Results 1 - 10 of 717
Results 1 - 10 of 717. Search took: 0.031 seconds
|Sort by: date | relevance|
[en] A critical analysis of the current state of theoretical studies on stratospheric ozone destruction was performed. The main principles of the theory of chain processes in the ozone layer were proposed and compared with the data of other authors. The goal of this study was to prove the validity of the developed principles by critically comparing the results with the available literature data. The existing methods for determining the rate of ozone destruction in the catalytic cycles and their chain length often neglect the chain nature of the destruction of stratospheric ozone. This leads to significant errors in the calculated data. The paper presents the algorithms for correct determination of the above values based on the laws of chemical kinetics and the theory of chain processes.
[en] A brief introduction is given on how the ozone layer formed and about the factors depleted ozone layer such as chloro bromo compounds and so on; then, it follows the processes which destroy the troposphere. The damaging effect of ultraviolet radiation is described. Finally,the action taken to reduce the depletion of ozone layer is presented
[en] Full Text: This paper presents results of measurements of solar ultraviolet radiation and its spectral distribution obtained by highy sensitive receivers of ultraviolet radiation that have been developed on the basis of laminar crystals A3B6. These investigations have been conducted in Apsheron peninsula during summer solstice and in year of higher solar activity. Our investigations showed that the developed ultraviolet receiver can be used for the creation of small-size ultraviolet dosimeters as well as the receivers for control and investigations of atmosphere ozone layer
[en] UNEP Governing Council in 1981 called for reduction in CFC use and production capacity and recommends convention for protection of ozone layer. UNEP Ad Hoc Working Group of Legal and Technical Experts for the Preparation of a Global Framework Convention for the Protection of the Ozone Layer and the same time the International Institute of Refrigeration Congress in Paris focused on ozone depletion and global warming, the Natural Resources Defence Council sued U.S. EPA for failure to protect the ozone layer as required by the Clean Air Act (UNEP, 1998a)
[en] Complete text of publication follows. The aim of our work was the evaluation of analytical performance of the Cavity Ring Down Spectroscopy (CRDS) using Diode Laser as a light sources. In CRDS, a laser pulse is stored in a high-finesse optical cavity containing the analyte, then the pulse decay is monitored by the detector that measures the intensity of light transmitted through one of the mirrors. In this presentation to examples of the analytical use of CRDS will be presented. The first case study is focus on the determination of fluorine, because fluorine compounds could destruct the ozone layer of atmosphere, thus increase a greenhouse effect. Fluorine atoms were produced with the use of microwave induced plasma (MIP), where plasma gas enriched in SF6 was used. The second example includes investigations of the presence of nitrogen compounds in the atmosphere and the analytical performance for the determination of NO2 and NO3 were evaluated. The important part of the measurement system build up in our laboratory was laser used as a source of light. For this purpose laser semiconductor diodes were used. In the case of the determination of NO2, blue laser operation at 415nm was used. In the case of NO3· and fluorine determination red laser operated at 662 nm and 685 nm was used. A great advantage of the semiconductor diodes laser was the possibility of retuning of the wavelength which was found as a great advantage in respect of the sensitivity of the measurements. The authors kindly acknowledge the financial support from the Ministry of Science and High Education of Poland (No. MNiSW N202 085 31/0548).
[en] The ozone column depletion over the western side of South America has been previously explained as a consequence of winds in the area of the depletion, which lead to the compression and thinning of the ozone layer. However, humidity and methane (originated in the Amazon forest and the Pacific Ocean) transported by these winds toward the stratosphere may also have a role in the ozone depletion. Oxidation of methane generates additional humidity, which in turn reacts with ozone, destroying it. Humidity and methane levels were measured by NASA and HALOE during an ozone depletion event (January 1998) that occurred along with El Nino. By analyzing these measurements, we found that, at different altitudes, changes in the humidity seem to be associated with changes in the ozone such that an increment of humidity may lead to an ozone depletion. Moreover, we found that during the event, the sum 2CH4+H2O was roughly constant only at altitudes lower than 50 km; the ratio CH4/H2O exhibited an exponential decay with the altitude that may allow assessing the generation mechanism of stratospheric humidity from methane.
[en] Before the present time disturbed state the stratospheric ozone layer over the northern hemisphere usually demonstrated three regions of high total ozone values. Estonia belonged to one of these regions. The reliable data about the geographical distribution of total ozone exist since 1957. Extrapolating them back we can speculate that our biosphere has been better protected from the ultraviolet irradiation than most part of the same latitude. A short review of the key moments of the total ozone research history has been presented. Except the chemical loss during polar spring the total ozone values are dependent on stratospheric synoptic scale motions. Negative ozone anomalies tend to coincide with low pressure in stratosphere (tropospheric highs) and vice versa. On the mean heights of the ozone layer the tropical air, the mid latitude air and the air inside the winter polar vortex are strongly isolated. The exchange through these strong wind barriers is possible only in the form of thin filaments or air tongues. Those filaments of ozone poor air from tropical latitudes are the main reason of ozone mini holes during most part of year. The results of total ozone variations in 1994-1996 have been discussed. In all cases the values in spring often are below the undisturbed latitude mean. In summer the results are close to the mean but especially in summer 1995 several synoptic scale mini holes were recorded (author)
[en] The summary of achievements in the field of ozone layer protection in atmosphere is presented. The stratosphere ozone changes above Kazakhstan territory on the base of ozone-measuring station data during 1973-1992 are given. It was established that the sum ozone departures have been decreased on minus of 3,2 % every year in comparison with average values. This process can conduct to increase of ultraviolet radiation coming to lower troposphere layers