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Thermally, the lithosphere may be defined as that outer portion of the earth in which heat is transferred primarily by conduction. It generally includes the crust and part of the mantle. The thermal regime of continental lithosphere is determined by many factors including heat flow from the asthenosphere, the vertical and lateral variation of both thermal conductivity and radiogenic heat production, tectonic history, and such superficial processes as climatic history and the shallow hydrothermal regime. From studies of the global heat flow data set, two generalizations regarding continental lithosphere have arisen, namely that: 1) there is a negative correlation between heat flow and tectonic age of continental lithosphere; and 2) the thermal evolution of continental lithosphere is similar to that of ocean basins with the result that the “stable geotherm” is similar in both environments. When continental heat-flow data are studied from a regional rather than a global point of view, considerable doubt arises as to the general applicability of either statement. R. U. M. Rao and his associates have demonstrated that while Precambrian terranes do have demonstrably lower heat flows than, say, Tertiary terranes, the data are not normally distributed and it is not possible to establish a negative correlation between heat flow and age in any rigorous statistical way. The scatter in the relation may be explained in terms of the variations in the duration, intensity and even the sign of continental thermotectonic events in contrast to the simple situation (creation of new oceanic lithosphere at mid-ocean ridges) which prevails in the oceans. The scatter also is partially attributable to the large and laterally variable radiogenic component of heat flow on continents. For a province for which a heat flow-heat production relation has been established, much of the scatter in surface heat flow due to crustal radiogenic heat production versus age is eliminated by determining reduced heat flow (surface heat flow minus radiogenic component) as a function of tectonic age, but much scatter remains, and it is still not possible to establish a heat flux-age relation in a rigorous way. Primarily because of the spatial variability in radiogenic heat production, no single geotherm can be used to characterize the thermal regime of a stable continental terrane. Thus, while some sites on stable continental blocks may have a geotherm fortuitously similar to that for old ocean basins, there is no reason to expect that this will be true generally, and many stable continental terranes will be characterized by geotherms markedly different from the geotherm for old ocean basins. 相似文献
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中国南京与美国德克萨斯稻田甲烷排放的比较 总被引：8，自引：0，他引：8
Field measurements of methane emission from rice paddies were made in Nanjing, China and in Texas, USA, respectively. Soil temperature at approximately 10 cm depth of the flooded soils was automatically recorded. Aboveground biomass of rice crop was measured approximately every 10 days in Nanjing and every other week in Texas. Seasonal variation of soil temperature in Nanjing was quite wide with a magnitude of 15.3℃ and that in Texas was narrow with a magnitude of 2.9℃. Analysis of methane emission fluxes against soil temperature and rice biomass production demonstrated that the seasonal course of methane emission in Nanjing was mostly attributed to soil temperature changes, while that in Texas was mainly related to rice biomass production. We concluded that under the permanent flooding condition, the seasonal trend of methane emission would be determined by the soil temperature where there was a wide variation of soil temperature, and the seasonal trend would be mainly determined by rice biomass production if there are no additional organic matter inputs and the variation of soil temperature over the rice growing season is small. 相似文献
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A comprehensive model inter-comparison study investigating the water budget during the BALTEX-PIDCAP period 总被引：2，自引：0，他引：2
D. Jacob B. J. J. M. Van den Hurk U. Andræ G. Elgered C. Fortelius L. P. Graham S. D. Jackson U. Karstens Chr. Köpken R. Lindau R. Podzun B. Rockel F. Rubel B. H. Sass R. N. B. Smith X. Yang 《Meteorology and Atmospheric Physics》2001,77(1-4):19-43
Summary A comparison of 8 regional atmospheric model systems was carried out for a three-month late summer/early autumn period in
1995 over the Baltic Sea and its catchment area. All models were configured on a common grid using similar surface and lateral
boundary conditions, and ran in either data assimilation mode (short term forecasts plus data assimilation), forecast mode
(short term forecasts initialised daily with analyses) or climate mode (no re-initialisation of model interior during entire
simulation period). Model results presented in this paper were generally post processed as daily averaged quantities, separate
for land and sea areas when relevant. Post processed output was compared against available analyses or observations of cloud
cover, precipitation, vertically integrated atmospheric specific humidity, runoff, surface radiation and near surface synoptic
observations.
The definition of a common grid and lateral forcing resulted in a high degree of agreement among the participating model results
for most cases. Models operated in climate mode generally displayed slightly larger deviations from the observations than
the data assimilation or forecast mode integration, but in all cases synoptic events were well captured. Correspondence to
near surface synoptic quantities was good. Significant disagreement between model results was shown in particular for cloud
cover and the radiative properties, average precipitation and runoff. Problems with choosing appropriate initial soil moisture
conditions from a common initial soil moisture field resulted in a wide range of evaporation and sensible heat flux values
during the first few weeks of the simulations, but better agreement was shown at later times.
Received September 8, 2000 Revised April 3, 2001 相似文献
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Lees's topographic correction for a simple idealized hill is discussed and extended to a monoclinal structure. It is valuable as giving very simply the order of magnitude of the correction. A number of new measurements of temperature in Tasmanian boreholes has been made and the previous rather high value of over 2 cal/cm2 sec for the heat flux has been confirmed. The variation of thermal conductivity through the thickness of a differentiated tholeiite sheet has been measured and found to be in reasonably good agreement with values calculated from chemical and modal analyses. 相似文献
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Calcium chloride brines are, as a rule, relatively rich in strontium, but the enrichment is usually limited and is found to be related to the concentration of calcium. The limiting mechanisms were evaluated as a model which comprises simple interactions between minerals and solutions. Based on the known ranges of strontium concentration in minerals, mineral solubilities and partition coefficients of strontium (both poorly known in certain cases), six fields of molar ratios were defined in terms of participating minerals and processes: (a) 0.38?1.56 × 10? 3 by dolomitization of calcite; (b) 1.5?2.2 × 10? 2 due to dolomitization of aragonite; (c) 0.4?1.4 × 10? 2 as a result of solution-reprecipitation of calcite; (d)0.12?0.20 through transformation of aragonite to calcite; (e)0.10?0.60 through equilibrium of the pair calcite-strontianite; and (f)0.01?0.08 by equilibrium with gypsum and celestite.The model was applied to the analysis of two groups of brines from southern Israel which are originated in the coastal plain (group C) and in the rift valley (group R). The low ratios of both water groups point to dolomitization as the main subsurface modifying process. ratios of brines belonging to group C are consistent with dolomitization of aragonitic surface sediments at the beginning of their evolution. Brines of group R bear evidence to a similar pathway at the beginning of their evolution, but most of them were further affected by interaction with limestone. 相似文献
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Climate Dynamics - Regional climate models (RCM) are an important tool for simulating atmospheric information at finer resolutions often of greater relevance to local scale climate change impact... 相似文献
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Mapping groundwater discharge zones at broad spatial scales remains a challenge, particularly in data sparse regions. We applied a regional scale mapping approach based on thermal remote sensing to map discharge zones in a complex watershed with a broad diversity of geological materials, land cover and topographic variation situated within the Prairie Parkland of northern Alberta, Canada. We acquired winter thermal imagery from the USGS Landsat archive to demonstrate the utility of this data source for applications that can complement both scientific and management programs. We showed that the thermally determined potential discharge areas were corroborated with hydrological (spring locations) and chemical (conservative tracers of groundwater) data. This study demonstrates how thermal remote sensing can form part of a comprehensive mapping framework to investigate groundwater resources over broad spatial scales. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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The John’s creek valley (Johnsbachtal) is presented as a long-term, interdisciplinary cooperation platform in upper Styria (Austrian Alps) that brings together the interests and knowledge of persons with different backgrounds (scientists, teachers, students, as well as local actors and the population) with the central aim to generate mutual benefit for all involved parties. It covers an area of around 65 km2 with elevations between 600 and 700 m in the valley to over 2,300 m in the summit regions. Annual mean temperature ranges from approximately 8 °C in the lower elevations of the valley to below 0 °C in the summit regions. Annual precipitation mounts to values of 1,500 mm and more than 1,800 mm in the lower elevations and summit regions, respectively. To allow for a long-term monitoring of the complex meteorological and hydrological conditions in the area, a hydroclimatological monitoring network has been installed that is described in detail in this paper. A special characteristic of the installed meteorological stations is that they cover a large range of altitudes and, therefore, allow to capture the gradients in meteorological variables induced by the complex Alpine topography. Furthermore, the hydroclimatological monitoring network in John’s creek valley is largely independent of regular third-party project funding, and therefore, not temporarily limited in its existence. A number of catchment research activities that cover a variety of disciplines (e.g., climatology, hydrology, (hydro)geology, geomorphology) and that largely benefit from the hydroclimatological data recorded in John’s creek valley are presented together with preliminary results. The latter include spatial distributions of meteorological and hydrological variables (e.g., precipitation, evapotranspiration and snowmelt) calculated for the test site using the hydrometeorological model AMUNDSEN. Furthermore, the results of hydrogeological investigations that have been carried out at the Etzbach spring are presented and discussed. 相似文献