基于SRTM数据的中国新一代天气雷达覆盖和地形遮挡评估

利用航天飞机雷达地形测绘数据(Shuttle Radar Topography Mission,SRTM)3 s高分辨率地形数据对全国已建成的158部新一代天气雷达分别进行了地形遮挡和覆盖能力计算,并提出了3个定量指标:覆盖比、高度—面积指数和等效覆盖半径.按照这些指标,对各雷达进行了计算和统计,并分析典型雷达站点的覆...     

Characterization of cloud microphysical properties in different cloud types over East Asia based on CloudSat/CALIPSO satellite products

利用CloudSat/CALIPSO卫星资料,本文揭示了东亚三个代表性区域的云微物理属性,为评估和改进模式云微物理过程提供重要的观测基础.研究的云微物理量包括云水/冰质量,数浓度和有效半径.研究表明:暖云中云水质量和数浓度随高度增加而减小,有效半径处于8-14μm范围.对于冰云,云冰质量和有效半径随高度增加而减小,而数浓度在垂直方向上变化不大.此外,云微物理属性在不同云型之间存在显著差异:积云的云水质量和数浓度最大,而卷云的云水质量和数浓度最小.从三个区域的对比结果来看,相比于华东和西北太平洋地区,青藏高原地区暖云的云水质量和数浓度较小,而冰云的则较大.     

云滴谱的不确定性对中尺度降水的影响

云滴的谱分布通过改变云滴的有效半径影响辐射传输过程,改变大气的热力、动力状况,进而影响云的发展,因此云滴谱将影响云和辐射的相互作用,从而改变地面降水。利用包含详细云微物理方案的MM5V3中尺度模式对1998年6月8日华南暴雨和2002年7月22日长江暴雨进行了数值模拟,研究了中尺度模式中云滴谱的不确定性对地面降水的影响。模拟结果表明,云滴谱在中尺度地面降水中起着重要的作用,其不确定性对地面降水的范围影响很小,却能明显地改变降水强度,能显著地改变地面降水中心的降水量和中心位置,还可能改变降水的起止时间;云滴谱的不确定性能够引起最大超过10％的平均降水强度的改变,而且其差异在白天比夜间更明显。     

用轴对称的平衡模式对热带气旋发展过程中 积云动量垂直混合作用的模拟

引入一个轴对称的平衡数值模式,在该模式中考虑积云动量垂直混合等物理过程,然后以此模式对热带气旋形成和发展的过程进行了模拟。所作研究表明,引入积云动量垂直混合作用之后热带气旋发展更为迅速,并且成熟气旋的强度更强;在气旋生成的初期,积云动量混合的作用并不大,只有在气旋发展到了一定阶段,积云对流十分旺盛时,才会产生较大的作用;在空间分布上,积云动量垂直混合主要发生在对流层的中低层,而高层则相对较弱,对热带气旋的影响很小。另外,发展成熟的热带气旋其辐散层较厚,质量辐合主要集中在边界层;热带气旋的内部结构和环流特征造成了各个高度层次上熵的不同分布形态。     

地震应变加速释放模型在华东地区应用

根据华东地区的地震活动特点,定义较简单的半径搜索方法,遵循一定的准则挑选出1976年以来华东地区满足震前累积应变加速释放模型(ASR)的14次ML≥4.5地震序列。将破裂—时间分析法的非线性方程分成两个线性方程,采用线性最小二乘法拟合参数k/m与主震矩的经验关系,确定华东地区的ASR模型,并用来预测主震的时间和震级。经检验该方法预测震级误差约为±0.3,发震时间误差约±1.68 a。     

First records, pathways and distributions of four new Ponto-Caspian amphipods in France

In Europe, the number of establishment of non-native species, especially from Ponto-Caspian area, has dramatically increased over the past decades and induced important changes in macroinvertebrate assemblages, mainly in large rivers. However, although many Ponto-Caspian species were established in adjacent countries, only two Ponto-Caspian amphipods were formally observed in French hydrosystems since 1996. To update our knowledge on the present distribution of the Ponto-Caspian species in France, we collected amphipods from 203 sites in the Rhine, Meuse and Seine River basins in 2008 and again in 2009. Thirteen amphipod species were found in the study area. Among them, four were first formally recorded in France (Dikerogammarus haemobaphes, Dikerogammarus bispinosus, Echinogammarus ischnus, and Echinogammarus trichiatus). Our study revealed three different corridors used by these species to arrive in France. We also observed a different pattern of colonization for each species, which might indicate some between-species differences in their preferences for environmental conditions. The snapshot of the early distributions of these recently established species may hence be used to study the invasion pattern in France in order to manage their potential impact in and outside France.     

Seasonal variation in the transverse and layered structure of estuarine circulation in Ariake Bay, Japan

Seasonal variation in the transverse and layered structure of estuarine circulation in Ariake Bay, Japan was investigated by box model analysis using monthly salinity data from 1990 to 2000. Two-layered gravitational estuarine circulation was intensified from autumn to spring (vertically well mixed season) accompanied by a small river discharge. Two-layered circulation was weakened accompanying the transversely segregated cyclonic circulation in the upper layer during summer (stratified season) with a large river discharge. Such seasonal variation in the transverse and layered structure of estuarine circulation is because the bay width of Ariake Bay (20 km) is narrower than the external Rossby deformation radius (235 km) but wider than the internal Rossby deformation radius (3–5 km).     

Neuston: A relevant trophic resource for apple snails?

Apple snails are known for the strong impacts they provoke in wetlands and aquatic crops by their macrophytophagous habits. Interestingly, they are able to persist after they have eradicated most palatable aquatic macrophytes in the invaded wetlands. Pedal surface collecting is a distinctive mechanism that apple snails use to capture materials in the water surface. We were interested in knowing the relevance of neuston, the organisms associated with the air–water interface, as an alternative trophic resource. Using the invasive Pomacea canaliculata as a model, our experiments with simulated trophic resources in the laboratory showed that neuston is highly consumed even in the presence of abundant palatable macrophytes. P. canaliculata was able to grow efficiently using neuston as an alternative trophic resource both under laboratory and natural conditions. Neuston probably plays a relevant role specially when other trophic resources are inedible or absent or have been depleted by apple snails. Pedal surface collecting probably evolved in apple snails as an adaptation to cope with fluctuating trophic resources.     

竖向掏土纠倾孔周塑性区计算研究

采用桩筏基础的高层建筑倾斜后,常采用竖向孔掏土进行地应力解除实现纠倾,工程设计与施工依据经验进行,缺乏理论指导。将一定深度处的竖向孔孔周应力重分布问题简化为平面应变问题,采用摩尔?库仑强度条件推导了塑性区半径的解析解。该解析解表明,塑性半径随土体抗剪参数的降低而增大,随掏土孔半径的增大而增大,随地应力的增大而增大。结合解析解的表达式,探讨了存在地下水、注水、抽水、循环掏土扰动等因素对塑性区半径的影响。最后用数值分析方法对该解析解进行模拟验证,表明公式的正确性与适用性。该研究成果对纠倾工程的设计与施工具有积极的指导作用。     

地表移动土体受力规律及其对土体强度影响

地表移动分为初始移动过程和土体固结过程,用有限元分析了厚松散土层初始移动过程中地表土体的孔隙水压和横向有效应力的变化规律、有效应力路径和横向有效应力随深度的变化;对比了初始移动结束时和土体固结后横向有效应力随沉降量和下沉影响半径的变化规律,基于横向有效应力和土体强度的关系分析了土体强度的变化.