A unified linear theory of wavelike perturbations under general ocean conditions

A linearized instability analysis model with five unknowns was proposed to describe disturbance motions under general oceanic background conditions, including large-scale current shear, density stratification, frontal zone, and arbitrary topography. A unified linear theory of wavelike perturbations for surface gravity waves, internal gravity waves and inertial gravity waves was derived for the adiabatic case, and the solution was then found using Fourier integrals. In this theory, we discarded the assumptions widely accepted in the literature concerning derivations of wave motions such as the irrotationality assumption for surface gravity waves, the rigid-lid approximation for internal gravity waves, and the long-wave approximation for inertial gravity waves. Analytical solutions based on this theory indicate that the complex dispersion relationships between frequency and wave-number describing the propagation and development of the three types of wavelike perturbation motions include three components: complex dispersion relationships at the sea surface; vertical invariance of the complex frequency; and expressions of the vertical wave-number (phase). Classical results of both surface waves and internal waves were reproduced from the unified theory under idealized conditions. The unified wave theory can be applied in the dynamical explanation of the generation and propagation properties of internal waves that are visible in the satellite SAR images in the southern part of the China Seas. It can also serve as the theoretical basis for both a numerical internal-wave model and analytical estimation of the ocean fluxes transported by wavelike perturbations.     

Formation conditions of rainfall-generated mudflows in mountain regions

A new method for the assessment of formation conditions of rainfall-generated mudflows is proposed. The method introduces two new criteria: minimum (critical) values of rainfall and meteorological force of rain obtained from the data of observations of rainfalls from 1953 to 2014. This is important for the early warning about the risk of mudflows and for timely taken protection measures in restdential areas and other economic obj ects situated in the zone of the possible negative impact of mudflows.     

A theory of the formation of ice crystals

Summary As is known from laboratory experiments and investigations in the free atmosphere, ice crystal formation is initiated either at vapor saturation with respect to water or by crystallization of a droplet. Nuclei with special properties are needed. An explanation of their effectiveness can be given by application of the laws of oriented overgrowth (Epitaxy) between two crystals. Any host crystal having a plane with a geometrical pattern similar to, for instance, the base plane of the ice crystal, can orient an adsorbed layer of H₂O molecules already in the ice crystal pattern. The closer the fit between the two crystal planes, the greater the area of oriented H₂O molecules will be. By piling up other layers of H₂O molecules a very small ice crystal, called ice seed, is created which can grow in supercooled water. This crystal is so small that according to theThomson-Gibbs Law a high supersaturation would be needed to create it directly from vapor. Calculations of the effective temperature of mica, AgI and quartz as freezing nuclei are in fairly good agreement with the experiment. This theory permits an explanation of the observed thresholds of ice formation which occur at about –20°, –30°, –40° and –60°C. Occasionally capillary condensation of water molecules on a freezing nucleus will occur when the vapor is saturated with respect to ice but not with respect to water; this has frequently been erroneously ascribed to ice formation by a real sublimation nucleus.

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Zusammenfassung Nach Untersuchungen im Laboratorium und in der freien Atmosphäre entsteht Eis entweder aus Wasserdampf auf dem Umwege über vorherige Kondensation des dampfes oder unmittelbar aus der flüssigen Phase durch Kristallisation. Zur Einleitung des Kristallisationsprozesses sind Kerne (Gefrierkerne) mit besonderen Eigenschaften notwendig. Eine Erklärung ihrer Wirkungsweise wird durch Anwendung der Gesetze über das orientierte Aufwachsen eines Kristalls auf einem anderen gewonnen. Besteht zwischen einer Gitternetzebene irgendeines Kristalls und z. B. der Basisebene des Eiskristalles eine gewisse Ähnlichkeit, die sich nachRoyer hauptsächlich auf die geometrische Anordnung der Kristallbausteine in beiden Flächen bezieht, dann orientiert sich die erste auf der Kristallfläche adsorbierte Moleküllage des Gastkristalls in der für sie typischen Gitteranordnung. Eine weitere, wesentliche Bedingung ist sehr gute Benetzbarkeit des Wirtkristalls durch die Bausteine des Gastkristalls, ohne daß es jedoch zur Auflösung des Wirtkristalls kommen darf. Solche Benetzbarkeit zeigt z. B. eine frisch gespaltete Glimmerfläche. Auf der Oberfläche eines gewöhnlichen, nach seiner Struktur geeigneten Aerosolteilchens werden jedoch nur wenige solcher aktiver Stellen vorhanden sein. Je besser dann die geometrische Ähnlichkeit beider Kristallflächen ist, um so größer ist die Fläche des Gastkristalls, die orientiert werden kann.Diese erste orientierte Molekülschicht des Gastkristalls wirkt orientierend auf die Wassermoleküle der Umgebung oder die durch den Kondensationsprozeß angelagerten Moleküle; dadurch entsteht ein kleiner Eiskristall. Dieses Kriställchen wirkt bei einer bestimmten kritischen Temperatur als Kristallisationskeim für das gesamte Wasser. Die Beziehung zwischen seiner Größe und seiner Wirkungstemperatur kann berechnet werden nach einer vonJ. J. Thomson abgeleiteten Formel. Je größer es ist, um so näher am Gefrierpunkt wirkt es; trotzdem ist es aber noch so klein, daß nach dem Thomson-Gibbsschen Gesetz eine große Übersättigung notwendig wäre, um es direkt aus dem Dampf zu bilden. Durch Analyse der geometrischen Ähnlichkeit zwischen der Basisfläche eines Eiskristalls einerseits und der Spaltfläche von Glimmer, der Basisfläche von Silberiodid und der Basisfläche eines Quarzkristalls anderseits war es möglich, die Größe der Fläche zu berechnen, über die die adsorbierten Wassermoleküle in der Basisflächenstruktur von Eis orientiert werden können. Dadurch war die Größe des Eiskeimes gegeben, dessen kritische Wirkungstemperatur nachJ. J. Thomsons Formel berechnet werden konnte.Die so berechneten Werte stimmen gut mit den experimentell festgestellten Gefriertemperaturen von Wasser auf Glimmer, Silberiodid und Quarz überein. Versuche mit Glimmer deuten darauf hin, daß in der Nähe des Gefrierpunktes eine besonders gute Ableitung der Gefrierwärme erforderlich ist, um den Kristallisationsprozeß in Gang zu bringen. Die Theorie gestattet eine Erklärung der verschiedentlich beobachteten Temperaturschwellen der Eisbildung in den Intervallen –19 bis –24°C, –30 bis –35°C, –39 bis –42° C und –60 bis –65°C. — Kapillarkondensation, durch die an unlöslichen Kondensationskernen Kondensation schon bei 90% rel. Feuchte einsetzen kann, kann das Vorhandensein eines Sublimationskernes vortäuschen.

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Résumé D'après les recherches faites au laboratoire et dans l'atmosphère libre, la glace se forme soit à partir de la vapeur d'eau en passant par la condensation préalable, soit directement par cristallisation à partir de la phase liquide. Le processus de cristallisation exige la présence de noyaux de congélation aux propriétés particulières pour s'amorcer; l'action d'un noyau peut s'expliquer par les lois relatives à la croissance orientée d'un cristal sur un autre. S'il existe entre le réseau moléculaire d'un cristal quelconque et le plan de base d'un autre cristal une certaine ressemblance qui d'aprèsRoyer se rapporte essentiellement à la distribution géométrique des éléments cristallins des deux plans de contact, alors la première couche moléculaire du cristal secondaire qui est adsorbée sur une face du premier s'oriente suivant le réseau typique de celui-ci. Une autre condition importante est celle de la parfaite mouillabilité du cristal primitif vis-à-vis du nouveau cristal, sans toutefois que le premier risque de se dissoudre; une face fraîchement clivée de mica par exemple présente cette propriété. Mais la surface d'une particule d'aérosol de structure convenable ne présente que peu de «points actifs» de ce genre. Plus les deux surfaces cristallines mises en présence sont géométriquement semblables, plus la surface du cristal secondaire qui peut être orientée est grande.La première couche moléculaire orientée du cristal secondaire exerce un effet directeur sur les molécules d'eau du milieu ou sur les molécules déposées par le processus de condensation; ainsi naît un petit cristal de glace. A une température critique déterminée, ce dernier joue le rôle de germe de cristallisation pour toute l'eau disponible. La relation entre la grosseur de ce cristal et sa température efficace peut se calculer par une formule due àJ. J. Thomson. Plus le cristal est gros, plus il agit près du point de congélation; cependant il est encore si petit que d'après la loi deThomson-Gibbs il faut une grande sursaturation pour qu'il se forme directement à partir de la vapeur. Par l'analyse de la similitude géométrique entre la surface de base d'un cristal de glace d'une part et la surface de clivage de mica, la surface de base de iodure d'argent ou d'un cristal de quartz d'autre part, on pouvait calculer la grandeur des surfaces sur lesquelles les molécules d'eau adsorbées peuvent être orientées selon la structure de la surface de base de la glace. On obtenait ainsi la grosseur du germe de glace dont on pouvait calculer la température critique efficace d'après la formule deThomson.Ces valeurs calculées sont en bon accord avec les températures de congélation de l'eau sur mica, iodure d'argent et quartz déterminées expérimentalement. Des essais faits avec du mica semblent montrer qu'au voisinage du point de congélation la chaleur de congélation doit pouvoir s'écouler facilement pour mettre en train le processus de cristallisation. La théorie permet d'expliquer les seuils de température de la formation de la glace souvent observés dans les intervalles de –19° à –24°, –30° à –35°, –39° à –42° et de –60° à –65°C. La condensation capillaire par laquelle une condensation peut se produire sur des noyaux insolubles pour une humidité relative de 90% déjà est de nature à faire croire à la présence d'un noyau de sublimation.

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With 8 Figures.     

Conditions of the formation and runoff of shelf waters in different water areas of the Arctic and Antarctic

The comparative analysis of hydrometeorological and topographic conditions of the formation and runoff of dense shelf waters on the shelves and continental slopes in different water areas of the Arctic and Antarctic demonstrates that they are similar in many aspects but there are some differences as well. In the Antarctic, these conditions are more favorable. The thermohaline conditions of the formation and runoff of shelf waters in the Arctic and Antarctic are also similar. The similarity of different conditions enables to construct the adaptive physical model of the shelf and slope cascading of shelf waters generalized for different polar water areas. It is based on the analysis of historical and present-day in situ data in the areas of margins of shelves and slopes in the Arctic and Antarctic, observations in the areas of flaw polynyas, and passing ice and meteorological observations, as well as on taking account of some general results of laboratory and theoretical investigations of the dense liquid runoff along the inclined bottom.     

Use of dust storm observations on satellite images to identify areas vulnerable to severe wind erosion

Blowing dust is symptomatic of severe wind erosion and deterioration of soils in areas undergoing dessication and/or devegetation. Dust plumes on satellite images can commonly be traced to sources in marginally arable semiarid areas where protective lag gravels or vegetation have been removed and soils are dry, as demonstrated for the Portales Valley, New Mexico. Images from Landsat and manned orbiters such as Skylab and the Space Shuttle are useful for illustrating the regional relations of airborne dust plumes to source areas. Geostationary satellites such as GOES are useful in tracking the time-histories of episodic dust storms. These events sometimes go unrecognized by weather observers and are the precursors of long-term land degradation trends. In areas where soil maps and meteorological data are inadequate, satellite images provide a means for identifying problem areas where measures are needed to control or mitigate wind erosion.     

Elements of theory of avalanche-like motion of a mudflow with hyperconcentration of debris

A criterion ratio is proposed which allows to estimate the possibility of origination of avalanche-like motion of a mudflow with hyperconcentration of debris in a certain mudflow-bearing watercourse.     

华南前汛期低空西南急流-锋面暴雨过程初期的中—中间尺度波状降水过程

在华南前汛期低空西南急流一锋面暴雨过程的初期.存在着一种自西南向东北方向传播的中尺度波状雨带或中到中间尺度的波状雨区.波状雨区的波长为20—100公里左右,传播速度为20—45公里/小时,对应的降水周期为1—4小时.波状雨区出现在500百帕槽前、850百帕冷切变线南面和地面锋面的暖区,以及850百帕冷切变南侧低空西南急流移近、加强的过程中.估计这种波状降水可能是暴雨过程中1—4小时的周期性强非地转西南风风速脉动造成的辐合或重力波触发产生的.中尺度波状雨区的持续旺盛发展可能产生新的中到中间尺度雨成冷性切变线雨带,形成强降水和第一个暴雨区.     

Vortex erosion in a shallow water model of the polar vortex

The erosion of a model stratospheric polar vortex in response to bottom boundary forcing is investigated numerically. Stripping of filaments of air from the polar vortex has been implicated in the occurrence of stratospheric sudden warmings (SSWs) but it is not understood in detail what factors determine the rate and amount of stripping. Here a shallow water vortex forced by topography is used to investigate the factors initiating stripping and whether this leads the vortex to undergo an SSW. It is found that the amplitude of topographic forcing must exceed some threshold (of order 200–450 m) in order for significant stripping to occur. For larger forcing amplitudes significant stripping occurs, but not as an instantaneous response to the forcing; rather, the forcing appears to initiate a process that ultimately results in stripping several tens of days later. There appears to be no simple quantitative relationship between the amount of mass stripped and the topography amplitude. However, at least over the early stages of the experiments, there is a good correlation between the amount of mass stripped and the global integral of wave activity, which may be interpreted as a measure of the accumulated topographic forcing. Finally there does not appear to be a simple correspondence between amount of mass stripped and the occurrence of an SSW.     

我国季风区湿度场的一些统计特征

在计算我国7站(其中东部季风区5个站)10年逐日大气湿度参量的基础上,对大气湿润状况的一些基本统计性质,包括均方差、标准误差、偏度及不同等压面上湿度变化的相关性等,进行了分析。结果表明,这些统计量的地理分布、季节变化及不同高度之间的差异等均与季风气候的特征有着密切的联系。     

Evaluation of wind erosion in the Tarim Basin based on parameter localization

Theoretical and Applied Climatology - Air density strongly constrains the characteristics of an airflow and the resulting flow of sand and therefore, it should not be neglected in sand transport...     

矩阵论中的图论匹配法

G.Birkhoff用代数的方法证明了如果一个矩阵是双随机矩阵,则它能表示成置换矩阵的凸线性组合.设G是具有两分类(X,Y)的二部图,则G中含有饱和X中的所有顶点的匹配M的充分必要条件为:对∀S⊆X,有d_G(S)≥|S|.文章借助上述二部图的匹配思想,给出这一结论的图论证明.     

热带气旋形成的多尺度组合理论——流体动力学实验模拟与合成分析的结合

结合流体动力学实验模拟(物理模型)与大量记录的合成分析,本文提出了热带气旋形成的多尺度组合理论。它强调了热带中尺度深厚对流云系的作用,同时它也着重说明了大尺度环境气流与小尺度积云对流的重要作用。 本理论可解释一些有关热带气旋以前所不能解释的观测事实,特别是它解释了热带气旋前期低压环流的形成。     

One-dimensional motion equation of cohesive mudflow with variable discharge along the way and some partial solutions

Hydraulic motion equations of the cohesive mudflow with variable discharge along the way, based on the energy principle and derived by theoretical means, are given. They can form the base for the discovery of algorithms of open hydrological problems in the field of dynamics of cohesive mudflows for both prismatic and non-prismatic channels.     

Assessment of the climate preparedness of 30 urban areas in the UK

Cities are increasingly aware of the need to mitigate greenhouse gas emissions and adapt to changes in weather patterns leading to the production of urban climate change plans. The few existing systematic studies of these plans have focused on either adaptation or mitigation issues, and are typically based on surveys completed by city officials rather than analysis of documented evidence. To gain insight into the status of adaptation and mitigation action across the UK, climate change documents from 30 urban areas (representing ~28 % of the UK’s population) were analysed. An Urban Climate Change Preparedness Score, which could be applied to other urban areas outside the UK, has been devised for comparative analysis. This analysis characterizes progress against (i) Assessment, (ii) Planning, (iii) Action, and (iv) Monitoring, for both adaptation and mitigation. The Preparedness Score allows a quantitative comparison of climate change strategies across the urban areas analysed. This methodology can be transferred to other countries and makes an international comparison of urban areas and their climate change adaptation and mitigation plans possible. We found that all areas acknowledge climate change being a threat and that adaptation and mitigation planning and action is required. However, two urban areas did not have official adaptation or mitigation plans. Typically, mitigation activities across all cities were more advanced than adaptation plans. Emissions reduction targets ranged from 10 %–80 % with differing baselines, timeframes and scopes, for defining and meeting these targets. Similar variability was observed across adaptation plans. Several reasons for these differences are considered, but particularly notable is that a combination of incentives and regulation seem to stimulate more comprehensive strategies and action in many urban areas.     

棉花产量要素预测模型

引起棉花产量波动的主要产量构成要素是株铃数和单铃重,作者将大田监测与气候统计相结合道德预测单株现蕾数,成铃雍铃重,对对最终产量进行预后,提高了产量预后准确率。     

北非地区海-陆热力差异与夏季江淮流域旱涝的关系

基于NCEP/NCAR月均再分析资料和中国743站降水资料,根据夏季江淮流域51 a(1954-2004年)区域旱涝指数的年代际变化特征,确定北非地区作为研究的关键区.分析发现,关键区的地表温度异常在冬季具有较好的持续性,冬季北大西洋涛动是导致这种异常持续性的重要原因之一.通过对前冬北非地区地表温度和夏季江淮流域降水的SVD分析发现:当北非大陆地区偏冷,其西北侧的海区偏暖时,江淮流域夏季的降水将整体偏多;反之,江淮流域夏季的降水整体偏少.进一步研究发现,北非地区海陆地表温度异常的对比,要比其中单一海洋或陆地区域的异常对夏季江淮流域的旱涝有更好的指示能力.文中定义了一个海陆热力差异指数来表征这种地表温度异常的对比程度,该指数和夏季江淮流域旱涝指数呈较好的正相关关系,并且对夏季江淮流域极端旱涝年份也有较好的指示,认为该指数可以作为一个指示江淮流域整体旱涝事件的预报因子.     

发展贫困山区气象产业的几点看法

发展是硬道理，这是新世纪一个极其重要的指导思想，也是保证气象产业的持续快速健康发展，必须要有的新思路。对贫困山区气象产业结构进行战略性调整，就是新思路的重要内容之一。气象产业结构调整的首要任务就是要解决影响贫困山区气象产业持续快速发展的一些长期性的矛盾和问题。改革开放２０多年来，气象产业从无到有，从少到多，从简单到复杂的方向迅速发展，产业结构也出现了科学化、专业化、现代化之间的良性互动，为气象产业的持续快速发展奠定了良好的基础。但是，气象科技服务与产业规模化程度低，实体过多，集约化程度低，“小而…     

中国不同地区气溶胶消光特性分析

利用多波段太阳光度计在中国四个点（北京的密云，广东的新丰，青海的瓦里关，西藏的当雄）观测了４５０—９００ ｕｍ范围中多波长气溶胶光学厚度和Ａｎｇｓｔｒｏｍ指数。本文分析了这些参数从１９９８年２月到１９９９年１月这一年中的特点。结果表明，在干旱和半干旱地区，如密云（１７．１２°Ｅ，４０．６５°Ｎ）和瓦里关（１００．９０°Ｅ，３６．２９°Ｎ），春季出现气溶胶光学厚度的最大值，大约是其它季节的２倍。在湿润地区，如新丰（１１４．２°Ｅ，２４．５°Ｎ），虽然春季气溶胶光学厚度值也是最大，但只是比其它季节稍微大一些 瓦里关春季的Ａｎｇｓｔｒｏｍ指数有最小值，约０．１５，表明有比较大的粒子、密云和新丰的Ａｎｇｓｔｒｏｍ指数也有很大的月际变化。但没有明显的季节倾向。这表明，气溶胶的源比较复杂。     

中国北方沙尘暴与气象要素关系的初步研究

为研究沙尘暴形成机理以及各气象要素对沙尘暴的作用,利用1954～2000年我国北方地区7个台站的月降水量、大风日数、月平均气温和沙尘暴日数资料,以相关性分析为基础,采用了建立大风修正指数,线性拟合,滑动相关的方法,深入探讨其相关关系。结果表明沙尘暴与同期降水呈负相关,而与前一年降水的相关不明显,但有极值对应;与大风和大风修正指数呈明显正相关,并从结果比较可知大风修正指数可以很好地反映沙尘暴的发生规律;沙尘暴日数与前冬气温呈负相关,但是减去趋势后负相关消失,这反映了两者的相关关系主要是趋势相关;计算20年滑动相关,由6个台站一致的变化趋势得出结论：相关值的大小与下垫面的荒漠化程度有很大关系。