Deformation-induced microstructures in soils affected by mass movements

The soil deformation produced by mass movements gives rise to specific microscopic features. The study of some markers of deformation, such as the orientation of rigid clasts and the morphology of fine-grained intercalations, indicates that, in most cases, mass movements can be related to simple shear. The development of these features varies according mainly to the type of mass movement (solifluction, debris flow or earth slide). Different factors play a significant role in their formation: intrinsic soil characteristics such as the grain size of the matrix, water content and matrix/element viscosity ratios, and external factors such as the intensity and homogeneity of deformation. A careful study of the microscopic features leads to a better understanding of the dynamics of mass deposits.     

High salinity winter outflow from a mega inverse-estuary—the Great Australian Bight

Conductivity-temperature-depth (CTD) observations taken in the Great Australian Bight (GAB) during ORV Franklin cruise Fr 07/94 in July 1994 indicated the presence of a dense bottom layer at the head of the GAB, which flowed along the sea floor towards the shelf-break as a gravity current The north central region of the GAB was stratified with a maximum salinity difference of between 0.4 and 0.5. The outflow was confined to the shelf and was directed in a south-easterly direction with little evidence of cross-shelf transport. The flow exhibited a well-defined bottom interface evident from the head of the GAB to near the mouth of Spencer Gulf (SG), where the surface-bottom salinity difference was about 0.3. The mean thickness of the outflow was about 15 m. An estimate of the speed of the outflow at the discharge over the shelf-break was made using the zero entrainment assumption. This yielded a speed of <16 cm s⁻¹, which remarkably was consistent with near bottom current meter measurements (16 cm s⁻¹) on the continental shelf edge, reported south of the Eyre Peninsula. A mass budget analysis indicated that the outflow, which probably is partially maintained by the gravity current and partly by a wind-driven circulation would exist over the period, July–December, with a peak transport of about 10⁶ m³s⁻¹ (1 Sverdrup) which is approximately twenty times that of the bottom outflow from the adjoining Spencer Gulf.     

修正的质量通量积云对流方案及其模拟试验研究Ⅰ:方案介绍及对1991年洪涝过程的模拟

文中在综合比较各类积云对流参数化方案优缺点的基础上 ,主要参考陈伯民等修正的ECMWF质量通量积云参数化方案 ,对其进行简化和修改 ,发展了一个质量通量积云对流参数化方案 ,文中表示为 MFS(Mass Flux Scheme)。MFS是一种综合型的方案 ,既考虑了大尺度水汽辐合的重要性 ,又考虑了积云中的上升运动、下沉运动、环境中的补偿下沉运动 ,以及卷入、卷出和蒸发等 ,用总体云模式来描述积云与环境的相互作用 ,同时考虑了深对流和浅对流。将 MFS植入 NCAR区域气候模式 Reg CM2中 ,对 1 991年 5～ 7月江淮地区特大降水过程的夏季风气候特征和变化进行了模拟 ,并与 NCAR Reg CM2选用 Kuo方案 ,在同样初、边值条件和其它物理过程选择下的模拟结果进行了对比分析。分析结果表明 ,植入 MFS后的模式能够模拟这次极端的降水气候事件。在某些方面 ,如地表气温 ,降水的模拟上 ,植入 MFS后的模式的模拟结果要比原模式的结果更合理     

误差扣除法在云南中尺度数值模式中对气压梯度力的计算试验

使用云南中尺度数值预报试验模式^[1]，引入实际地形，选用静力扣除格式、回插格式、局地等温格式、经典修正格式以及模式中原计算格式（Corby格式）等5种计算格式计算气压梯度力，对气压梯度力的误差和扣除法进行了模拟试验。比较了这5种格式在有、无误差扣除时的模拟结果之后，发现误差扣除法与上述格式结合使用时，均能够不同程度地提高预报效果，尤其是在与经典修正格式结合使用以后，预报效果进一步改善，得到了较满意的模拟效果。     

Effects Of Changing Surface Heat Flux On Atmospheric Boundary-Layer Flow Over Flat Terrain

We examine the unsteady response of a neutral atmospheric boundary layer (ABL) of depth h and friction velocity u _* when a uniform surface heat flux is applied abruptly or decreased rapidly over a time scale t<inf>θ</inf> less than about h /(10u _*). Standard Monin–Obukhov (MO) relationships are used for the perturbed eddy viscosity profile in terms of the changes to the heat flux and mean shear. Analytical solutions for changes in temperature, mean wind and shear stress profile are obtained for the surface layer, when there are small changes in h /|L_MO| over the time scale t_MO~|L _MO|/(10u_*) (where L _MO and t _MO are the length and time scales, respectively). They show that a maximum in the wind speed profile occurs at the top of the thermal boundary layer for weak surface cooling, i.e. a wind jet, whereas there is a flattening of the profile and no marked maximum for weak surface heating. The modelled profiles are approximately the same as those obtained from the U.K. Met Office Unified Model when operating as a mesoscale model at 12-km horizontal resolution. The theoretical model is modified when strong surface heating is suddenly applied, resulting in a large change in h /|L _MO| (>>1), over the time scale t _MO. The eddy structure is predicted to change significantly and the addition of convective turbulence increases the shear turbulence at the ground. A low-level wind jet can form, with convective turbulence adding to the mean momentum of the flow. This was verified by our laboratory experiment and direct numerical simulations. Additionally, it is shown that the effects of Coriolis acceleration diminish (rather than as suggested in the literature, amplify) the formation of the wind jets in the situations considered here. Hence, only when the surface heat flux changes over time scales greater than 1/f (where f is the Coriolis parameter) does the ABL adjust monotonically between its equilibrium states. These results are also applicable to the ABL passing over spatially varying surface heat fluxes.     

Pressure Forces On Small-Scale Three-Dimensional Hills In Stable Conditions

Numerical simulations are presented of flow over small-scale three-dimensional hills embedded within the stable boundary layer. Large surface forces are associated with internal gravity waves excited by Fourier modes aligned with the ridge axes closely parallel to the wind. Even moderate anisotropy of the topography may then lead to the surface forces (in a frame aligned with the wind) being strongly sensitive to wind direction. However, the impact of the waves on forces in the direction of the geostrophic wind is relatively minor.The British Crowns right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.     

氯化钠传压介质高温高压岩石变形实验的应力和围压修正

该固体围压介质高温高压岩石变形实验装置的应力和围压修正方法是从长春地质学院岩石变形实验室的三轴实验系统中经过实验总结出来的,简便易行,可应用于同类系统的实验设备。确定了该实验装置采用氯化钠传压介质时氯化钠的传压特性和内部摩擦力的大小,并进一步确定出样品实际所受的围压和应力与表观值间的关系,求出修正量,从而应用于具体的实验研究中     

1994年青海省天气异常的特征分析

１９９１年是青海省最热的年份之一，而且青海省各地降水量时空分布不均匀。本文分析了导致今年天气异常发生的主要原因。     

Geo-botanical evidence of late quaternary mass wasting in block field areas of Virginia

Studies of block fields at Massanutten Mountain, Virginia, document and provide information on the magnitude and frequency of mass movement on these coarse-grained slopes. Block fields, which traditionally have been considered relicts of Pleistocene climate, occur on and downslope from resistant Massanutten Sandstone in Passage Creek basin. Slopes are strewn with boulders and vegetative cover on the open block fields is absent to sparse. Several block fields were investigated for evidence of recent movement using the degree of lichen growth, differences in block weathering, and rock-fall damaged trees. Temporal and spatial aspects of geomorphic processes can be inferred through dendrogeochronology. Corrasion scars and stem ages infer a minimum age for a geomorphic or hydrologic event. High flows on Passage Creek coincided with tree-ring determined dates of block-field movement. Although, Pleistocene periglacial climate may have facilitated original formation of block fields, some block fields now continue to spread downslope during intense runoff events. Present block-field mass wasting may be the principal erosional process in these areas of resistant rock.     

气压变化及其对地壳形变和深井水位的影响

根据北京塔院地区1984和1985年的微气压计记录采用频谱分析和调和分析两种方法得出了大气潮谱的详细结构;用负荷勒甫数代替潮汐勒甫数,仿照固体潮的有关公式,导出了大气潮引起的地壳应变和地倾斜公式;使用北京塔院井的水位观测资料结合当地的气压资料,分析了气压变化对深井水位的影响.理论计算和实测资料的分析结果基本相符,特别是两种结果都得出S₂大气潮引起的体膨胀约为S₂固体潮体膨胀的20％.