Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 157-165). Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 47-49). Also available on the World Wide Web.

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Joseph A. Shaw. Includes bibliographical references (leaves 91-94).

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Philip Durkee. Includes bibliographical references (p. 79-83). Also available online.

Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, December 1994. / "December 1994." Thesis advisor(s): Teddy R. Holt. Bibliography: p. 79-81. Also available online.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, June 2003. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph.D.) -- McMaster University, 2000. / Includes bibliographical references (leaves 141-147). Also available via World Wide Web.

Arctic clouds are poorly represented in numerical models due to the complex, small-scale interactions which occur within them. Modelled cloud fractions are often significantly less than observed in this region; therefore, the radiative budget is not accurately simulated and forecasts of the melting cryosphere are fraught with uncertainty. Our ability to accurately model Arctic clouds can be improved through observational studies. Recent in situ airborne measurements from the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are presented in this thesis to improve our understanding of the cloud microphysical interactions unique to this region. Aerosol-cloud interactions - where aerosol particles act as ice nucleating particles (INPs) or cloud condensation nuclei (CCN) - are integral to the understanding of clouds on a global scale. In the Arctic, uncertainties caused by our poor understanding of these interactions are enhanced by strong feedbacks between clouds, the boundary layer, and the sea ice. In the Arctic spring, aerosol-cloud interactions are affected by the Arctic haze, where a stable boundary layer allows aerosol particles to remain in the atmosphere for long periods of time. This leads to a heightened state of mixing in the aerosol population, which affects the ability of particles to act as INPs or CCN. Aerosol particle compositional data are presented to indicate which particles are present during the ACCACIA campaign, and infer how they may participate in aerosol-cloud interactions. Mineral dusts (known INPs) are identified in all flights considered, and the dominating particle classes in each case vary with changing air mass history. Mixed particles, and an enhanced aerosol loading, are identified in the final case. Evidence is presented which suggests these characteristics may be attributed to biomass burning activities in Siberia and Scandinavia. Additionally, in situ airborne observations are presented to investigate the relationship between the Arctic atmosphere and the mixed-phase clouds - containing both liquid cloud droplets and ice crystals - common to this region. Cloud microphysical structure responds strongly to changing surface conditions, as strong heat and moisture fluxes from the comparatively-warm ocean promote more turbulent motion in the boundary layer than the minimal heat fluxes from the frozen sea ice. Observations over the transition from sea ice to ocean show that the cloud liquid water content increases four-fold, whilst ice crystal number concentrations, N_ice, remain consistent at ~0.5/L. Following from this study, large eddy simulations are used to illustrate the sensitivity of cloud structure, evolution, and lifetime to N_ice. To accurately model mixed-phase conditions over sea ice, marginal ice, and ocean, ice nucleation must occur under water-saturated conditions. Ocean-based clouds are found to be particularly sensitive to N_ice, as small decreases in N_ice allow glaciating clouds to be sustained, with mixed-phase conditions, for longer. Modelled N_ice also influences precipitation development over the ocean, with either snow or rain depleting the liquid phase of the simulated cloud.

We conduct an investigation into the role that turbulence plays in the formation of stars. In small clouds, with masses of ~ 30 Mʘ and where the turbulence is only injected at the start, we find that the turbulence does not trigger star formation. Instead, the dissipation of the kinetic energy allows the mean Jeans mass of the cloud to control the formation of stars. The equipartition of the kinetic and thermal energies in the final stages before star formation, allows the pre-protostellar clumps to fragment. Binary and multiple systems are thus a natural product of star formation in a turbulent environment. We find that globally unbound clouds can be the sites of star formation. Furthermore the star formation efficiency is naturally less than 100%, thus in part providing an explanation for the low efficiency in star forming regions. Globally unbound GMCs not only form stars, and naturally disperse, within a few crossing times, but also provide a mechanism for the formation of OB associations.

Made available in DSpace on 2014-10-09T12:34:16Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:20Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP