Chemical Ozone Loss in the Arctic Winter 1994/95 as Determined by the Match Technique     

M. Rex  P. Von Der Gathen  G.O. Braathen  N.R.P. Harris  E. Reimer  A. Beck  R. Alfier  R. Krüger-carstensen  M. Chipperfield  H. De Backer  D. Balis  F. O'Connor  H. Dier  V. Dorokhov  H. Fast  A. Gamma  M. Gil  E. Kyrö  Z. Litynska  I.S. Mikkelsen  M. Molyneux  G. Murphy  S.J. Reid  M. Rummukainen  C. Zerefos 《Journal of Atmospheric Chemistry》1999,32(1):35-59

The chemically induced ozone loss inside the Arctic vortex during the winter 1994/95 has been quantified by coordinated launches of over 1000 ozonesondes from 35 stations within the Match 94/95 campaign. Trajectory calculations, which allow diabatic heating or cooling, were used to trigger the balloon launches so that the ozone concentrations in a large number of air parcels are each measured twice a few days apart. The difference in ozone concentration is calculated for each pair and is interpreted as a change caused by chemistry. The data analysis has been carried out for January to March between 370 K and 600 K potential temperature. Ozone loss along these trajectories occurred exclusively during sunlit periods, and the periods of ozone loss coincided with, but slightly lagged, periods where stratospheric temperatures were low enough for polar stratospheric clouds to exist. Two clearly separated periods of ozone loss show up. Ozone loss rates first peaked in late January with a maximum value of 53 ppbv per day (1.6 % per day) at 475 K and faster losses higher up. Then, in mid-March ozone loss rates at 475 K reached 34 ppbv per day (1.3 % per day), faster losses were observed lower down and no ozone loss was found above 480 K during that period. The ozone loss in hypothetical air parcels with average diabetic descent rates has been integrated to give an accumulated loss through the winter. The most severe depletion of 2.0 ppmv (60 %) took place in air that was at 515 K on 1 January and at 450 K on 20 March. Vertical integration over the levels from 370 K to 600 K gives a column loss rate, which reached a maximum value of 2.7 Dobson Units per day in mid-March. The accumulated column loss between 1 January and 31 March was found to be 127 DU (36 %).  相似文献   

Designing river water quality policy interventions with scarce data: the case of the Middle Tagus Basin,Spain     

Antonio Bolinches  Lucia De Stefano  Javier Paredes-Arquiola 《水文科学杂志》2020,65(5):749-762

ABSTRACT

Anthropic pressures deteriorate river water quality, so authorities need to identify their causes and define corrective actions. Physically based water quality models are a useful tool for addressing physicochemical pollutants, but they must be calibrated with an amount of data that is often unavailable. In this study, we explore the characterization of a model to design corrective interventions in a context of sparse data. A calibration indicator that is both simple and flexible is proposed. This approach is applied to the Middle Tagus Basin in central Spain, where the physicochemical concentration of pollutants is above legal standards. We quantify the effects of the main existing pressures (discharge from wastewater treatment plants, agricultural diffuse pollution and a major inter-basin water transfer) on the receiving waters. In particular, the study finds that wastewater treatment plant effluent concentrations should be reduced to up to 0.65 mg/L of ammonium and 0.55 mg/L of phosphate to achieve the environmental goals. We propose and prioritize a set of policy actions that would contribute to the good status of surface water bodies in the region.  相似文献   

The great 1983 floods in South American large rivers: a continental hydrological modelling approach     

Ayan Santos Fleischmann  Vinícius Alencar Siqueira  Sly Wongchuig-Correa  Walter Collischonn  Rodrigo Cauduro Dias De Paiva 《水文科学杂志》2020,65(8):1358-1373

ABSTRACT

This study provides a spatio-temporal analysis of the great floods that occurred in South America in 1983 using hydrometeorological data and outputs from a continental-scale hydrological-hydrodynamic model. In the extreme year 1983, there were three main flooding periods (February, June and July) in many South American river basins, such as the Araguaia, Tocantins, São Francisco, Uruguay, La Plata and its tributaries, resulting in high discharge of the Paraguay River for many months. Depth–area–duration curves show that 3-day precipitation events in northern regions of South America were among the largest 15 events in the period 1980–2015 but only for specific locations, whereas in southern areas, the most extreme events in the same period were for larger durations (≥7-day precipitation). Modelled total export of water volume to the oceans indicates that rivers draining to the South Atlantic reached an anomaly of 3.7 during 1983, followed by 1998 (1.9) and 1992 (1.1), all of them corresponding to El Niño years.  相似文献   

Revision of lunar Rb-Sr ages     

J.R De Laeter  M.J Vernon  W Compston 《Geochimica et cosmochimica acta》1973,37(3):700-702

Becalibration of ‘spikes’ using stoichiometric Rb and Sr salts recently issued by the National Bureau of Standards shows that our determinations of the ratio ${}^{87}\text{Rb}{}^{86}\text{Sr}$ in lunar samples have been low by 1.8 per cent, which we attribute to non-stoichiometry of the salts previously used for calibration, particularly RbCl. As a result, our lunar age-determinations must be decreased by this amount.  相似文献   

Volcanology and petrology of the Assab Range (Ethiopia)     

M. De Fino  L. La Volpe  L. Lirer 《Bulletin of Volcanology》1973,37(1):95-110

The results of petrological and volcanological investigations of the Assab area (Ethiopia) are reported. Fissure activity — which produced basaltic lava flows and several spatter cones — and central activity — represented by a cumulus dome and two explosive craters — have been recognized. The area is characterized by E-W and NE-SW tectonic trends, whereas the NNW-SSE « Eritrean trend » is absent. Transverse tectonics is limited to the blocks bordering the Danakil Depression, and never extends into the Depression itself. Mineralogical composition and chemical data point to an alkaline nature of the Assab lavas, which have been classified as: picritic basalts tending to ankaramites; alkali olivine basalts; hawaiites; and all the rock types ranging from mugearites to trachytes. Two rock groups have been identified which could be due to crystal fractionation processes controlled by different degree of oxidation. The petrological difference between the rocks from Afar proper and those from the Danakil block (unquestionably alkaline rock types in the Danakil block, and transitional rock types in Afar) is emphasized.  相似文献   

Studies of volcanic ash from two recent Central American eruptions     

W. I. Rose Jr.  S. Bonis  R. E. Stoiber  M. Keller  T. Bickford 《Bulletin of Volcanology》1973,37(3):338-364

The 1971 eruptions of Cerro Negro volcano in Nicaragua and Fuego volcano in Guatemala produced ash blankets with minimum volumes of 7 × 10⁷ m³ and 6 × 10⁷ m³, respectively. Seven new chemical analyses show that ash produced by both eruptions was basaltic and similar to previously — erupted lavas of both volcanoes. Both ash blankets were sampled areally and stratigraphically before they were affected by rain. Chemical analyses of soluble materials leached from these ashes show that near the end of both eruptions the concentrations of soluble materials increased by about an order of magnitude. These changes are believed to reflect changes in the composition of eruptive gases.  相似文献   

Disturbances due to time-dependent body forces in a non-isotropic elastic medium     

Sasadhar De 《Pure and Applied Geophysics》1971,87(1):128-133

Summary In this paper, the disturbances produced due to time-dependent body forces in an anisotropic elastic medium resting on a semi-infinite non-isotropic layer have been discussed.  相似文献   

On the wave propagation in inhomogeneous non-isotropic media     

Sasadhar De 《Pure and Applied Geophysics》1971,89(1):118-125

Summary FollowingEason, we have discussed here the propagation of elastic waves in non-homogeneous spheres and cylinders when the curved surface is given a uniform normal loading. The material is assumed to be transversely isotropic with respect to a direction of symmetry, the stress and displacement components within the body may be assumed to depend on one space co-ordinate and time alone. The particular case in which the elastic parameters are proportional to (radius) ⁿ has been considered.  相似文献   

Problem on the vibrations of plates     

Sasadhar De 《Pure and Applied Geophysics》1971,92(1):45-51

Summary In this paper, the problem on the vibrations of rectangular, elliptical and circular plates of non-isotropic material have been solved by using Galerkin's method. With the help of this method, the same problem for an isotropic circular plate has also been considered at the end.  相似文献   

On love waves in heterogeneous media     

Tapan Kumar De 《Pure and Applied Geophysics》1968,70(1):18-21

Summary Love waves in a half space with one homogeneous elastic layer overlying a semiinfinite medium having elastic properties varying with depth has been considered. The frequency equation for small wave lengths has been obtained, considering general variation, and has been shown to involve the first three derivatives of the rigidity of the heterogeneous medium at its interface with the homogeneous layer.  相似文献