EPON协议参考模型

结合G.983规范的建议, 介绍了EPON协议参考模型,并重点描述了协议参考模型中的基于帧的仿真子层,以及点到点仿真子层和共享仿真子层的工作过程.     

Impacts of XBT, TAO, Altimetry and ARGO Observations on the Tropical Pacific Ocean Data Assimilation

This study aims at assessing the relative impacts of four major components of the tropical Pacific Ocean observing system on assimilation of temperature and salinity fields. Observations were collected over a period between January 2001 through June 2003 including temperature data from the expendable bathythermographs （XBT）, thermistor data from the Tropical Ocean Global Atmosphere Tropical Atmosphere-Ocean （TOGA-TAO） mooring array, sea level anomalies from the Topex/Poseidon and Jason-1 altimetry （T/P-J）, and temperature and salinity profiles from the Array for Real-time Geostrophic Oceanography （ARGO） floats. An efficient three-dimensional variational analysis-based method was introduced to assimilate the above data into the tropical-Pacific circulation model. To evaluate the impact of the individual component of the observing system, four observation system experiments were carried out. The experiment that assimilated all four components of the observing system was taken as the reference. The other three experiments were implemented by withholding one of the four components. Results show that the spatial distribution of the data influences its relative contribution. XBT observations produce the most distinguished effects on temperature analyses in the off-equatorial region due to the large amount of measurements and high quality. Similarly, the impact of TAO is dominant in the equatorial region due to the focus of the spatial distribution. The Topex/Poseidon-Jason-1 can be highly complementary where the XBT and TAO observations are sparse. The contribution of XBT or TAO on the assimilated salinity is made by the model dynamics because no salinity observations from them are assimilated. Therefore, T/P-J, as a main source for providing salinity data, has been shown to have greater impacts than either XBT or TAO on the salinity analysis. Although ARGO includes the subsurface observations, the relatively smaller number of observation makes it have the smallest contribution to the assimilation syst     

泰国日全食纪念邮票（本专栏题头）

泰国日全食纪念邮票（本专栏题头）１９９５年１０月２４８日全食带经过伊朗、印度、＄甸、泰国、柬埔寨。马来西亚等国。泰国为此发行了纪念邮票。邮票底色为深蓝色，右上方为全食时的太阳，明亮的日见带着多种色彩，左边是泰国地图，上面标出了全食带，下方是一台折射式...     

集合KALMAN滤波和最优插值方法在不同观测分布的比较理想试验

目前一种比较流行并且可行的同化方法-集合Kalman滤波(EnKF)能够计算依赖于流的误差统计量。理论上,EnKF能够比最优插值、三维变分等更准确地计算误差统计量,能更好地融合背景场和观测场的信息。作者利用二维平流扩散方程经过10天的同化循环,比较不同观测分布的情况下EnKF和最优插值(OI)的模拟能力。理想试验结果显示,随着观测分布密度的减小,尤其是当观测的分辨率大于OI估计的相关尺度时,集合Kalman滤波的结果比最优插值有更明显的改进。     

自动测量一体化系统的功能及应用

本文介绍了自动测量一体化系统AMIS的主要功能以及在港口湾水库大坝基准网复测中的应用实例，并与传统测量法进行了对比，表明AMIS系统是进行各种控制网测量等的理想系统．     

S^2MP结构分析

Ｓ＾２ＭＰ是ＳＧＩ刚刚推出的新一代体系结构,既具有ＭＰＰ的可扩展性,又具有ＳＭＰ的可编程性。将两者的优势集于一身。将Ｓ＾２ＭＰ与历史上曾经出现的两种多机结构进行比较,指出了Ｓ＾２ＭＰ结构的特点,分析结果认为Ｓ＾２ＭＰ是当代ＭＩＮＭＤ机器最具代表性的结构。     

A mathematical formulation for optimal control of air pollution

In recent years the urban air pollutions caused by emissions from industry, transportation and energy consuming for daily living are getting worse in many major cities of China. Peoples awareness on air quality is increasing. Routine monitoring and foreca…     

伴随方法在海洋数值模式中的应用

本文通过对变分资料同化方法在气象学和海洋学方面特别是在海洋数值模式中应用的简单回顾，评价了伴随方法在方法论上的优越性，首先引入包含海洋数值模式控制方程组的拉格朗日乘子，说明变分资料同化的数学原理；介绍伴随方法应用中目标函数的构造方法，简单说明了伴随方法中伴随方程的导出和伴随方法实际应用的步骤，最后就近几年国外研究进展做了简单概括。     

基于观测、模拟和同化数据的PM2.5污染回顾分析

基于观测数据空间插值、数值模拟以及最优插值同化方法构建了京津冀地区PM2.5(空气动力学当量直径小于等于2.5μm的颗粒物,即细颗粒物)空间插值数据、模拟数据和同化数据,并首次比较分析了三种数据在PM2.5污染回顾分析上的应用潜力和优缺点。针对2014年2月19~28日京津冀地区PM2.5污染过程的分析发现:(1)观测空间插值数据难以完整表征PM2.5污染的时空演变特征,在没有观测覆盖区域误差较大,容易出现虚假的高低值中心;(2)模拟数据具有较高时空分辨率,对PM2.5污染时空演变特征描述更加细致,但在这次污染过程中仍存在较大不确定性,其均方根误差大于100μg/m3;(3)同化数据不仅能对PM2.5空间分布特征进行细致描述,其数据精度在独立验证站点也显著高于模拟数据,其均方根误差比模拟数据低约50%,与站点观测数据的相关系数也比模拟数据高0.2以上。基于PM2.5同化数据,对这次京津冀PM2.5污染过程的时空演变特征进行了详细回顾分析,发现这次污染过程存在自京津冀南部PM2.5污染累积并向北输送发展的生成特点,消亡过程为风向转换下自北向南清除,造成京津冀南部城市先污染后清除,北部城市后污染先清除,并且有慢累积、快清除的特征。从发展演变过程中污染所占空间面积来看,25日PM2.5污染范围最大,覆盖模式第三区域60.5%面积。     

MODEL STUDY OF THE EFFECT OF SOIL NO EMISSIONS ON SURFACE OZONE

The effect of soil NO emissions on surface ozone in autumn in East China has been studied byusing TCTM(Troposphere Chemical Transport Model)with the input of meteorological variablesfrom RAMS.The chemical mechanism for ozone variation caused by soil emissions has also beeninvestigated.The model results reveal that soil NO emissions are important to regional ozoneformation and distribution and the effect of soil NO emissions shows spatial inhomogeneity.Ozoneover most areas in northern China decreases with maximum average decrement reaching 5 ppbwhile it increases over most areas of central and southern China with maximum average incrementreaching 7 ppb caused by soil NO emissions.This situation of ozone variation is mainly determinedby nonlinear photochemical mechanism.For the low NOx areas(≤3 ppb),ozone increases as NOxincreases;for the high NOx areas(>3 ppb),ozone decreases as NOx increases.The effect of soilNO emissions on ozone depends on the transition value and NOx concentrations.