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  • 1
    Online Resource
    Online Resource
    Large nitric acid particles at the top of an Arctic stratospheric cloud
    American Geophysical Union (AGU) ; 2003
    In:  Journal of Geophysical Research: Atmospheres Vol. 108, No. D16 ( 2003-08-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 108, No. D16 ( 2003-08-27)
    Abstract: In early December 2001, balloon‐borne in situ measurements of particle composition, size, number, phase, and backscatter were completed in an Arctic stratospheric cloud composed of three distinct layers between 22 and 26 km. Below 24.5 km, liquid solution droplets of water, nitric acid, and sulfuric acid and a thin ice layer were observed. Above this layer the particles were primarily solid nitric acid trihydrate. Just above 26 km, at cloud top, where temperatures were near or above the equilibrium temperature for nitric acid trihydrate, there was a thin layer of solid particles narrowly distributed around a radius of 2.0 μm at concentrations of 〈 0.001 cm −3 . Lidar backscatter and particle phase measurements approximately 200 km upwind of the in situ measurements indicate a similar vertical structure for the cloud. These in situ measurements represent, to our knowledge, the most comprehensive in situ observations of all phases of polar stratospheric cloud particles, while the large particles at cloud top have not been previously observed and may have implications for producing particles large enough to remove reactive nitrogen from the polar stratosphere.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2003JD003479
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2003
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Climatology of polar stratospheric clouds based on lidar observations from 1993 to 2001 over McMurdo Station, Antarctica
    American Geophysical Union (AGU) ; 2004
    In:  Journal of Geophysical Research: Atmospheres Vol. 109, No. D24 ( 2004-12-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 109, No. D24 ( 2004-12-27)
    Abstract: A climatology of polar stratospheric clouds (PSCs) based on lidar measurements performed at McMurdo Station, Antarctica (78°S, 167°E) from 1993 to 2001 is presented here. The observations are discussed in terms of occurrence and temporal and spatial variability of PSC types. The climatological analysis reveals that in McMurdo PSCs mainly occur between July and mid‐August. During this time their altitude changes from 22 to 14 km, following the stratospheric temperature minimum trend. At the beginning of the accounted period (1993–1994), volcanic aerosols from the Mt. Pinatubo eruption in 1991 were still present in the southern polar vortex. Therefore these 2 years have been corrected for the direct contribution of the volcanic aerosol to the backscatter signal. A close examination of the data set evidences that most PSCs appear either as rather thin layers ( 〈 1 km) or as layers with a considerably higher thickness. Therefore all observed PSCs have been divided into two classes, depending on the variation of the backscattering ratio with respect to the altitude (e.g., small‐scale variations, or SSV, and large‐scale variations, or LSV). The seasonal behavior and the occurrence of PSC types under each class have been studied, keeping 1993 and 1994 separated to better highlighting the effect of the volcanic aerosol load on cloud properties. Finally, in order to shed some light on PSC formation, back‐trajectory analysis has been performed for retrieving thermal histories of opportunely selected PSCs.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2004JD004800
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2004
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    In situ mountain‐wave polar stratospheric cloud measurements: Implications for nitric acid trihydrate formation
    American Geophysical Union (AGU) ; 2003
    In:  Journal of Geophysical Research: Atmospheres Vol. 108, No. D5 ( 2003-03-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 108, No. D5 ( 2003-03-16)
    Abstract: Particle size distribution, composition, and optical properties of polar stratospheric clouds (PSCs) have been measured above northern Scandinavia during a nocturnal balloon flight within the polar vortex on 19 January 2000. The mountain‐wave PSC mainly consisted of nitric acid trihydrate (NAT) particles with number densities between 0.01 and 0.2 cm −3 , median radii of 1 to 2 μm and volumes up to 1 μm 3 cm −3 . A comparison between optical PSC data and optical simulations based on the measured particle size distribution indicates that the NAT particles were aspherical with an aspect ratio of 0.5. The NAT particle properties have been compared to another PSC observation on 25 January 2000, where NAT particle number densities were about an order of magnitude higher. In both cases, microphysical modeling indicates that the NAT particles have formed on ice particles in the mountain‐wave events. Differences in the NAT particle number density can be explained by the meteorological conditions. We suggest that the higher NAT number density on 25 January can be caused by stronger wave activity observed on that day, larger cooling rates and therefore higher NAT supersaturation.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2001JD001185
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2003
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Physical properties of stratospheric clouds during the Antarctic winter of 1995
    American Geophysical Union (AGU) ; 1998
    In:  Journal of Geophysical Research: Atmospheres Vol. 103, No. D9 ( 1998-05-20), p. 10859-10873
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 103, No. D9 ( 1998-05-20), p. 10859-10873
    Abstract: Lidar observations collected during winter 1995 at McMurdo Station, Antarctica (78°S‐167°E), are analyzed to determine polar stratospheric cloud (PSC) physical properties. A scheme to infer PSC phase from lidar depolarization and backscatter profiles is presented. Interpretation is supported by collocated temperature soundings and by isentropic back trajectories. The analysis shows that first appearance of PSC is consistent with frozen sulfates, mixing with liquid ternary solutions (H 2 SO 4 ‐HNO 3 ‐H 2 O) when temperature lowers. Finally, solids consistent with HNO 3 mixing ratios form as mixed phases first, then followed by full solid phases. Mixed phases (i.e., coexisting solid and liquid aerosols) are detected during the whole winter. While mixed phase PSCs form particularly in the altitude range 15–20 km and are the last to disappear, full solid phases are mainly observed above 20 km and last until the end of August. Mixed phases possess the largest PSC surface areas and, as a result of selective growth, can reach large, fast settling sizes. The considerable denitrification and halogen activation observed in the Antarctic lower stratosphere, where the ozone hole takes place, appears to be well correlated with the action of this kind of PSC.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/98JD00280
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1998
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Polar stratospheric clouds observed during the Airborne Polar Experiment–Geophysica Aircraft in Antarctica (APE‐GAIA) campaign
    American Geophysical Union (AGU) ; 2004
    In:  Journal of Geophysical Research: Atmospheres Vol. 109, No. D7 ( 2004-04-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 109, No. D7 ( 2004-04-16)
    Abstract: In this work, observations of polar stratospheric clouds (PSC) carried out during one flight of the stratospheric research aircraft Geophysica deployed in the Airborne Polar Experiment–Geophysica Aircraft in Antarctica (APE‐GAIA) campaign in September–October 1999 are presented. An analysis of data from the two lidars and a backscatter sonde on board the Geophysica aircraft is presented, coupled with temperature measurements. The observations are analyzed with the aid of a mesoscale model to provide air mass thermal histories and a microphysical box model to simulate PSC formation. The results obtained from this comparison are discussed in view of the theories for PSC formation processes.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2003JD003930
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2004
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
    Location Call Number Limitation Availability
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