The Environments And Associated Physical Mechanisms That Cause Size And Structure Changes In A Tropical Cyclone

Persistent Link:
http://hdl.handle.net/10150/338896
Title:
The Environments And Associated Physical Mechanisms That Cause Size And Structure Changes In A Tropical Cyclone
Author:
Stovern, Diana Rose
Issue Date:
2014
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:
Tropical cyclones (TCs) can make significant size changes during their lifetime. Being able to accurately forecast TC size change is important for predicting the onset of storm surge as well as the spatial extent of damaging winds. TC size changes can occur from internal storm dynamics, such as eyewall replacement cycle or from changes in the synoptic environment. In this study, the impacts of changing the atmospheric temperature and air-sea temperature difference on TC size and structure are investigated. The study is conducted in two parts: the first part uses the WRF-ARW model to test the sensitivity of TC size changes to simple changes in the environment; the second part to validates the results from the first part by characterizing the environments associated with real cases of TC size change in the North Atlantic basin. It is found that when the simulated atmosphere is cooled, the initial specific humidity and convective available potential energy (CAPE) decrease but the surface energy fluxes from the ocean increase. The higher surface fluxes produce a wider area of radially-inflowing air in the boundary layer, which supports a larger precipitation field and the formation of outer-core spiral rainbands. The larger precipitation field translates to a larger wind field, which is likely related to the diabatic production of potential vorticity. In contrast, when the atmosphere is warmed the surface energy fluxes reduce, which ultimately inhibits the growth of the TC wind field. The higher initial CAPE and moisture content, however, allow the TC to spin up more rapidly with a compact core of intense precipitation. Thus, it is not the temperature of the atmosphere that is causing the size changes, but instead it is the higher surface energy fluxes that arise from the increased air-sea temperature difference. Diagnostics show that fluxes of angular momentum from the environment are not responsible for the simulated TC size increases, even when the gradient in Earth vorticity is included. Rather, it is the production of energy due to the fluxes from the ocean that is responsible for the TC size increases in these simulations. Finally, a larger TC will increase in size more than a smaller TC in the same environment. In the second part of the study, the environments associated with real cases of TC size change in the North Atlantic Basin were characterized. Size changes were evaluated using the Tropical Cyclone Extended Best Track Dataset, and the environments associated with these size changes were examined using the 6-hourly, ERA-Interim global reanalysis dataset. Environmental composites show that the TCs that made size changes in the deep tropics were typically associated with more environmental, mid-level humidity and higher air-sea temperature difference. The TCs that made large size changes in the extratropics were associated with highly-baroclinic environments and high mid-level moisture south of the TC-circulation center. In general, the environments that were associated with TC size increases in the North Atlantic showed similar characteristics to the size change environments simulated in the first part of this study. In addition, the presence of high, mid-level moisture in both the deep tropics and extratropics was consistent with the results of other modeling studies that have explored the impact of environmental moisture on TC size changes.
Type:
text; Electronic Dissertation
Keywords:
reanalysis; size; structure; tropical cyclone; WRF; environment; Atmospheric Sciences
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Atmospheric Sciences
Degree Grantor:
University of Arizona
Advisor:
Ritchie, Elizabeth A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleThe Environments And Associated Physical Mechanisms That Cause Size And Structure Changes In A Tropical Cycloneen_US
dc.creatorStovern, Diana Roseen_US
dc.contributor.authorStovern, Diana Roseen_US
dc.date.issued2014-
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.abstractTropical cyclones (TCs) can make significant size changes during their lifetime. Being able to accurately forecast TC size change is important for predicting the onset of storm surge as well as the spatial extent of damaging winds. TC size changes can occur from internal storm dynamics, such as eyewall replacement cycle or from changes in the synoptic environment. In this study, the impacts of changing the atmospheric temperature and air-sea temperature difference on TC size and structure are investigated. The study is conducted in two parts: the first part uses the WRF-ARW model to test the sensitivity of TC size changes to simple changes in the environment; the second part to validates the results from the first part by characterizing the environments associated with real cases of TC size change in the North Atlantic basin. It is found that when the simulated atmosphere is cooled, the initial specific humidity and convective available potential energy (CAPE) decrease but the surface energy fluxes from the ocean increase. The higher surface fluxes produce a wider area of radially-inflowing air in the boundary layer, which supports a larger precipitation field and the formation of outer-core spiral rainbands. The larger precipitation field translates to a larger wind field, which is likely related to the diabatic production of potential vorticity. In contrast, when the atmosphere is warmed the surface energy fluxes reduce, which ultimately inhibits the growth of the TC wind field. The higher initial CAPE and moisture content, however, allow the TC to spin up more rapidly with a compact core of intense precipitation. Thus, it is not the temperature of the atmosphere that is causing the size changes, but instead it is the higher surface energy fluxes that arise from the increased air-sea temperature difference. Diagnostics show that fluxes of angular momentum from the environment are not responsible for the simulated TC size increases, even when the gradient in Earth vorticity is included. Rather, it is the production of energy due to the fluxes from the ocean that is responsible for the TC size increases in these simulations. Finally, a larger TC will increase in size more than a smaller TC in the same environment. In the second part of the study, the environments associated with real cases of TC size change in the North Atlantic Basin were characterized. Size changes were evaluated using the Tropical Cyclone Extended Best Track Dataset, and the environments associated with these size changes were examined using the 6-hourly, ERA-Interim global reanalysis dataset. Environmental composites show that the TCs that made size changes in the deep tropics were typically associated with more environmental, mid-level humidity and higher air-sea temperature difference. The TCs that made large size changes in the extratropics were associated with highly-baroclinic environments and high mid-level moisture south of the TC-circulation center. In general, the environments that were associated with TC size increases in the North Atlantic showed similar characteristics to the size change environments simulated in the first part of this study. In addition, the presence of high, mid-level moisture in both the deep tropics and extratropics was consistent with the results of other modeling studies that have explored the impact of environmental moisture on TC size changes.en_US
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectreanalysisen_US
dc.subjectsizeen_US
dc.subjectstructureen_US
dc.subjecttropical cycloneen_US
dc.subjectWRFen_US
dc.subjectenvironmenten_US
dc.subjectAtmospheric Sciencesen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAtmospheric Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRitchie, Elizabeth A.en_US
dc.contributor.committeememberRitchie, Elizabeth A.en_US
dc.contributor.committeememberSerra, Yolandeen_US
dc.contributor.committeememberZeng, Xubinen_US
dc.contributor.committeememberHirschboeck, Katherineen_US
dc.contributor.committeememberMoore, Daviden_US
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