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111.
112.
P.B. Price D. Lal A.S. Tamhane V.P. Perelygin 《Earth and Planetary Science Letters》1973,19(3):377-395
This paper concerns the identification of heavy ion tracks in minerals by measurements of track-etch rates and total etchable track lengths. With beams of Si, Cl, Ti, Fe, Zn and Kr at energies up to 10.35 MeV/nucleon we have irradiated nine minerals commonly used to study fossil cosmic ray tracks in meteorites and lunar samples. From our measurements of etched track length as a function of residual range, we have determined response curves for various minerals as a function of ionization rate, using the expression previously derived by Price, Fleischer and Moak. These curves increase smoothly with ionization rate instead of rising abruptly at some critical value as was previously thought. We have shown that the track etch rate concept accounts qualitatively for total etchable track length distributions, but that the positions of the peaks of different elements in these histograms occur at shorter lengths for fossil tracks than for fresh tracks. Our annealing data indicate that, at maximum lunar surface temperatures, tracks in olivine, orthopyroxenes and feldspars may be significantly shortened whereas tracks in clinopyroxenes will not be affected. We cite additional evidence that gradual rearrangement of radiation damage at ambient temperature makes the properties of fresh tracks and of ancient tracks different. It is thus not surprising that the histograms of fresh and fossil tracks do not match perfectly. 相似文献
113.
Summary The planetary albedo of the earth has been evaluated from the turbidity measurements in India by usingÅngström's empirical relation [1]2) and the same has been presented in this paper. The diurnal and seasonal variations of the planetary albedo have been discussed. It has been found that during the morning hours, albedo is usually more than that during afternoon hours. Further, it shows a minima during winter season and a maxima during hot summer months. 相似文献
114.
Calculation of the second vertical derivative of gravity field 总被引:1,自引:0,他引:1
Summary Two formulas, using Taylor's series expansion method, have been developed by means of which the second vertical derivative of gravity field may be computed at any point in the horizontal plane of observation. A comparative study of the resolving powers of different approaches by performing numerical and filter response tests suggests that the formulas provide a definite improvement over many existing methods.NGRI Contribution No. 69-130. 相似文献
115.
A sounding rocket was launched in March 1982 from Thumba, India, shortly after sunrise. The measurements included the concentration of nitric oxide and ozone, the total ion density and the Lyman-α flux. Hence most parameters important for the formation of the D-region during daytime are available with the exception of solar radiation other than Lyman-α which only becomes important above 95 km. The mutual agreement is satisfactory which adds weight to the measurements. 相似文献
116.
Devendra Lal Christina D. Gallup Loïc Vacher Anthony J.T. Jull Robert C. Speed Amos Winter 《Geochimica et cosmochimica acta》2005,69(24):5717-5728
We present results of measurements of cosmogenic 10Be, 26Al and 36Cl, and the indigenous (intrinsic) concentrations of the stable elements Be, Al and Cl in 120-200 kyr old corals from Barbados and Puerto Rico. The concentration levels of these radionuclides in the corals lie in the range 104 to 108 atoms/g. A comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that (i) the radionuclides 26Al and 36Cl are derived from in situ cosmic ray interactions in the corals after their formation, but that (ii) the radionuclide 10Be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals. 相似文献
117.
Role of in situ cosmogenic nuclides 10be and 26al in the study of diverse geomorphic processes 总被引:1,自引:0,他引:1
K. Nishiizumi C. P. Kohl J. R. Arnold R. Dorn I. Klein D. Fink R. Middleton D. Lal 《地球表面变化过程与地形》1993,18(5):407-425
The central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings. In the light of these general models, we discuss the information that can be derived about geomorphic processes, utilizing concentrations of in situ produced cosmogenic radionuclides 10Be (half-life=1·5 ma) and 26A1 (half-life=0·7 ma) in a variety of geomorphic contexts: glacial polish and tills; meteorite impact craters; alluvial fans; paleo-beach ridges; marine terraces; sand dunes; and bedrock slopes. We also compare 10Be-26Al data with results obtained by other dating methods. We conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time-scales in a wide range of geomorphological problems. 相似文献
118.
Summary A two-dimensional radiative-convective model has been developed to calculate mean annual zonally-averaged temperature profiles for 18 latitudinal belts each of 10° width. The model includes meridional heat transport and impacts of surface albedo and lapse rate feedback mechanisms. In view of its flexibility and computational efficiency compared to a three-dimensional general circulation model, this model may serve as a useful tool in studying the climate sensitivity to external forcings.The model has been successfully applied to reproduce the meridional variation of climatic elements for the standard atmosphere. Next, the climate sensitivity to a doubling of atmospheric CO2 has been examined. The surface temperature response ranges from 1.6 °C near the equator to 4 °C in polar regions with a global mean of 2.1 °C. The meridional distribution of surface warming due to doubled CO2 simulated by our model agrees qualitatively with those obtained by NCAR and GFDL global circulation models in that the largest warmings in all three simulations are found at high latitudes in the Northern Hemisphere. An interesting feature of our findings is that the maximum response due to doubled CO2 tends to descend from the upper troposphere at low latitudes to the surface at high latitudes. The responses of the transport of sensible and latent heat are in opposite direction thus leading to only slight but positive changes in the total meridional heat flux.
With 9 Figures 相似文献
Zusammenfassung Es wurde ein zweidimensionales Strahlungs-Konvektions-Modell entwickelt, um zonal gemittelte Temperaturprofile für 10° breite Gürtel zu berechnen. Das Modell beinhaltet meridionalen Wärmetransport, Einflüsse der Albedo und des vertikalen Temperaturgradienten. Aufgrund seiner Flexibilität und rechnerischen Effizienz im Vergleich zu dreidimensionalen Modellen der allgemeinen Zirkulation, kann dieses Modell gut zum Studium der Sensitivität des Klimas auf äußere Antriebe verwendet werden.Das Modell wurde zuerst erfolgreich angewandt, um die meridionale Variabilität der Klimaelemente für die Standardatmosphäre zu reproduzieren. Dann wurde die Sensitivität gegenüber einer Verdoppelung des atmosphärischen CO2 untersucht. Die Veränderungen an der Erdoberfläche reichten von 1.6 °C nahe dem Äquator bis zu 4 °C in Polnähe mit einem globalen Mittel von 2.1 °C. Die meridionale Verteilung stimmt qualitativ mit den Modellergebnissen von NCAR und GFDL überein. Alle prognostizieren die größten Erwärmungen in den hohen Breiten der Nordhemisphäre. Ein interessantes Ergebnis dieser Untersuchung ist, daß die größte Erwärmung von der oberen Troposphäre in niedrigen Breiten in hohen Breiten zur Oberfläche absinkt. Die Prognosen für die Änderung des Transports von fühlbarer und iatenter Wärme zeigen den umgekehrten Effekt. Das führt zu einem geringen Anstieg des meridionalen Wärmeflusses.
With 9 Figures 相似文献
119.
Most modelling endeavours concerning the CO2-climate problem address only the question of the climatic response to increasing atmospheric carbon dioxide, while the amounts of other atmospheric gases remain fixed. But associated changes, either climatologically or anthropogenically induced, of minor atmospheric constituents can also be of significance in producing a substantial global warming. We have analysed the climatic response to changes in a number of atmospheric trace gases as they may enhance or counteract CO2-induced warming if their abundance should change. A comparison of the increase in equilibrium global-mean surface temperature due to plausible changes in the concentration of several trace gases in the atmosphere based on our calculations with a one-dimensional radiative-convective model is presented in this paper. Our results indicate that roughly 35% of global surface warming could be due to changes in trace gases other than CO2 and water vapour. The possible climatic consequences of the ongoing anthropogenic changes in the minor constituents of the atmosphere are also discussed. 相似文献
120.
A semi-empirical approach has been used to obtain an analytical expression for the annealing of charged particle tracks in minerals as a function of time and temperature. The new formalism allows quantitative evaluation of the extent of annealing in samples for any specified temperature and track production history. The validity of the present approach depends upon the applicability of the Arrhenius equation to the process of annealing of nuclear tracks in solids. Laboratory track annealing studies confirm the predictive aspects of the present approach and also the applicability of Arrhenius' equation to track annealing over a wide time-temperature range (5 seconds/1200 K to 5 × 106 seconds/500 K). The present quantitative treatment of track annealing in rock minerals should permit an in-depth study of a variety of problems in meteoritics and earth sciences. 相似文献