内蒙古中西部地区不同土壤类型下土壤水分的研究

以2002—2003年连续两年自行观测的内蒙古中西部地区二连浩特、乌拉特中旗和乌海的土壤水分为基础，重点分析了沙尘暴发生季节反映下垫面特征的土壤水分的时间变化以及大气影响对不同土壤类型(棕钙土，灰漠土，栗钙土)水分的作用。土壤水分的变化被分为3个阶段进行分析，分别是解冻期至沙尘暴开始的春季、雨期的秋季和冰雪覆盖的冬季。土壤水分受气象条件和土壤类型的影响较大。在气象条件的影响下，土壤水分含量在土壤融化期最低，在雨季达到最大值，其中以栗钙土受的影响最明显。沙尘暴发生依赖于土壤融化时间、土壤融化期的土壤条件和上年冬季的冻土深度。     

The Eruptive Flare of 15 November 1991: Preflare Phenomena

We present and interpret observations of the preflare phase of the eruptive flare of 15 November, 1991 in NOAA AR 6919. New flux emerged in this region, indicated by arch filaments in Hα and increasing vertical flux in vector magnetograms. With increasing frequency before the eruption, transient dark Hα fibrils were observed that crossed Hα bright plage and the magnetic inversion line to extend from the region of flux emergence to the filament, whose eruption was associated with the flare. These crossing fibrils were dynamic, and were often associated with sites of propagating torsional motion. These sites propagated from the region of flux emergence into the filament flux system. We interpret these morphological and dynamic features in terms of relaxation after magnetic reconnection episodes which create longer field lines within the filament flux system, as envisioned in the tether cutting model, and transfer twist to it, as well. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005086108043     

Vietnamese activity in the Adelaide real estate market

Significant real estate activity by Vietnamese households in Adelaide did not occur until 1979, and since then the groups buying activity has been heavily concentrated in the northwest region of the metropolitan area. Therefore, the median housing price paid by Vietnamese buyers has not kept pace with the median price paid by all buyers. Concentration also causes Vietnamese buyers to be disproportionately active in the middle‐to‐lower end of the market, within which there has been a strong preference for rural properties and for houses rather than home units and maisonettes. Amongst Vietnamese buyers who subsequently sell their properties, the majority have not re‐entered the market and their capital gain from ownership has been marginal.     

A laboratory simulation of rock breakdown due to freeze-thaw in a maritime Antarctic environment

Results of freeze-thaw simulations on three large blocks of quartz-micaschist are presented. Three types of water to ice phase change were identified from temperature and ultrasonic measurements. It is suggested that the type of phase change results from a particular combination of rock moisture content, solute concentration, freeze amplitude, and rate of fall of temperature. The temperature at which ice thawed inside the rock (?0.7 to ?1.9°C) was also found, and this indicates the possibility of freeze-thaw effects without positive temperatures. Approximately 80 per cent of the water that will freeze under natural conditions, in the Maritime Antarctic environment under study, appears to have done so by ?6°.     

Collisional plateaus

In the fifteen years since the importance of collisional plateaus with thickened continental crust began to be recognized as one of the inevitable consequences of the processes of plate tectonics, rapid progress in their understanding has come from studies of the world's only active terminal collision zones in the Himalayan-Tibetan and Turkish-Iranian plateaus.Ancient collisional plateaus are being recognized throughout the geological record (back to 3.8 Ga) from the occurrence of extensive areas (typically > 500,000 km²) of 8 kbar metamorphism in granulite facies or from the occurrence of extensive areas of higher level minimum-melt composition granite rocks whose isotopic signatures indicate reactivation of existing continental crust rather than addition of new crust from the mantle at the time of collision. Recognition of strike-slip faulting in the ancient collisional plateau areas indicates that “tectonic escape” may have been as important in the past as it is today.Earth may not be the only planet on which collisional plateaus are important. The highlands of Venus (approximately 7% of the surface with elevations over 1.5 km above mean planetary radius) can only exist as a result of crustal thickening, and not as a product of lithospheric thinning. Most of these highlands can be explained by models involving volcanic construction. However, the highest peaks, including Maxwell Montes, the highest mapped area of Venus rising over 10 km above mean planetary radius, require much greater crustal thickening to support them than can reasonably be explained by a volcanic mechanism. Geological features of Maxwell Montes inferred from radar images suggest some analogy between Maxwell Montes and the Tibetan plateau.It is somewhat paradoxical that extensional tectonics are commonly associated with continental collision, and that collision-related rifts may be the only sites where the uppermost layers of a collision-thickened crust are preserved from erosion. Extensional stress fields are generated during continental collision, primarily in areas associated with strike-slip faulting and “tectonic escape”. Additional extensional stresses are gravitationally generated associated with the topography and thickened crust in a collision zone. Tectonically thickened crust is particularly susceptible to rifting as its lithosphere is weak as a result of heating associated with magmatism. This lithosphere is also compositionally weak because of the relatively thick crust, dominated by a weak quartz rheology, and thin mantle lithosphere, dominated by a strong olivine rheology, in comparison with a lithosphere with a more normal crustal thickness. Thus, the common association of rifts and collision zones may be a consequence of both stresses generated during collision and modification of the lithosphere by collision.     

Neotectonics of Hispaniola: plate motion, sedimentation, and seismicity at a restraining bend

A series of different plutons from the Lhasa-Xigaze segment of the Gangdese (Transhimalaya) belt has been studied by high-resolution UPb analyses of zircon (using zircon fractions of 5–100 grains each, selected upon specific grain characteristics). For two diorites, located east of Xigaze (Dazhuka), the zircons yield concordant ages of 93.4 ± 1.0 and 94.2 ± 1.0 m.y., respectively. Also concordant ages of 41.1 ± 0.4 and 41.7 ± 0.4 m.y. have been obtained for two granodiorites, collected southwest of Lhasa (Qushui). The precision on the ages of two granites from the Xigaze and Lhasa area, is limited by two factors: the presence of inherited radiogenic lead and the occurrence of subsequent lead loss. However, some concordant zircons, detected in both granites, define approximate ages of about 67 and 53 m.y., respectively. The inherited lead components show that melting of Precambrian material was involved in magma genesis.The UPb ages substantiate a magmatic activity lasting from mid-Cretceous (Cenomanian) to Eocene (Lutetian) time. Such a period of plutonism at the southern margin of Eurasia, as well as the occurrence of magma generation from continental crust, suggest that the Gangdese range results from the subduction of Tethys oceanic lithosphere (Indian plate) underneath Eurasia (Eurasian plate). If this model is true, the collision of India with Eurasia (along the Lhasa-Xigaze sector) postdates the emplacement of the 41 m.y. old Gangdese granodiorites, i.e. the collision occurred after Lutetian time.     

Experimental and model transport and diffusion studies in complex terrain with emphasis on tracer studies

The U.S. Department of Energy (DOE) Atmospheric Studies in Complex Terrain (ASCOT) program began in the fall of 1978 as a multiple DOE and other Federal Laboratory program devoted to developing a better physical understanding of atmospheric boundary layer flows in areas of complex terrain. The first technical challenge undertaken by the program was an investigation of atmospheric boundary layer phenomena associated with the development, continuation and breakup of nocturnal drainage wind flows. This paper discusses the general objectives the program has addressed during the past several years and focuses on results from a major field experiment conducted in 1980 in The Geysers area of northern California. Specifically, results from measurements of simultaneous tracer releases are compared to calculations from a mass-consistent wind field model coupled to a particle-in-cell transport and diffusion model. Results of these comparisons show that model calculations agree with measurements within a factor of 5 approximately 50 percent of the time. Part of the difficulty faced by the models in these comparison studies is associated with large variabilities between measurements made by samplers located one or two x apart when compared to the resolution of the models. Space and time averaging improves the comparisons considerably, although the design of the field experiment did not allow the determination of optimum spacial and temporal averages.     

Results of Seepage Meter and Mini-Piezometer Study, Lake Mead, Nevada

The seepage meter and the mini-piezometer were utilized in an attempt to evaluate ground-water reservoir interactions over a 12-month period at Echo Bay in Lake Mead. In conjunction with these techniques three standard piezometers, refraction seismic data, and water chemistry data were utilized to interpret seepage device results. During a four-month period, from December 1979 to March 1980, an 8 ft (2.5 m) rise in reservoir stage, the reservoir contributed water to Echo Wash bank storage at rates of up to 0.29 gpd/ft² (12 lpd/m²). Ground-water discharge occurred for the remainder of the project, during a stage decline from April 1980 to May 1980, a rise in June 1980, and leveling off and slight decline for the remainder of the year, July 1980 to December 1980. The maximum seepage meter ground-water discharge rate of 3.0 gpd/ft² (122 lpd/m²) was recorded in December 1980. Seepage meter water chemistry data for June were similar to Lake Mead water chemistry and were interpreted to be previously recharged Lake Mead water. September water chemistry data showed two possible components of ground-water discharge, a high SpC calcium sulfate Echo Wash ground water and a lower SpC Lake Mead recharged bank storage water. December ground-water chemistry data showed discharge to be a high SpC calcium sulfate water similar to Echo Wash ground-water quality which was apparently unaffected by Lake Mead inflow. Mini-piezometer data were collected at each seepage meter site. However, these data usually did not provide correlative results with seepage meter data probably because of suspended sediment in the piezometer water column and plugging of the perforated tip. Seepage meters were successfully utilized to characterize reservoir ground-water interaction in Echo Bay.