Persistent Link:
http://hdl.handle.net/10150/184693
Title:
Structure and dynamics of the Arizona Monsoon Boundary.
Author:
Adang, Thomas Charles.
Issue Date:
1989
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:
The Arizona Monsoon Boundary is defined as the boundary separating two distinctly different air masses over Mexico, the southwestern United States, and the adjacent Pacific during the summer. The structure and dynamics of this boundary are examined by cross-sectional analysis using three different data sources: (1) a time-height cross section, constructed using radiosonde observations, at the time the boundary initially passed through Tucson in 1984; (2) a composite cross section through the boundary, constructed from the Fleet Numerical Oceanography Center analysis; and (3) a cross section through the boundary using high-resolution fields of temperature, moisture, and geopotential height obtained from the VISSR Atmospheric Sounder (VAS). All three cross sections showed similar structure. In some respects, the Arizona monsoon boundary resembles a mid-latitude front with a distinct and relatively sharp air mass change across the boundary, forced almost entirely by confluence. A direct ageostrophic circulation is produced by this forcing, giving weak ascent on the warm, moist side of the boundary. The gradients and flow associated with the composite boundary are weaker, by a factor of four, than those associated with strong mid-latitude fronts. However, the VAS cross section suggests that, at times, the strength of the boundary approaches that of middle-latitude fronts. The wind shear suggested by the composite boundary ought to be unstable to baroclinic or barotropic processes. Disturbances developing along the boundary have been observed. One example of such a disturbance is examined using GOES imagery, lightning strike data, cloud track winds, and VAS data. Satellite images show the disturbance resembling a mid-latitude occluded cyclone, with an apparent low pressure center over northern Baja California and front-like cloud features extending eastward and southward from the low. Lightning strike data show convective activity occurring along the front-like features. Wind data indicate the presence of a cyclonic circulation south of San Diego along the Baja California coast. Cross sections using VAS data suggest that barotropic and baroclinic energy sources are present and suggest the front-like nature of the cloud feature extending southward from the low pressure center. Additionally, a second disturbance that eventually interacted with the monsoon boundary is briefly examined using satellite imagery.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Thunderstorms -- Arizona.; Air masses -- Arizona.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Atmospheric Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Gall, Robert L.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleStructure and dynamics of the Arizona Monsoon Boundary.en_US
dc.creatorAdang, Thomas Charles.en_US
dc.contributor.authorAdang, Thomas Charles.en_US
dc.date.issued1989en_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.abstractThe Arizona Monsoon Boundary is defined as the boundary separating two distinctly different air masses over Mexico, the southwestern United States, and the adjacent Pacific during the summer. The structure and dynamics of this boundary are examined by cross-sectional analysis using three different data sources: (1) a time-height cross section, constructed using radiosonde observations, at the time the boundary initially passed through Tucson in 1984; (2) a composite cross section through the boundary, constructed from the Fleet Numerical Oceanography Center analysis; and (3) a cross section through the boundary using high-resolution fields of temperature, moisture, and geopotential height obtained from the VISSR Atmospheric Sounder (VAS). All three cross sections showed similar structure. In some respects, the Arizona monsoon boundary resembles a mid-latitude front with a distinct and relatively sharp air mass change across the boundary, forced almost entirely by confluence. A direct ageostrophic circulation is produced by this forcing, giving weak ascent on the warm, moist side of the boundary. The gradients and flow associated with the composite boundary are weaker, by a factor of four, than those associated with strong mid-latitude fronts. However, the VAS cross section suggests that, at times, the strength of the boundary approaches that of middle-latitude fronts. The wind shear suggested by the composite boundary ought to be unstable to baroclinic or barotropic processes. Disturbances developing along the boundary have been observed. One example of such a disturbance is examined using GOES imagery, lightning strike data, cloud track winds, and VAS data. Satellite images show the disturbance resembling a mid-latitude occluded cyclone, with an apparent low pressure center over northern Baja California and front-like cloud features extending eastward and southward from the low. Lightning strike data show convective activity occurring along the front-like features. Wind data indicate the presence of a cyclonic circulation south of San Diego along the Baja California coast. Cross sections using VAS data suggest that barotropic and baroclinic energy sources are present and suggest the front-like nature of the cloud feature extending southward from the low pressure center. Additionally, a second disturbance that eventually interacted with the monsoon boundary is briefly examined using satellite imagery.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectThunderstorms -- Arizona.en_US
dc.subjectAir masses -- Arizona.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.advisorGall, Robert L.en_US
dc.contributor.committeememberStaley, Dean O.en_US
dc.contributor.committeememberYoung, Kenneth C.en_US
dc.contributor.committeememberHerman, Benjamin M.en_US
dc.contributor.committeememberSlater, Philip N.en_US
dc.identifier.proquest8919017en_US
dc.identifier.oclc702373074en_US
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