华北旱涝变化的混沌性质分析

利用华北海河流域近７００多年的旱涝等级序列，从功率谱特点、吸引子分数维和可预报时间等方面分析了历史旱涝变化的混沌性质。由专门设计的误差控制计算方案得到的旱涝变化分数维大于４。只有经过大平滑处理，旱涝序列的分数维才能显著地降至３．５。通过分析系统的局部Ｋｏｌｍｏｇｏｒｏｖ熵，发现偏早态和偏涝态的可预报时间基本相同，即约４ａ。但经平滑处理后偏涝态的可预报性改善较多，说明从较长时间尺度看，干旱期的旱涝预报比之湿润期要更困难些。     

用于地震可预测性CSEP计划的南北地震带地区地震最小完整性震级Mc研究

为确定“地震可预测性国际合作研究计划”(CSEP)中的“CSEP中国检验中心”研究区范围,本研究采用“完整性震级范围”(EMR)方法研究了2008年10月1日至2011年5月31日期间南北地震带地区的最小完整性震级Mc的空间分布特征,并使用Bootstrap方法评估Mc的不确定度.对该地区整体Mc的研究结果表明,Mc ...     

Temporal and spatial circulation patterns in the East Frisian Wadden Sea

This work deals with the analysis of simulations carried out with a primitive equation numerical model for the region of the East Frisian Wadden Sea. The model, with 200-m resolution, is forced by wind, air–sea heat, and water fluxes and river runoff and is nested in a German Bight 1-km-resolution numerical model, the latter providing tidal forcing for the fine resolution model. The analysis of numerical simulations is focused both on responses due to moderate conditions, as well as to extreme events, such as the storm surge Britta, for which the model demonstrates very good skills. The question addressed in this paper is how well the model output can be compressed with the help of empirical orthogonal function analysis. It is demonstrated that, for the short-time periods of the order of a spring–neap cycle, only a few modes are necessary to almost fully represent the circulation. This is just an illustration that the circulation in this region is subject to the dominating tidal forcing, creating clear and relatively simple response patterns. However, for longer periods of about several months, wind forcing is also very important, and correspondingly, the circulation patterns become much more complex. Possible applications of the results in hindcasting and forecasting of hydrodynamics and sediment dynamics in the coastal zone are considered.     

33模Lorenz系统的混沌特征及其可预报性分析

简述了33模Lorenz系统的导出及求解过程,并从功率谱、关联维数和Lyapunov指数等三方面验证其33个谱模分量及流场和扰动温度场得到的时空序列具有混沌特性,并对其进行可预报性分析。结果表明,对于混沌系统而言,对其时空序列取平均并不能延长可预报时效。     

Signatures of low-dimensional chaos in hourly water level measurements at coastal site of Mariupol,Ukraine

Variations of water levels in ports and estuaries are important for ship guidance and navigation and are influenced by a variety of factors. The hourly data that was collected from the coastal site at the Port of Mariupol, Ukraine during January–December 2005 were analysed with an objective to reveal features of chaotic behaviour. The concepts and methods of chaos theory (average mutual information, correlation dimension, false nearest neighbours, Lyapunov exponents) were applied. The manifestation of low-dimensional chaos was found in the time series. The possibility of nonlinear prediction was concluded.     

基于TIGGE资料的沂沭河流域6小时降水集合预报能力分析

全球多模式集合预报(TIGGE)资料为发展局地水文风险预报方法提供了新基础。对不同预报系统的集合预报资料进行评价与对比,可为综合应用多源资料实现超集合预报提供参考。本文以沂沭河流域内10个站点观测降水作为参照,对2007～2010年7、8、9月中BABJ(北京)、ECMF(欧洲)、EGRR(英国)、RJTD(日本)和KWBC(美国NCEP)五种预报模式的6h集合预报降水做了相关系数、均方根误差、Nash效率系数、TS评分(风险评分)和Brier评分等定量评估和对比。对于各模式集合平均预报,EGRR表现最好,4日预见期内的相关系数达0.48,Nash系数为0.21,BABJ最差,其他三模式预报能力相当。对于确定的控制性预报,4日预见期内RJTD表现最优,相关系数为0.19,Nash系数为0.13,其次为BABJ和EGRR。各模式集合平均与控制性预报相比,预报能力都占绝对优势,而多模式集合平均其预报能力又强于任何单模式集合平均。在4日预见期内,多模式平均的相关系数达0.49,Nash系数达0.24。在不同百分位阈值下TS评分和Brier评分也表明了类似的各模式评比结果,但多模式平均虽然在较低阈值下评分较优,但不占据绝对优势。各中心资料均具有一个随预见时长增加的稳定衰减期,其中EGRR衰减期最长(达9天)且最为稳定,而其他资料则存在不同稳定程度的衰减,稳定衰减期都能持续4天以上。各中心资料对较大降水的预报还存在各自不同的系统性偏差。     

On the efficiency and predictability of strain energy for the evaluation of liquefaction potential: A numerical study

Strain energy concept has been employed by the researchers for the assessment of liquefaction phenomenon which is a disastrous type of earthquake-induced failure in saturated soils. The efficiency and predictability conditions of strain energy concept for liquefaction potential assessment are investigated herein using effective stress numerical analyses. Several earthquake ground motions were introduced to the base of a calibrated numerical model using an advanced fully coupled constitutive model. Results of the numerical analyses indicate that earthquake-induced excess pore pressure is more rigorously proportional to strain energy compared with the other examined intensity measures. Subsequently, a simple relationship was derived using the results of dynamic analyses to predict cumulative strain energy density in terms of magnitude, source to site distance, and effective overburden pressure. This relationship, which tries to guarantee the predictability condition of strain energy demand, has demonstrated a successful capability in discrimination between the liquefied and non-liquefied case histories recorded after several well-known earthquakes. This study has provided a practical linkage between numerical analysis and field observations. Finally, it is concluded that although strain energy approach possesses a great conceptual efficiency in liquefaction potential assessment, its precise prediction in actual field conditions involves some difficulties.     

Seasonal Variation Features of Western North Pacific Tropical Cyclone Tracks with Their Predictability

Analysis is done of monthly and seasonal variations as climatic features of the tracks from 1196 tropical cyclones originating in the western North Pacific over the period 1949 to 1980, followed by the investigation of 301 onland cyclone tracks over China mainland in terms of methodology for nonlinear system. Obtained by computing the accumulated distance distribution function of the tracks Cm (l) is the characteristic chaos quantity for the related dynamic systems and then the fractual dimensionality d = 4.86 and Kolmogorov entropy approximation K2 = 0.0164, thereby leading to the predictability time scale = 2.54 days. It is found that the reference path among the onland typhoon No.23 of 1971, or Bess in the international nomenclature. Our results could be of operational use as a kind of reference.     

4DVAR data assimilation in the Intra-Americas Sea with the Regional Ocean Modeling System (ROMS)

We present the background, development, and preparation of a state-of-the-art 4D variational (4DVAR) data assimilation system in the Regional Ocean Modeling System (ROMS) with an application in the Intra-Americas Sea (IAS). This initial application with a coarse model shows the efficacy of the 4DVAR methodology for use within complex ocean environments, and serves as preparation for deploying an operational, real-time assimilation system onboard the Royal Caribbean Cruise Lines ship Explorer of the Seas. Assimilating satellite sea surface height and temperature observations with in situ data from the ship in 14 day cycles over 2 years from January 2005 through March 2007, reduces the observation-model misfit by over 75%. Using measures of the Loop Current dynamics, we show that the assimilated solution is consistent with observed statistics.     

论动力相似预报的物理基础问题

为了更好地发展动力相似预报的策略和方法,基于非线性动力学成果,综合探讨了动力相似预报的物理基础问题。分析表明,“相似预报—低频流型—可预报性”在物理上存在密切联系,这在统计相似预报和动力相似预报问题中均适用。通过类比集合预报,并对实际大气不同尺度模式预报的个例分析,初步证实了相似初值对应的动力预报结果及其预报误差行为具有相似性。在此基础上,进一步提出三类相似性问题,并归纳了动力相似预报的物理基础：在初始状态相似性持续的情况下,动力预报结果以及预报误差行为具有相似性。