Slow quasigeostrophic unstable modes of a lens vortex in a continuously stratified flow     

Hai Yen Nguyen  Richard Schopp  Xavier Carton 《地球物理与天体物理流体动力学》2013,107(3):305-319

This work addresses the linear dynamics underlying the formation of density interfaces at the periphery of energetic vortices, well outside the vortex core, both in the radial and axial directions. We compute numerically the unstable modes of an anticyclonic Gaussian vortex lens in a continuously stratified rotating fluid. The most unstable mode is a slow mode, associated with a critical layer instability located at the vortex periphery. Although the most unstable disturbance has a characteristic vertical scale which is comparable to the vortex height, interestingly, the critical levels of the successively fastest growing modes are closely spaced at intervals along the axial direction that are much smaller than the vortex height.  相似文献   

渤海海效应暴雪的三维热力结构特征   总被引：1，自引：0，他引：1  

杨成芳 《中国海洋大学学报(自然科学版)》2010,40(2)

采用烟台多普勒天气雷达、天气图等观测资料和中尺度模式(RAMS4.4)进行数值模拟,分析了2008年12月4~6日发生的一次海效应暴雪的时空分布和三维热力结构特征。结果表明:(1)渤海海效应降雪并非传统认为的仅发生在蓬莱以东的山东半岛地区,而是广泛分布于山东半岛、莱州湾、渤海中东部和黄海西部洋面上;降雪源地有暖海面和陆地,即莱州湾、渤海中部至渤海海峡和山东半岛。(2)浅层对流是海效应降雪的重要热力特征,当强冷空气流经渤海时,暖海面通过湍流交换等作用向冷空气底层输送感热和潜热,使得低层增温增湿,产生对流层中上层干冷低层暖湿的对流性不稳定。(3)冷空气的强弱影响渤海暖海面及山东半岛地区的垂直热力结构,导致降雪强度在不同时段存在显著差异。海气温差与热通量成正比,初期冷空气弱,对流层中低层的垂直温差小,海面上空的暖湿层浅薄,不稳定能量弱,产生的降雪量小;中后期冷空气强盛,对流层中低层的垂直温差大,暖湿层较为深厚,不稳定能量增强,导致降雪强度和降雪量大。(4)与单一要素温度和湿度相比,对流层低层相当位温的水平分布对强降雪落区具有更好的指示意义,强降雪发生在高相当位温脊线附近。  相似文献   

Theoretical analyses of acidization dissolution front instability in fluid‐saturated carbonate rocks     

Chongbin Zhao  B. E. Hobbs  A. Ord 《国际地质力学数值与分析法杂志》2013,37(13):2084-2105

This paper presents an instability theory that can be used to understand the fundamental behavior of an acidization dissolution front when it propagates in fluid‐saturated carbonate rocks. The proposed theory includes two fundamental concepts, namely the intrinsic time and length of an acidization dissolution system, and a theoretical criterion that involves the comparison of the Zhao number and its critical value of the acidization dissolution system. The intrinsic time is used to determine the time scale at which the acidization dissolution front is formed, while the intrinsic length is used to determine the length scale at which the instability of the acidization dissolution front can be initiated. Under the assumption that the acidization dissolution reaction is a fast process, the critical Zhao number, which is used to assess the instability likelihood of an acidization dissolution front propagating in fluid‐saturated carbonate rocks, has been derived in a strictly mathematical manner. Based on the proposed instability theory of a propagating acidization dissolution front, it has been theoretically recognized that: (i) the increase of the mineral dissolution ratio can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (ii) the increase of the final porosity of the carbonate rock can destabilize the acidization dissolution front, while the increase of the initial porosity can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (iii) the increase of the mineral dissolution ratio can cause an increase in the dimensionless propagation speed of the acidization dissolution front; (iv) the increase of the initial porosity can enable the acidization dissolution front to propagate faster, while the increase of the final porosity can enable the acidization dissolution front to propagate slower in the acidization dissolution system. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

磁尾宽频带静电噪声的一种新的激发机制          下载免费PDF全文

沐建林  濮祖荫  方正知 《地球物理学报》1988,31(6):613-621

本文提出了磁尾宽频带静电噪声强谱段的一种新的激发机制。在等离子体片边界层中存在着瞬时的局域性的晨昏电场。电子和离子对该电场的响应不同:在电场存在的区域内,电子作回旋漂移运动,而离子轨道在的时间尺度内可视为直线。由于等离子体片边界层中等离子体是非均匀的,这就导致了电荷分离的产生,从而可激发静电不稳定性。本文通过求解含电场的Vlasov方程,计算了由此产生的不稳定波的频率和增长率,考察了波矢方向。上述计算结果均与强谱段静电噪声的观测特征一致。  相似文献   

冻土的蠕变及蠕变强度   总被引：10，自引：7，他引：10  

马巍  吴紫汪 《冰川冻土》1994,16(2):113-118

基于试验，本本讨论分析了冻土三轴蠕变规律及温度和围压对冻土蠕变强度的影响，给出了土蠕变及蠕变强度随时间降低的方程式，进而提出了冻土蠕变强度的物型屈服准则。通过改变参数可将冻土的瞬时强度准则与冻土的瞬时强度准则与冻土的蠕变强度准则统一为同一个方程描述。  相似文献   

The effect of a finitely conducting layer in the mantle on magnetic instability in the core     

C. J. Lamb 《Geophysical Journal International》1995,121(3):763-774

  相似文献   

条件性对称不稳定与梅雨锋暴雨   总被引：2，自引：3，他引：2  

寿绍文  励申申 《南京气象学院学报》1993,16(3):364-367

  相似文献   

简单的热带海气耦合波——Rossby和Kelvin波的相互作用   总被引：5，自引：1，他引：5       下载免费PDF全文

巢纪平  王彰贵 《气象学报》1993,51(3):257-265

本文分析了当大气和海洋中未经耦合前的自由波分别为Kelvin波和Rossby波,经相互作用后所产生的耦合波的性质。结果表明,不管大气的自由波为Kelvin波或Rossby波,而海洋的自由波为Rossby波或Kelvin波,经相互作用后的耦合波可以分成两类。一类耦合波的色散关系接近自由的Kelvin波;另一类则由不同经圈模的Rossby波经相互作用后的耦合波。这两类波都具有不稳定性。文中讨论了耦合波的传播和不稳定的物理机制,并指出这类不稳定的热带耦合波,对研究ENSO事件中的某些现象有一定的参考意义。  相似文献   

弱耗散作用下非线性Rossby波的调制不稳定          下载免费PDF全文

罗德海 《大气科学》1993,17(2):163-172

本文使用WKB方法对弱耗散作用下基本气流具有弱切变的行星大气中非线性Rossby波进行了研究,得到了弱耗散的非线性Rossby波振幅所满足的复系数非线性Schrdinger方程,并分别就无耗散和弱耗散的Rossby波的边带稳定性问题进行了讨论,得到了一些新结果.  相似文献   

地球弓激波前的低频磁流体波     

李少峰  孙炜 《地球物理学报》1990,33(2):239-241

一、引言 在地球弓激波前存在着低频磁流体波。这种低频磁流体波是太阳风在地球弓激波上的反射粒子和太阳风粒子之间相互作用产生的。根据人造卫星的观测资料可以得到,在地球弓激波前,Pc3-4脉动频率范围内的低频磁流体波的主频率和行星际磁场强度  相似文献