Persistent Link:
http://hdl.handle.net/10150/184277
Title:
Airborne lidar studies of Arctic polar stratospheric clouds.
Author:
Poole, Lamont Rozelle.
Issue Date:
1987
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Airborne lidar measurements of Arctic polar stratospheric clouds (PSCs) in January 1984 and January 1986 are reported. The locales and altitudes of the clouds coincided in both years with very cold ambient temperatures. During the 1984 experiment, PSCs were observed on three flights north of Thule, Greenland; peak backscatter occurred near 20 km (at temperatures below 193 K). A single PSC formation was seen between Iceland and Scotland during the 1986 experiment, with beak backscatter occurring near 22 km (at temperatures from 188-191 K). A sequence of observations in this same area by the SAM II satellite sensor depicts the history of cloud development and dissipation. Enhancements in aerosol backscattering in excess of a factor of 100 were measured during the 1984 experiment at latitudes near the Pole where 50-mb temperatures approached the frost point. Depolarization in the backscattered signal was estimated as 30-40%, similar to that measured in cirrus clouds. Farther south, with 50-mb temperatures several degrees warmer, backscatter enhancement factors ranged from 20-30, and little or no depolarization was observed. Results similar to the latter were found during the 1986 experiment--enhancement factors near 50 (at the 30-mb level, with temperatures 3-5 K above the frost point), and little depolarization. The contrast in observations suggested the existence of distinct cloud growth regimes delineated by temperatures, as proposed in recent articles addressing Antarctic ozone depletion. A theoretical model was developed which interposes a stage of nitric acid trihydrate deposition between the two stages of cloud formation and growth assumed in earlier models (aerosol droplet precursors and ice particles). The calculated temperature dependence of backscatter and extinction agreed well with experimentally observed values, except for small systematic errors at the 30-mb level which may be due to poor characterization of the temperature field there. A companion theoretical study of PSC formation at 70 mb in the Antarctic showed that about 80% and 30% of the nitric acid and water vapor supplies, respectively, may be sequestered in relatively large (4-μm radius) cloud particles at a temperature near 189 K. Such large particles would fall at a rate of about 2 km wk⁻¹, suggesting that PSCs may act as a sink for these stratospheric trace gases.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Stratosphere.; Clouds -- Arctic regions.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Atmospheric Sciences; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAirborne lidar studies of Arctic polar stratospheric clouds.en_US
dc.creatorPoole, Lamont Rozelle.en_US
dc.contributor.authorPoole, Lamont Rozelle.en_US
dc.date.issued1987en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractAirborne lidar measurements of Arctic polar stratospheric clouds (PSCs) in January 1984 and January 1986 are reported. The locales and altitudes of the clouds coincided in both years with very cold ambient temperatures. During the 1984 experiment, PSCs were observed on three flights north of Thule, Greenland; peak backscatter occurred near 20 km (at temperatures below 193 K). A single PSC formation was seen between Iceland and Scotland during the 1986 experiment, with beak backscatter occurring near 22 km (at temperatures from 188-191 K). A sequence of observations in this same area by the SAM II satellite sensor depicts the history of cloud development and dissipation. Enhancements in aerosol backscattering in excess of a factor of 100 were measured during the 1984 experiment at latitudes near the Pole where 50-mb temperatures approached the frost point. Depolarization in the backscattered signal was estimated as 30-40%, similar to that measured in cirrus clouds. Farther south, with 50-mb temperatures several degrees warmer, backscatter enhancement factors ranged from 20-30, and little or no depolarization was observed. Results similar to the latter were found during the 1986 experiment--enhancement factors near 50 (at the 30-mb level, with temperatures 3-5 K above the frost point), and little depolarization. The contrast in observations suggested the existence of distinct cloud growth regimes delineated by temperatures, as proposed in recent articles addressing Antarctic ozone depletion. A theoretical model was developed which interposes a stage of nitric acid trihydrate deposition between the two stages of cloud formation and growth assumed in earlier models (aerosol droplet precursors and ice particles). The calculated temperature dependence of backscatter and extinction agreed well with experimentally observed values, except for small systematic errors at the 30-mb level which may be due to poor characterization of the temperature field there. A companion theoretical study of PSC formation at 70 mb in the Antarctic showed that about 80% and 30% of the nitric acid and water vapor supplies, respectively, may be sequestered in relatively large (4-μm radius) cloud particles at a temperature near 189 K. Such large particles would fall at a rate of about 2 km wk⁻¹, suggesting that PSCs may act as a sink for these stratospheric trace gases.en_US
dc.description.noteDigitization note: p. 41 missing from original (appears to be pagination error).en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectStratosphere.en_US
dc.subjectClouds -- Arctic regions.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAtmospheric Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.committeememberKrider, Philipen_US
dc.contributor.committeememberYoung, Kennethen_US
dc.contributor.committeememberStaley, Deanen_US
dc.contributor.committeememberFrieden, Royen_US
dc.contributor.committeememberSarid, Droren_US
dc.identifier.proquest8804186en_US
dc.identifier.oclc700067686en_US
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