土壤热异常影响地表能量平衡的个例分析和数值模拟

The statistical relationship between soil thermal anomaly and short-term climate change is presented based on a typical case study. Furthermore, possible physical mechanisms behind the relationship are revealed through using an off-line land surface model with a reasonable soil thermal forcing at the bottom of the soil layer.In the first experiment, the given heat flux is 5 W m-2 at the bottom of the soil layer (in depth of 6.3 m)for 3 months, while only a positive ground temperature anomaly of 0.06℃ can be found compared to the control run. The anomaly, however, could reach 0.65℃ if the soil thermal conductivity was one order of magnitude larger. It could be even as large as 0.81℃ assuming the heat flux at bottom is 10 W m-2. Meanwhile, an increase of about 10 W m-2 was detected both for heat flux in soil and sensible heat on land surface, which is not neglectable to the short-term climate change. The results show that considerable response in land surface energy budget could be expected when the soil thermal forcing reaches a certain spatial-tem poral scale. Therefore, land surface models should not ignore the upward heat flux from the bottom of the soil layer. Moreover, integration for a longer period of time and coupled land-atmosphere model are also necessary for the better understanding of this issue.     

岩溶地区桩基的有限元分析

岩溶地区长桩存在着遇洞率的问题。为了研究岩溶地区桩的受力特点,采用有限元法模拟岩溶地区桩基的工作方式,分析了岩层厚度对桩的影响以及桩的受力状态,并研究了去桩的可能性。计算结果表明:岩层厚度对桩的影响较大,岩层的位置对桩的应力不产生影响,仅对桩的位移产生影响。     

华北汛期降水异常与100hPa高度场异常的关系

利用华北17站1951～2000年的逐月降水资料,与前期的100 hPa高度场(1958～1997年)求相关,找到了100 hPa高度场影响华北地区汛期降水的关键影响区为25°～35°N,85°～105°E,对应的关键影响时段为前一年3～5月.然后用SVD方法证实了前一年春季正是与华北汛期降水相关最显著的时段;而所选关键区正是处于一种范围更大的100 hPa高度场空间分布型的关键部位,而华北地区是关键区影响中国东部降水的最显著的区域之一.     

p—σ混合坐标全球模式模拟夏季气候的性能及系统性误差分析

将球带范围的ｐ－σ混合坐标系五层原始方程模式发展成为包含极区的全球大气环流模式，并用ＧＦＤＬ多年平均气候分析资料检验了模式对夏季气候平均状态的模拟性能，分析了ｐ－σ混合坐标系全球大气环流模式模拟夏季气候的系统性误差。结果表明：ｐ－σ混合坐标系全球大气环流模式能较好地模拟夏季气候平均态，各高度上的主要环流系统都可以模拟出来，与球带模式的结果相比有一定的改进，而且陆地上的模拟结果优于海洋上的。     

陆面特征非均一作用参数化及其对区域气候影响的数值模拟试验

本文首先改进了陆地下垫面特征非均一性的次网格尺度参数化方法，然后利用三维地气耦合的区域气候模式，设计一系列值试验，研究了下垫面特征改变对区域气候环境变化的影响，主要分析了陆地表面特征变化对我国苏南附近地区夏季温度化的影响，结果表明采用地下垫面特征非均一作用的次网格尺度参数化方法对于改进数值模拟结果的质量有一定效果。     

二维温盐环流模式研究14C在海洋中的分布

海洋碳循环模式中常使用放射性同位素14C来检验该模式的物理模型是否较好地反映了海洋中的大尺度变化的过程。本工作使用的物理模型是包括太平洋、大西洋和南大洋在内的二维温盐环流模式，在给定的年平均海表强迫下积分4000年后，环流达到准稳态，其定常流场用来驱动14C模式。对14C模式积分5000年以上，可得到14C稳态的分布。使用不同的二氧化碳海气交换系数和垂直湍流扩散系数值进行了7个实验，发现使用Broecker等的交换系数方程和扩散系数值依深度从0.6增加到1.45 cm2/s，模拟的结果较好。使用观测到的大气中14C含量，进一步研究了工业革命后及核试验后的14C在海洋中的穿透，模拟结果与现有的一些资料进行了比较，总体上给出了合理的结果。     

用土的分形结构确定土的水份特征曲线

运用筛析法和比重计法，分析了宁夏膨胀土的颗粒分布，发现粒径介于0．002～0．1mm的粒度分布是分形的，分维介于2．46～2．67；运用上孔隙分布的分维确定水份特征曲线，得到了很好的结果。此外，还探讨了粒度分形分布的机制。     

Bearing capacity of unsaturated expansive soils

It is difficult to determine the bearing capacity of a foundation in unsaturated expansive soil, although this is most important. The bearing capacity of unsaturated expansive soil is related to the drying and wetting environment. Swelling pressure occurs when the soil volume change is constrained as an expansive soil is inundated. The expansive lateral pressure, induced by the swelling pressure is similar to the passive earth pressure. By considering the effect of the expansive lateral pressure in Terzaghi's bearing capacity formula, the bearing capacity of unsaturated expansive soil is derived. Because it is very difficult to measure suction in situ, the bearing capacity is expressed using the expansive lateral pressure offers a feasible approach to calculate the bearing capacity of a foundation in unsaturated expansive soil, when suction is not measured. Plate load tests to measure the bearing capacity in situ were performed for the foundation in natural soil and saturated soil immersed by water. The verification of the bearing capacity formulae presented in this paper is conducted by comparing the predicted results with the results of the plate load tests on unsaturated expansive soils in Handan and Bingxia, China.     

基于三角网的"种子法"多边形生成

将传统上广泛使用的“种子法”和“矢量求交法”的思想相结合 ,提出了一种基于约束Delaunay三角网结构的多边形生成算法。详细描述了该方法的基本思想 ,在实验基础上分析了算法的特点。     

一种组合优化的多边形化简方法

以多边形轮廓为目标 ,依据曲线特征点将其分解为一系列的弯曲特征 ,并对此弯曲特征集实施组合优化 ,将入围弯曲首尾相连 ,即可得到最终的化简结果