双台风条件下水汽的中尺度输送特征与收支诊断

应用WRF(v3.4)模式输出资料,揭示双台风条件下水汽的输送与收支特征及其对台风强度的影响.分析表明,"菲特"台风与副热带高压、中高纬地区槽脊、西面大陆高压及其东南面尾随台风"丹娜丝"存在周边系统相互作用,这种相互作用使得"菲特"台风背景风场改变,从而影响其水汽输送通道的调整.水汽输送特征分析表明,周边系统相互作用,特别是尾随"丹娜丝"台风作为水汽"收集-输送"站的作用,对"菲特"台风在近海强度的维持及后期偏北强降水有重要影响.水汽通量辐合带的分布和演变与台风强对流带的分布和演变具有一致性,即水汽的输送对台风内核区强对流带的强度和结构具有重要影响.水汽收支诊断分析表明,水汽输送对两类台风强度的变化具有重要影响,即总的水汽通量与台风强度随时间的变化均具有较好的一致性.东边界是台风的主要水汽输送来源,南、北边界次之,西边界为负贡献;各边界水汽输送主要分布在对流层底层,西边界的对流层中低层为负贡献.水汽的垂直输送对台风内部水汽的再分配起着重要作用,同时水汽垂直输送大值带的持续时间与台风研究区域内强对流大值带的持续时间一致,说明水汽的垂直输送对"U"型和"V"型台风区域的强对流也具有重要的影响.     

中国夏季大气水分循环特征及再分析资料对比分析

大气水分循环过程耦合了降水、蒸发、水汽输送等多个环节.本文利用ERA-Interim与MERRA再分析资料,研究了中国1979—2012年夏季大气水分循环的时空变化特征及其对全球气候变化的响应,并对两套再分析资料在中国地区的适用性进行了评估.结果表明:1)中国夏季降水、蒸发、可降水量均自东南沿海地区向西北内陆递减;降水与蒸发相互联系、相互制约,由于不同地区下垫面物理条件的差异,它们之间同时存在正、负反馈的影响机制,可降水量主要集中在地面至700 h Pa高度,约占总量的75%;2)近34年大气水分循环显著变化的区域主要集中在西部和东北地区,西部内陆地区可降水量显著增加,北方大部分地区纬向水汽输送通量显著减小,西北北部地区经向水汽输送通量显著增大,蒸发量与水汽输送的气候变化可能是造成可降水量增加的主要原因;3)Interim与MERRA资料对降水量时空变化特征的再现能力要优于蒸发量,此外,它们对降水与蒸发气候变化趋势的模拟结果差别较大,使用时应该慎重;两套资料对可降水量与水汽输送通量的时空变化特征以及气候变化趋势的模拟比较一致,可信度较高;4)Interim资料对西南、东南以及东北区域夏季水循环均有较好的描述能力;而MERRA资料更适用于研究西南和西北区域的水汽收支情况.     

Spatiotemporal characteristics of laser emission. II

The electrodynamic laser theory of a nonstationary nonlinear oscillatory system with spatially distributed parameters, constructed in the first part, and applied there to semiconductor lasers (electron-beam pumped injection lasers) is used in this second part to investigate the spatiotemporal characteristics of emission in the near and far zones and for giant laser light pulse generation in Q-switched lasers (Chap. 1) and the electrodynamics of a laser with planar open cavities, particularly at high pump levels (Chap. 2). In the third chapter is set forth a procedure for the investigation of the wavefront deformation in laser amplifiers. We consider also the possibility of improving the laser divergence by using mirrors comprising systems of inverting prisms—triple prisms or corner reflector (Chap. 4). The fifth chapter is devoted to a procedure for the investigation of the spatiotemporal characteristics of laser radiation with spherical mirrors. In the sixth chapter the spatial structure of propagating Bessel beams, is determined and a comparison is made with other laser beams.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 51 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Spatiotemporal characteristics of laser emission. I

The first chapter describes the general premises of the electrodynamic theory of the laser as a nonstationary nonlinear oscillatory system with spatially distributed parameters. Maxwell's equations are used to derive an equation for the complex amplitude of the electromagnetic field in a cavity filled with transversely inhomogeneous active medium. The self-conssitent analysis includes a simultaneous solution of the equations for the field and for the inverted population. In the second chapter, electrodynamic theory is applied to injection and electron-beampumped semiconductor lasers. The threshold characteristics, the field structure in the near and far zones, the lasing regimes of semiconductor lasers, and the influence of nonlinearity of the refractive index are considered.Division of Quantum Radiophysics, Lebedev Physics Institute. Translated from Preprint No. 33, Lebedev Physics Institute, Moscow, 1990.     

Oscillation characteristics of a laser-induced cavitation bubble in water at different temperatures

Comprehensive numerical and experimental analyses of the effect of temperature on cavitation oscillations are performed. In the experimental study, the oscillation of a laser-generated single cavitation bubble near a rigid boundary is obtained using a fiber-optic diagnostic technique based on optical beam detection (OBD). The maximum and minimum bubble radii as well as the oscillation times for each oscillation cycle are determined according to the characteristic signals. And cavitation bubble tests are performed using water at different temperatures, and its temperature ranges from freezing point (0 °C) to near boiling. Furthermore, a modified Rayleigh-Plesset equation is derived for calculating the temporal development of the bubble radius at different temperatures. Both the experimental and the numerical results show that the maximum bubble radius and bubble lifetime both increase as temperature increases. The mechanism behind it has also been discussed.     

Spatiotemporal control of ultrashort optical pulses by refractive-diffractive-dispersive structured optical elements

Structured optical elements that control the spatial and temporal characteristics of femtosecond light pulses are analyzed and synthesized. We show that unique spatiotemporal effects can be attained based on the diffraction, refraction, and dispersive effects that appear in the femtosecond regime. We argue that the design requirements for ultrafast optics are beyond the achromatization considerations that are usually applied to incoherent illumination because of the need to consider coherent effects. Despite fundamental limitations in the space-time control of ultrashort pulses, we show the potential of this technique to improve simultaneously the spatial and the temporal resolution of a lens and to generate ultrafast pulse sequences.     

Characteristics of high-frequency atmospheric eddies over the mediterranean area in different seasons

Summary We examine the properties of atmospheric eddies over Europe and the Mediterranean, as revealed by an analysis of high-pass filtered time series of geopotential height. The data used are seven years of 6-hourly initialized analyses, prepared at ECMWF. The application of a time-filter with cut-off around 6 days allows us to isolate the variability associated with travelling eddies, which generally come from the Atlantic and whose properties (spatial structure, propagation characteristics) are deeply modified when they pass over the Mediterranean region. Different statistical indicators have been derived to reveal these modifications, that are particularly evident in the lower troposphere. It appears that the orography surrounding the Mediterranean region is the main factor influencing eddy behaviour. This conclusion is supported, among other considerations, by the comparison between winter and summer statistics: notwithstanding the different climatological properties of the mean atmospheric circulation and of the surface heat fluxes in the two seasons, some peculiar properties of the high-frequency components over the European and Mediterranean region, such as the vertical and horizontal structure, do not vary much as a function of the season.

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Riassunto Sono esaminate le proprietà dei vortici atmosferici sull'Europa e il Mediterraneo, mediante un'analisi di serie temporali di altezza di geopotenziale, filtrate con un filtro passa alto. I dati utilizzati sono costituiti da sette anni di analisi inizializzate, disponibili ad intervalli di 6 ore, preparate dal Centro Europeo di Previsione Meteorologica a Medio Termine (ECMWF). L'applicazione di un filtro temporale con un periodo di taglio di circa 6 giorni permette di isolare la variabilità associata con vortici viaggianti che generalmente provengono dall'Atlantico e le cui proprietà (struttura spaziale, caratteristiche di propagazione) sono profondamente modificate allorquando essi transitano sopra la regione mediterranea. Sono stati calcolati diversi indicatori statistici allo scopo di rivelare tali modifiche, che sono particolarmente evidenti nella bassa troposfera. L'orografia che circonda la regione mediterranea rappresenta il fattore principale che influenza il comportamento dei vortici. Questa conclusione è rafforzata, fra l'altro, dal confronto tra le statistiche riferite ai periodi invernale ed estivo: nonostante le differenti proprietà climatologiche della circolazione atmosferica media e dei flussi di calore alla superficie durante le due stagioni, alcune proprietà peculiari delle componenti di alta frequenza della circolazione sulla regione europea e mediterranea, quali la struttura orizzontale e verticale, non variano molto in funzione della stagione.

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Резюме Мы исследуем свойства атмосферных вихрей над Европой и над Средиземным морем, которые были обнаружены при анализе фильтрованных временных последовательностей для геопотенциальной высоты. Данные собирались в течение семи лет. Применение временного фильтра с обрезанием в 6 дней позволяет нам выделить изменчивость, связанную с перемещаюимися вихрями, которые обычно приходят из Атлантики и чьи свойства (пространственная структура, характеристики распространения) сильно изменяются, когда вихри проходят над областью Средиземного моря. Используются различные статистические индикаторы, чтобы обнаружить эти изменения, которые наблюдаются в нижней части тропосферы. Оказывается, что орография, окружающая область Средиземного моря, является основным фактором, влияющим на поведение вихрей. Это утверждение подтверждается также сравнением зимней и летней статистик: несмотря на различные климатологические свойства средней атмосферной циркуляции и поверхностных потоков в течение двух сезонов, некоторые свойства высокочастотных компонент над Европой и областью Средиземного моря, такие как вертикальная и горизонтальная структуры, существенно не изменяются в зависимости от сезона.

     

中国旱涝时空分布特征分析

基于帕尔默干旱指数 (Palmer drought severity index, PDSI) 中国数据库和中国160个站点的月降水资料, 运用趋势分析、对比分析和EOF等方法, 对1961–2010年间中国旱涝时空演化特征进行了分析. 结果表明: 春季的PDSI的年代际空间分布特征与PDSI 的年代际空间分布特征相似; 夏季和秋季的PDSI的地区差异比较明显, 尤其是秋季更为明显. 从时间演化上来看, 中国华北、东北、西南地区的变干趋势较明显, 另外变湿比较明显的区域为西北西部. 对1961–2010年夏季的PDSI进行经验正交函数 (EOF) 分析, 可以发现, 20世纪80年代以来, 中国夏季干旱和洪涝更加频繁, 且旱涝强度也增加, 尤其是华北、西南、东北地区的干旱和华东地区的洪涝. 关键词： PDSI 干旱 洪涝 EOF     

ERA-Interim中的中国地区水分循环要素的时空演变特征分析

本文利用1979–2011年欧洲中期天气预报中心 (ECMWF) 的再分析资料 (ERA-Interim), 运用经验正交函数展开 (EOF) 和相似系数等方法, 对中国地区水分循环诸要素的时空特征进行了计算与分析. 研究结果表明: 在空间分布特征上, 蒸发量、纬向水汽通量和经向水汽通量均与大气可降水量的空间分布最相似, 大气可降水量和降水量均与蒸发量的空间分布最相似, 降水量与纬向水汽通量的相似系数略大于其与经向水汽通量的相似系数; 在时间演变上: 年降水量在1979–2002年间, 呈现非常显著的上升趋势; 在2002–2011 年间, 呈现显著的下降趋势. 年蒸发量在该两个时段的变化趋势与年降水量一致, 但均比年降水量明显; 年蒸发量在1979–2011年间呈现非常显著的上升趋势, 其年际变化明显小于年降水量. 可降水量和水汽通量散度在1979–2011年间的长期变化趋势不明显, 但可降水量的年际变化呈阶段式增大, 水汽通量的年际变化一直较大. 纬向与经向水汽通量均存在2–3年为周期的年际变化; 此外, 纬向水汽通量在1979–2011年间还存在显著的下降趋势. 春、秋季的水汽通量都存在显著下降的长期变化趋势, 夏、冬季的长期变化趋势不明显. 四季都存在2–3年为周期的年际变化. 此外, 夏季还存在明显的年代际转折. 关键词： 水分循环 时空特征 EOF 相似系数     

弯张换能器装配预应力及入水后的变化

精确控制施加于驱动元件上的预应力，对换能器的设计及其工作过程都有重要意义，特别对于稀土磁致伸缩换能器来说，有助于发挥其最大潜能.利用有限元方法，计算了VII型水声弯张换能器壳体给驱动元件施加一定预应力时，壳体所需的装配位移的大小，并通过实验作了验证；弯张换能器随入水深度的不同， 驱动元件两端所受到的总的预应力是不同的.利用有限元方法，计算了换能器入水深度与预应力的关系.本文方法可适合于其他任何类型的换能器. 关键词： 弯张换能器 装配位移 预应力 入水深度     

Hydrodynamics of pulsed supersonic underexpanded jets: Spatiotemporal characteristics

The gasdynamic parameters of nonsteady expansion of He, Ar, N₂, and SiH₄ from a sonic nozzle into a space with reduced background gas pressure were experimentally studied for moderate values of n (10³–10⁶) and the Reynolds number (Re_L∼10⁰–10²). The jet set times necessary for the formation of pulsed jets of a given finite duration are determined. The results are generalized in terms of dimensionless similarity parameters. The laws of motion of the leading and trailing fronts in pulsed jets of various gases are established. The leading front of a pulsed jet propagates at a velocity significantly smaller than the limiting steady value. The jet expansion dynamics is determined by the ratio of the momentum of the expanding gas to that of the background gas displaced from the flow region. The length of the steady flow region in a pulsed jet monotonically decreases downstream from the source and drops with increasing background gas pressure because of the loss of jet particles in the trailing rarefaction wave; this length increases with the initial momentum because the background gas is more intensively displaced from the flow region.     

Spatiotemporal distribution characteristics and attribution of extreme regional low temperature event

Based on an objective identification technique for regional low temperature event(OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events(ERLTEs), which are included in the 690 regional low temperature events(RLTEs). The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century.In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-h Pa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 h Pa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter.     

中国东北区域盛夏雨季的客观识别

鉴于我国东北三省雨季客观识别方法不尽相同,且无东北区域统一的雨季监测指标.为了更好地开展区域关键天气过程的客观化识别和监测,本文从区域角度出发,采用东北三省102站逐日降水量资料,通过对东北区域多年平均5点平滑处理的4月1日—10月31日逐日降水量序列的综合分析,及对历年逐日滑动平均雨量的对比试验,确定了东北盛夏雨季判别的阈值参数及通过阈值后的持续时间参数,进而研发了适合东北区域盛夏雨季开始和结束日期的客观识别方法.并采用美国环境预报中心和国家大气研究中心逐日再分析的风场、位势高度场资料,通过对盛夏雨季前、中、后期不同高度层大气环流场的对比分析,验证了该客观识别方法的合理性.结果表明,东北区域1981—2010年气候态平均的盛夏雨季的起止日期分别为每年的6月26日和8月30日.     

Analysis of trace elements in water by ESCA

A new method for the analysis of trace elements in water using ESCA (X-ray photoelectron spectroscopy) is described. The method is applicable to the si     

Spatiotemporal dynamics of the amplitude-phase characteristics of stimulated Raman scattering

A numerical model describing the processes of generation of stimulated Raman scattering (SRS) is developed; the calculations are performed and different scenarios of generation of Stokes radiation in compressed hydrogen are analyzed. The spatiotemporal profiles of intensities and phases of interacting waves, the radiation spectra, and the functions of spatial coherence are obtained by way of numerical simulation for different conditions of SRS generation. A substantial difference between these parameters in the cases of nonstationary and quasi-stationary regimes of SRS generation is revealed. The nonstationary regime of generation is characterized by more complicated spatiotemporal dependences than the quasi-stationary regime. However, in the quasi-stationary regime, the phase of the Stokes wave radiation varies over a larger interval during the pump pulse duration, which leads to a decrease in the degree of spatial coherence to lower values. For both regimes of generation, the value of the degree of spatial coherence decreases with an increase in the conversion factor to a certain threshold value and then stabilizes, which is in agreement with experimental data. The presence of a moving focus of SRS focusing of the Stokes beam is demonstrated. This effect is governed by the spatiotemporal shape of the pump beam intensity (the Gaussian profile), by a high SRS gain, and by the processes of diffraction. The results of the numerical simulation are in qualitative and quantitative agreement with experimental data obtained previously.     

节点结构互异的复杂网络的时空混沌反同步

研究了节点结构互异的离散型时空混沌系统构成复杂网络的反同步问题. 通过构造合适的Lyapunov函数, 确定了复杂网络中连接节点之间的耦合函数的结构以及控制增益的取值范围. 以物理中具有时空混沌行为的激光相位共轭波空间扩展系统、Gibbs电光时空混沌 模型、Bragg声光时空混沌模型以及一维对流方程的离散形式作为 网络节点构成的复杂网络为例进行了仿真模拟, 发现整个网络存在稳定的混沌反同步现象.     

Comparative study of different Schlieren diffracting elements

This paper presents an analysis of diffraction effects taking place at different Schlieren diffracting elements. Two types of diffraction effects are prominent in the Schlieren schemes. One is diffraction of direct light (source image) at the Schlieren element, which limits the sensitivity and resolution of Schlieren systems. The second type is the diffraction of light deflected from the test object at the Schlieren-diffracting element. This second type of diffraction degrades the quality of Schlieren results. Experimental results showing the effect of diffraction of light deflected from the test object at a phase knife-edge, corner of a square phase aperture and an optical fiber tip as Schlieren diffracting elements have been presented and discussed.      

南海北部浅海声场起伏及统计特性

水下声场的时间积分声强和峰值声强是声呐检测中的重要物理量,而海洋中的内波等动力学过程会造成声场强度的起伏。对南海北部浅海内波环境下定点声起伏实验数据分析,结合数值仿真,总结了试验海域近海底发射和近海底接收条件下内波引起接收信号强度起伏的统计特性.分析结果表明:接收信号的时间积分声强起伏小于峰值声强起伏;时间积分声强与峰值声强起伏的概率分布与对数正态分布较为接近.时间积分声强和峰值声强起伏大小与信号的频率有关,同一收发距离,中心频率650 Hz信号的声强起伏较中心频率310 Hz和375 Hz信号的声强起伏更为剧烈。对于同一频率,当海底较平坦时,声强起伏的闪烁指数随传播距离的增加而增大;当水深随传播距离逐渐变深时,声强起伏规律受内波和水深变化共同影响而更为复杂,闪烁指数先随传播距离增加而增大,之后又随传播距离的增加而逐渐变小.     

不同燃料循环方案的可持续性与经济性分析

基于核燃料循环政策技术的成熟度,选取了一次通过循环方案(OTC)、单次复用循环方案(TTC)、快堆闭式循环方案(FRC)及混合堆闭式循环方案(HRC)四种典型的核燃料循环方案进行分析。采用平衡物质流模型对不同燃料循环方案的可持续性进行研究,基于平准化电力成本计算方法对不同方案的燃料成本和乏燃料处置成本进行分析。研究结果表明：闭式燃料循环可极大减少核废料产生; 燃料可自持的FRC方案及HRC方案可使用贫铀做燃料而不消耗天然铀; 仅考虑燃料成本和乏燃料处置成本时,HRC方案的经济性最高而TTC方案的经济性最差。