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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Solar cycle variation of stratospheric ozone: Multiple regression analysis of long-term satellite data sets and comparisons with models

Soukharev, B. E., Hood, L. L. 31 October 2006 (has links)
Previous multiple regression analyses of the solar cycle variation of stratospheric ozone are improved by (1) analyzing three independent satellite ozone data sets with lengths extending up to 25 years and (2) comparing column ozone measurements with ozone profile data during the 1992–2003 period when no major volcanic eruptions occurred. Results show that the vertical structure of the tropical ozone solar cycle response has been consistently characterized by statistically significant positive responses in the upper and lower stratosphere and by statistically insignificant responses in the middle stratosphere (∼28–38 km altitude). This vertical structure differs from that predicted by most models. The similar vertical structure in the tropics obtained for separate time intervals (with minimum response invariably near 10 hPa) is difficult to explain by random interference from the QBO and volcanic eruptions in the statistical analysis. The observed increase in tropical total column ozone approaching the cycle 23 maximum during the late 1990s occurred primarily in the lower stratosphere below the 30 hPa level. A mainly dynamical origin for the solar cycle total ozone variation at low latitudes is therefore likely. The amplitude of the solar cycle ozone variation in the tropical upper stratosphere derived here is somewhat reduced in comparison to earlier results. Additional data are needed to determine whether this upper stratospheric response is or is not larger than model estimates.
72

Spatial and temporal distribution of tropospheric ozone over Southern Africa

Bundi, Peter Miriti 16 November 2006 (has links)
Student Number: 0201936W - MSc research report - School of Geography, Archaeology and Environmental Sciences - Faculty of Science / Tropospheric ozone over southern Africa is characterised using the Southern Africa Regional Science Initiative (SAFARI) 2000 aircraft datasets collected from surface to just above the boundary layer, and satellite remotely sensed ozone column depth. Ozonesonde datasets for Irene, South Africa; Lusaka, Zambia; Nairobi and Malindi, both Kenyan stations were, used to supplement the aircraft and satellite data. The period studied is the dry biomass burning season between August and September, 2000 Source areas of ozone precursors have been identified by trajectory analysis. Fivepoint, back trajectory clusters in the region reveal well-defined air mass transport corridors. Enhanced ozone concentrations, above 70 ppb, were regularly encountered in the lower troposphere (3.5 km above ground level) in air masses distributed over the sub-region by distinct re-circulation pathways, which prevailed during the study period. Occasional, episodes of significant higher ozone pollution, above 100 ppbv are identified. Savannah fire products transported from seasonal biomass burning regions of western Zambia, northern Zimbabwe and Mozambique have been found to be the major sources of ozone pollution over the sub-region. Another source, though on a lesser scale, is the Highveld industrial region of South Africa. In situ air observations established that the western and eastern sectors of the southern Africa, north of 23°S latitude, were the major sources of regional ozone precursor gases. The regions southwards of 23°S were observed to have lower ozone pollution.
73

Solid reagents for ozone analysis

Wallace, Steven Leo January 2011 (has links)
Digitized by Kansas Correctional Industries
74

Drivers of future stratospheric and tropospheric ozone

Banerjee, Antara January 2015 (has links)
No description available.
75

Ozone Depletion and Global Warming

Fow, Alista John January 2006 (has links)
Abstract This thesis examines global warming and the possible contribution that ozone depletion provides to this warming. An examination is performed to determine the extent of any warming/cooling events within the Earth-atmosphere system. The change in energy corresponding to this warning of the Earth- atmosphere system is estimated as being equivilent to an increase of mean solar input of 0.22W/m2. This is compared to the predicted changes of solar input for the two most common global warming scenarios: greenhouse gases and solar irradiance variance; and for a less well explored scenario, snow-ice albedo change. Examination of ozone depletion data shows that an absence of ozone in the stratosphere produces an increase in UV-B radiation at the surface of the Earth. This increase in UV-B light has not previously been thourougly examined in any of the global warming scenarios. This is presented as a fourth scenario for global warming. An analytical three layer model of the Earth-atmosphere, based on an earlier two layer model, is developed. Using this model it is determined that greenhouse gases, solar irradiance, snow-ice albedo feedback and ozone depletion can cause warming of the Earth's atmosphere. After comparison with other models, a snow-ice albedo mechanism is incorporated into the three layer model. This produces an amplification effect of any warming that occurs. Compared to the observed increase of surface temperature between 1975-2000 of 0.55 K, the model using a snow-ice albedo feedback, produced an increase of temperature of 1.4 K for greenhouse gases, 0.294 K for a solar irradiance increase and 0.119 K caused by a decrease in the ozone layer. Of the greenhouse gas, solar irradiance and ozone depletion scenarios, ozone depletion demonstrates the most realistic relative changes with a cooling of the stratosphere and a warming of the troposphere and Earth's surface as has been observed. It is concluded that ozone depletion is likely for a reasonable part of observed global warming.
76

The effects of ozone on the growth, rhizosphere population dynamics, and mycorrhizal colonization of wheat

Kimball, Shannon M. 08 December 1994 (has links)
Graduation date: 1995
77

Modelling tropospheric ozone and related tracers in a 3-D chemical transport model : an investigation of biogenic NOx and VOC modelling techniques and changing emissions scenarios /

Little, Magda Caroline Sadek. January 1900 (has links)
Thesis (Ph.D.)--York University, 20--. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 234-239). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99205
78

Development and characterization of the OSIRIS USASK Obsevatory

Stoicescu, Michael Barry 06 July 2006
The OSIRIS instrument on board the Odin satellite uses limb viewing techniques to measure scattered sunlight and so determine the vertically resolved concentrations of atmospheric constituents including ozone. Initially, a proof of concept instrument was built and tested. This instrument, the Developmental Model, is now housed at the third floor clean room of the Physics Building on the University of Saskatchewan campus. <p> The Developmental Model was incorporated into a system designed to monitor scattered sunlight above Saskatoon. The system was set up to transmit skylight to the Developmental Model using a fiber optic cable and to perform all measurements automatically and with minimal user interaction. The system was calibrated to determine the pixel to wavelength response. Characterizations of the point spread function and relative intensity response of the detector were also made. A shutter system was designed and constructed to measure the detector dark current. An enclosure was built on the top of the Physics Building to provide a weather proof environment and so allow data collection throughout the year. Zenith sky measurements were taken during twilight hours to provide information on the depth of absorption in the Chappuis band, an indicator of the total ozone column. The absorption depth was converted to a Dobson Unit measurement for the ozone column. <p> Analysis of collected data provides two conclusions. The first is that a measurement set in the presence of clouds shows different signatures than a clear measurement set. The second conclusion is the detection of a diurnal trend in the total ozone column with greater amounts measured in the morning. The OSIRIS USASK Observatory is now operational and collecting data for future analysis of scattered sunlight measurements above Saskatoon.
79

Development and characterization of the OSIRIS USASK Obsevatory

Stoicescu, Michael Barry 06 July 2006 (has links)
The OSIRIS instrument on board the Odin satellite uses limb viewing techniques to measure scattered sunlight and so determine the vertically resolved concentrations of atmospheric constituents including ozone. Initially, a proof of concept instrument was built and tested. This instrument, the Developmental Model, is now housed at the third floor clean room of the Physics Building on the University of Saskatchewan campus. <p> The Developmental Model was incorporated into a system designed to monitor scattered sunlight above Saskatoon. The system was set up to transmit skylight to the Developmental Model using a fiber optic cable and to perform all measurements automatically and with minimal user interaction. The system was calibrated to determine the pixel to wavelength response. Characterizations of the point spread function and relative intensity response of the detector were also made. A shutter system was designed and constructed to measure the detector dark current. An enclosure was built on the top of the Physics Building to provide a weather proof environment and so allow data collection throughout the year. Zenith sky measurements were taken during twilight hours to provide information on the depth of absorption in the Chappuis band, an indicator of the total ozone column. The absorption depth was converted to a Dobson Unit measurement for the ozone column. <p> Analysis of collected data provides two conclusions. The first is that a measurement set in the presence of clouds shows different signatures than a clear measurement set. The second conclusion is the detection of a diurnal trend in the total ozone column with greater amounts measured in the morning. The OSIRIS USASK Observatory is now operational and collecting data for future analysis of scattered sunlight measurements above Saskatoon.
80

Ozone (o3) efficacy on reduction of phytophthora capsici in recirculated horticultural irrigation water

McDonald, Garry Vernon 15 May 2009 (has links)
Microorganisms that cause plant disease have been isolated in recirculated irrigation water and increase the risks of disease incidence in horticultural operations. Ozone is an effective oxidizer used to disinfect drinking water supplies and treat industrial wastewater. The objective of this research was to investigate using ozone gas as part of a strategy to reduce the incidence of Phytophthora deBary in recirculated irrigation water. An isolate of Phytophthora capsici Leonian was cultured to induce sporulation. Spore dilutions were placed in aliquots of reverse osmosis water and bubbled with ozone gas (O3) to concentrations of 0 to 1.5 mg·L-1. Ozonated samples were plated and observed for colony forming units. Increasing ozone concentrations reduced the number of colony forming units to 0 at 1.5 mg· L-1 03. Turbidity effects on efficacy on Phytophthora capsici were tested using bentonite clay at 0 to 2.0 nephelometric turbidity units and ozone concentrations of 0 to 1.5 mg· L-1. Increasing bentonite did not affect the efficacy of increasing ozone concentrations on reducing colony formation to 0 at 1.5 mg·L-1 O3. Bioassays using Phytophthora capsici on Capsicum annuum L. seedlings confirmed apparent pathogenicity. Reverse osmosis water, containing a soluble fertilizer at 0 to 300 mg· L-1 N, was ozonated to concentrations of 0 to 1.5 mg·L-1 O3 and used to irrigate Chrysanthemum x morifolium T. de Romatuelle. Increasing ozone concentrations did not interact with increasing fertilizer levels to affect the final growth parameters. Chrysanthemum exposed to ozone gas concentrations of 0.5 to 1.5 mg·L-1 showed symptomatic ozone damage. Complete soluble fertilizer solutions with micronutrients were ozonated from 0 to 1.5 mg·L-1 O3 and analysed for nutrient content. Increasing ozone levels did not interact with fertilizers to affect macronutrients. Increasing ozone interacted with iron at a high fertilizer level. Ozone did not affect the efficacy of paclobutralzol in controlling growth in Viola x wittrockiana. Ozone was effective in controlling Phytophthora capsici in recirculated irrigation water with minimum impact on plant growth. Adjustments in fertility regiemes may be needed to counteract the oxidizing affect of ozone on micronutrients.

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