不同时间尺度的西北太平洋海洋表面温度距平模态的比较

本文利用经验正交分解法(Empirical Orthogonal Function,EOF)对不同月平均和10天平均的西北太平洋海洋表面温度距平数据进行分解,得到月平均和10天平均的西北太平洋海洋表面温度距平分布模态,并对分布模态进行比较。发现尽管数据源相同,但是不同时间分辨率的EOF结果出现正好相反的情况,文章最后从数学的角度解释了月平均和10天平均的海洋表面温度距平模态及其时间系数发生反向的原因。     

The DynaMICCS perspective

The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties, atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies. The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle) and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM) and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA missions (PICARD, LYRA, maybe ASPIICS).     

Quantitative estimation presort of glacier lake outburst debris flow based on bucket effect

Glacier-lake outburst debris flow(GLODF),unique in high altitude mountains where modern glacier is active,is significantly large in its scale of time and space,and strong in power of destroy.Following the world’s becoming warmer,GLODF frequency gradually rises.In late years,quantitative estimation methodologies has been put into use of mass GLODF estimations.To improve former methodologies,this article suggests that the glacier(or the massif)on the trailing edge and the moraine dam are the two major systems providing independent glacier lake outburst possibilities.Bucket Effect exists in GLODF issues.Therefore focusing on the relatively unstable one of the above two provides better accuracy in estimation on GLODF possibility.Thus,this article summarizes method of presort through specific GLODF evaluation.     

Internal wave eigenmodes and their weak nonlinear resonant interaction in a nonlinearly stratified fluid—A preliminary theoretical and experimental study

A preliminary theoretical and experimental study was conducted on internal wave modes and their weak nonlinear resonant interaction in a nonlinearly stratified fluid. An asymptotical solution of the modes and a dispersion relation of internal waves in a stratified fluid with density profile similar to that in our experiment were obtained theoretically. The resonant-interaction mechanism to 2nd order approximation is also discussed. The resonant interaction of the 3rd and 4th mode internal waves excited by the unstable 1st mode wave is analyzed on the basis of data obtained by conductivity probes. The resonant-interaction condition, i.e., ,k ₁+k ₃+k ₄=0, is examined. It is shown that the resonant instability increases with pycnocline thickness and wave maker driving frequency. This work is supported by the National Natural Science Foundation of China.     

Simplified vibratory characterization of alluvial basins

For the analysis of seismic wave amplification, modal methods are interesting tools to study the modal properties of geological structures. Modal approaches mainly lead to information on such parameters as fundamental frequencies and eigenmodes of alluvial basins. For a specific alluvial deposit in Nice (France), a simplified modal approach involving the Rayleigh method is considered. This approach assumes a set of admissible shape functions for the eigenmodes and allows a fast estimation of the fundamental frequency of the basin. The agreement with other numerical results (Boundary Element Method) and experimental ones is fully satisfactory. The simplified modal method then appears as an efficient mean for the global vibratory characterization of geological structures towards resonance. To cite this article: J.-F. Semblat et al., C. R. Geoscience 335 (2003).     

Use of non-linear localization for isolating structures from earthquake-induced motions

The dynamic response due to earthquake-induced excitations of multi-storey buildings simulated by a cantilever (with attached concentrated masses) supported on a flexible foundation, is reconsidered when stiffness non-linearities are included. To this end, a suitable non-linear spring-mass device is placed between the ground and the mass of the foundation, which under certain conditions can absorb a significant amount of seismic energy over a large frequency range, thus drastically reducing the seismic response of the foundation. This is achieved by the stiffness non-linearity that gives rise to a localization phenomenon, according to which motions generated by external disturbances remain passively localized close to the point of seismic excitation instead of ‘spreading’ to the entire structure. The implications of these findings to the design of earthquake-resistant structures are discusssed. Copyright © 1999 John Wiley & Sons, Ltd.     

人工影响天气碘化银催化剂研究进展

碘化银（AgI）类催化剂是人工影响天气外场试验和业务作业中使用最广泛的催化剂,其核化效率和核化机制在很大程度上影响催化效果。在总结美国、中国和欧洲多个国家利用云室和风洞研究AgI类催化剂的核化机制、核化阈温及成核率的室内实验成果的基础上,梳理利用室内实验成果发展的AgI数值催化模式,旨在为下一步优选新型高效AgI类催化剂和改进数值催化模式提供借鉴。AgI类催化剂核化机制包括凝华核化、接触冻结核化、凝结冻结核化和浸没冻结核化,其核化过程受大气温湿条件、催化剂粒子大小、成分等多种因素影响,并与催化剂粒子的燃烧溶液法、燃烧焰剂法和爆炸法等发生方式有关。目前国内外使用的AgI类催化剂含有不同成分,有多种催化剂粒子产生方式,催化剂粒子的核化机制和成核率有很大差异。将来应重点基于高性能云室和风洞,分析不同催化剂配方的核化机制和成核率,优选新型高效催化剂,改进AgI数值催化模式。     

中国东部夏季风雨带季内变化各模态的环流及海温特征

本文根据中国气象局国家气候中心提供的中国160站月平均降水量,NCEP/NCAR再分析的850 hPa风场,及NOAA扩展重建的海温场资料,用合成分析和相关分析,研究了1951～2005年间中国夏季风雨带季内变化各模态的西太平洋副高夏季各月活动特点的差异,及其与前期冬季东亚季风和太平洋海温异常的联系,并分析了我国夏季风雨带季内变化各模态与夏季雨型的关系。结果表明,不仅不同模态对应的西太平洋副高自春至夏的两次北跳有明显不同的过程,而且两次北跳还具有相对独立性。第一次北跳主要对6月的雨带特征有重要影响,第二次北跳对7、8两月的雨带分布有决定性意义。太平洋海温异常对我国夏季风雨带季内变化的影响是多态的,在不同季风—ENSO循环的位相有不同的表现。第一模态主要出现在El Ni?o减弱位相,第二模态在La Ni?a发展位相,第三模态在El Ni?o发展位相,第四模态在La Ni?a减弱位相,第五模态ENSO的信号较弱,第六模态在La Ni?a持续位相。此外,不同海洋关键区的海温异常对我国雨带季内变化也有不同的调控作用。黑潮区的海温与6月的雨带活动关系密切,而赤道东太平洋的ENSO循环对7、8两月的雨带有重要影响。对我国夏季风雨带季内变化模态与夏季雨型关系的分析则表明,它们之间存在某些联系,但这并不意味着可以相互取代。     

ENSO事件次表层海温的两个模态及其对大气环流的影响

利用SODA海洋同化资料和NCEP再分析大气资料,分析了热带太平洋次表层海温异常(subsurfaceoceantemperatureanomaly,SOTA)与厄尔尼诺与南方涛动(ElNi?o-SouthernOscillation,ENSO)循环的联系,及SOTA对大气环流的影响。回顾传统ENSO研究,指出存在的问题,提出了ENSO影响大气研究的新思路,得到以下结果:(1)以SOTA为基本资料的研究发现, ENSO事件有两个模态,主要出现在冬季的第一模态对冬季及夏季亚洲-北太平洋-北美地区上空中高纬大气环流有重要影响,主要出现在夏季的第二模态对该地区上空夏季热带和副热带大气系统有重要作用。(2)ENSO事件通过与ENSO相联系的热带太平洋海面温度异常(ENSO-relatedseasurface temperatureanomaly,RSSTA)对大气的异常热通量输送,强迫Walker环流和Hadley环流变化,导致热带和北太平洋及周边地区上空大气环流异常,进而影响相关地区冬季和夏季的气候。(3)海表面温度异常(seasurfacetemperatureanomaly,SSTA)包含RSSTA和大气异常导致的海温变化(sea temperature anomaly caused by atmospheric anomaly, STA)两部分, RSSTA是ENSO事件过程中海洋内部热动力结构调整导致的海面温度变化,在海洋对大气的热输送过程中,它随ENSO事件演变不断更新;STA是大气受RSSTA海洋异常加热后导致的大气环流异常对海面温度的影响,在海洋浅表层STA对RSSTA有重大影响。本文最后讨论了ENSO事件期间热带海洋对大气热输送过程,指出ENSO事件通过海洋内部热动力结构调整产生RSSTA,它直接对大气异常加热,导致大气环流和气候异常,局地海气之间负反馈过程产生STA,反过来抑制RSSTA。结果还指出,人们常用的SSTA变率实际上主要由秋冬季节RSSTA主导,丢失了春夏季ENSO信息,用SSTA研究ENSO事件存在局限性,这也可能是ENSO事件春季预报障碍的原因之一。