) was recognized in two occurrences on the basis of electron probe and X-ray data. One occurrence is in grains of platinum-metal sand from California, the other in a platinum-metal nugget from Western Ethiopian laterites. California erlichmanite has Os 68.0, Ir 2.6, Rh 3.8, Ru 0.4, Pd 0.5, and S 25.2, summation of 100.5 wt. %, the number of metal atoms being 1.06 on the basis of 2.00 sulfurs. Ethiopian material has higher Rh and Ir and lower Os. Both are optically isotropic. Spotty X-ray reflections from a 15-micron particle of California erlichmanite give rise to d spacing which match those of synthetic cubic osmium disulfide. Erlichmanite is defined as a cubic disulfide in which osmium is the most abundant metal atom.
    Keywords: GEOPHYSICS
    Type: American Mineralogist; 56; Sept
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