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The polar vortex is a large scale cyclone located in the middle atmosphere near to the planet’s geographic poles. These vortices form during the hemispheric winter and break down in the spring of the following year. They may also break down in mid winter, causing a sudden stratospheric warming event (SSW). The vortex is thought to be preconditioned leading up to these warming events, resulting in the breakdown of the vortex. Integral diagnostics are used to investigate the stripping of air from the vortex as part of this preconditioning. Contour diagnostics of mass and circulation are calculated using ERA-40 reanalysis data for the stratosphere. The edge of the vortex is easily identifiable in these diagnostics as a high gradient of Ertel’s potential vorticity (PV), and the warming events are also clearly visible. From these the amount of air removed from the vortex is determined from the balance equation of the mass integral. These terms show that there are significant amounts of air removed from the vortex, with several stripping events identifiable in them through the winter, especially in those during which a major sudden warming event occurred. These stripping events can be seen in corresponding PV maps, where tongues of PV can be seen to be stripped from the vortex and mixed into the surrounding surf zone of turbulent air. From the integral diagnostics a Lagrangian measure of the meridional circulation in the stratosphere is also calculated. In the final part of the thesis a shallow water model is used to investigate a quantitative link between forcing and the amount of stripping of the vortex. It is found that when the forcing is large enough there is significant stripping of mass from the vortex. This does not lead to SSWs in all cases, and the total amount of stripping is not found to be proportional to the maximum amplitude of the forcing.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

In the thesis, epitaxial ZnO films were grown by chemical vapor deposition method (CVD) on LiGaO2 (001) substrate. Zinc 2,4-pentanedionate monohydrate [Zn (C5H7O2) 2. H2O] , used as the zinc precursor, was vaporized at the temperature between 130 to 140¢J. Then the vapor was carried by a mixture of N2/O2 gas flow into the furnace where the (001) LGO substrate located. The parameters of growth temperature, growth pressure and growth time were adjusted to found the best ZnO films growth conditions. After CVD growth, the crystal structure, crystal quality, surface morphology, optical properties, surface roughness and micro-structure properties of the specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), atomic force microscopy (AFM) and transmission electron microscopy (TEM). This study was divided into three parts. In the first parts, the dependence of growth characteristics on the different growth temperatures was investigated. The best surface morphology and crystal quality of ZnO films were grown under the growth temperature of 550 ¢J. In the second parts, the growth of ZnO films under various pressures was investigated. High orientation (0002)ZnO films were grown at lower growth pressure of 50 torr. In the third parts, the dependence of growth time on the ZnO films quality was investigated under growth temperature of 550 ¢Jand growth pressure of 50 torr.

Both non-polar (10-10) (m-plane) and polar (0001) (c-plane) zinc oxide (ZnO) have a good lattice match with lithium aluminum (LiAlO2, LAO) (200) substrate, so it is difficult to control the epitaxial orientation. Therefore, this research is to explore how the growth parameters influence on the crystal orientation of ZnO film grown by plasma assisted molecular beam epitaxy. The experimental results show that m-plane ZnO can be grown with low zinc flux and low oxygen pressure. Increasing zinc flux and oxygen pressure will lead to increase in growth rate, and consequently, c-plane ZnO will nucleate on the substrate besides m-plane zinc oxide. The substrate temperature is one of the main factors that influence the choice of zinc oxide epitaxial orientation. High temperature will promote the m-plane zinc oxide nucleation, while low temperature will conduct to the c-plane zinc oxide nucleation. Under low zinc flux and low oxygen pressure, epitaxy of ZnO with different crystalline orientations can be achieved through changing the substrate temperature. The surface morphology and roughness of the substrate will affect the particle size and surface morphology of ZnO epilayers. When the substrate is smooth, the crystal size of the epitaxial film is large and the surface is flat with many rectangular stripes, taking on the platform-like morphology. If the substrate is rough with many scratches, the particle size becomes small and the surface is granular-like and rather rough. Furthermore, when the substrate is rough, it is difficult to control the different orientations of ZnO epitaxial films through changing the substrate temperature.

Understanding the spatiotemporal pattern of near-surface ozone is the key part of polar atmospheric environment. The near-surface ozone can be depleted by the catalytic bromine chemistry in the heterogeneous phase but produced due to the snow photochemistry of nitrogen. In addition to the local chemistry, ozone pattern is also affected by regional meteorology and air-mass transport. Since the polar region is quite sensitive to the climate change, these conditions can be also affected by climate change and variability. Based on the analysis of large amount of dataset combined with in-situ observations, satellite measurements, model simulations, and global reanalysis data, the characteristics of polar ozone pattern and relation to the regional and large-scale atmospheric situations were investigated. At first, the characteristics of tropospheric ozone depletion events (ODEs) in the Arctic spring (April 2008) with satellite measured BrO and backtrajectories. Analysis of these data shows that the ODEs are due to either local halogen chemistry or short-range transport from adjacent high-BrO regions. Sometimes local ozone loss is surprisingly deep, particularly the unstable boundary layer at Churchill seems contribute to free-tropospheric BrO. Continually the influences of large-scale atmospheric patterns to the polar surface ozone are investigated. In years with frequent ODEs at Barrow and Alert, the WP teleconnection pattern is usually in its negative phase, during which the Pacific jet is strengthened but the storm track from western Pacific is weakened. Both factors tend to reduce the transport of ozone-rich airmass from mid-latitudes to the Arctic, creating a favorable environment for the Arctic ODEs. Comparison between Barrow and Alert shows the initiation of ODEs in spring is decided by the solar intensity and the termination is by the surface air temperature. Monthly frequency of ODEs also indicate the wind strength from the Arctic Ocean is largely influential to ODEs. The surface ozone at South Pole reveals year-round reversal trends during 3 decades, which is consistent with what lower-tropospheric temperature shows. Their strong correlation implies the possibility of large meridional mixing in warm conditions, which enhances the background level of ozone and nitrogen at South Pole.

No description available.

The exchange of carbon dioxide between the atmosphere and the polar caps on Mars creates a seasonal cycle of growth and retreat of the polar caps. As the major component of the Martian atmosphere, CO2 condenses in the polar regions of the planet during the winter seasons and precipitates as CO2 frost. It then sublimes during the spring and summer seasons in response to solar radiation. Through natural radioactivity or when exposed to cosmic rays, elements in the Martian near-subsurface (uppermost meter) emit gamma rays with distinct, characteristic energies. The Gamma Ray Spectrometer (GRS) onboard the 2001 Mars Odyssey satellite is used to measure the gamma rays coming from the Martian regolith to calculate elemental distributions, abundances, and temporal variations in the gamma ray flux. Changes in the CO2 frost over time can be quantified by observing attenuation effects of H (2223 keV hydrogen) and 40K (1461 keV potassium) gamma ray signals transmitted through various depths of polar CO2 overburden throughout the Martian seasons.Conclusions are drawn about the spatial extent, column density, and mass of Mars' seasonal polar caps as a function of time utilizing GRS data. Columnar thickness and mass results are discussed and plotted for latitudes including +/-60 degrees and poleward. GRS observations are compared to predictions from the NASA Ames Research Center Mars General Circulation Model (ARC GCM) and to similar experimental results from the Mars Odyssey High Energy Neutron Detector (HEND) and the Neutron Spectrometer (NS). Models for north and south polar atmosphere and regolith distributions are incorporated, and the results indicate that the assumption of a 100% H2O-ice residual cap underlying the seasonal frost in the north is accurate. The GRS CO2 frost observations are in good agreement with the other studies mentioned, in particular for the timing of the beginning of frost deposition to the complete sublimation of surface CO2 back into the atmosphere. The total amount of condensed CO2 mass derived from GRS data is on the order of 6.0 x 10^15 kg and verifies previous reports that ~25% of the total Martian exchangeable-CO2 reservoir participates in the ground-atmosphere cycle.

Inuit estimates of polar bear characteristics from tracks could complement ongoing capture-mark-recapture methods to frequently monitor polar bear populations in response to climate-induced habitat changes. Before the inclusion of these Inuit track estimates, they need to be evaluated for reliability and accuracy. Building on previous work, which showed increased reliability among active Inuit hunters, this thesis research reports i) reliability in estimates of sex, age, size, and age of track of a larger number of tracks by a larger number of Inuit hunters; ii) preliminary accuracy assessments of sex and size estimates; iii) semi-structured interviews with Inuit hunters regarding their polar bear tracking experience and techniques; and iv) potential relations between Inuit hunting experience and reliability and accuracy in diagnosing tracks. The Inuit hunters were reliable and consistent as a group in making estimates of sex (α=0.74 and mean corrected item-total correlation=0.45), age (α=0.81 and mean corrected item-total correlation=0.63), and size (α=0.91 and mean corrected item-total correlation=0.73), as well as age of track estimates with the exclusion of a single participant (α=0.85 and mean corrected item-total correlation=0.63). Preliminary accuracy assessments suggest Inuit hunters are generally accurate in their estimates of sex (mean 65.28% agreement with genetic sex estimates) and potentially size from tracks, warranting further efforts to determine accuracy in these estimates as well as age and age of track. Semi-structured, open-ended interviews with each hunter revealed they use similar tracking techniques, which may explain their high agreement in making estimates. In addition, Inuit tracking experience and the use of particular tracking methods may correlate with individual reliability and accuracy in track diagnoses. These results suggest the information that Inuit hunters provide may inform any tracking-based polar bear survey. / Thesis (Master, Biology) -- Queen's University, 2010-08-15 13:06:07.948

Global polar bear (Ursus maritimus) population numbers are expected to decline steadily over the next 50 years. A noninvasive genetic survey of polar bear numbers may be a useful addition to traditional aerial capture mark recapture (CMR) surveys undertaken throughout the Canadian polar bear population. We attempted a pilot study of noninvasive genetic survey techniques in M’Clintock Channel between May-June 2006-2009. Throughout the survey, we compared our values to the most recent (CMR) survey, conducted by Taylor et al. (2006) between March-June 1998-2000 where 133 cubs, sub-adults and adults were tagged. A total population size of 300 bears was estimated from this aerial CMR survey (Taylor et al. 2006). We found noninvasive sampling stations are sufficient for the capture of a large amount of data on individual bears in an area. Across 4 years, we collected a total of 300 hair samples, and found between 59 and 82 individual bears entered our sampling stations, depending on the stringency of our identification parameters. We estimated genotyping error from duplicated samples, and found this was low (range: 0%-6%), but large enough to not be ignored. There appeared to be a discrepancy between the capture ratio of male adult bears; the CMR survey (1998-2000) captured 25% male bears, while we estimated approximately 64% of our captured bears were male. We felt the most likely explanation of this result is that our traps have a sex bias. However, further research is required to confirm this hypothesis. On the whole, our methods are very important for the management of polar bears, but more research must be done before it can be fully implemented. / Thesis (Master, Biology) -- Queen's University, 2010-12-23 15:35:50.16