Low Frequency Characteristics of Tropical Pacific Wind Stress Anomalies in Observations and Simulations from a Simple and a Comprehensive Models     

Ni Yunqi  Zhang Qin 《大气科学进展》1996,13(4):445-460

Low frequency characteristics of tropical Pacific wind stress anomalies in observation and simulations; from the CZ simple atmospheric model and COLA R15 AGCM are analyzed. The results show that ENSO event may be a multi-scale process, that is, ENSO time scale has the period longer than three yean; biennial oscillation and annual variability Dynamical characteristics are involved in the evolution process of wind stress anomaly with ENSO time scale: 1) the development and eastward movement of a cyclonic anomaly circulation in subtropical northwestern Pacific and weakening of Southern Oscillation result in the eastward propagation of westerly anomaly along the equator, there?fore, interactions between flows in subtropics and in tropics play an important role in the evolution of wind stress anomaly with ENSO time scale; 2) easterly and westerly anomalies with ENSO time scale are one kind of propagating wave, which differs from Barnett’s (1991). It is interesting that the evolution of observed and simulated wind stress anomalies with biennial time scale bears a strong resemble to that with ENSO time scale although their period it dif?ferent. Observed annual variability it weak during 1979-1981 and intensified after 1981, especially it reaches to max?imum during 1982-1984, and the spatial structure of the first mode is the ENSO-like pattern.  相似文献   

Response　Process　of　Oceanto　AtmosphericForcing　and　Optimal　Response　Frequency　in　the　CZ　Ocean　Model     

Ni Yunqi  Zou Li  Wu Aiming 《大气科学进展》1996,13(1):43-58

ＲｅｓｐｏｎｓｅＰｒｏｃｅｓｓｏｆＯｃｅａｎｔｏＡｔｍｏｓｐｈｅｒｉｃＦｏｒｃｉｎｇａｎｄＯｐｔｉｍａｌＲｅｓｐｏｎｓｅＦｒｅｑｕｅｎｃｙｉｎｔｈｅＣＺＯｃｅａｎＭｏｄｅｌＮｉＹｕｎｑｉ（倪允琪），ＺｏｕＬｉ（邹力）ａｎｄＷｕＡｉｍｉｎｇ（吴爱明）（...  相似文献   

1998年夏第二阶段梅雨期乌拉尔山阻塞形势的维持   总被引：7，自引：1，他引：7  

Li Shuanglin  Ji Liren  Lin Wantao  Ni Yunqi 《大气科学进展》2001,18(1):87-105

１９９８年夏季长江流域发生了近５０年来最严重的洪水。洪水形成最直接、最主要的原因是梅雨异常。异常梅雨的形成与东亚夏季风偏弱及热带外环流持续异常有关，其中一个明显特征是乌拉尔山地区长时间维持阻塞形势。本文结合诊断分析和数值试验，从瞬变对基本流的强迫（大气内部强迫）及热带热源强迫（外源强迫）两方面，分析了与第二段梅雨相对应的乌拉尔长时间阻塞的维持机制。利用共轭敏感性分析方法，计算了最有利于乌拉尔阻塞发展和维持的敏感扰动，发现扰动的分布位置，刚好与观测到的，从东大西洋到欧洲区域的异常增强的瞬变活动区相重叠。Ｅ矢量及斜压线性静止波模式的诊断进一步表明，异常期间的增强瞬变活动有利于乌拉尔出现正高度异常。计算了持续异常期间的高空急流及大气加热场，发现北美到大西洋的高空急流及热带加热都出现明显异常。中期天气预报模式 ＩＡＰ Ｔ４２Ｌ９的集合预报试验表明，热带地区的加热异常，尤其是热带中西太平洋和大西洋的加热异常，有利于乌拉尔正高度异常的形成。最后，提出了一种热带异常热源驱动下，瞬变波与定常波双向相互作用的阻塞形成与自维持的可能机制。  相似文献   

Effect of nonlinear dynamic process on formation and breakdown of blocking     

Zhang Pei  Ni Yunqi 《大气科学进展》1991,8(1):41-50

With the L-P approximate method (variation of parameter method), a barotropic channel model in β-plane is used to study the effect of nonlinear interaction between two waves with different scales on the formation of blocking. The approximate analytical solution, which can describe the process of the blocking formation, maintenance and breakdown, has been obtained by using the method of approximate expansion. The importance of nonlinear interaction between two waves with different scales is stressed in the solution. The result suggests that the nonlinear interaction is the main dynamic process of the blocking formation. Some required conditions of blocking formation are also discussed.  相似文献   

中国及邻区现代构造应力场的数值模拟   总被引：53，自引：5，他引：53       下载免费PDF全文

汪素云  陈培善 《地球物理学报》1980,23(1):35-45

我国及邻区的现代构造应力场作为一平面应力问题用有限单元法进行了计算。将本区地壳看成是一不均匀的弹性板,根据各地区杨氏模量E、泊松比v和地壳厚度T的不同,组成12种材料区。全区被分成288个三角形单元。考虑了五种应力和位移边界条件,这些边界条件分别反映了印度洋板块、太平洋板块及菲律宾海板块对我国及邻区施加应力的相对大小。将计算得到的最大剪应力值与强震分布进行对比,将最大主压应力方向与震源机制解的最大主压应力方向进行对比,选择一种和实际符合得最好的边界条件作为可取的模式。结果表明:来自印度洋板块的作用力最大,大约是来自太平洋板块和菲律宾海板块作用力的两倍。  相似文献   

A NUMERICAL EXPERIMENT STUDY FOR INFLUENCE OF THE TRANSITION ZONE MIGRATION ON SUMMER DROUGHT IN NORTH CHINA^*          下载免费PDF全文

Zheng Weizhong  Ni Yunqi 《Acta Meteorologica Sinica》1999,13(4):403-413

In this paper,the summer climate of 1991 is taken as a case to study the influence of the transition zone migration on summer drought in North China by using the regional climate model (RegCM2).The results show that the transition zone migrates inland,the summer monsoon rainband of 1991 also moves inland.The intensive rainband in the Changjiang River Valley during the Meiyu period moves north.The precipitation in North China increases and the surface air temperature decreases.As a consequence,it results in a good circle between ecosystem and climate.The transition zone migration changes flux transfers between land and atmosphere,and excites secondary circulation or circulation cells around it.All those are closely related with the variation of precipitation.  相似文献   

川滇地区上地幔顶部Pn速度细结构   总被引：20，自引：0，他引：20  

黄金莉  宋晓东  汪素云 《中国科学D辑》2003,33(Z1):144-144

利用中国地震年报、四川和云南区域地震台网观测报告的23298个Pn波到时资料,反演得到川滇地区及周边的Pn波速度细结构及各向异性。结果表明:该区Pn波速度在7.7～8.3km/s范围内变化,横向变化较为明显,在滇西南部、腾冲火山区、攀西构造带,Pn波速度都明显较低,这些地区地震和构造活动十分活跃,且在地表观测到较高的大地热流值;另一方面较为稳定的地区,如:扬子地合中部,Pn波速度相对较高;研究区内最明显的Pn高速区位于成都东南部的四川盆地;上述结果说明该区Pn波速度与现代构造活动及地热活动存在较明显的关联。Pn各向异性的变化呈现出区域内岩石形变的复杂图像,从藏东块体经川滇菱形块体到滇西南部,Pn快波方向里左旋运动,这可能与印-欧板块碰撞挤压,致使青藏高原物质向东南方向逃逸有关。由此表明区域内壳幔间存在较强的耦合关系,由事件和台站的静延迟分布可以看出从青藏高原到中国东部地区地壳由厚减薄,这与人工地震测深所得到的地壳厚度变化具有较好的一致性。  相似文献   

L ateral Variation of Pn velocity beneath northeastern marginal region of Qinghai—Xizang plateau   总被引：1，自引：0，他引：1  

许忠淮  汪素云  裴顺平 《地震学报(英文版)》2003,16(1):26-33

Pn arrival time data are collected from the bulletins of both national and regional seismological network in China-These data are tomographically inverted to map the lateral variation and anisotropy of Pn velocity in the northeast-ern marginal region of Qinghai-Xizang plateau.The average Pn velocity in this region is 8.09km/s,being a little higher than the average for whole China,Higher velocity is found in tectonically stable Qaidam basin,while lower velocity is seen in and around tectonically active Shanxi graben.The region where the 1920 Haiyuan great earth-quake occurred shows a slightly low Pn velocity.A noticeable result is that,differing from the tectonically com-pressive Tianshan region.where Pn velocity is low,the Qilianshan region,where the Neotectonic deformation is also primarily compressive,shows high Pn velocity,In the uppermost mantle beneath the Ordos plateau Pn veloc-ity is inhomogeneous,varying from higher velocity in southwestern part to lower one in northeastern part.This may be attributed to possible movement of the Ordos block,as there are strong earthquakes all around the block.  相似文献   

Velocity structure of uppermost mantle beneath China continent from Pn tomography   总被引：6，自引：0，他引：6  

汪素云  许忠淮  Thomas Hearn  James Ni  俞言祥  张晓东 《中国科学D辑(英文版)》2002,45(2):143-150

39473 Pn travel times are inverted to tomographically image both lateral variation and anisotropy of uppermost mantle velocities beneath China continent. The result indicates that the overall average Pn velocity of uppermost mantle in the studied region is 8.0 km/s and the regional velocity fluctuation varies from ?0.30 km/s to +0.35 km/s. Pn velocities higher than 8.2 km/s are found in the regions surrounding Qingzang Plateau, such as Junggar Basin, Tarim Basin, Qaidam Basin and Sichun Basin. Pn velocities slightly lower than the average are found in western Sichuan and Yunnan, Shanxi Graben and Bohai Bay region. A Pn velocity as low as 7.8 km/s may exist in the region striding the boundary between Guangxi and Guangdong provinces. In general, Pn velocity in tectonically stable region like cratonic platform tends to be high, while that in tectonically active region tends to be low. The regions in compressive setting usually show higher Pn velocity, while extensional basins or grabens generally display lower one. Anisotropy of Pn velocity is seen in some regions. In the southeastern region of Qingzang Plateau the directions of fastest Pn velocity show a rotation pattern, which may be related to southeastward escape of the plateau material due to the collision and compression of Indian Plate to Asia along Himalaya arc. Notable anisotropy also exists around Bohai Bay region, likely indicating crustal extending and possible magma activity therein.  相似文献   

Seismic characteristics near the epicenter of the 1303 Hongtong M=8 earthquake, Shanxi Province and its implication     

王健  吴宣  张晓东  汪素云 《地震学报(英文版)》2004,17(4)

Introduction A great earthquake occurred on Sept. 25 of 1303 (Seventh of Dade, Yuan Dynasty) around Zhaocheng and Hongtong in Shanxi Province. The great earthquake is a very famous one, which is affirmed as the first earthquake with magnitude 8 in Chinese history. The catastrophes took place; meanwhile, huge archives of the disaster were recorded. According to these disaster recordings, the first isoseismal map in China was delineated, which provide us with abundant information of intensi…  相似文献