A supposed error in Smithsonian Solar Constant determinations     

Prof. Dr. Kurt Wegener 《Pure and Applied Geophysics》1950,16(1-2):16-18

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Zur Definition des Begriffes der Intensität der Sonnenstrahlung     

Univ.-Prof. i. R. Dr. Kurt Wegener 《Pure and Applied Geophysics》1952,23(1):147-150

Summary Two definitions of solar intensity are discussed. It is shown, thatK. Wegener's definition, which includesBoltzmann-radiation of the instrument and the atmosphere, leads to conclusions opposite to representative measurements. The usual definition basing on energy-flux is proved by different methods and in very different climates. Yet there are still many problems to resolve before the solar constant will be known by an accuracy of ±1%.

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Résumé On discute deux définitions de l'intensité du rayonnement solaire. On met en évidence que la définition deK. Wegener qui inclut le rayonnement thermique (Boltzmann) et de l'instrument et de l'atmosphère conduit à des conclusions contraires à l'expérience. La définition classique qui se base sur le flux d'énergie tient l'épreuve dans des climats très différents et ne dépend pas de la methode employée. Pourtant ils restent encore beaucoup de problèmes à résoudre jusqu'à ce que la constante solaire soit connue au ±1% près.

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Die Verdunstung im Schnee Grönlands     

Kurt Wegener 《Pure and Applied Geophysics》1962,52(1):227-228

Summary The evaporation does not be restricted to the surface of the snow. The evaporated quantity is demonstrated.  相似文献   

Image tube spectra of pluto and triton from 6800 to 9000 Å     

D. Chris Benner  Uwe Fink  Richard H. Cromwell 《Icarus》1978,36(1):82-91

To search for a possible atmosphere on Pluto and Triton, spectra of these objects as well as comparison stars were obtained with a three-stage Varo image tube for the spectral region from 6800 to 9000 Å. Ratio spectra indicate an absorption feature near 8900 Å, although the steeply diminishing response of the image tube at that wavelength casts some doubt on the reality of this feature. The feature appears more definitive in the spectrum of Pluto and less certain in the spectrum of Triton. The absorption was analyzed using our recently determined band-model parameters for methane. Under the assumption of a pressure higher than 0.01 atm an abundance of 3 m-amagat was determined. For pressures limited by the methane abundance itself, an abundance of 50 m-amagat and a pressure of 10^?3 atm was derived (using g = 0.20 g⊕ for both Pluto and Triton). This pressure is close to the pressure that can be expected from the equilibrium vapor pressure of a methane frost. If the absorption at 8900 Å is spurious, our analysis will be applicable as an upper limit for the presence of methane gas on Pluto or Triton.  相似文献   

OH-initiated degradation of several hydrocarbons in the atmosphere simulation chamber SAPHIR     

D. Poppe  T. Brauers  H. -P. Dorn  M. Karl  T. Mentel  E. Schlosser  R. Tillmann  R. Wegener  A. Wahner 《Journal of Atmospheric Chemistry》2007,57(3):203-214

Degradation of isoprene, m-xylene, n-octane, propene, and methacrolein by hydroxyl radicals has been studied in the simulation chamber SAPHIR under burden of trace gases as they are typical for the moderately polluted planetary boundary layer. Measured time series of the hydrocarbon mixing ratios and the OH concentrations were used to determine the rate constants. The hydrocarbons were measured with gas chromatography and proton transfer reaction mass spectrometry. OH was measured with the Jülich DOAS (differential optical absorption spectroscopy) instrument. In all cases except methacrolein good agreement was found with the reference rate constants taken from the Master Chemical Mechanism (MCM3.1). The data for methacrolein are consistent with the results of Karl et al. (J. Atmos. Chem 55, 2006, doi:) who reported a 12% smaller value. The degradation of hydrocarbons provides an independent method to analyse precision and accuracy of the OH measurements. A precision of better than 4% over a period of nearly 4 months was found. The accuracy is within the limitations given by the light absorption cross section of OH. Both results are consistent with earlier results by Hausmann et al. (J. Geophys. Res. 102:16011–16022, 1997).  相似文献   

Multi-proxy Reconstruction of Trophic State,Hypolimnetic Anoxia and Phototrophic Sulphur Bacteria Abundance in a Dimictic Lake in Northern Germany over the past 80 Years     

Mirko Dreßler  Thomas Hübener  Solvig Görs  Petra Werner  Uwe Selig 《Journal of Paleolimnology》2007,37(2):205-219

During monthly investigations from 1996 to 2000, a hypolimnetic layer of phototrophic sulphur bacteria (Chromatium spp.) were observed in Lake Dudinghausen, a small dimictic lake in northern Germany. This paleolimnological study was initiated to detect if the occurrence of sulphur bacteria was related to cultural eutrophication or reflected natural conditions. Therefore, diatoms, algal pigments, okenone, geochemical proxies, and ²¹⁰Pb and ¹³⁷Cs were used in four sediment cores to investigate historical changes in trophic development, hypolimnetic redox conditions, anoxia and phototrophic sulphur bacteria abundances. Fossil diatoms, pigments, the ratio of chlorophyll derivatives to total carotenoids and the ratio of chlorophyll a to its derivatives suggest two phases of eutrophication coupled with hypolimnetic anoxia over the last ~80 years: a first phase from about 1923–1932 and a second from 1952 to 1982. In the first phase the ratios of Fe–Mn as well as Fe–Ca increased, suggesting seasonal anoxia. However, hypolimnetic anoxia was only weak because low levels of okenone suggest no mass development of sulphur bacteria. In contrast, sulphur bacteria increased during the early stages of the second eutrophication phase, suggesting increased temporal and spatial hypolimnetic anoxia. Surprisingly, the ratios of Fe–Mn as well as Fe–Ca decreased during this time. Possibly Fe, Mn and Ca were equally reduced through the intense anoxia. In the final stage, sulphur bacteria decreased again. As these bacteria need both anoxic conditions and a certain amount of light, the increased nutrient load probably led to low Secchi depth and therefore insufficient light conditions. In more recent years, diatoms and pigments suggest a decrease in nutrient levels. A second mass development of sulphur bacteria occurred, probably due to improved light conditions and continued anoxia in the upper hypolimnion. We conclude that the recent development of phototrophic sulphur bacteria do not represent natural conditions in Lake Dudinghausen. Furthermore, the upper sediments contain a completely new diatom flora that never occurred in older sediments of Lake Dudinghausen. Therefore, nutrient levels may eventually reach natural conditions, however they may not represent biological background reference conditions.  相似文献   

Recent evolution of surge-related events and assessment of coastal flooding risk on the eastern coasts of the English Channel     

Paolo Antonio Pirazzoli  Stéphane Costa  Uwe Dornbusch  Alberto Tomasin 《Ocean Dynamics》2006,56(5-6):498-512

This paper is based on statistical analysis of hourly tide measurements for some 285 equivalent full years from the stations of Weymouth, Bournemouth, Portsmouth, Newhaven, Dover and Sheerness in the UK, and of Cherbourg, Le Havre, Dieppe, Boulogne, Calais and Dunkirk in France. For each tidal value, surge heights have been determined and correlated with hourly or three-hourly wind and air pressure data from nearby meteorological stations. Major surges in the area are generally produced by storms associated with wind from north-west or south-west that tend to push oceanic water into the Channel. Recent medium-term climate evolution does not seem to increase the flooding risk at French stations, where surge-related winds tend to decrease in frequency and speed (Cherbourg, Dieppe and Boulogne) or show little change (Le Havre). However, the long-term risk of flooding will increase through the loss in land elevation due to a continuation of the local relative sea-level rise, especially if this effect will be enhanced by an acceleration in the global sea-level rise predicted by climatic models. The northern side of the Channel (Weymouth, Bournemouth and Portsmouth) is mainly exposed to southerly winds that show variable trends. It is also apparently affected by strong subsidence trends during the last two decades. If lasting, such trends can only increase long-term flooding risk. The flooding risk has not increased near the eastern end of the Channel. The duration of significant cyclonic events tends to decrease near Cherbourg but tends to increase near Weymouth, with no conclusive trends in other stations (Portsmouth, Calais and Dunkirk), where extreme surges may occur also in relatively high-air-pressure situations. In conclusion, medium-term coastal flooding risk seems to increase especially at Weymouth, Bournemouth and Portsmouth, and also, but less so, at Le Havre and Sheerness. In addition, few extreme surges occurred during the last decades at the time of spring high tide, which would seem to be a fortunate coincidence or, in some cases, an effect of tide–surge interaction. The risk of occurrence of less favourable random events in the near future is therefore of concern, and flood potential would greatly increase if the global sea-level rise expected in the near future is also considered.  相似文献   

Regional application of a fish yield estimation procedure to lakes in north-east Germany     

Uwe Brämick  Roland Lemcke 《Limnologica》2003,33(3):205-213

Primary production and total phosphorus, respectively, have recently been used as the main variables to estimate the fish yield potential of lakes. In order to improve the accuracy of the estimation procedure for regional applications, two major adaptations were implemented. Both the relations between total phosphorus and primary production as well as primary production and corresponding fish yield potential were adjusted to specific regional conditions in north-east Germany and production patterns in shallow lakes, respectively. Applied to 786 lakes, the adapted procedure led to estimated fish yield potentials in the range of 8 … 67 kg/ha · a with shallow lakes showing significantly higher potentials than stratified ones. A comparison of estimated yield potentials with current yield statistics revealed an improved conformity of estimates attained by using the adapted procedure.  相似文献   

The effects of a variation of the radial viscosity profile on mantle evolution     

Uwe Walzer  Roland Hendel  John Baumgardner 《Tectonophysics》2004,384(1-4):55-90

The present paper describes a set of numerical experiments on the mantle's thermal evolution with an infinite Prandtl number fluid in a compressible spherical shell heated mainly from within. We used the anelastic liquid approximation with Earth-like material parameters. The usual variable-viscosity approach in mantle-convection models is the assumption of a temperature dependence only. The resulting thermal boundary layers are included in our model also, but an additional viscosity profile of the interior mantle was derived: The Birch–Murnaghan equation was employed to derive the Grüneisen parameter and other physical quantities as a function of depth from observational values provided by PREM. We computed the melting temperature and a new mantle viscosity profile, called eta3, using the Grüneisen parameter, Lindemann's law and some solid-state physics considerations. The new features of eta3 are a high-viscosity transition layer with rather high viscosity gradients at its boundaries, a second low-viscosity layer beginning under the 660-km discontinuity, and a strong viscosity increase in the central parts of the lower mantle. The rheology is Newtonian but it is supplemented by a viscoplastic yield stress, σ_y. A viscosity-level parameter, r_n, and σ_y have been varied. For a medium-sized Rayleigh-number–yield-stress area, eta3 generates a stable, plate-tectonic behavior near the surface and simultaneously thin sheet-like downwellings in the depth. Outside this area, three other types of solution were found. Not only the planforms but also the evolution of the Rayleigh number, the reciprocal Urey number, the Nusselt number, the surface heat flow, etc., have been studied. We repeated this investigation with two very different basic viscosity profiles, etaKL5a and etaKM, of other authors. A comparison reveals that eta3 facilitates the generation of surface plates and thin sheet-like downwellings in the depth considerably more than etaKL5a or even etaKM. The presence of two internal low-viscosity layers is obviously conducive for plateness and thin sheet-like downwellings. For an infinite yield stress, the thin cold sheet-like downwellings are reticularly connected. However, the distribution of the downwellings is more Earth-like if a realistic yield stress is added.  相似文献   

The 1992 drill core from the Kalkkop impact crater, Eastern Cape Province, South Africa: stratigraphy, petrography, geochemistry and age     

Wolf Uwe Reimold  Christian Koeberl  Jacobus S. V. Reddering 《Journal of African Earth Sciences》1998,26(4):573-592

New drill core data are provided which support earlier interpretations that the Kalkkop structure, a 600–630 m wide, near-circular feature south-southwest of Graaff-Reinet in the Eastern Cape Province of South Africa, is a meteorite impact crater. Shock metamorphosed clasts in suevitic crater fill and Re---Os isotope data of this breccia indicate the presence of a minor (0.05%) meteoritic component in the suevite. The new data come from a 1992 borehole, which transected the complete crater fill and extended from about 160 to 380 m depth into the sedimentary basement belonging to the Koonap Formation of the Beaufort Group (Karoo Supergroup). Dyke breccias were found in the otherwise coherent Beaufort Group sediments forming the floor to the Kalkkop Crater. Mostly narrow zones of different breccia types, including injections of lithic impact breccia, a possible pseudotachylite veinlet and cataclasite occur predominantly in an approximately 65 m wide zone below the crater floor, with a few other cataclasite occurrences found lower down in the basement. Stratigraphical crater constraints provide information for the depth-diameter scaling and breccia volumes associated with such small, bowl-shaped impact craters formed in sedimentary targets.U---Th series dating of limestone samples from near the top and the bottom of the crater sediment fill constraints the age of the Kalkkop impact event to about 250 ± 50 ka, similar to the age of the Pretoria Saltpan impact crater, also located in South Africa. The variety of different breccia types (polymict and monomict impact breccias; local formations of pseudotachylitic and cataclastic breccias) observed in the crater fill of the Kalkkop Crater indicates the need to carefully distinguish different breccia types in order to assess the respective importance of each formation.  相似文献