The response of subaqueous dunes to floods in sand and gravel bed reaches of the Dutch Rhine

Abstract The branches of the River Rhine in the Netherlands, characterized by a sand–gravel bed in the upstream part and a sand bed in the downstream part of the river system, show migrating dunes, especially during floods. In the last 20 years, these dunes have been studied extensively. High-resolution echo-sounding measurements of these dunes, made with single and multibeam equipment, were analysed for three different sections of the Rhine river system during several floods. This analysis was done to quantify the growth, decay and migration rates of the dunes during floods. In addition, the migrating dunes were used to calculate bedload transport rates with dune tracking. The results of dune growth and decay and migration rate are shown to be very different for the various sections during the various floods, and these differences are related to differences in grain size of the bed and to differences in the distribution of discharge over the main channel and the floodplain. The relations are used to show that the growth and migration rate of dunes, and the calculated bedload transport rates during the rising stage of a flood wave can be predicted from the mobility of the bed material with simple power relations.     

Numerical models of tectonic deformation at the Baltica–Avalonia transition zone during the Paleocene phase of inversion

Predictions from dynamic modelling of the lithospheric deformation are presented for Northern Europe, where several basins underwent inversion during the Late Cretaceous and Early Cenozoic and contemporary uplift and erosion of sediments occurred. In order to analyse the evolution of the continental lithosphere, the equations for the deformation of a continuum are solved numerically under thin sheet assumption for the lithosphere. The most important stress sources are assumed to be the Late Cretaceous Alpine tectonics; localized rheological heterogeneities can also affect local deformation and stress patterns. Present-day observations available in the studied region and coming from seismic structural interpretations and stress measurements have been used to constrain the model. Our modelling results show that lateral variation in lithospheric strength below the basin systems in Central Europe strongly controls the regional deformation and the stress regime. Furthermore, we have demonstrated that the geometry of the boundary between Baltica and Avalonia, together with different rheological characteristics of the two plates, had a crucial role on local crustal deformation and faulting regime resulting in the Baltica–Avalonia transition zone from the S–N Alpine convergence.     

Global thermal and dynamical perturbations due to Cretaceous mantle avalanche

The numerical models of mantle convection agree to depict avalanches behaviour according to the level of endothermicity of the spinel → perovskite phase change. Their potential effects on the global thermal and dynamical states of the mantle have been computed thanks to a numerical code, which takes into account both the 400-km exothermic and the 660-km endothermic phase changes. The cycle followed by the avalanches is: local layering, destabilization of the 660-km thermal layer, travelling and spreading on the core, and reappearing of the local layering. Therefore, mantle convection is characterized by quiet periods of partial layering embedded in catastrophic events. During the avalanche, the amplitude of the surface velocity is multiplied by two, which would imply an enhanced plate tectonic and ridge activities. The global thermal effects of the avalanche are compatible with a high mantle temperature and an acceleration of Earth's rotation during the Cretaceous. They also offer a coherent explanation to locate the origin of mantle plumes both within the CMB and just below the transition zone.     

“2002.6.30”滇中低涡暴雨的中尺度分析

利用MICAPS常规资料和GMS卫星云图，3830—C多普勒雷达观测资料，对2002年6月30日发生于滇中地区的暴雨天气过程进行诊断和分析，发现暴雨过程由中低层低涡切变造成，暴雨区与垂直速度及涡度所表现的强烈上升区对应，并伴有高能高湿条件；同时卫星云图上有中尺度低涡云团发展。多普勒雷达回波资料分析表明，暴雨过程中出现了明显的中尺度系统，如中尺度辐合线、中尺度气旋、逆风区等，具有典型的对流型特征。     

云南中部一次飑天气过程的雷达回波特征

利用地面资料和雷达回波，分析了2002年9月8日云南中部一次飑天气的发生、发展和演变情况，得出低纬高原飑天气出现时天气和要素变化为：雷暴最先出现，随后湿度急升，气温直线下降。在这突变过程中出现大风、大雨和冰雹，气压出现跳跃。飑线水平尺度长不到100km，宽仅10km，生消史两个小时左右。其雷达回波有前期征兆，发生演变过程，有一定特征。     

对地观测小卫星的相位噪声分析与控制

结合传输型对地观测小卫星一体化设计的特点，介绍了一种用于对地观测小卫星系统的锁相接收机的-构成及原理，并对系统的相位噪声性能进行了详尽的分析，提出了对其相位噪声进行技术控制的方法。通过文中的分析与研究，消除了由于对地观测小卫星相位噪声所引起的系统误码率的恶化，提高了系统的可靠性，为下一步对地观测小卫星的发展与应用打下了良好的技术基础。     

卫星云图、雷达回波在人工增雨时机选择中的应用

概述了干旱期间选择飞机和高炮人工增雨作业时机的方法，以2000年6～7月哈尔滨地区特大干旱期间进行的飞机和高炮人工增雨作业为例，利用卫星云图和雷达回波资料选择的作业时间和作业区域应是比较有利的。因为从卫星云图中的水汽图、红外和可见光云图上可分析出云系中的含水量、云顶温度、云系强度，在此基础上利用天气雷达跟踪订正，可直接指挥飞机和高炮在有利的区域和时间内进行作业，获得了明显的效果。     

GPS载波相位三差观测方程的改化

本文根据相关测量平差原理推导出改化ＧＰＳ载波相位三差观测方程的算法，使改化后的协因数呈分块对角体。这种改化算法不但顾及观测值的相关性，而且节省大量的存储单元。使采用严密平差法平差三差观测值成为一种最简单的数据处理方法之一。     

论光电测距仪的周期误差和相位不均匀性误差

论述了测距仪周期误差及相位不均匀性误差的性质，分析了这些误差对距离测量的影响，给出了实验结果，提出了改进有关误差检定的建议     

单块积云降水参数的直接估算

介绍了单块积云的雷达回波参数与降雨参数的一元、二元回归分析分析结果表明，单块积云的降雨量、雨强和持续时间与雷达皮的顶高、面积的相关性较好。