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91.
92.
Current knowledge of the chemistry of the stratosphere is reviewed using measurements from the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment to test the accuracy of our treatment of processes at mid-latitudes, and results from the Airborne Antarctic Ozone Experiment (AAOE) to examine our understanding of processes for the polar environment. It is shown that, except for some difficulties with N2O5 and possibly ClNO3, gas phase models for nitrogen and chlorine species at 30°N in spring are in excellent agreement with the data from ATMOS. Heterogeneous processes may have an influence on the concentrations of NO2, N2O5, HNO3, and ClNO3 for the lower stratosphere at 48°S in fall. Comparison of model and observed concentrations of O3 indicate good agreement at 30°N, with less satisfactory results at 48°S. The discrepancy between the loss rate of O3 observed over the course of the AAOE mission in 1987 and loss rates calculated using measured concentrations of ClO and BrO is found to be even larger than that reported by Anderson et al. (1989, J. geophys. Res. 94, 11480). There appear to be loss processes for removal of O3 additional to the HOC1 mechanism proposed by Solomon et al. (1986, Nature 321, 755), the ClO-BrO scheme favored by McElroy et al. (1986, Nature 321, 759), and the ClO dimer mechanism introduced by Molina and Molina (1987, J. phys. Chem. 91, 433). There is little doubt that industrial halocarbons have a significant impact on stratospheric O3. Controls on emissions more stringent than those defined by the Montreal Protocol will be required if the Antarctic Ozone Hole is not to persist as a permanent feature of the stratosphere. 相似文献
93.
94.
Theoretical models are attempted for eight moderate excitation planetary nebulae which have been intensively observed with the image-tube scanner at Lick and in other investigations. The models are uniform density structures, often truncated, with central star energy distributions and chemical compositions so adjusted as to give an optimum fit with the observations. Although a satisfactory representation can be obtained for most of the stronger, usually observed lines, those arising from the 3p
3 configuration, specifically the nebular transitions of [Sii], [Cliii], and [Ariv], often give difficulties. A comparison with results of model predictions with those from simple, traditional procedures generally shows a good agreement, except in those instances where different judgments are made in interpreting emissions of ions of 3p
n configurations. 相似文献
95.
96.
Atmospheric composition in the turbopause regime was determined by four rocket-borne mass spectrometers, which employed shock-freezing cryo-ion sources. Number densities of N2, O2, O, Ar and CO2 are presented for these experiments. The results are compared with those of other rocket experiments taken from the literature. Ar/N2 ratios are analyzed with respect to atmospheric turbulence. Magnitude and variability of atomic oxygen layer maximum density and layer content are discussed. Variations of O densities and simultaneous Ar/N2 ratio changes are compared. Six CO2 measurements are discussed in terms of CO2/N2 ratios. 相似文献
97.
Ross PS 《Marine pollution bulletin》2004,48(7-8):806-7; author reply 808-9
98.
User generated content such as the georeferenced images and their associated tags found in Flickr provides us with opportunities to explore how the world is described in the non‐scientific, everyday language used by contributors. Geomorphometry, the quantitative study of landforms, provides methods to classify Digital Elevation Models (DEMs) according to attributes such as slope and convexity. In this article we compare the terms used in Flickr and Geograph in Great Britian to describe georeferenced images to a quantitative, unsupervised classification of a DEM, using a well established method, and explore the variation of terms across geomorphometric classes and space. Anthropogenic terms are primarily associated with more gentle slopes, while terms which refer to objects such as mountains and waterfalls are typical of steeper slopes. Terms vary both across and within classes, and the source of the user generated content has an influence on the type of term used with Geograph, a collection which aims to document the geography of Great Britain, dominated by features which might be observed on a map. 相似文献
99.
Richard J. Stancliffe Ross P. Church George C. Angelou John C. Lattanzio 《Monthly notices of the Royal Astronomical Society》2009,396(4):2313-2318
There is an apparent dichotomy between the metal-poor ([Fe/H]≤−2) yet carbon-normal giants and their carbon-rich counterparts. The former undergo significant depletion of carbon on the red giant branch after they have undergone first dredge-up, whereas the latter do not appear to experience significant depletion. We investigate this in the context that the extra mixing occurs via the thermohaline instability that arises due to the burning of 3 He . We present the evolution of [C/Fe], [N/Fe] and 12 C/13 C for three models: a carbon-normal metal-poor star, and two stars that have accreted material from a 1.5 M⊙ AGB companion, one having received 0.01 M⊙ of material and the other having received 0.1 M⊙ . We find the behaviour of the carbon-normal metal-poor stars is well reproduced by this mechanism. In addition, our models also show that the efficiency of carbon-depletion is significantly reduced in carbon-rich stars. This extra-mixing mechanism is able to reproduce the observed properties of both carbon-normal and carbon-rich stars. 相似文献