Simulating and understanding effects of water level fluctuations on thermal regimes in Miyun Reservoir

ABSTRACT

Water temperature dynamics in a reservoir are affected by its bathymetry, climatic conditions and hydrological processes. Miyun Reservoir in China is a large and deep reservoir that experienced a large water level decline in 1999–2004 due to low rainfall and relatively high water supply to Beijing. To study changes of stratification characteristics in Miyun Reservoir from 1998 to 2011, the one-dimensional year-round lake model MINLAKE2010 was modified by adding a new selective withdraw module and a reservoir hydrological model. Simulation results under three scenarios demonstrated that the new MINLAKE2012 model accurately predicted daily water levels and temperature dynamics during the water level fluctuation period. The water level decline led to 7.6 and 3.8°C increases in the maximum and mean bottom temperatures and about 29 days reduction in the stratification days. These simulation results provide an insight into the thermal evolution of Miyun Reservoir during the planned future water filling process.

Editor D. Koutsoyiannis Associate editor M. Acreman     

Dynamic model of mesoscale eddies. Eddy parameterization for coarse resolution ocean circulation models

In the framework of the eddy dynamic model developed in two previous papers (Dubovikov, M.S., Dynamical model of mesoscale eddies, Geophys. Astophys. Fluid Dyn., 2003, 97, 311–358; Canuto, V.M. and Dubovikov, M.S., Modeling mesoscale eddies, Ocean Modelling, 2004, 8, 1–30 referred as I–II), we compute the contribution of unresolved mesoscale eddies to the large-scale dynamic equations of the ocean. In isopycnal coordinates, in addition to the bolus velocity discussed in I–II, the mesoscale contribution to the large scale momentum equation is derived. Its form is quite different from the traditional down-gradient parameterization. The model solutions in isopycnal coordinates are transformed to level coordinates to parameterize the eddy contributions to the corresponding large scale density and momentum equations. In the former, the contributions due to the eddy induced velocity and to the residual density flux across mean isopycnals (so called Σ-term) are derived, both contributions being shown to be of the same order. As for the large scale momentum equation, as well as in isopycnal coordinates, the eddy contribution has a form which is quite different from the down-gradient expression.     

芦山7.0级地震医疗建筑震害与启示

鉴于医疗建筑在防灾救灾中的重要地位和作用,本科考小组对雅安地区医疗建筑在芦山地震中的震害进行了调查,调查包括不同烈度区、不同结构类型和建筑年代、不同级别的医疗卫生机构,对结构构件、非结构构件、医疗设备的震害特征,以及其他影响医疗秩序和使用功能的因素做了阐述和分析,并总结了汶川灾后新建及重建项目的抗震效果.调查表明,雅安地区医疗建筑在建筑结构的抗震安全性及救灾功能的实现方面仍存在很多问题,反映了我国医疗建筑的普遍问题.因此,对医疗建筑的抗震设防,需要作进一步系统的研究.     

Monitoring wetland ditch water levels in the North Kent Marshes,UK, using Landsat TM imagery and ground-based measurements

Abstract

An understanding of hydrology is a prerequisite for ensuring the successful management, conservation and restoration of wetland environments. Frequently, however, little is known about historical hydrological conditions, such as water levels, within wetlands. Moreover, many channel and ditch systems in wetlands are not routinely monitored, except perhaps for research purposes. A methodology is presented herein which makes use of satellite imagery to indirectly provide remotely sensed observations of water levels within channels and ditches. Using multi-temporal Landsat Thematic Mapper (TM) imagery and simultaneous ground-based measurements of water levels, statistical relationships are established between satellite-derived effective wet ditch widths and measured water levels in the drainage system of the Elmley Marshes, southeast England. These relationships can be used subsequently to estimate historical ditch water levels and to monitor contemporary ditch water levels in the wetland. The study shows that satellite imagery has much to offer in monitoring changes in the hydrological regime of wetlands and in providing complimentary approaches to field monitoring.     

朱集矿首采面观测站高程连接测量与数据处理

结合淮南朱集煤矿首采面地表移动观测站的高程连接测量第一次全面观测,设计了首采面地表移动的三等水准控制网,利用抗差估计模型剔除粗差,结合最小二乘估计模型对观测结果进行了处理,并从精度、可靠性和置信度等三个方面进行分析并得出结论。为以后采集各个阶段的地表移动数据,求出参数并且得出结论提供有效的基础数据,从而为朱集矿的后期采煤提供有效的技术保证。     

龙门山断裂带南段应力状态与强震危险性研究

龙门山断裂带可分为南段、中段和北段,2008年汶川M8.0级地震发生在该断裂带中-北段. 龙门山断裂带南段是否存在发生强震的危险性倍受关注. 利用1977-2012年四川区域地震台网资料,获得了龙门山断裂带南段的地震活动性参数b值图像以及汶川地震前、后b值的差值Δb图像. 同时,根据宽频带数字地震波形资料,计算了2007年以来南段及附近区域M_L≥3.8级地震的视应力. 结果表明,2008年汶川地震后,龙门山断裂带南段天全-芦山、泸定和宝兴北部等区域应力增强,而靠近汶川余震区南端的大邑地区应力水平降低. 天全至宝兴段应力水平相对较高,具有发生中-强地震的条件. 鲜水河断裂带康定以南段应力水平低,短期内发生强震的可能性较小.     

Three-dimensional trees for virtual globes

One of the problems in virtual globes technologies is the real-time representation of vegetal species. In forest or garden representations, the low detailed plants produce a lack of realism. Efficient techniques are required to achieve accurate interactive visualisation due to the great number of polygons the vegetal species have. This article presents a multi-resolution model based on a geometric representation of vegetal species that allows the application to perform the progressive transmission of the model, that is, the transmission of a simple representation followed by successive refinements of it. It has a hardware-oriented design in order to obtain interactive frame rates. The geometric data of the objects are stored in the graphics processing unit and, moreover, the change from one approximation to another is obtained by performing mathematical calculations in this graphics hardware. The multi-resolution model presented here enables instancing: as many vegetal species as desired can be rendered with different levels of detail, while all of them are accessing the same geometric data. This model has been used to build a real-time representation of a not imaginary scenario.     

一等水准点之记标准化与规范化研究

为保证一等水准点之记精度与质量,提高测绘人员野外工作效率,对目前的一等水准点之记进行了探讨与分析,指出了其详细位置图与点位,详细说明表达、标石断面图绘制和经纬度书写及交通路线描述中存在的缺点,并基于此提出了若干改进意见,这在一定程度上促进了一等水准点之记信息的标准化与规范化。     

精密水准测量中重力改正的归算

传统水准测量是高精度水准测量的重要手段之一。文章基于DiNi电子水准仪测量数据,针对长距离、高精度水准测量高程的多值性,对水准面不平行改正和重力异常改正的原理进行详述。将其应用于某城市二等水准网平差计算中,证明了精密水准改正的有效性和必要性。