一次飑线过程多普勒雷达资料分析   总被引：3，自引：0，他引：3  

李淑玲  刁秀广  朱敏  刘爱荣 《气象》2009,35(3):60-65

利用济南CINRAD/SA多普勒雷达产品,针对2006年7月5日飑线天气过程,分析回波发展演变、流场结构,讨论外流边界、强下沉气流与大风的关系,分析组合反射率因子、垂直液态含水量、中气旋产品特征.结果发现,飑线过境时风速出现两个极大值,一个出现在外流边界影响时段,另一个发生在强回波下沉气流影响时段;在横槽南下过程中,飑线后部强入流不断补充,前侧暖湿气流沿着后部入流爬升,不断产生新的单体,使得风暴得以维持发展;在垂直流场结构上表现为前侧暖湿气流倾斜上升,然后主体部分向后倾斜,后部有冷空气注入,形成下沉气流,下沉气流在地面附近辐散,与前侧入流形成低层阵风锋,是造成地面破坏性大风的主要因素.在水平流场结构上表现为低层存在气流辐合上升运动,中层有气旋性旋转气流,风暴高层为辐散气流.飑线消散阶段后期中层出现MARC,带来大风天气,而同时伴有冰雹天气的风灾产生在飑线达到最强至开始减弱的时段.当回波强度≥50dBz,且垂直液态含水量≥35kg·m-2,当有中气旋时,有利于产生冰雹和大风天气;外流边界的出现,反映了强对流回波后部下沉气流较强,是灾害性大风的前兆.  相似文献   

夏季黔东南州局地暴雨与西太副高环流的关系   总被引：5，自引：0，他引：5  

池再香  白慧  黄红  龚雪芹  牛俊玫 《高原气象》2008,27(1):176-183

通过对黔东南州1996-2005年夏季发生局地暴雨的主要影响系统、各种物理量场的特征、地形等的综合分析,得出9次局地暴雨都与西太平洋副热带高压位置变化密切相关,西太平洋副热带高压外围的SW气流均增强为急流,并输送大量水汽和不稳定能量,而且特别有利的地形的强化作用,造成黔东南暴雨的落区不同.根据暴雨的不同落区,将其归纳为四种类型,即西部型暴雨、南部型暴雨、中部型暴雨、东部型暴雨.但中、南部型暴雨还有中低层低涡切变线配合产生.  相似文献   

不对称环流对台风强度变化的影响   总被引：6，自引：0，他引：6  

河惠卿  王振会  金正润 《热带气象学报》2008,24(3):249-253

利用卫星云图和NCEP再分析风场资料对0207号台风HALONG云系和风场变化特征进行了分析.结果表明,台风云系不对称的结构,台风西侧高空急流向台风中心的移动和辐散是台风迅速减弱的主要原因.为了了解不对称台风环流对台风强度的影响,还对比分析了0417号台风AERE、0216号台风SINLAKU在中国沿海减弱和重新加强的环流特征.在低层流入台风中心南侧的西风分量大,在高层流入台风中心西侧的北风分量小,有利于台风的加强.台风南、北两侧的东西向风场垂直切变梯度差异不利于台风加强.东西向风场垂直切变对台风强度的影响比南北向风场更重要.  相似文献   

一次长寿命风暴的CINRAD/SA雷达反射率及中气旋产品特征与流场结构分析   总被引：10，自引：8，他引：2  

刁秀广  杨晓霞  朱君鉴  王俊  黄秀韶 《高原气象》2008,27(3):657-667

利用济南观测站的探空、涡度、地面资料和CINRAD/SA雷达产品,对2004年6月24日发生在山东西部地区的强风暴过程进行了分析。结果表明,风暴低层存在中尺度辐合现象,风暴前侧的入流依靠后部低层冷空气池的向前推进而得到支撑,产生逆环境风切变方向的主上升气流区;中层为双涡旋结构,这种深厚的内部涡旋结构可与环境风相持,形成近似刚体的风暴柱,环境风绕风暴而过,不会吹穿风暴,有利于风暴长时间维持;风暴成熟阶段表现为超级单体结构特征并伴有中气旋;三体散射(TBSS)出现在中高层,TBSS出现10~15 min后地面出现大冰雹,TBSS消失后维持10~20 min的降雹。  相似文献   

离岸型背景风和海陆风对珠江三角洲地区灰霾天气的影响   总被引：18，自引：0，他引：18  

陈训来  冯业荣  范绍佳 《大气科学》2008,32(3):530-542

不同类型的背景场和海陆风对珠江三角洲地区大气灰霾有不同的影响。作者主要利用空气质量模式系统Models-3 (MM5/SMOKE/CMAQ)研究离岸型背景风和海陆风对珠江三角洲一次灰霾天气的影响, 结果表明, 中尺度气象模式MM5对珠江三角洲地区这次灰霾天气的气象模拟, 较好地模拟了风速和风向的变化。多尺度空气质量模式CMAQ模拟出了PM10浓度的变化, 与观测值比较一致。在这次灰霾天气过程中, 由于离岸型背景风与陆风风向一致, 在陆风维持的情况下, 内陆源区的PM10被输送到沿海地区, 导致沿海城市和海面上PM10浓度比较高; 而在海风维持的情况下, 海风与离岸型背景风方向相反, 造成海风较小, 致使整个珠江三角洲地区灰霾天气都比较严重。敏感性试验结果表明离岸背景风和海陆风的相互作用对灰霾天气的生成与分布有重大的影响。  相似文献   

Solar Wind Effects Associated with a Recurrent,High-Latitude Coronal Brightness Enhancement     

Gary D. Parker 《Solar physics》2009,257(1):155-167

During the descent of Ulysses following the 2001 solar north pole passage, the SOHO LASCO C2 telescope recorded a particularly strong sequence of recurrent polarization brightness (pB) features at latitudes of around 55°. As Ulysses passed overhead, solar rotation swept the interplanetary extensions of these persistent coronal structures over the spacecraft. Comparison of solar remote sensing and Ulysses in situ observations through 2002 reveals the solar wind effects of very bright and recurrent K-coronal structures at high solar latitudes and of a steeply inclined heliospheric neutral sheet (HNS). Despite the high level of solar activity, the HNS at high latitude still organizes solar wind stream structure much as it did near the previous solar minimum. The recurrent coronal streamers originate slow solar wind and mark the northern extremity of a very tilted HNS whose passage at Ulysses is accompanied by slow, dense solar wind, enhanced temperature, depressed α abundance, enhanced magnetic fields, and magnetic field directional changes that evolve with spacecraft latitude.  相似文献   

Effects of strong ground motion on the susceptibility of gully type debris flows   总被引：5，自引：0，他引：5  

Chia-Nan Liu  Jia-Jyun Dong  Yih-Ferng Peng  Hsiao-Fung Huang 《Engineering Geology》2009,104(3-4):241-253

Typhoon Herb in 1996 caused widespread debris flows in central Taiwan. The 7.3 Chi-Chi earthquake on September 21, 1999, which also took place in central Taiwan, induced many landslides in the region. These landslides turned into debris flows when Typhoon Toraji struck Taiwan in 2001. This research selects three regions which suffered a ground motion class of 5, 6, and 7 on the Richter scale during the Chi-Chi earthquake as study areas. Air photos from 1997 and 2001 of these regions are used to map the gully-type debris flows that took place after Typhoons Herb and Toraji, respectively. The gullies adjacent to the debris flow, but without a trace of debris flows, are also mapped as the non-debris flow data. The topography, hydrogeology, and rainfall factors – where debris flow occurred and in which there was no occurrence of debris flows in these gullies were retrieved from DTM, geological maps, and iso-countour maps, and of rainfall through GIS processing. These characteristic are introduced into a probabilistic neural network to build a predicting model for the probability of the occurrence of debris flows. Three series of cross analyses are conducted to compare the probability of the occurrence of debris flows of the same dataset predicted by different prediction models. The results reveal that the susceptibility of debris flows was elevated after the Chi-Chi earthquake struck. The upsurge of susceptibility was more obvious for the regions that received a higher class of ground motion.  相似文献   

A morphological, sedimentological and geophysical investigation of the Woore Moraine, Shropshire, England     

Aidan A. Parkes  Richard I. Waller  Ian G. Stimpson  Keith T. Mason 《Proceedings of the Geologists' Association. Geologists' Association》2009,120(4):233-73

The Bar Hill-Whitchurch-Wrexham Morainic Complex is a large-scale glacial landform thought to represent either the maximum extent or the re-advance of the British-Irish Ice Sheet during the Late Devensian. The origin of the moraine remains uncertain as its key characteristics have not been studied in detail due to a lack of exposures from which its large-scale structure can be determined. The development of new technologies has enabled detailed examination of the topography and internal structure of such large-scale landforms. This paper describes a multi-disciplinary approach involving digital geomorphological mapping using enhanced resolution NextMAP™ digital surface models, geophysical imaging (electrical resistivity tomography) and conventional sedimentological analyses. This combination of techniques is useful for elucidating the origin of a large glacial landform in a region of poor exposure. Digital elevation models such as NextMAP™ offer an efficient and accurate method for landform-mapping, whilst electrical resistivity tomography was able to map the major constituent sediments of the moraine, which had in turn been identified in the single exposure available. Additional geophysical techniques should however be applied to provide further structural data and thereby enable a more detailed interpretation of the moraine's internal structure. Preliminary findings indicate that the moraine is a glaciotectonic landform composed of diamicton and glaciofluvial sediments, an origin consistent with recent suggestions that the Cheshire Plain contained an active ice lobe during the last glacial maximum.  相似文献   

Decoupling between the middle and upper crust during transpression-related lateral flow: Variscan evolution of the Aston gneiss dome (Pyrenees, France)     

Yoann Denle  Philippe Olivier  Grard Gleizes  Pierre Barbey 《Tectonophysics》2009,477(3-4):244

We present a structural, AMS, microstructural and kinematic study of the Aston gneiss dome (French Pyrenees), which consists of a core made up of orthogneiss and paragneiss intruded by numerous sills of Carboniferous peraluminous granite. The orthogneiss corresponds to a former Ordovician granitic laccolith. Four Variscan events have been evidenced in this gneiss dome: (i) D1 deformation observed only as relics in the orthogneisses and their country-rocks located above the sillimanite isograd, and characterized by a NS to NE–SW non coaxial stretch associated to top to the south motions (NS convergence); (ii) D2-a deformation observed in the orthogneisses and their country-rocks, mainly migmatitic paragneisses, located below the sillimanite isograd and in the peraluminous granites whatever their structural level, and characterized by an EW to N120°E stretch associated to a top to the east flat shearing (lateral flow in the hot middle crust in a transpressive regime); (iii) D2-b deformation characterized by EW-trending megafolds corresponding to the domes in the middle crust and by EW-trending tight folds with subvertical axial planes in the metasedimentary upper crust; (iv) subvertical medium-temperature mylonitic bands developed by the end of the transpression.The Aston massif is a good example of decoupling between a cold upper crust and a hotter middle crust overheated by a thermal event originated in the upper mantle. This decoupling allowed the lateral flow of the migmatitic middle crust along a direction at high angle with respect to the more or less NS-trending direction of convergence. We suggest that the HT-LP metamorphism developed before the formation of the domes during D2-a, coevally with the emplacement of numerous sills of peraluminous granite, whereas the emplacement of the large calc-alkaline plutons in the upper crust occurred by the end of D2-b. Our data invalidate the previous geodynamical models based on either early or late extensional regime to explain the development of the HT-LP metamorphism. This new interpretation of the dynamics of the Variscan crust of the Pyrenees is consistent with recent studies conducted in Archaean and Palaeoproterozoic hot continental crusts having undergone oblique convergence, and characterized by a competition between vertical thickening and lateral flow induced by the important rheological contrast between two thermally different levels.  相似文献   

太阳爆发过程中的大尺度磁重联电流片:理论和观测     

吴宁  李燕  沈呈彩  林隽 《天文学进展》2012,30(2):125-158

从理论和观测两个方面来介绍和讨论出现在太阳爆发过程中的磁重联电流片及其物理本质和动力学特征。首先介绍在理论研究和理论模型中,磁重联电流片是如何在爆发磁结构当中形成并发展的,对观测研究有什么指导意义。然后介绍观测工作是从哪几个方面对理论模型预测的电流片进行证认和研究的。第三,将介绍观测研究给出了哪些过去所没有能够预期的结果,这些结果对深入研究耀斑一CME电流片以及其中的磁重联过程的理论工作有什么重要的、挑战性的意义。第四,讨论最新的与此有关的理论研究和数值实验。最后,对未来的研究方向和重要课题进行综述和展望。  相似文献