北半球温带气旋的变化   总被引：8，自引：0，他引：8  

王新敏  邹旭恺  翟盘茂 《气候变化研究进展》2007,3(3):154-157

许多学者对近半个世纪以来温带气旋的频数、强度和路径的年际、年代际变化等特征进行了研究,并探讨了温带气旋变化与大气环流的关系,试图揭示气候变暖背景下温带气旋变化的可能原因。较为一致的研究结论是：在全球变暖背景下,北半球气旋活动的变化显示出在中纬度明显减少,而在高纬度增加的趋势,意味着气旋的路径已经明显地北移。研究还表明,气旋活动的变化与对流层斜压性、急流以及北大西洋涛动、海温梯度等因素有关。  相似文献   

A sedimentological proxy indicator linking changes in loess and deserts in the Quaternary   总被引：9，自引：2，他引：7  

Zhongli Ding  Jimin Sun  Dongsheng Liu 《中国科学D辑(英文版)》1999,42(2):146-152

From Yulin, which is located in the transitional zone between the Loess Plateau and the Mu Us desert, to Weinan in the southernmost part of the Loess Plateau, 9 loess sections were studied. Grain size analyses show that the advance-retreat changes of the deserts in northern China may be the most important factor controlling changes in the sand particle percentage of the loess-soil sequences during the last glacial-interglacial period. It is thus suggegted to use the sand grain content of loess deposits as a proxy indicator of desert variations. Applying this indicator to the last glacial loess deposits in the northwestern part of the Loess Plateau reveals that there were many millennial-scale cycles of the desert environments. Project supported by the National Natural Science Foundation of China (Grant No. 49525230)  相似文献   

Rundle模式地震释放的能量及其标度关系   总被引：2，自引：0，他引：2  

李丁一 《中国地震》1999,15(3):278-283

本文扼要介绍了有关Ｒｕｎｄｌｅ模式地震分叉结构及其爆发判据的主要研究结果。在此基础上推导出强地震过程释放的能量及其标度关系。本系列的研究工作,对地震预报研究有参考价值。  相似文献   

Study on moist potential vorticity and symmetric instability during a heavy rain event occurred in the Jiang-Huai valleys   总被引：2，自引：0，他引：2  

Shou Shaowen  Liu Yaohui 《大气科学进展》1999,16(2):314-321

In the light of the theory on moist potential vorticity (MPV) investigation was undertaken of the 700 hPa vertical (horizontal) component MP1 (MPV2) for the heavy rain event occurring in Ju-ly 5-6,1991. Results show that the distribution features of the two components were closely related to the development of a mesoscale cyclone as a rainstorm-causing weather system in the lower troposphere in such a way that the ambient atmosphere of which MPV1>0 and MPV2<0 with |MPVl|≥|MPV2| favored the genesis of conditional symmetric instability (CSI) and that, as in-dicated by calculations, a CSI sector was really existent in the lower troposphere during the heavy rain happening and contributed greatly to its development.  相似文献   

Rayleigh–Taylor instability of the upper mantle and its role in intraplate orogeny     

Emily A. Neil  & Gregory A. Houseman 《Geophysical Journal International》1999,138(1):89-107

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温度对数压力图的计算机绘制原理   总被引：1，自引：0，他引：1  

郑建萌  张万诚 《气象科学》1999,19(2):201-205

本文根据温度对数压力图上几种物理过程的控制方程,提出了计算机上绘制完整温度对数压力图的方法。给出了湿绝热线求解的数学模型,使绘制的湿绝热线精确性很高,并能绘制任意探空站的温度对数压力图以及计算各种大气稳定指数。  相似文献   

Ulysses observations of nonlinear wave-wave interactions in the source regions of type III solar radio bursts     

G. Thejappa  R. J. MacDowall 《Journal of Astrophysics and Astronomy》2000,21(3-4):447-450

The Ulysses Unified Radio and Plasma Wave Experiment (URAP) has observed Langmuir, ion-acoustic and associated solar type III radio emissions in the interplanetary medium. Bursts of 50&amp;#x2013;300 Hz (in the spacecraft frame) electric field signals, corresponding to long-wavelength ion-acoustic waves are often observed coincident in time with the most intense Langmuir wave spikes, providing evidence for the electrostatic decay instability. Langmuir waves often occur as envelope solitons, suggesting that strong turbulence processes, such as modulational instability and soliton formation, often coexist with weak turbulence processes, such as electrostatic decay, in a few type III burst source regions.  相似文献   

A survey of unbalanced flow diagnostics and their application   总被引：9，自引：0，他引：9  

Zhang Fuqing  Steven E. Koch  Christopher A. Davis 《大气科学进展》2000,17(2):165-183

1.IntroductionImbalanceisdefinedintermsoftowhatextenttheflowdepartsfromabalancedstate.Despitetheapparentcomplexityofatmosphericmotions,thepressure(massfield)andvelocity(momentum)distributioncanberelatedbyrathersimpleapproximateforcebalances(sothatparcelaccelerationscanbeignored).Davisetal.(1996)pointedoutthattheunderlyingassumptionofbalanceddingnosticsisthatthenowevolvesinawayconsistentwiththerestrictionsimplicitwithinthediagnosticframework.ThesimplesttwobalancerelationsaregeostrOPhl'cbalance…  相似文献   

The impact of nonlinear stability and instability on the validity of the tangent linear model   总被引：10，自引：0，他引：10  

Mu Mu  Guo Huan  Wang Jiafeng  LiYong 《大气科学进展》2000,17(3):375-390

l.Intr0ducti0nTheequationsgoverningthemotionsoftheatmosphereandoceanaren0nlinear0nes.Itisdiffcultandcomplicatedtodealwiththenonlinearproblem.Sothetangentlinearmodel(TLM),whichisobtainedbylinearizingthenonlinearmodelinthevicinityofthebasicflow.iswidelyutilizedinthetheoreticalresearchandpracticalimplementationintheatmosphericandoceanicsciences.First-TLMcanbeusedtoestimatetheev0luti0nofsmallPerturbati0nsinaf0recastmodel.Second,itisadoptedinextendedKalmanfilterinthedataassimilation(Evensen,l99…  相似文献   

SLOPE INSTABILITY HAZARDS IN GRANITES OF THE LESSER HIMALAYAN EXAMPLE OF THE PALUNG GRANITE OF CENTRAL NEPAL     

I.R.Humagain  et al 《地学前缘》2000,(Z1)

Granites are hard and sound rock at relatively fresh or unweathered condition. Steep rocky slopes are the characteristic features in the area occupied by granites of the Lesser Himalaya including Kathmandu nappe. Almost vertical to sometimes overhanging slopes in granites look stable in dry season, but the steeper slopes in the areas occupied by granitic rocks are metastable to unstable. The instabilities are related to: variation in texture and mineral composition of granite, nature and intensity of weathering (mechanical and chemical), altitude of the area, orientation of natural slope with reference to the predominant joint sets, quality of rock mass, stress release and activity of subsurface water during monsoon. The study is supposed to be an example for the study of the slope instabilities in the other part of the Himalaya occupied by granitic bodies.  相似文献