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911.
N. Mölders U. Haferkorn J. Döring G. Kramm 《Meteorology and Atmospheric Physics》2003,84(1-2):137-156
Summary ¶Various water budget elements (water supply to the atmosphere, ground water recharge, change in storage) are predicted by HTSVS for a period of 2050 days. The predicted water budget elements are evaluated by routine lysimeter data. The results show that land surface models need parameterizations for soil frost, snow effects and water uptake to catch the broad cycle of soil water budget elements. In principle, HTSVS is able to simulate the general characteristics of the seasonal changes in these water budget elements and their long-term accumulated sums. Compared to lysimeter data, there is a discrepancy in the predicted water supply to the atmosphere for summer and winter which may be attributed to the hardly observed plant physiological parameters like root depth, LAI, shielding factor, etc., the lack of measured downward long-wave radiation, and some simplifications made in the parameterizations of soil frost and snow effects. The fact that high resolution data for the evaluation of model results are missing and evaluation is made on the basis of the data from routine stations of a network is typical for the results of long-term studies on climate. Taking into account the coarse resolution of climate models, the coarse vertical resolution that is used in their LSMs, and the lack of suitable parameters needed, it seems that discrepancies in the order of magnitude found in this study are a general uncertainty in the results of land surface modeling on typical spatial and temporal scales of the climate system.Received October 8, 2001; revised February 15, 2002; accepted September 20, 2002
Published online: April 10, 2003 相似文献
912.
T.W. Foresman T. Cary T. Shupin R. Eastman J.E. Estes N. Faust J.R. Jensen K.K. Kemp 《ISPRS Journal of Photogrammetry and Remote Sensing》1997,52(6):294-300
The Remote Sensing Core Curriculum (RSCC) was initiated in 1993 to meet the demands for a college-level set of resources to enhance the quality of education across national and international campuses. The American Society of Photogrammetry and Remote Sensing adopted the RSCC in 1996 to sustain support of this educational initiative for its membership and collegiate community. A series of volumes, containing lectures, exercises, and data, is being created by expert contributors to address the different technical fields of remote sensing. The RSCC program is designed to operate on the Internet taking full advantage of the World Wide Web (WWW) technology for distance learning. The issues of curriculum development related to the educational setting, with demands on faculty, students, and facilities, is considered to understand the new paradigms for WW-influenced computer-aided learning. The WWW is shown to be especially appropriate for facilitating remote sensing education with requirements for addressing image data sets and multimedia learning tools. The RSCC is located at http://www.umbc.edu/rscc 相似文献
913.
An unusual liptinite coal component has been reported in the Chinese literature over the past sixty years. It has been described as a maceral in the Chinese National Standard (1991), but it has not been named internationally. In Chinese literature it is called “barkinite”, on the basis of its morphological features and because it is believed to have originated as bark tissue.“Barkinite” occurs in Late Permian, marine-influenced coals and is best represented in the Changguang, Leping and Shuicheng Basins of southern China.The material originates from plant periderm or the bark of higher plants. However, “bark” contains a variety of substances, including resin and suberin, which are recognised as the precursors of the resinite and suberinite macerals. “Barkinite” is distinguished by (i) its thickness; individual pieces can be more than ten cells thick and several centimetres long and (ii) it fluoresces strongly at 0.6% vitrinite reflectance and loses its fluorescence at about 1.1% vitrinite reflectance.The reporting of “barkinite” from only Chinese coals may be due to its origin from Lepidodendron and Psaronius flora, which was common in the Northern Hemisphere during the Carboniferous, but which was isolated to China by the Late Permian. It is proposed that the remnant flora evolved into unique forms in China by the Late Permian. Lepidodendron and Psaronius remains, coupled with a strongly marine-influenced, peat-forming environment have given rise to “barkinite” and to its restricted distribution. 相似文献
914.
J. TORRES§ L. DROZ† B. SAVOYE E. TERENTIEVA‡ P. COCHONAT N. H. KENYON M. CANALS§ 《Sedimentology》1997,44(3):457-477
The Petit-Rhône Fan Valley (north-western Mediterranean) is a broad, sinuous, filled valley that is deeply incised by a narrow, sinuous thalweg. The valley fill is differentiated into three seismic subunits on high-resolution seismic-reflection profiles. The lower chaotic subunit probably consists of channel lag deposits that seem to be in lateral continuity with high-amplitude reflections representing levee facies. The intermediate transparent subunit, which has an erosional base and clearly truncates levee deposits, is interpreted to be mass-flow deposits resulting from the disintegration of the fan-valley flanks. The upper bedded subunit shows an overall lens-shaped geometry and the seismic reflections onlap either onto the top of the underlying transparent subunit or onto the Rhône levees. Piston core data show that the upper few meters of this upper subunit consist of thin turbidites, probably deposited by overflow processes. The few available 14C ages suggest that the upper stratified subunit filled the Petit-Rhône Fan Valley between 21 and 11 kyr BP. The upper bedded subunit is deposited within the Petit-Rhône Fan Valley downslope of a major decrease in slope gradient. This upper subunit and the thalweg are genetically related and represent a small channel/levee system confined within the fan valley. Previous studies interpreted this thalweg to be an erosional feature resulting from a recent avulsion of the major channel course. Our interpretation implies that the thalweg is not a purely erosional feature but a depositional/erosional channel. This small channel/levee system is superimposed on a large muddy channel/levee system after the sediment supply changed from thick muddy flows during the main phase of aggradation of the Rhône Fan levees, to thin, mixed (sand and mud) flows at the end of Isotope Stage 2 (~16–18 ka BP). The pre-existing morphology of the Petit-Rhône Fan Valley played a determinant role in the sediment dispersal leading to the creation of this small and confined channel/levee system. These mixed flows have undergone flow stripping resulting from the changes in the slope gradient along the thalweg course. The finer sediment overflowed from the thalweg and were deposited in the Petit-Rhône Fan Valley. Coarser channelled sediment remaining in the thalweg were deposited as a ‘sandy’lobe (Neofan). As indicated by 14C dating, sedimentation on this lobe continued until very recently, suggesting a further evolution of the turbidity flows from small mixed flows to small sandy flows. the deposition of this study lobe and the sedimentary fill of the Petit-Rhône Fan Valley may be related to widespread shelf edge and canyon wall failures with a resulting downslope evolution of failed sediment into turbidity currents. 相似文献
915.
JOHAN N. J. VISSER 《Sedimentology》1997,44(3):507-521
The Late Westphalian to Artinskian glaciomarine deposits of the Karoo and Kalahari basins of southern Africa consist of massive and stratified diamictite, mudrock with ice-rafted material, sandstone, silty rhythmite, shale and subordinate conglomerate forming a cyclic succession recognizable across both basins. A complete cycle comprises a resistant basal unit of apparently massive diamictite overlain by softer, bedded stratified diamictite, sandstone and mudrock with a total thickness of as much as 350 m. Four major cycles are observed each separated by bounding surfaces. Lateral facies changes are present in some cycles. The massive diamictites formed as aprons and fans in front of the ice-grounding line, whereas the stratified diamictites represent more distal debris-flow fans. The sandstones originated in different environments as turbidite sands, small subaqueous outwash channel sands and delta front sands. The rhythmites and mudrock represent blanket deposits derived from turbid meltwater plumes. Cycles represent deglaciation sequences which formed during ice retreat phases caused by eustatic changes in the Karoo and Kalahari basins. Evidence for shorter-term fluctuation of the ice margin is present within the major advance-retreat cycles. Hardly any sediment was deposited during lowstand ice sheet expansion, whereas a deglaciation sequence was laid down during a sea-level rise and ice margin retreat with the volume of meltwater and sediment input depending on temporary stillstands of the ice margin during the retreat phase. The duration of the cycles is between 9 and 11 Ma suggesting major global tectono-eustatic events. Smaller cycles probably linked to orbital forcing were superimposed on the longer-term events. A sequence stratigraphic approach using the stacking of deglaciation sequences with the ice margin advance phases forming bounding surfaces, can be a tool in the framework analysis of ancient glaciomarine basin fills. 相似文献
916.
Exhumation during crustal folding in the Namche-Barwa syntaxis 总被引:6,自引:0,他引:6
Jean-Pierre Burg Philippe Davy Peter Nievergelt Felix Oberli Diane Seward Zhizhong Diao Martin Meier 《地学学报》1997,9(2):53-56
Geological observation in the eastern end of the Himalaya shows that the Asia/India Suture is folded. Metamorphic rocks derived from India occur structurally below the suture, in the core of a regional antiform. Isotopic and fission track dating establish cooling-exhumation of rocks from c.30 km depth within the last 4 Myr. We argue that exhumation is caused by ~ 10 mm yr-1 erosion coeval with crustal scale folding. 相似文献
917.
Saturated and aromatic biomarker ratios continue to change systematically through the oil window and into the gas-condensate window to high vitrinite reflectances (Ro = 1.16%) in mature marine and lacustrine Mesozoic clastic samples from a South African basin. Two of the ratios reverse above Ro = 0.9%. These unusual maturation effects result from isolated periods of high rates of maturation increase. The basin cooled regionally after the break-up of Gondwana but high heating rates prevailed during the late Cretaceous-early Tertiary, as Africa moved across a hotspot, and again in the late Tertiary as a result of a possible hotspot and hydrothermal event. 相似文献
918.
The Sakoa Group is the lowermost stratigraphical succession of the Karoo Supergroup and the oldest sedimentary unit in Madagascar, spanning the Late Carboniferous through Early Permian epochs. The Sakoa Group is exposed in the southern Morondava Basin. It is predominantly a siliciclastic sequence comprising seven lithofacies associations: (1) diamictites; (2) conglomeratic sandstones; (3) sandstones; (4) interbedded thin sandstones and mudstones; (5) mudstones; (6) coals; and (7) limestones. These facies represent deposition in the early extensional stages of continental rift development. The sediments were deposited predominantly on alluvial fans, and in braided to meandering stream and overbank environments. Locally lacustrine and coal swamp environments formed in low areas of the basin floor during rift initiation. Subsidence rates remained fairly constant throughout the Early Permian and were accompanied by a gradual reduction in relief of the basin margins and an increased geomorphic maturity of the fluvial systems flowing across the basin floor. Near the end of the Early Permian the southern Morondava Basin was inundated by a marine transgression , which resulted in deposition of the Vohitolia Limestone. Subsequent tectonic uplift and erosion resulted in a regional unconformity between the Sakoa Group and the overlying Sakamena Group. 相似文献
919.
An auto-biographical approach to understanding migration: the case of Hong Kong emigrants 总被引:1,自引:0,他引:1
Summary This paper seeks to make a methodological contribution by evaluating the autobiographical approach and its application to migration research. The migration act is seen as a manifestation of an individual's identity. This is moulded by many social influences over an individual's lifecourse. The paper explores the realm of practical consciousness (Giddens 1984) using a biographical approach in an attempt to identify the values underpinning the intentions of professional emigrants from Hong Kong. 相似文献
920.
Electrical anisotropy of young oceanic crust at mid-ocean ridges is detectable by observation of the rate and geometry of the diffusion of electromagnetic fields. The anisotropy in electrical properties arises from the presence of conductive seawater in an interconnected network of mostly ridge-parallel cracks. In this paper, we first justify the choice of a triaxial model to represent young oceanic crust, with three distinct electrical conductivities in the vertical, strike and spreading directions. We then present an algorithm to calculate the transient electromagnetic responses generated by an electric dipole source over such a triaxially anisotropic seafloor. We show that if the transient passages are measured with three distinct electric dipole-dipole configurations, it is possible to discern all three unknown conductivities independently of each other. 相似文献