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J. A. Pyle 《Pure and Applied Geophysics》1980,118(1):355-377
Results are presented from a two-dimensional, time-dependent model of the atmosphere which has been used to investigate perturbations to the ozone layer due to chlorofluorocarbons. The unperturbed stratosphere is modelled well with the observed features of the ozone distribution reproduced. The main features of the perturbation calculations are the large latitudinal and seasonal variations found in the modelled ozone reductions with greates reductions where the total ozone amounts are largest. The importance of at least a two-dimensional study in problems of this kind is stressed and the important role of dynamical and radiative processes, as well as chemical, is indicated. 相似文献
2.
Anthony H. McDaniel Chris A. Cantrell James A. Davidson Richard E. Shetter Jack G. Calvert 《Journal of Atmospheric Chemistry》1991,12(3):211-227
The infrared absorption cross-sections for eight commonly used halogenated methanes and ethanes have been measured as a function of temperature from 203 to 293 K. High resolution spectra (0.03 cm-1) have been used to derive integrated band strengths and peak cross-sections associated with the spectral features in the infrared region from 600 to 1500 cm-2. The values obtained in this study are compared to those from previous reports, and recommendations are made for uses in atmospheric sensing and radiative energy transfer models. The observed temperature dependence in the spectral features is also discussed. 相似文献
3.
Intrinsic aquifer vulnerability assessment: validation by environmental tracers in San Miguel de Allende, Mexico 总被引：1，自引：0，他引：1
Jürgen Mahlknecht Ma. Guadalupe Medina-Mejía Jaime Gárfias-Solis Irene Cano-Aguilera 《Environmental Geology》2006,51(3):477-491
Vulnerability maps are important tools for water decision makers and land-use planners for protection of aquifers against contamination. The vulnerability map, according to the parametric method SINTACX for assessing intrinsic aquifer vulnerability, was validated in a case study with chlorofluorocarbon tracer technologies (CFC-11, CFC-12, and CFC-113) of groundwater. The tested area was the 1,295 km2 volcano-sedimentary area of San Miguel de Allende (SMA), Mexico. From the results of this area, it appears that the vulnerability map is in parts inconsistent with the underlying groundwater flow system. Thus, the vulnerability map was corrected with tracer information. The validated vulnerability map indicates that the degree of vulnerability varies from low to moderate-high. Low vulnerability values are found in the graben extending from north to south along the SMA fault system and high values in recharge areas southeast and northwest of the study area. The investigation is a demonstration that the scientific reliability of results of the parametric method can be improved by validation with tracer techniques representing the groundwater dynamics. The flexible structure of SINTACX allows revising and adjusting scores and weights of the parameter maps to rebuild a new vulnerability map consistent with the hydrological system. 相似文献
4.
《Comptes Rendus Geoscience》2018,350(7):384-392
The atmospheric observations of ozone-depleting substances (ODSs) have been essential for following their atmospheric response to the production and use restrictions imposed by the Montreal Protocol and its Amendments and Adjustments. ODSs have been used since the first half of the 20th century in industrial and domestic applications. However, their atmospheric growth went unnoticed until the early 1970s, when they were discovered using gas chromatograph-electron capture detection (GC-ECD) instruments. Similar instrumentation formed the basis of global flask and in situ measurements commenced by NOAA and ALE/GAGE/AGAGE in the late 1970s. The combination of these networks, supported by a number of other laboratories, has been essential for following the tropospheric trends of ODSs. Additionally, ground-based remote sensing measurements within NDACC and aircraft-based observation programs have been crucial for measuring the evolution of the ODS abundances over the entire atmosphere. Maintaining these networks at least at their current state is vital for ensuring the on-going verification of the success of the Montreal Protocol. 相似文献
5.
Circulation and Mixing of Water Masses of Tatar Strait and the Northwestern Boundary Region of the Japan Sea 总被引：2，自引：0，他引：2
The deep waters of the northern portions of the Japan Sea are examined. It is found that the flow regime south of the southern
Tatar Strait region is generally cyclonic in the upper ocean, with only weak flows present below depths of a few hundred meters.
The Japan Sea appears to be remarkably well-mixed below depths of a few hundred meters, both horizontally and vertically.
Based on chlorofluorocarbon measurements, it is concluded that the deep waters of the Japan Sea have been only weakly ventilated
in recent decades. Results from a simple box model suggest two possible scenarios for the ventilation of the Japan Sea since
the 1930s. In the first scenario, deep ventilation of the Japan Sea was relatively weak, but constant, from the 1930s to the
present, with a deep-water residence time of approximately 500 years. In the second scenario, ventilation was relatively vigorous
through the mid-1960s, with a deep-water residence time of approximately 100 years; after the mid-1960s, the ventilation of
the deep waters stopped. The model results are consistent with the idea that presently the ventilation of the deep water of
the Japan Sea is weak or nonexistent.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
John L. Bullister David P. Wisegarver 《Deep Sea Research Part I: Oceanographic Research Papers》2008,55(8):1063-1074
Methods are described for the rapid (11 min) automated shipboard analysis of dissolved sulfur hexafluoride (SF6) in small volume (200 cm3) seawater samples. Estimated precision for the SF6 measurements is 2% or 0.02 fmol kg−1 (whichever is greater). The method also allows for the simultaneous measurement of chlorofluorocarbon-11 (CFC11) and chlorofluorocarbon-12 (CFC12) on the same water sample, with significantly improved sensitivity over previous analytical methods. 相似文献
7.
Translating CFC-based piston ages into probability density functions of ground-water age in karst 总被引：1，自引：0，他引：1
Temporal age distributions are equivalent to probability density functions (PDFs) of transit time. The type and shape of a PDF provides important information related to ground-water mixing at the well or spring and the complex nature of flow networks in karst aquifers. Chlorofluorocarbon (CFC) concentrations measured for samples from 12 locations in the karstic Madison aquifer were used to evaluate the suitability of various PDF types for this aquifer. Parameters of PDFs could not be estimated within acceptable confidence intervals for any of the individual sites. Therefore, metrics derived from CFC-based apparent ages were used to evaluate results of PDF modeling in a more general approach. The ranges of these metrics were established as criteria against which families of PDFs could be evaluated for their applicability to different parts of the aquifer. Seven PDF types, including five unimodal and two bimodal models, were evaluated. Model results indicate that unimodal models may be applicable to areas close to conduits that have younger piston (i.e., apparent) ages and that bimodal models probably are applicable to areas farther from conduits that have older piston ages. The two components of a bimodal PDF are interpreted as representing conduit and diffuse flow, and transit times of as much as two decades may separate these PDF components. Areas near conduits may be dominated by conduit flow, whereas areas farther from conduits having bimodal distributions probably have good hydraulic connection to both diffuse and conduit flow. 相似文献
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