Existence of the solutions and the attractors for the large-scale atmospheric equations

The atmosphere is a kind of fluid surrounding therotating earth, and its state can be described by thevelocity vector v, the temperature T, the density ρ, andthe pressure p at each point. Its evolution process isessentially governed by the Navier-Stockes equationand the temperature equation. Due to the specialty andthe complexity of the atmospheric problem, althoughsome modified and simplified work have made onthese fluid mechanics and temperature equations, theyare still a very complex forc…     

On the existence of atmospheric attractors

In this paper, we consider the long-time dynamics for the primitive equations of large-scale dry at- mosphere. First, by energy methods, we obtain the existence and uniqueness of global strong solu- tions of the problem. Second, by studying the long-time behavior of strong solutions, we construct a global attractor which captures all the trajectories.     

风的垂直切变对滞弹性大气中静力适应过程的影响

本文基于描写滞弹性大气静力适应过程的线性方程组,从波动频散关系、气团运动规律和能量转换的角度出发,研究了水平基流及其垂直切变对该模式大气静力适应过程的影响.构造四种水平基流垂直分布模型进行比较,分别为常数型、线性切变型、反气旋切变型和气旋切变型,得到结论：（1）具有重力波性质的波动是滞弹性大气静力适应过程中扰动能量传播的方式,当垂直折射指数大于零时,基本气流及其垂直切变的存在,不仅改变了波动频率的大小,而且改变波动传播的方向;（2）在静力适应过程中气块的运动轨迹呈椭圆形,水平基流及其垂直切变影响椭圆的扁率,同时也影响扰动物理量之间的偏振关系;（3）水平基流的垂直切变是扰动能量和水平基流能量发生转换的媒介,当存在垂直向上的动量输送时,正的垂直风切变对应扰动能量的衰减,水平基流能量的增加,负的垂直风切变对应扰动能量的增加,水平基流能量的衰减;（4）不同的风的垂直切变模型,对静力适应过程的影响不同;对于水平基流呈反气旋切变型和气旋切变型,扰动发展的波动垂直结构为,急流轴上方波动等相位线自下而上向西倾斜,急流轴下方波动等相位线自下而上向东倾斜,反之亦然.

     

The chaotic attractor of the precursory field of the seimogenic system and its fractal dimension

In this paper we outlined the chaotic attractor of the precursory field evolution of the seismogenic system and its fractal dimension of the precursory time and space distribution. We developed the calculative method of reconstruction complex system dynamics from single time series and analysed the descent dimension phenomena of the precursory distribution before large earthquakes. We also showed the time-space synthesis method constructed complex system dynamics by many stations or many methodes in the seismogenic system consists of large area tectonic network. This method can describe the self-organization behavior of the system more accurately and get rid of the uncertainty and randomness caused by single station or single method. As an example, we calculated the chaotic attractor of the precursory field evolution and the fractal dimension of the precursory time and space distribution and its change tendencies before large earthquakes in Beijing-Tianjing area. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 463–469, 1993.     

Some comparisons between the middle atmosphere dynamics of the Southern and Northern Hemispheres

Comparisons are drawn between certain middle atmosphere dynamical processes in the Southern Hemisphere and the Northern Hemisphere. Attention is focused on the zonal-mean climatological state, stationary waves, transient waves of various types, stratospheric sudden warmings and polar ozone minima. Observations of the similarities and differences between the hemispheres are mentioned, and ways in which these comparisons may be used to enhance our dynamical knowledge of the whole middle atmosphere are discussed.     

The early history of oxygen and ozone in the atmosphere

There may have been three stages in the growth of oxygen in the terrestrial atmosphere. Prior to the origin of photosynthesis the only source of oxygen was photolysis of water vapor followed by escape of hydrogen to space. The rate of this process was probably less than the rate of release of reduced gases (principally hydrogen) from volcanoes, so the oxygen partial pressure was held to negligibly low values by photochemical reactions with an excess of hydrogen. The photosynthetic source of oxygen was probably in operation as long ago as 3.8 billion years. It released oxygen to the ocean. Presumably most of this oxygen was destroyed in the ocean as long as its rate of supply was less than the rate of supply of readily oxidizable material (principally Fe²⁺) provided by the weathering of rocks. This phase appears to have lasted until about 2 billion years ago, during which period most banded iron formations were deposited. During this period the production of oxygen by algae was limited by competition with photosynthetic bacteria, which preempted the supply of nutrient phosphorus as long as reduced chemicals were available in the environment. Once the photosynthetic oxygen source exceeded the rate of supply of reduced minerals exposed by erosion and weathering, the accumulation of oxygen in the ocean and atmosphere could be controlled only by reaction of oxygen with reduced organic material. This is the stabilization mechanism that operates today. It seems unlikely that oxygen could be consumed at a significant rate by this process until oxygen levels sufficiently high to support respiration had been achieved. I therefore suggest that atmospheric oxygen rose rapidly from essentially zero to approximately its present value (within a factor of 10) when the photosynthetic source of oxygen rose above the weathering source of reduced minerals, probably about 2 billion years ago. The ozone layer and the ultraviolet screen were absent prior to this time and essentially fully developed after this time.Presented at IAGA/IAMAP Symposium on Minor Neutral Constituents in Middle Atmosphere-Chemistry and Transport, Seattle, August, 1977.     

A simple theory for the vertical structure of the tropical atmosphere

It is suggested that the gross mean vertical structure of the undisturbed tropical atmosphere may be understood in terms of convective boundary layers driven in different ways and on different time scales by the evaporation of water from the sea surface. The mixed layer on a short time scale is driven partly by the buoyancy produced by the light weight of the water vapor; the trade cumulus layer on an intermediate time scale by the buoyancy (but not heating) produced by the condensation of the water vapor in shallow trade cumulus clouds; and the troposphere itself on a long time scale by the buoyancyand heating produced by the condensation of the water vapor in the deep cumulonimbus clouds.May 1985This paper was issued as a Harvard University report in 1974. For this version only Section 5 has been rewritten. There has been sufficient interest in this work over the years to warrant making it more widely available through the open literature.Contribution No. 783 from NOAA/Pacific Marine Environmental Laboratory     

Perturbations of the upper atmosphere in the cleft region

In the dayside polar region—loosely referred to as the cleft region—particle precipitation and Joule heating cause significant perturbations of the upper atmosphere. Here Dynamics Explorer-2 satellite data are used to present a synopsis of these disturbance effects. Documented are an increase in electron temperature and a decrease in electron density; increases in ion drift speed and ion temperature; an increase in the upward-directed ion velocity; increases in zonal wind speed and neutral gas temperature; and changes in the neutral gas composition and mass density. It is suggested that the increase in electron temperature is partly controlled by the decrease in electron density; that the ion upflow velocity mainly depends on the electron temperature, less frequently on the ion temperature; and that the observed decrease in thermospheric mass density is due to a decrease in the atomic oxygen density, which in turn is caused by diverging wind flows.     

大气三圈环流的动力系统模型

定常情况下,本文利用球坐标系（λ,φ,r）的动力、热力学方程导出三维速度场（vλ,vφ,vr）的动力系统.这种包括摩擦力和热传导的不可压缩大气运动的动力系统,无论从定性上还是从定量上都能描述由赤道和极地间的加热不均匀造成的三圈环流.定性上表明,在北半球经向速度vφ和纬向速度vλ同符号,地表刮北风（vφvλvφ>0）和刮西风（vλ>0）相对应.在南半球,经向速度vφ和纬向速度vλ符号相反,刮北风（vφvλ>0）相对应,刮南风（vφ>0）和刮东风（vλp可以用球调和函数plm（sinφ）cosmλ来表达.当取l=6,m=0时即可导出三圈环流.在经圈剖面（φ,r）上,地表的φ1=±56°和φ2=±28°左右,以及赤道是速度场的奇点,它们都是鞍点,说明在副热带是下沉运动,在中纬度是上升运动,这正是三圈环流中的Ferrel环流的特征.这样经向速度vφ和纬向速度vλ相联系,经向速度vφ又和垂直速度相联系,那么三圈环流的三维速度场就构成了一个整体.     

耗散大气中的声波射线追踪

基于分层大气中声波的局地色散关系方程,建立一种计入真实大气衰减效应的有耗大气声波射线追踪模型.在色散方程的虚部中导出声波在运动大气中的耗散系数和竖直方向上的增长因子,并利用真实大气中的衰减理论对所得到的耗散系数进行修正.利用Hamilton方程组解出大气声波在考虑耗散效应下的射线微分方程组.该有耗射线追踪模型的数值模拟结果表明,声波的耗散效应对声波的传播路径存在一定影响,在近场情况下,这种影响可以忽略,但是对于声波的远场传播,则影响较大.     

论不同模式大气中的静力适应过程

为了研究大气静力平衡适应过程的本质,利用波动理论和能量转换角度,分别对完全可压缩的等温大气模型、滞弹近似下的等温大气模型和层结中性大气模型进行研究比较.结果表明：大气静力平衡适应过程的本质是声波和混合声重力波对扰动能量的频散过程,滞弹近似模型和层结中性模型均不能完全描述此适应过程;在波动假设下,此三类大气模型中扰动物理量之间的偏振关系同波动的性质有关,气团的运动方程均为椭圆方程,声波和混合声重力波对气团运动的作用差异较显著.
大气静力平衡适应过程中扰动能量以有效势能、有效弹性势能、动能或波动能量的形式存在并相互转换;扰动有效势能与其他形式能量之间的转换与混合声重力波或者重力内波有关,扰动有效弹性势能与其他形式能量之间的转换与声波有关.在完全可压缩的等温大气模型中,扰动有效势能增加1个单位,其中69.9%来自扰动垂直动能,其余30.1%来自扰动有效弹性势能.     

The radiative energy budget of the middle atmosphere and its parameterization in general circulation models

The thermal regime of the middle atmosphere is determined to a great extent by the balance between the incoming solar and outgoing infrared radiation. To account for these processes in numerical models of the middle atmosphere, parameterizations that are capable of quickly and accurately calculating infrared cooling and solar heating rates are required. These parameterizations should include the breakdown of local thermodynamic equilibrium (LTE) conditions and allow for feedbacks by ensuring that dependencies on all input parameters are accounted for. This paper discusses the major mechanisms responsible for maintaining the radiative energy budget of the middle atmosphere and presents a brief review of approaches and numerical schemes currently available for use in general circulation models. The main focus of the paper is on the approaches and schemes designed for non-LTE treatment.     

Approximation of the infra-red radiation flux in an atmosphere with cloud

Summary A three-stream infra-red radiation scheme for use particularly in boundary layer models is described. Local uniformity of the atmosphere (i.e. a generalization of the cooling to space approximation in clear air) is assumed, and the radiation equation is solved by simple collocation rather than by the full discrete ordinate method. In clear air the scheme corresponds to the usual approximation, which incorporates the Elsasser factor in the transmission function to account for diffuse radiation. The band models of Goody for water vapour and Elsasser for carbon dioxide are used for the band averaging of the transmission functions. Consistent with this, the band averaging of the radiation flux in cloud is undertaken by replacing the rapidly varying absorption coefficients for the gases by the actual band-averaged values of those coefficients. The band averaging is precise in the limits of strong and weak gaseous absorption.     

Geophysical radar for the observation of ionized clouds in the atmosphere above the earthquake preparation region

The authors propose to use a modified geophysical radiolocator for the detection and investigation of local quasi-plasma anomalies in the atmosphere. This radiolocator should control the large region of the atmosphere, filled with scattering objects, connected with the precipitation of radioactive substances. Such phenomena could arise in connection with earthquakes and could also be caused by technogenic origins. Contrary to standard radar, the noise of scattering objects is the aim of the analysis of geophysical radar. The discussion of technical characteristics of such radar is presented.     

夏季北极平流层大气基本结构特征

北极地区(60°N~90°N)平流层纬向风和气压场有明显的季节变化,不同高度层季节变化的时间有差异.北极平流层从冬至夏,季节转换从上向下推进,从夏至冬,季节转换从下向上推进.以20 hPa为例,平均而言,4月上旬以前,北极被极涡控制;4月中旬北极地区高压的势力开始超过低压,5月上旬,北极高压正式建立;7月份达到最强,8月份开始减弱,8月底结束.北极高压中心位置随时间的变化可分为北美型、欧亚型和过渡型三种.平流层下层,气压场和风场的结构与平流层中上层有明显不同,而且南亚高压与北极高压连在一起;从垂直结构看,北极高压从上至下与100 hPa的南亚高压连在一起,高压中心轴线是倾斜的.     

The joint influence of the Coriolis force and the stratification on stationary motions in the zonal model of equatorial atmosphere

Summary In the framework of a zonal model of the equatorial atmosphere, the joint influence of the Coriolis force and stratification on stationary motion is studied. In addition we assume a Boussinesq approximation and consider the equatorial region as a macrodisturbance localized round the Equator, against a background of an isothermal atmosphere with a zonal distribution. Exact analytical solutions of the system of equations (1)–(5) are obtained and analyzed. An interesting result is that the equatorial atmosphere could exist in different stationary states in each of them separately, as well as in a number of them simultaneously.     

Sediment yield of the lower Tana River,Kenya, is insensitive to dam construction: sediment mobilization processes in a semi‐arid tropical river system

Dam construction in the 1960s to 1980s significantly modified sediment supply from the Kenyan uplands to the lower Tana River. To assess the effect on suspended sediment fluxes of the Tana River, we monitored the sediment load at high temporal resolution for 1 year and complemented our data with historical information. The relationship between sediment concentration and water discharge was complex: at the onset of the wet season, discharge peaks resulted in high sediment concentrations and counterclockwise hysteresis, while towards the end of the wet season, a sediment exhaustion effect led to low concentrations despite the high discharge. The total sediment flux at Garissa (c. 250 km downstream of the lowermost dam) between June 2012 and June 2013 was 8.8 Mt yr^‐1. Comparison of current with historical fluxes indicated that dam construction had not greatly affected the annual sediment flux. We suggest that autogenic processes, namely river bed dynamics and bank erosion, mobilized large quantities of sediments stored in the alluvial plain downstream of the dams. Observations supporting the importance of autogenic processes included the absence of measurable activities of the fall‐out radionuclides ⁷Be and ¹³⁷Cs in the suspended sediment, the rapid lateral migration of the river course, and the seasonal changes in river cross‐section. Given the large stock of sediment in the alluvial valley of the Tana River, it may take centuries before the effect of damming shows up as a quantitative reduction in the sediment flux at Garissa. Many models relate the sediment load of rivers to catchment characteristics, thereby implicitly assuming that alterations in the catchment induce changes in the sediment load. Our research confirms that the response of an alluvial river to external disturbances such as land use or climate change is often indirect or non‐existent as autogenic processes overwhelm the changes in the input signal. Copyright © 2015 John Wiley & Sons, Ltd.     

一阶弹性波方程数值模拟中的混合吸收边界条件

Liu和Sen（2010和2012）在地震波场数值模拟中提出一种混合吸收边界条件. 该方法具有计算量小、容易实现及吸收效果好等优点. 但现有的混合吸收边界条件是针对二阶位移-应力方程设计的,存在稳定性问题. 本文首先推导了两种速度-应力单程波方程：二阶Higdon单程波方程和一阶Higdon单程波方程. 进而提出基于一阶弹性波方程的混合吸收边界条件方法. 在内部区域和边界之间引入一个过渡区域,通过单程波与双程波方程平滑过渡来消除人工边界反射. 为了改善混合吸收边界条件的吸收效果和稳定性,我们采用了能同时吸收纵、横波反射的一阶单程波方程和与变量位置有关的加权系数. 为了验证混合吸收边界条件的有效性,将其与常规分裂完全匹配层（PML）方法进行了比较. 数值模拟结果表明,与PML边界条件相比,混合吸收边界条件在耗用更小计算时间和存储量的前提下,可以获得更好的吸收效果. 另外,本文提出的两种混合吸收边界条件中,混合一阶Higdon吸收边界条件具有更好的稳定性.     

湖-气热传输模型及参数敏感性研究

在一维涡扩散模型的基础上,发展了考虑冬天结冰和夏天蒸发等水体相变问题及对流混合过程的湖-气热传输模型.模型采用焓代替温度作为预报变量,这也更加方便处理水的相变问题.模型的计算结果与以色列Kinneret湖的观测资料进行对比,验证了模型的合理性,说明了加入对流混合过程是符合湖-气热传输的实际物理机制的.对风速和湖面摩擦速度作了敏感性实验,证明他们对湖面温度和蒸发潜热有着重要的影响.     

An investigation of the dependence of structural parameters of the middle atmosphere on the intensity of photochemical and dynamical processes

Using a numerical model for temperature and neutral and ion composition behaviour at middle atmospheric heights, an analysis has been made of the dependence of atmospheric structural parameters on temperature, solar activity, and on turbulent transfer intensity. For mesospheric heights, an inverse dependence of the nitric oxide density on the temperature has been found. It is thus possible to explain experimentally obtained temperature variations over a cyclc of solar activity at mesospheric and lower thermospheric heights. Numerical simulation results indicate that the temperature in the height range 75–120 km depends considerably on both the absolute values of turbulent transfer coefficients and their vertical gradients.