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  • GEOPHYSICS  (9)
  • 1
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    The January 30, 1989 Arctic polar stratospheric clouds (PSC) event - Evidence for a mechanism of dehydration (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In-situ particle measurements made aboard the NASA ER-2 in the Arctic on 890130 (YYMMDD) show Type 1 PSC particles over much of the flight, with instances of embedded Type 2 PSCs. The Type 2 particles were observed at temperatures warmer than the local frost-point temperature of water; extended up to the upper size cutoff of the instrument (about 24-micron diameter); and are shown to contain too large a volume to be primarily NAT. Based on measured vertical temperature profiles, it is concluded that the Type 2 particles observed on this day were formed above the aircraft in a region where saturation with respect to ice was achieved and were sufficiently large to have fallen into the path of the ER-2. Although the amount of material in the particles, expressed as water, is small by comparison to the total (vapor + aerosol) water concentration, the flux of water from the falling particles is of sufficient magnitude, if sustained, to lead to dehydration of the source region. These observations verify the mechanism for dehydration of polar vortex air masses by precipitation of ice particles.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 457-460
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  • 2
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    A survey of particle measurements in the Arctic from the Forward Scattering Spectrometer Probe model 300 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new instrument, the Forward Scattering Spectrometer Probe (FSSP) 300, was used on the NASA ER-2 during the Airborne Arctic Stratospheric Expedition (AASE) to count and size particles in the size range 0.4-24 microns in diameter. A brief description of the instrument is presented, and observations for each ER-2 flight are summarized. Measurements were made in both type I and type II polar stratospheric clouds as well as in the background sulfuric-acid particles. Total particle concentrations up to 16/cu cm with total particle volumes up to 10 cubic micron/cu cm were observed in some of the polar-stratospheric-cloud events.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 409-412
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  • 3
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    The polar stratospheric cloud event of January 24, 1989. I - Microphysics (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Rapid adiabatic cooling induced by synoptic forcing led to polar stratospheric cloud (PSC) formation on January 24, 1989, at altitudes sampled by the ER-2 aircraft. Particle characteristics measured by the Forward Scattering Spectrometer Probe (FSSP) on the ER-2 were compared to those calculated using a theoretical PSC microphysics model. Although calculations were sensitive to local changes in cooling rate, generally favorable agreement was found, that in particle surface area being especially important since this parameter dictates heterogeneous chemical rates. The overall model performance suggests that the current approach for simulating Type 1 (nitric acid trihydrate) PSC formation under rapid cooling conditions is well founded and can be used to study the effects of heterogeneous chemistry on stratospheric composition.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 537-540
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  • 4
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    Observed particle evolution in the polar stratospheric cloud of January 24, 1989 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Particle-size distributions measured from the NASA ER-2 with the new Forward Scattering Spectrometer Probe 300 in a type I polar stratospheric cloud (PSC) on January 24, 1989 show a volume mode near 0.8 micron in diameter. The large increase in particle concentration and volume after cloud entry did not occur until the apparent saturation ratio of nitric acid with respect to nitric acid trihydrate reached 10, but at ratios near 1 subtle changes in the size distribution suggest some type I particles were present. Particle concentrations in cloud of 15-17/cu cm were greater than the CN concentrations of 5-7/cu cm just outside of cloud, suggesting nucleation on more than just sulfate particles. Some particles greater than 4 microns in diameter were observed in a region which was saturated with respect to ice.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 413-416
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  • 5
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    In situ observations of aerosol and chlorine monoxide after the 1991 eruption of Mount Pinatubo - Effect of reactions on sulfate aerosol (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Highly resolved aerosol size distributions measured from high-altitude aircraft can be used to describe the effect of the 1991 eruption of Mount Pinatubo on the stratospheric aerosol. In some air masses, aerosol mass mixing ratios increased by factors exceeding 100 and aerosol surface area concentrations increased by factors of 30 or more. Increases in aerosol surface area concentration were accompanied by increases in chlorine monoxide at mid-latitudes when confounding factors were controlled. This observation supports the assertion that reactions occurring on the aerosol can increase the fraction of stratospheric chlorine that occurs in ozone-destroying forms.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 261; 5125; p. 1140-1143.
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  • 6
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    In situ measurements constraining the role of sulphate aerosols in mid-latitude ozone depletion (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: In situ measurements of stratospheric sulphate aerosol, reactive nitrogen and chlorine concentrations at middle latitudes confirm the importance of aerosol surface reactions that convert active nitrogen to a less active, reservoir form. This makes mid-latitude stratospheric ozone less vulnerable to active nitrogen and more vulnerable to chlorine species. The effect of aerosol reactions on active nitrogen depends on gas phase reaction rates, so that increases in aerosol concentration following volcanic eruptions will have only a limited effect on ozone depletion at these latitudes.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 363; 6429; p. 509-514.
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  • 7
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    Analysis of the physical state of one Arctic polar stratospheric cloud based on observations (1994)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: During the Arctic Airborne Stratospheric Expedition (AASE) simultaneous measurements of aerosol size distribution and NO(y)(HN03 + NO + NO2 + 2(N205)) were made along ER-2 flight paths. The flow characteristics of the NO(y) instrument allow us to derive the condensed NO(y) amount (assumed to be HN03) present during polar stratospheric cloud (PSC) events. Analysis of the January 24th flight indicates that this condensed HN03 amount does not agree well with the aerosol volume if the observed PSCs are composed of solid nitric acid trihydrate (NAT), as is generally assumed. However, the composition agrees well with that predicted for liquid H2S04/HN03/H20 solution droplets using a new Aerosol Physical Chemistry Model (APCM). The agreement corresponds in detail to variations in temperature and humidity. The weight percentages of H2SO4, HN03, and H2O derived from the measurements all correspond to those predicted for ternary, liquid solutions.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2475-2478
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  • 8
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    A case of type I polar stratospheric cloud formation by heterogeneous nucleation (1992)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The NASA ER-2 aircraft flew on January 24, 1989, from Stavanger to Spitsbergen, Norway, at the 430-440 K potential temperature surface (19.2-19.8 km pressure altitude). Aerosols were sampled continuously by an optical particle counter (PMS-FSSP300) for concentration and size analyses, and during five 10-min intervals by four wire and one replicator impactor for concentration, size, composition, and phase analysis. During sampling, the air saturation of H2O with respect to ice changed from 20 to 100 percent, and of HNO3 with respect to nitric acid trihydrate (NAT) from subsaturation to supersaturation. Data from both instruments indicate a condensation of hydrochloric acid and, later, nitric acid on the background aerosol particles as the ambient temperature decreases along the flight track. This heterogeneous nucleation mechanism generates type I polar stratospheric cloud particles of 10-fold enhanced optical depth, which could play a role in stratospheric ozone depletion.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; D8 M
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  • 9
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    The Arctic polar stratospheric cloud aerosol - Aircraft measurements of reactive nitrogen, total water, and particles (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: In situ aircraft measurements in the lower stratosphere are used to investigate the reactive nitrogen, NO(y), total water, and particle components of the polar stratospheric cloud (PSC) aerosol in the Arctic. The results are compared to findings from the Antarctic derived using similar measurements and interpretive techniques. The Arctic data show that particle volume well above background values is present at temperatures above the frostpoint, confirming the result from the Antarctic that the observed PSCs are not water ice particles. NO(y) measurements inside a PSC are enhanced above ambient values consistent with anisokinetic sampling of particles containing NO(y). In the Arctic data over long segments of several flights, calculations show saturation with respect to nitric acid trihydrate without significant PSC particle growth above background.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; D8 M
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