Moisture transport associated with the summertime North American monsoon.

Persistent Link:
http://hdl.handle.net/10150/187277
Title:
Moisture transport associated with the summertime North American monsoon.
Author:
Schmitz, Jeffrey Todd.
Issue Date:
1995
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 origins and transport of water vapor into the semi-arid Sonoran Desert region of southwestern North America are examined for the July-August wet season. Vertically-integrated fluxes and flux divergences of water vapor are computed for the 8 summers, 1985-1992, from ECMWF mandatory-level analyses possessing a spectral resolution of triangular 106 (T106). The intraseasonal variability of water vapor transports are also examined. Composite wet and dry periods defined from rain gauge data for southeast Arizona, are compared. Cloud top temperature (CCT), wind, specific humidity, precipitable water (PW), convective indices, moisture flux, and parcel trajectories are all examined. The ECMWF analyses indicate that transports of water vapor by the time-mean flow dominate the transports by the transient eddies. Climatologically, upper-level (above 700 mb) moisture over the Sonoran Desert arrives from over the Gulf of Mexico and the northern fringe of the moist air mass over western Mexico, while at low-levels (below 700 mb) the water vapor comes predominantly from over the northern Gulf of California. There is no indication of moisture entering the Sonoran Desert at low-levels directly from the southern Gulf of California or the tropical East Pacific. Water vapor from these regions can enter the Sonoran Desert aloft after vertical mixing along the western slopes of the Sierra Madre Occidental mountains of Mexico and subsequent horizontal transport aloft. Significant differences exist between wet and dry conditions over the Sonoran Desert for all fields considered. As the monsoon shifts from dry to wet conditions, the subtropical ridge shifts ∼5° latitude toward the north, and precipitable water increases by as much as ∼1.2 cm (∼0.5 inches). Parcels in the middle troposphere ascend into the region from the southeast, and the atmosphere becomes more unstable. The result is a significant increase in the frequency of deep convection, as determined from CTT < -38°C. During both monsoon regimes, most of the water vapor entering the Sonoran Desert at low-levels (below 700 mb) arrives from over the northern and central Gulf of California, with a slightly greater flux into the region occurring during the dry phase. Above 700 mb, moisture transported into the Sonoran Desert during both regimes is a mixture of water vapor from over the Gulf of Mexico and Gulf of California, and from residual convective inputs over the Sierra Madre Occidental mountains of Mexico. During wet periods, however, a longer fetch through the moist air mass above western Mexico results in a greater moisture flux into the Sonoran Desert aloft. Less water vapor from over the Gulf of Mexico flows into western Mexico and the Sonoran Desert under wet conditions than during dry phases, both above and below 700 mb.
Type:
text; Dissertation-Reproduction (electronic)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Atmospheric Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Mullen, Steven L.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMoisture transport associated with the summertime North American monsoon.en_US
dc.creatorSchmitz, Jeffrey Todd.en_US
dc.contributor.authorSchmitz, Jeffrey Todd.en_US
dc.date.issued1995en_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 origins and transport of water vapor into the semi-arid Sonoran Desert region of southwestern North America are examined for the July-August wet season. Vertically-integrated fluxes and flux divergences of water vapor are computed for the 8 summers, 1985-1992, from ECMWF mandatory-level analyses possessing a spectral resolution of triangular 106 (T106). The intraseasonal variability of water vapor transports are also examined. Composite wet and dry periods defined from rain gauge data for southeast Arizona, are compared. Cloud top temperature (CCT), wind, specific humidity, precipitable water (PW), convective indices, moisture flux, and parcel trajectories are all examined. The ECMWF analyses indicate that transports of water vapor by the time-mean flow dominate the transports by the transient eddies. Climatologically, upper-level (above 700 mb) moisture over the Sonoran Desert arrives from over the Gulf of Mexico and the northern fringe of the moist air mass over western Mexico, while at low-levels (below 700 mb) the water vapor comes predominantly from over the northern Gulf of California. There is no indication of moisture entering the Sonoran Desert at low-levels directly from the southern Gulf of California or the tropical East Pacific. Water vapor from these regions can enter the Sonoran Desert aloft after vertical mixing along the western slopes of the Sierra Madre Occidental mountains of Mexico and subsequent horizontal transport aloft. Significant differences exist between wet and dry conditions over the Sonoran Desert for all fields considered. As the monsoon shifts from dry to wet conditions, the subtropical ridge shifts ∼5° latitude toward the north, and precipitable water increases by as much as ∼1.2 cm (∼0.5 inches). Parcels in the middle troposphere ascend into the region from the southeast, and the atmosphere becomes more unstable. The result is a significant increase in the frequency of deep convection, as determined from CTT < -38°C. During both monsoon regimes, most of the water vapor entering the Sonoran Desert at low-levels (below 700 mb) arrives from over the northern and central Gulf of California, with a slightly greater flux into the region occurring during the dry phase. Above 700 mb, moisture transported into the Sonoran Desert during both regimes is a mixture of water vapor from over the Gulf of Mexico and Gulf of California, and from residual convective inputs over the Sierra Madre Occidental mountains of Mexico. During wet periods, however, a longer fetch through the moist air mass above western Mexico results in a greater moisture flux into the Sonoran Desert aloft. Less water vapor from over the Gulf of Mexico flows into western Mexico and the Sonoran Desert under wet conditions than during dry phases, both above and below 700 mb.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)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.chairMullen, Steven L.en_US
dc.contributor.committeememberDickinson, Robert E.en_US
dc.contributor.committeememberKrider, E. Philipen_US
dc.contributor.committeememberSchowengerdt, Robert A.en_US
dc.contributor.committeememberReagan, John A.en_US
dc.identifier.proquest9603725en_US
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