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221.
NUMERICAL SIMULATION OF EXTREMELY HEAVY RAIN AND MESO-β SCALE LOW VORTEX IN INVERTED TYPHOON TROUGH*
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JIANG Yongqiang WANG Changyu ZHANG Weihuan CHEN Zhongyi 《Acta Meteorologica Sinica》2004,18(2):195-210
Large-scale and mesoscale analyses are made for extremely heavy rain(EHR) and meso-β scale low vortex(MSLV) in Jiading District of Shanghai Municipality during 6-7 July 2001.It is shown that the EHR forms in the situation of northern westerly trough linking together with southern inverted typhoon trough at northwest side of the West Pacific Ocean subtropical high. Numerical simulation is made using a 21-layer improved REM(regional η coordinate model) for this course.The results show that the precipitation forms earlier than MSLV.and the strong convergence in wind velocity mate(WVM) triggers the strong precipitation.The formative reasons of WVM.especially the weak wind velocity center are discussed,and the formative mechanisms of the MSLV and EHR are discussed using high spatial and temporal resolution modeloutput physical fields.The results show that the heavy rain releases latent heat and warms the air column,and enhances the low level positive vorticity that existed before.Then it causes the formation of MSLV.There is a positive feedback mechanism between low vortex and precipitation,so CISK must be an important mechanism. 相似文献
222.
结合我国探月项目卫星VLBI测轨资料分析中的实际需求讨论了两个问题:一是在S、X波段时延测量精度均为1ns情况下,电离层延迟改正所能够达到的精度;二是在飞行器VLBI测轨过程中,不能确保S、X波段双频观测情况下获取电离层时延改正的可能途径,包括借助于相关电离层模型、利用常规VLB1历史观测资料积累、借助于局域GPS观测网和IGS网单站GPS测量以及借助于专门设计的单站GPS测量等。最后对电离层VLB1和GPS技术实测结果进行了比较和问题分析。 相似文献
223.
The tectonic history of the Western Mediterranean region during the Oligocene and Early Miocene is illustrated through a series of plate reconstructions, from chron C13n to chron C6n. The reconstructions are based on a new interpretation of published magnetic anomaly data and two-ships seismic data, and their integration with known geological constraints, in order to determine style and timing of the backarc extension processes in the Liguro-Provençal, Valencia and Algerian basins. In particular, a reinterpretation of the regional magnetic anomaly field allowed the calculation of the instantaneous Euler poles associated with the motion of 11 microplates relative to Eurasia and Iberia. Furthermore, a quantitative analysis of the acoustic basement morphology and the balancing of deep crustal profiles were used to estimate the closure and pre-rift rotation angles associated with the Euler poles of opening of the Ligurian, Provençal, Valencia and Algerian basins. This rigorous reconstruction of the geometry of the pre-rift continental margins of Iberia and Eurasia could furnish important insights into the study of Mediterranean tectonics for older times. 相似文献
224.
225.
Comparative studies of short-term ionospheric variability in the F region ionosphere during rapid sequence sounding campaign
“HIRAC/SolarMax” (23–29 April 2001) are presented. The ionospheric short-term fluctuations have been studied in detail using
measurements from vertical sounding at Ebro (40.8 °N, 0.5 ° E) and Průhonice (49.9 °N, 14.5 °E) in the period range from 15
minutes to 2 hours. The electron density measurements contain variations that indicate the possible presence of propagating
gravity waves. Regular wave-like bursts were found during quiet days at both stations in electron concentration in F region,
with an increase of the oscillation activity after sunrise and then during late afternoon, and at sunset and after sunset.
Solar Terminator is assumed to be one of the sources of the regular wave bursts detected in the ionosphere during campaign
HIRAC. As expected, substantial intensification in longer period gravity waves was found to occur during the disturbed period
on April 28. Particular enhancement of the wave-like activity during disturbed day is discussed, being significant evidences
of a change of the wave-like activity pattern at a height around 200 km. 相似文献
226.
从天气系统背景、FY-2C卫星产品、水汽通量分布特征和大气稳定度特征等方面,分析了受台风低压倒槽与东移锋面云系的共同影响,于2005年7月21日夜间到23日邯郸市出现的大范围的暴雨天气,结果发现:500hPa槽前中尺度切变线是直接影响产生暴雨的重要系统;地形作用使迎风坡降水增强;中尺度对流云团和雨团关系密切,暴雨中心位于OLR和TBB低值区下面;西部山区的暴雨区水汽主要来源于南海、东海,东部平原大暴雨水汽主要来源于南海;暴雨区上空低层为对流不稳定,高层为对称不稳定。 相似文献
227.
本文中的中国主要指我国的大陆、海南岛及台湾等地区的陆地部分。本文由中国早寒武世早期及晚期的岩相古地理图2幅及相应的文字论述组成。这两幅岩相古地理图的最大特征是“两槽和三台相间分布”。两槽即天山北山蒙辽吉槽地和昆仑秦岭槽地,三台即准噶尔蒙兴槽地、塔里木柴达木华北台地和西藏华南台地。两个槽地与三个台地之间的界限是根据大地构造、地层、岩石、岩相等资料综合判断而定的,绝大部分是比较确切的,有的地方是推断的。天山北山槽地可分出次级岩相古地理单元,其他槽地的次级岩相古地理单元尚难以划分。在三个台地中,华南、华北和西北地区的研究程度较高,它们的次级岩相古地理单元的划分均有确切的定量资料和图件为依据,是定量的,而且还能把早寒武世早期和晚期的岩相古地理区分开;其他地区的研究程度较低,难以再划分次级古地理单元,其古地理图都只能是定性的。这种研究程度有差异的、定量和定性兼有的、全国范围的岩相古地理图,既反映笔者等的研究成果,也反映我国当前地质工作的研究程度,优缺兼有,实虚共存。敬请读者指教。 相似文献
228.
229.
1998年第二季度,全球地震活动为中等水平。6级以上地震频度不高。美洲地震活动无新的活跃迹象。琉球海槽发生7级地震。西南太平洋岛弧地震强度不高,最高震级为6.5。亚欧带地震仍有继发性活动。南大西洋洋脊发生4次5~6级地震。 相似文献
230.
P. Eglitis I. W. McCrea T. R. Robinson T. Nygrén K. Schlegel T. Turunen T. B. Jones 《Annales Geophysicae》1998,16(10):1241-1250
The COSCAT system enables the detection of E-region auroral backscatter with the EISCAT remote receivers at magnetic aspect angles close to 90°. This is achieved by utilising a low-power transmitter stationed in Oulu, Finland. Many important observations of E-region irregularities have been achieved with this simple experiment. Recent studies have attempted to push the COSCAT system to its experimental limits. Firstly, the CW signal has been phase-modulated with 13-bit Barker codes with baud lengths of 40, 70 and 100 s. Interpretation of the received power allows the spatial distribution of the auroral scatterers to be determined. The second advance is in the use of a sophisticated correlator program which allows data to be buffered within the correlator at very high time resolution. This enables the coherent backscatter power to be sampled every 12.5 ms and the full auto-correlation function to be measured every 100 ms. These measurements allow the COSCAT system to be employed for the first time in an investigation of the growth and decay of the auroral irregularities. 相似文献