Hydroacoustic ex situ target strength measurements on juvenile cod (Gadus morhua L.)     

Nielsen  J. Rasmus; Lundgren  Bo 《ICES Journal of Marine Science》1999,56(5):627-639

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台湾岛对台风移动路径影响的分析   总被引：3，自引：0，他引：3  

张文舟  吴增茂 《海洋预报》1996,13(4):31-38

本文结合国内外近年来的观测事实和研究成果，针对过台泫岛地区台风的内力变化和诱生低压的产生机制进行动力学分析，从而说明台风经过该地区路径发生偏转和跳跃式不连续移动的可能原因。  相似文献   

Quantifying diffuse pathways for overland flow between the roads and streams of the mountain ash forests of central Victoria Australia     

Patrick N. J. Lane  Peter B. Hairsine  Jacky C. Croke  Ingrid Takken 《水文研究》2006,20(9):1875-1884

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The Effect of Asymmetric Wind Structures of Tropical Cyclones on Their Tracks     

XIANG Jie  WU Rongsheng 《Acta Meteorologica Sinica》2005,19(1):52-59

1. IntroductionStudies on the tracks of tropical cyclones (TCs)have been one of the core problems in TC dynamics.In earlier researches, TCs are often viewed aspoint vortices, Rankine vortices. For example, Yeh(1950) and Kuo (1969), adopting dynamical methods,studied the motions of TCs and the effects of environ-ments. Their findings indicated that the motion tracksof TCs are characterized by cyclonic trochoidal oscil-lations.Syono (1955), by solving the barotropic vorticityequation, obta…  相似文献   

Sensitivity of Cyclone Tracks to the Initial Moisture Distribution： A Moist Potential Vorticity Perspective     

Zuohao CAO  Da-Lin ZHANG 《大气科学进展》2005,22(6):807-820

In this study, the characteristics of moist potential vorticity （MPV） in the vicinity of a surface cyclone center and their physical processes axe investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV （NMPV） using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.  相似文献   

切分法固定断面测量     

林友仁  冯宇 《地理空间信息》2007,5(2):104-106

改变航迹线和交会定位公式进行水上固定断面测量,更新了传统水上固定断面复测定位法,新法具有不偏线、点位密、计算简便、精度高等优点,能为生产、设计、研究提供相对精确的地理模型。  相似文献   

青藏高原洞穴次生方解石的裂变径迹年代及地貌学意义   总被引：8，自引：1，他引：7  

高全洲  崔之久  刘耕年  洪云  伍永秋  张叶春  陈怀录 《海洋地质与第四纪地质》2000,20(3):61-65

古岩溶洞穴中残留的次生方解石晶体可以作为裂变径迹测年的材料。通过测定遍及青藏高原的２０组洞穴次生方解石晶体的裂变径迹年代,结果表明,晚第三纪青藏高原的古岩溶过程和缓慢构造抬升过程相伴进行,其间大约１０ＭａＢ．Ｐ．、１２ＭａＢ．Ｐ．和１９ＭａＢ．Ｐ．时溶穴次生化学沉积较为发育。由于地表切割程度的差异,晚第三纪岩溶过程在高原南部较为强烈,相对于第四纪期间的强烈抬升来说,高原晚第三纪的抬升速率较为缓慢,  相似文献   

基于主成分分析的人工智能台风路径预报模型   总被引：1，自引：0，他引：1  

黄小燕  金龙 《大气科学》2013,37(5):1154-1164

利用主成分分析可以从具有随机噪声干扰的气象场提取主要信号特征,排除随机干扰的能力,论文以1980～2010年共31年6～9月西行进入南海海域的台风样本为基础,综合考虑台风移动路径的气候持续因子和数值预报产品动力预报因子,采用主成分分析的特征提取与逐步回归计算相结合的预报因子信息数据挖掘技术,以进化计算的遗传算法,生成期望输出相同的多个神经网络个体,建立了一种新的非线性人工智能集合预报模型,进行了分月台风路径预报模型的预报建模研究。在预报建模样本、独立预报样本相同的情况下,分别采用人工智能集合预报方法和气候持续法进行了预报试验,试验对比结果表明,前者较后者在6、7、8和9月份台风路径预报中,平均绝对误差分别下降了7.4%、4.8%、12.4%、17.0%。另外,论文进一步在初选预报因子和样本个例相同的情况下,通过比较新模型与直接采用主成分分析方法选因子并分别运用逐步回归和遗传—神经网络集合预报模型进行计算的预报精度差异表明,前者具有更高的预报精度,其原因是该方法挖掘利用了全部备选预报因子的有用预报信息,而且遗传—神经网络集合预报模型的是由多个神经网络个体预报结果合成,集合模型的各个神经网络个体的网络结构,是通过遗传算法的优化计算确定的,因此,该集合预报模型的泛化能力显著提高,在实际天气预报中具有较好的实用性和推广价值。  相似文献   

试用新"回归系数估计"法制作南海责任区的热带气旋路径集成预报   总被引：2，自引：1，他引：1  

谢玲娟  万齐林 《热带气象学报》1995,11(4):324-331

在正确评估我国各种客观预报方法性能的基础上,应用新“回归系数估计”方法,将几种预报效果较好、操作方便的模式作为子方法加以集成,建立一个包括数值预报产品在内的优化的客观预报集成模式,经用１９９３年热带气旋样本试报及１９９４年台汛期实例试验,模式的性能稳定,预报精度进一步提高。  相似文献   

Dinosaur tracks in the Kokorkom Desert,Candeleros Formation (Cenomanian,Upper Cretaceous), Patagonia Argentina: Implications for deformation structures in dune fields     

《Cretaceous Research》2018

The Kokorkom desert extended over an area of 826 km² in the central-west sector of Neuquén and Río Negro provinces along the area of the backbulge basin within the Andean Foreland basin in the Neuquén Basin. Its deposits constitute the middle-upper section of the Candeleros Formation (Cenomanian) and reach approximately 130 m thick. Tracks are found on wet and dry interdune and within draa slipface deposits. They constitute biogenic deformation structures characterized by folded-up and/or brecciated sandstone levels formed under dry and/or wet substrate conditions with passive filling. The degree of preservation varies, but the identification of digit impression suggests that they were produced by theropods or iguanodontians.  相似文献