动态聚类在暴雨客观分类中的应用

在气象预报中,需要进行许多分类,例如:天气过程分类、环流型分类、降水量、气温的分类、天气区划、预报因子的归并、相似年、月的确定等等,都需要进行客观分类。目前应用较广的客观分类分析方法是聚类分析。聚类分析是研究样品或变量指标分类问题的一种多元统计分析方法。它可以用统计方法对样品或变量指标进行数字分类。定量地确定样品或变量指标间的相似程度:根据相似的差异性把其归入不同的类别。本文以动态聚类分析方法作河池地区暴雨客观分类。     

桂西北暴雨的MOS预报方法

汛期暴雨(日雨量≥50毫米)是桂北的主要灾害天气之一,而暴雨预报至今仍是天气预报中的难题。暴雨之所以预报难度大,其原因有:①形成暴雨的天气条件比较复杂,突发性强。②暴雨的时空分布很不规则,难以模拟。③暴雨是天气预报中的小概率事件。基于以上原因,暴雨过程和暴雨预报的研究,是当前国内外气象界的热题,暴雨落     

谐波缺陷下海洋管道屈曲传播压力的计算

本文采用一个具有初始缺陷的环,作为管道屈曲传播的分析模型,材料为理想弹塑性。首先根据大变形理论.计算出它在外力作用下的屈曲破坏外形,然后基于Croll准则,通过数值计算,求得了屈曲传播压力。证实了Croll提出的简化模型是符合实际的。     

CONTROLLING PROCESSES OF FAULTS OVER THE ORIGIN AND DEVELOPMENT OF ZHUJIANG DELTA

This paper discusses the origin and development of the Zhujiang Delta on the basis of the analyses of the fault systems, lithofacies, depositional thickness, ancient coastline and 14C dating. We consider that the delta is a multi-faulting block, whose external form, internal structure and configuration of its ancient coastline are all strictly controlled by three active sets of the NE, NW and WE faults.     

东亚夏季风期间水汽输送与西北干旱的关系

利用西北(区)168个测站1961—2000年6～9月月平均降水与温度资料,采用EOF、REOF方法分析了近40年降水异常特征,同时利用同期NCEP/NCAR月平均再分析资料,分析了强(弱)夏季风年西北区水汽通量场的特征及夏季风西北影响区的净水汽通量。结果表明:西北区6～9月降水可分为7个气候异常区;东亚夏季风对我国降水的影响主要位于100°E以东的地区;东亚夏季风西北影响区降水的水汽来源于南风水汽通量;强夏季风年,到达东亚夏季风西北影响区的水汽通量显著增加,该区降水偏多,弱夏季风年则反之。     

STUDY ON THE PHYSICAL PROCESS OF WINTER VALLEY FOG IN XISHUANGBANNA REGION

Xishuangbanna of Yunnan Province is a famous tropical foggy region. A field experiment wascarried out from November 23 to 30 of 1997 during which fogs occurred regularly every day. In thepaper the characteristics of macrostructure of fog are analyzed and the physical processes offormation and dissipation of fog are studied. The results show that the Xishuangbanna valley fogforms firstly in the lower atmosphere with two-layer structures and then develops suddenly in thevertical direction after reaching the ground. Furthermore, the vegetation effect on the formationand dissipation of fog is discussed specially.     

Some Unresolved Issues in Ocean Pipes Aspirating Fluid

This paper reviews the dynamics of ocean pipes aspirating fluid and presents a selective review of the research undertaken on it. It focuses on the equations of motion, fluid-solid interaction at the inlet of the free end of the pipe, the stability mechanism of pipes aspirating steady fluid, etc. In particular, some unresolved or partly resolved issues on these important aspects are discussed. Finally, the promising future development in this area is discussed.