Validation of Jason and Envisat Altimeter Dual Frequency Rain Flags

New rain flags based on the dual frequency capabilities of the new Jason Poseidon-2 and Envisat RA2 altimeters have been tested, developed and adopted for the operational processing of the altimeter data. Their validation conducted during the calibration/validation phases of the satellites is presented here. The Jason flag is validated by comparison with the TOPEX one, using the Tandem mission. The results show a very good agreement between the two sensors and the two rain flags The Envisat flag is validated by comparison with both Jason and TOPEX using global and collocated data sets. The results show similar performances for the three sensors. The f relations estimated during the calibration-validation period and presented here have been given to the altimeter ground processing facilities for operational use.     

一种基于双重距离的空间聚类方法

传统聚类方法大都是基于空间位置或非空间属性的相似性来进行聚类,分裂了空间要素固有的二重特性,从而导致了许多实际应用中空间聚类结果难以同时满足空间位置毗邻和非空间属性相近。然而,兼顾两者特性的空间聚类方法又存在算法复杂、结果不确定以及不易扩展等问题。为此,本文通过引入直接可达和相连概念,提出了一种基于双重距离的空间聚类方法,并给出了基于双重距离空间聚类的算法,分析了算法的复杂度。通过实验进一步验证了基于双重距离空间聚类算法不仅能发现任意形状的类簇,而且具有很好的抗噪性。     

The developmental characteristics and strategic ideas of urbanization in China

Since cities and towns are places where those nonagricultural industries are centralized, urbanization is greatly interrelated with industrialization and de-agriculturalization. By means of this kind of interrelationship, Chinese urbanization level may be estimated with the formulas: P1=I1/I0/u0, Pr = N1/N0/u0. The urbanization after the founding of the People's Republic of China can be divided into the following 5 stages: the stage at the out set of industrialization (1949-1957); the high-speed urbanization stage (1958-1960); the first counter-urbanization stage (1961-1965); the second counter-urbanization stage (1966-1976); and the high-speed urbanization stage (1978-now). The characteristics of Chinese urbanization are: the industrialization launched by the government; the simultaneous development of urbanization of cities and urbanization of rural areas; the quite low capability of urbanization to absorb nonagricultural labor force; the incoordinate development of cities, etc. Before establishing a     

鄂北一次超级对流单体的双偏振雷达特征分析

利用湖北省随州市S波段双偏振雷达资料及常规观测资料，对2020年5月4日鄂北随州出现的超级单体风暴进行分析。结果发现：①在有利天气背景作用下，形成了上干冷下暖湿的垂直层结、0~6 km中等强度垂直风切变以及地面辐合线，为强风暴的发生发展提供环境条件和触发条件。②超级单体发展过程中，观测到前侧“V”形入流缺口、中气旋、弱回波穹隆、悬垂回波、钩状回波等特征，且风暴顶高度、风暴质心高度、最大水平反射率因子高度以及垂直累积液态含水量等风暴参数均呈先升后降趋势。③超级单体的发展和成熟阶段，在0 ℃层以下的低层，于前侧下沉气流西侧的水平反射率因子大梯度区观测到浅薄的差分反射率因子Zdr大值区，即Zdr弧；④超级单体的初始阶段、发展阶段以及成熟阶段，在0 ℃层之上的中层，观测到强上升气流的正温度扰动使冰相粒子在附近融化而形成的Zdr环形大值区和相关系数环形小值区。⑤垂直方向上，在超级单体的初始阶段、发展阶段以及成熟阶段均观测到Zdr柱和差分相位常数Kdp柱。Zdr柱与弱回波穹隆区位置对应较好，其不同时期特征反映了上升气流强的变化；Kdp柱的变化反映了超级单体中含有大量液态水滴区域的变化。     

一种层状大地瞬变电磁响应正演计算的改进方法

频谱法是瞬变电磁法正演计算中常用的计算方法之一,其关键在于内层含贝塞尔函数的积分计算。对于重叠回线装置的瞬变电磁法正演的内层积分,以往采用在积分区间内寻找贝塞尔函数的零点分布,依次在相邻零点之间采用一般的数值积分法在求得各自的积分值后再叠加的方法进行计算。这种方法精度较高,但效率低。利用贝塞尔函数的大宗量渐近特性,提出一种新的计算方法。计算结果表明,该方法计算效率高、方法简单、精度可靠。     

基于Kiwi数据格式的地图显示研究

在分析Kiwi显示数据存储组织方法的基础上,研究了Kiwi显示数据在内存中的动态组织,改进了地图显示的二级缓存方法,提出了地图显示的双缓冲池策略。试验结果表明,本文研究的数据动态组织方法和地图显示策略提高了地图显示速度。     

VLBI观测的电离层延迟改正模型研究

电离层是大气层中的一个电离区域，高度范围大约在60－1000km。电磁波信号穿越电离层时其传播速度会发生变化，传播路径也会略微发生弯曲，从而使信号的传播时间乘以在真空中的光速不等于信号源至测站的几何距离。对VLBI观测来讲，电离层引起的差异可达近百米百米。文中从电磁波的传播原理出发，讨论了信号传播速度和传播路径变化引起的VLBI观测延迟；对目前采用的各种电离层延迟模型进行了分析总结；并指出单频率VLBI观测应顾及高阶项和路径弯曲的影响或使用区域性电离层延迟改正模型。     

双频梯度测量探查井巷漏水水力联系

介绍一种利用双频仪解决矿区井巷巷道中漏水水力联系的原理和方法。双频梯度测量法有抗干扰能力强、分辨率高、仪器轻便等特点,实践证明应用效果很好。     

Tensionless–frictionless interaction of flexible annular foundation with a transversely isotropic multi‐layered half‐space

A transversely isotropic multi‐layered half‐space, with axis of material symmetry perpendicular to the free surface, supports a flexible either annular or solid circle foundation. The contact area of the foundation and the half‐space is considered to be both frictionless and tensionless. The foundation is assumed to be affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems with different thickness of layers is the target of this paper. With the use of ring load Green's functions for both the foundation and the continuum half‐space, an integral equation accompanied with some inequalities is introduced to model the complex BVP. With the incorporation of ring‐shape FEM, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular and annular foundation with half‐space. Some new illustrations are presented to portray the aspect of the anisotropy and layering of the half‐space. Copyright © 2014 John Wiley & Sons, Ltd.     

How preferential flow delivers pre‐event groundwater rapidly to streams

Groundwater often accounts for a substantial fraction of flood hydrographs, but the processes responsible for this have been unclear. However, many aquifers have preferential flow and this explains how aquifers can be so responsive. In bedrock aquifers, weathering enhances the connectivity and apertures along the most efficient flow paths and hence enhances the permeability. This results in celerities and velocities of the preferential flow in these dual‐porosity aquifers that are two to three orders of magnitude higher than if the aquifers behaved as single‐porosity media. The celerities have been determined from artificial and natural flood pulses, from tidal lags, and from pumping tests. Preferential‐flow velocities have been calculated from tests using applied tracers. Celerities in bedrock aquifers are typically one to two orders of magnitude faster than velocities. The ubiquitous preferential flow in aquifers provides an additional explanation, besides groundwater ridging, for the rapid release of groundwater to streams during storm events.