published_or_final_version / Geography and Geology / Doctoral / Doctor of Philosophy

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The effects of cumulus cloud ensembles on the dynamics of mid-latitude explosive cyclones are studied both from a diagnostic and from a theoretical point of view. / A diagnostic study of an explosive winter storm shows that significant residuals attributable to cumulus convection are present in the horizontal momentum, thermodynamic and vorticity budgets, but not in the divergence budget, and that the finite-amplitude wave is well described by linear dynamics. / A scale analysis appropriate for mid-latitude synoptic-scale waves with intense convection indicates the importance of three mechanisms by which cumulus clouds can influence these storms. These mechanisms are the thermodynamic and dynamical effects of clouds, and certain cloud-induced non-geostrophic effects. / A series of experiments with linear models of moist baroclinic instability using an idealized basic state shows the significant role of the ageostrophic terms and the important damping due to the dynamical effects of clouds. With a realistic wintertime basic state, we conclude that the different cloud forcings are necessary to account for the observed features of explosive storms.

Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 153-164). / Electronic reproduction. / Also available by subscription via World Wide Web / xviii, 164 leaves, bound ill. (some col.) 29 cm

Over the last century, increases in anthropogenic greenhouse gases and global temperature in the atmosphere has drawn our attention to changes in extra tropical cyclones which influence daily weather patterns in the mid and high latitudes and redistribute energy, momentum and moisture across the globe. This study is aimed at examining changes in extra tropical cyclones: observed over the past two decades using the NCEP-DOE reanalysis II data (NCEP2); and simulated in the CSIRO Mark2 atmosphere-ocean coupled general circulation model (GCM) with increasingCO2. Furthermore, we attempt to explore the physical mechanisms driving such changes by modelling idealised experiments with the Melbourne University atmospheric GCM. The Melbourne University cyclone finding and tracking scheme is utilised to detect and track cyclones observed in NCEP2 and simulated in the two models. / The study demonstrates significant changes in Southern Hemisphere (SH) cyclone features from 1979-2000. SH cyclones have decreased in their number at the surface but increased at the 500 hPa level. On the other hand, SH cyclone physical features such as intensity, radius and depth have significantly increased over the two decades at the mean sea level and 500 hPa level. Moreover, cyclones became vertically better organized in both hemispheres, and particularly in the SH. The changes in the characteristics of Northern Hemisphere (NH) cyclones were statistically less significant than their SH counterparts in the period of 1979-2000. / Results from the coupled climate model simulation with enhanced CO2 suggest general reductions in cyclone frequency and intensity throughout the troposphere between the surface and500 hPa level but increases in cyclone radius and organization of vertical structure. These changes are persistent throughout the entire transient run with increasing CO2 and during a 100 year stabilisation period. It is found in the CSIRO simulation with enhanced CO2 that the geographical changes of cyclone features are similar in both hemispheres and between the surface and 500 hPa level. Furthermore, we conclude that some observed changes in extra tropical cyclone features seem to follow the patterns of simulated changes with increasing CO2 from 1xCO2 to 2xCO2 particularly in the SH. / Modelling latitudinal temperature gradient at different levels of the troposphere has revealed that the warming over the tropics at the upper troposphere causes cyclone frequency and depth to increase in the high latitudes but decrease in the mid latitudes. By contrast, the warming over the high latitudes at the lower troposphere results in decreases in the cyclone features in the high latitudes but increases in them in the mid latitudes. Therefore, the warming over the tropics seems to play an important role in the changes in SH summer cyclone frequency and depth appearing in the simulation with enhanced CO2, whereas the warming over both tropics and high latitudes affects the changes in SH winter cyclone features. In the NH, the change in latitudinal temperature gradient seems less influential in the changes of cyclone features than it does in the SH.

Thesis (Ph. D - Atmospheric Sciences) - University of Arizona. / Includes bibliographical references (leaves 139-146).

Thesis (Ph.D.) -- James Cook University, 2004. / Appendix 6 contained on CD-ROM. Typescript (photocopy). Bibliography: leaves 283-299.

Thesis (Ph.D.)--George Mason University, 2008. / Vita: p. 320. Thesis director: Michael Summers. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computational Sciences and Informatics. Title from PDF t.p. (viewed July 3, 2008). Includes bibliographical references (p. 291-319). Also issued in print.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 255-263).

Thesis (M.S. in Meteorology)--Naval Postgraduate School, June 1990. / Thesis Advisor(s): Wash, Carlyle H. Second Reader: Nuss, Wendell L. "June 1990." Description based on title screen as viewed on October 19, 2009. DTIC Indicator(s): Weather forecasting, computerized simulation, cyclogenesis, ERICA (Experiment on Rapidly Intensifying Cycloner over the Atlantic), NORAPS (Naval Operational Regional Atmospheric Prediction System), Theses. Author(s) subject terms: Rapid cyclogenesis, ERICA, NORAPS. Includes bibliographical references (p. 77-79). Also available in print.