The long-term patterns of phytoplankton taxonomic size-structure and their sensitivity to perturbation: A Lake Kinneret case study     

Yury Kamenir  Zvy Dubinsky  Tamar Zohary 《Aquatic Sciences - Research Across Boundaries》2006,68(4):490-501

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Progress in Predictability Studies in China （2003-2006）     

段晚锁  姜智娜  徐辉 《大气科学进展》2007,24(6):1086-1098

Since the last International Union of Geodesy and Geophysics General Assembly(2003),predictability studies in China have made significant progress.For dynamic forecasts,two novel approaches of conditional nonlinear optimal perturbation and nonlinear local Lyapunov exponents were proposed to cope with the predictability problems of weather and climate,which are superior to the corresponding linear theory.A possible mechanism for the"spring predictability barrier"phenomenon for the El Ni(?)o-Southern Oscillation (ENSO)was provided based on a theoretical model.To improve the forecast skill of an intermediate coupled ENSO model,a new initialization scheme was developed,and its applicability was illustrated by hindcast experiments.Using the reconstruction phase space theory and the spatio-temporal series predictive method, Chinese scientists also proposed a new approach to improve dynamical extended range(monthly)prediction and successfully applied it to the monthly-scale predictability of short-term climate variations.In statistical forecasts,it was found that the effects of sea surface temperature on precipitation in China have obvious spatial and temporal distribution features,and that summer precipitation patterns over east China are closely related to the northern atmospheric circulation.For ensemble forecasts,a new initial perturbation method was used to forecast heavy rain in Guangdong and Fujian Provinces on 8 June 1998.Additionally, the ensemble forecast approach was also used for the prediction of a tropical typhoons.A new downscaling model consisting of dynamical and statistical methods was provided to improve the prediction of the monthly mean precipitation.This new downsealing model showed a relatively higher score than the issued operational forecast.  相似文献   

日本数值预报产品在MM5模式中的应用     

张建海  张广周 《河南气象》2007,(4)

针对目前中尺度数值模式MM5所用初始场局限于NCEP和T213的现状,提出了应用日本数值预报产品(JMA,下同)格点资料做初始场的想法,并对试验过程进行了介绍。对台风Ranan im(0414)登陆浙江的路径、移速、强度和降水等方面的数值模拟结果表明,应用了JMA资料的MM5模式在原有基础上提高了预报精度,尤其在台风登陆时间和登陆地点上提高更为明显。  相似文献   

Hybridization of the probability perturbation method with gradient information     

Kent Johansen  Jef Caers  Satomi Suzuki 《Computational Geosciences》2007,11(4):319-331

Geostatistically based history-matching methods make it possible to devise history-matching strategies that will honor geologic knowledge about the reservoir. However, the performance of these methods is known to be impeded by slow convergence rates resulting from the stochastic nature of the algorithm. It is the purpose of this paper to introduce a method that integrates qualitative gradient information into the probability perturbation method to improve convergence. The potential of the proposed method is demonstrated on a synthetic history-matching example. The results indicate that inclusion of qualitative gradient information improves the performance of the probability perturbation method.  相似文献   

基于BGM的不同繁殖长度对集合预报的影响          下载免费PDF全文

于永锋  张立凤 《应用气象学报》2007,18(1):86-93

利用T63L9全球谱模式和NCEP/NCAR再分析资料, 对BGM方法中增长模的繁殖长度对集合预报效果的影响进行研究。结果表明:与控制预报相比, 不同繁殖长度的集合预报都能使预报效果得到一定程度的改进, 特别是第4天预报以后, 改进程度随预报时效而稳步提高。三组不同繁殖长度的集合预报对控制预报的改进存在差别, 分析结果表明:繁殖长度为2 d的集合预报明显效果最差, 而繁殖3 d和4 d的集合预报差别并不明显。对集合Talagrand分布以及离散度的初步分析表明, 繁殖长度取为3 d似乎最为合理。  相似文献   

夏季东亚西风急流扰动异常与副热带高压关系研究   总被引：7，自引：1，他引：7       下载免费PDF全文

杨莲梅  张庆云 《应用气象学报》2007,18(4):452-459

利用1979—2003年NCEP/NCAR月平均再分析资料, 探讨夏季 (6—8月) 200 hPa东亚西风急流扰动异常与南亚高压和西太平洋副热带高压的关系。研究指出:夏季200 hPa东亚西风急流扰动动能加强 (减弱), 东亚西风急流位置偏南 (偏北)、强度偏强 (偏弱); 东亚西风急流扰动动能强弱不仅与北半球西风急流强弱和沿急流的定常扰动有关, 而且还与东亚地区高、中、低纬南北向的扰动波列有关, 亚洲地区是北半球中纬度环球带状波列异常最大的区域。夏季200 hPa东亚西风急流扰动动能加强 (减弱), 南亚高压的特征为位置偏东 (偏西)、强度加强 (减弱); 西太平洋副热带高压的特征为位置偏南 (偏北)。东亚环流特别是500 hPa西太平洋副热带高压对东亚西风带扰动异常的响应由高空东亚西风急流南侧的散度场及其对流层中下层热带和副热带地区的垂直速度距平场变化完成。  相似文献   

弱二次切变流轴对称涡旋演变的解析研究     

衡骏遥  周伟灿 《南京气象学院学报》2007,30(1):72-78

运用格林函数方法,给出了弱二次切变流轴对称涡旋演变的解析解.结果表明:当环境流中弱二次切变强度增加(减少)时,扰动动能的最大值增加(减小),扰动动能的变化加速(减速);而扰动涡旋的范围对扰动动能的大小与变化也存在一定的影响.  相似文献   

武汉台形变观测与降雨参数之间的定量分析与研究          下载免费PDF全文

吕琳  杨艳芳  舒德亮 《地震工程学报》2020,42(1):136-142

基于“前兆台网(站)观测数据跟踪分析平台”,对武汉台形变观测资料进行了系统分析,提取出观测曲线受降雨干扰影响的事件,采用降雨总量、初始驱动降雨量和瞬时降雨量最大值等降雨参数对降雨干扰事件进行统计分析。结果表明:降雨总量达40 mm、初始驱动降雨量为0.3 mm或瞬时降雨量最大值达0.6 mm时,DSQ型水管倾斜仪易受降雨干扰;SSY型铟瓦棒伸缩仪当降雨总量超60 mm或瞬时降雨量最大值大于0.5 mm时易受降雨干扰;VS型垂直摆倾斜仪受降雨干扰与降雨总量、初始驱动降雨量和瞬时降雨量最大值无显著相关关系;降雨总量对形变仪器观测物理量的影响基本呈现线性;而形变仪器观测物理量与初始驱动降雨量、瞬时降雨量最大值无显著相关关系。认为武汉台形变观测受降雨影响主要来自降雨渗透影响和周边水体荷载变化影响两个方面。  相似文献   

Mass-Weighted Symplectic Forms for the N-Body Problem     

F. Varadi  M. Ghil  W. M. Kaula 《Celestial Mechanics and Dynamical Astronomy》1998,72(3):187-199

Mass-weighted symplectic forms provide a unified framework for the treatment of both finite and vanishingly small masses in the N-body problem. These forms are introduced, compared to previous approaches, and their properties are discussed. Applications to symplectic mappings, the definition of action-angle variables for the Kepler problem, and Hamiltonian perturbation theory are outlined This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Quasi-isotropic approximation of ray theory for anisotropic media     

Matthias Zillmer  Boris Kashtan  & Dirk Gajewski 《Geophysical Journal International》1998,132(3):643-653

Wave propagation in weakly anisotropic inhomogeneous media is studied by the quasi-isotropic approximation of ray theory. The approach is based on the ray-tracing and dynamic ray-tracing differential equations for an isotropic background medium. In addition, it requires the integration of a system of two complex coupled differential equations along the isotropic ray.
The interference of the qS waves is described by traveltime and polarization corrections of interacting isotropic S waves. For qP waves the approach leads to a correction of the traveltime of the P wave in the isotropic background medium.
Seismograms and particle-motion diagrams obtained from numerical computations are presented for models with different strengths of anisotropy.
The equivalence of the quasi-isotropic approximation and the quasi-shear-wave coupling theory is demonstrated. The quasi-isotropic approximation allows for a consideration of the limit from weak anisotropy to isotropy, especially in the case of qS waves, where the usual ray theory for anisotropic media fails.  相似文献