I. Microphysics of frost metamorphism : applications to Triton and Mars. II. A global analysis of the ozone deficit in the upper stratosphere and lower mesosphere. III. The diabatic circulation in the stratosphere as diagnosed from microwave limb sounder data

[摘要] The present thesis reflects work I have done as a graduate student at Caltech. It is devoted to two broad subjects, planetary frost metamorphism and the terrestrial middle atmosphere, and consists of three papers.Paper I considers frost metamorphism on the surfaces of Triton and Mars. Based on an analysis of the microphysical processes involved in pressureless sintering, it is concluded that fine-grained nitrogen and carbon dioxide frosts can undergo seasonal metamorphism into semitransparent layers on the surface of Triton and in the martian seasonal polar caps, respectively. The presence of such layers explains a host of facts about Triton's surface and about the martian seasonal caps. The Triton portion of the paper has been published in the Journal of Geophysical Research, while the Mars portion has been submitted to Icarus.Paper II is devoted to elucidating a long-standing issue in the terrestrial middle atmosphere chemistry, the so-called "ozone deficit problem." Based on an analysis of data acquired by the Limb Infrared Monitor of the Stratosphere (LIMS) instrument between October 1978 and May 1979, it is concluded that current photochemical models systematically underestimate observed ozone abundances in the upper stratosphere and lower mesosphere. Three modifications to the accepted photochemical scheme, capable of providing a global solution to this problem, are proposed and discussed. This paper is in press by the Journal of Geophysical Research.Paper III differs from the other two in that it reports on results from an ongoing research effort. It considers the diabatic circulation in the stratosphere and lower mesosphere, using ozone and temperature measurements acquired by the Microwave Limb Sounder (MLS) instrument onboard the Upper Atmosphere Research Satellite (UARS). The present study extends past analyses of the diabatic circulation by considering a full annual cycle November 1991 - November 1992 and by taking advantage of the high vertical resolution of MLS data. In the tropical upper stratosphere and lower mesosphere, a semiannual oscillation (SAO) is observed in the computed circulation, with the region of downwelling reaching maximum spatial extent ~1 month before the equinox. The projected lifetime of UARS should enable the present analysis to be extended to several SAO cycles.

[发布机构] University:California Institute of Technology;Department:Geological and Planetary Sciences

[关键词] Planetary Science and Geophysics