利用区域气候模式预估未来登陆中国热带气旋活动     

聂心宇  谭红建  蔡榕硕  高学杰 《气候变化研究进展》2023,19(1):23-37

鉴于热带气旋（TC）对我国沿海地区的影响,研究全球变暖背景下未来登陆我国TC活动的变化,对于我国沿海地区的防灾减灾具有重要意义。基于CMIP5中全球气候模式HadGEM2-ES数据,文中利用区域气候模式RegCM4开展了历史时期和3种情景（RCP2.6、RCP4.5和RCP8.5）下未来东亚区域气候的动力降尺度模拟,检验了模式对历史登陆我国TC活动及其相关大尺度环境场的模拟能力,并预估了3种情景下2030—2039年、2050—2059年和2089—2098年,登陆我国TC的路径、强度和频率的变化特征。结果表明：模式能合理地再现东亚区域历史时期（1986—2005年）大气环流场的空间结构以及登陆我国TC的特征;在3种情景下未来登陆我国TC的平均强度和数量均有不同程度的增加,尤其是台风及以上级别TC的总数明显增加,其中RCP8.5情景最突出,到21世纪末期（2089—2098年）登陆我国TC的平均强度、台风及以上级别TC总数的年平均值较历史时期将分别增加7.56%和1.05个;不同情景下未来登陆我国TC的路径均有不同程度的北移趋势,且全球升温的幅度越大,北移趋势越明显,这可能与未来中国近海显著变暖和垂直风切变减弱有关。未来我国沿海地区尤其是中高纬度很可能将面临日益严峻的TC灾害风险,亟需尽快开展防灾减灾及对策研究。  相似文献   

The impact of agriculture on solute and suspended sediment load on a Mediterranean watershed after intense rainstorms     

Luís Outeiro  Xavier Úbeda  Joaquim Farguell 《地球表面变化过程与地形》2010,35(5):549-560

The solute and suspended‐sediment load following five rainstorms (2005–2007) with varied intensities were studied at the Vernegà experimental watershed, north‐western Spain. Two land‐use areas are located within this watershed, the upstream one (forest) with 160 ha a 100% forested area, and the downstream one (agricultural) with 97 ha being 9 ha conventional agricultural field and 88 ha forest. This study investigates the capacity of each land‐use to yield water, suspended sediment concentration (SSC) and dissolved solid concentration (DSC). The hypothesis is that DSC and SSC from the agricultural area are greater than DSC and SSC of the forest area. Results showed that the agriculture area produced significantly greater mean DSC than in the forest area, the main contribution was the Ca²⁺ (24·68 ± 46·52 mg l^?1) ion at the agricultural area. A long‐term sediment production rate at the agricultural outlet was calculated (69·1 tonnes per 100 years) based on the total sediment discharge (TSD) and the recurrence interval of the largest event of the five rainstorms (October 2005). Geographic information system (GIS) spatial data layers of the watershed were produced to determine the relation of tracks, landforms, slopes and forest management to SSC yield in the forest outlet (133·89 ± 308·14 mg l^?1) during the five rainstorms. Agriculture practices are the main cause of soil erosion at the study area. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A protoceratopsid skeleton with an associated track from the Upper Cretaceous of Mongolia     

Grzegorz Nied?wiedzki  Tomasz SingerGerard D. Gierliński  Martin G. Lockley 《Cretaceous Research》2012,33(1):7-10

The Djadokhta Formation of the Gobi Desert is known for the number and diversity of dinosaur and other vertebrate bones and skeletons found there, but only theropod, hadrosaur and supposed ankylosaurid footprints have been reported from this stratum. Dinosaur footprints are also noted from the Nemegt Formation, and occur as typical dinosaur track accumulations (tracksites). An articulated protoceratopsid skeleton - specimen ZPAL Mg D-II/3 - was collected by the Polish-Mongolian Expedition of 1965 from the Djadokhta Formation of Flaming Cliffs in Mongolia. Recently, the natural cast of a tetradactyl digitigrade footprint was found underneath the pelvic girdle while the skeleton and matrix were being prepared. This is possibly the first find of a dinosaur track in close association with an articulated skeleton. Although Protoceratops is an extremely common dinosaur in Mongolia, its footprints have never previously been reported from the Late Cretaceous of the Gobi Desert.  相似文献   

山东诸城早白垩世莱阳期古地震事件与恐龙迁移   总被引：1，自引：0，他引：1  

何碧竹  乔秀夫  田洪水  张艳霞 《地质学报》2012,86(8):1320-1330

在诸城断陷皇华镇大山村黄龙沟存在丰富的、多样的恐龙足迹化石,在紧邻化石埋藏层下伏及上覆地层中发现了下白垩统莱阳群杨庄组多套古地震记录,主要包含波状褶皱、底劈构造、液化砂岩脉、液化角砾岩、粒序断层、卷曲变形和震积不整合等塑性、脆性软沉积物变形构造。分析表明初始沉积物、沉积相及构造作用确定了地震活动作用时形成的软沉积物变形构造类型。在早白垩世莱阳群沉积中期,地震活动具有阶段性及频发性,以单向挤压的丘-槽构造及双向挤压的波状变形为主,且后期有构造活动强度加大的特征。根据已识别的古地震记录发育及古地震活动强度分析,推测此时期发震断裂可能是断陷的南缘断裂——五莲断裂。区域构造作用使得该时期沉积环境发生变化,由湖相逐渐过渡到河流相,在突发古地震事件发生之后,在滨浅湖区域留下了丰富的恐龙迁徙足迹。古地震记录的研究,可建立古地震事件与沉积、构造演化的联系,约束构造作用的属性、频次及时限,为确定盆地及周缘构造-沉积演化历史提供证据。  相似文献   

DYNAMIC ANALYSIS OF INHERENT CAUSES FOR DEVIATION OF TROPICAL CYCLONE TRACKS     

雷小途 《热带气象学报(英文版)》2001,7(1):53-62

To have a clearer picture of mechanisms responsible for the deviation of tropical cyclone (to be simplified as TC hereafter) tracks, the current work assumes the TC as a circular vortex with a radius of R. A general motion equation of TC is then determined by averaging its horizontal motion equation over the sentire region of TC. In the meantime, with the moving track of TC assumed as a characteristic arc, the curvature equation is derived for the track of movement and patterns of its deviation due to TC structure and variation are discussed. The result shows that the scale, size, maximum wind speed and radius are factors causing the deviation of TC tracks. In addition, asymmetric structure of TC is also important for the deviation of tracks. The results, achieved with hypothesis, agree with facts in some cases but disagree with them in others, which are to be verified with more observations or numerical simulations.  相似文献   

New dinosaur tracks from the Lower Cretaceous (Valanginian-Hauterivian) Saniri Formation of Yeongdong area,central Korea: Implications for quadrupedal ornithopod locomotion     

《Cretaceous Research》2016

Newly discovered tracks of a large quadrupedal ornithopod and a theropod with trail trace, and a bird track from the Cretaceous Saniri Formation of Yeongdong area are described. One ornithopod trackway is very unusual in having large (length width ∼15 and >15 cm respectively) clover-leaf-like manus tracks situated anteromedial to the pes tracks with atypical negative, inward rotation of 45°. Ornithopod pes tracks are quadripartite with three separated, elongate-oval, nearly parallel sided, wide digit impressions and a separate suboval heel impression (mean length and width about 41 and 36 cm respectively: l/w ratio 1.13). Manus track morphotypes are a clover-leaf-shaped configuration of three digit impressions, representing digits II–IV, in triangular configuration and registered just in front of (anteromedial to) pes track digits II and III. The pes morphotype is typical of Caririchnium, but the manus morphotype is quite distinct from previously described ichnotaxa, thus justifying a new ichnotaxon: Caririchnium yeondongensis ichnosp. nov., probably representing a facultatively-quadrupedal Iguanodon-like trackmaker.Theropod tracks are composed of three tapered pes digit impressions with interdigital angles between digits II and IV 45°. Length and width about 22.8 cm and 15.5 cm, respectively. Pace, stride, and pace angles are about 51 cm, 101 cm, and 170°, respectively. Theropod tracks are characteristically associated with a nearly continuous tail trace, which is up to 360 cm in length, 4.5 to 6 cm in width, and broad “U” shaped in cross section. Expulsion rims and dragging striae occur intermittently. In addition, dinosaur skin impressions, poorly preserved large sauropod tracks, a bird track, invertebrate and plant fossils are found from the lake margin deposits also containing rain drop impressions and desiccation cracks. Dinosaur tracks of the Yeongdong area represent the oldest (Valanginian-Hauterivian) dinosaur tracks of Korea.  相似文献   

中国西南攀西地区下侏罗统益门组蜥脚类足迹:分类学与潜在的造迹者     

邢立达  Lockley Martin G  尤海鲁  彭光照  唐翔  冉浩  王涛  胡健  Persons Ⅳ W Scott 《地质通报》2016,35(6):851-855

恐龙足迹和骨骼的记录往往出现在不同的地区。然而,一些地层显示了关系紧密的骨骼和足迹,它们都指向同一个来源。报道了来自四川省攀西地区会理县通安镇通保村下侏罗统益门组中上部的蜥脚类足迹(雷龙足迹Brontopodus),其地理和地层归属均与真蜥脚类的何氏通安龙极为接近。通保足迹与造迹者的关联是可能的,但目前还需要更多的证据。通保的雷龙足迹是攀西地区首次发现侏罗纪的蜥脚类足迹,这也表明,在早侏罗世,原始蜥脚类和基干蜥脚型类共存于中国西南地区。  相似文献   

台风移动的一个简单模型     

刘式适  刘式达 《海洋预报》1996,13(2):1-5

本文分析了在江河中摆渡船的运行，并将台风比拟为摆渡船，给出了台风移动的一个简单模型。研究指出：若船速为Ｖ１→，流速为Ｖ２→，船驶向对岩的目标为Ｆ，则当│Ｖ１→│〈〈│Ｖ２→│时，船的运行轨迹为一直线；而当│Ｖ１→│≈│Ｖ２→│时，船的运行轨迹为以Ｆ为焦点的抛物线，将上述分析应用于台风，则台风速度相当于Ｖ１→，台风环境空气的速度相当于Ｖ２→，因台风主要是切向运动，可利用角动量守恒原理计算它在台风范围  相似文献   

Preservation of dinosaur tracks induced by microbial mats in the Sousa Basin (Lower Cretaceous), Brazil     

《Cretaceous Research》2013

Dinosaur footprints and tracks in the Sousa Basin (Lower Cretaceous, Brazil) occur in at least 37 localities, in distinct stratigraphic positions. Footprints are rare in the Antenor Navarro (lower) and Rio Piranhas (upper) formations, where lithofacies analyses point to sedimentation in ancient alluvial fan to fluvial braided palaeoenvironments. In the Sousa Formation, the generally finer grain sized sediments rendered them more suitable for footprint preservation, where lithofacies analyses point to sedimentation in warm, small/shallow and temporary lakes, swamps and meandering fluvial palaeoenvironments. Microbially induced sedimentary structures are observed in many of the fine-grained lithofacies where dinosaur tracks are also found, and the large number of these tracks in the Sousa Basin (particularly in the Sousa Formation, Lower Cretaceous) may be related to the role of the mats in their preservation. Observations on recent microbial mats show that footprint morphology is related to the mat thickness and to the water content of the mat and the underlying sediment. In dry mats, generally poorly defined or no footprints are produced, while in saturated ones the imprints are well-defined, sometimes with well-defined displacement rims. The formation of well-defined displacement rims around the prints of large dinosaurs occurs in thick, plastic, moist to water-unsaturated microbial mats on top of moist to water-unsaturated sediment. These aspects are commonly observed in the tracks of the Passagem das Pedras site in the Sousa Basin. The footprint consolidation and its early lithification probably occurred due the existence of microbial mats that allowed a more cohesive substrate, preventing the footprints from erosion. The sediments were initially stabilized by early cementation and by the mat fabric over the tracks. Successive flooding, and subsequent sediment influx allowed the large number of layers with dinosaur tracks and sedimentary structures.  相似文献   

珠江三角洲台风龙卷的活动特征及环境条件分析     

黄先香  俞小鼎  炎利军  李彩玲  李兆明 《气象》2019,45(6):777-790

利用常规观测、自动气象站、多普勒雷达等资料分析珠江三角洲台风龙卷的活动特征及其产生的环境条件。结果表明:台风龙卷发生在6—10月,时间多为10—20时,出现在台风登陆后1.3～21.3 h的时段内;多数龙卷位于台风中心的东北象限,台风中心在广东湛江一广西东南部或北部湾附近时是珠江三角洲龙卷发生的高风险期。高层辐散、低层辐合及中低空强东南急流在珠江口附近叠加是龙卷产生的有利环流背景。强或弱龙卷环境条件的共同特征为低抬升凝结高度、强深层和低层垂直风切变及较大风暴相对螺旋度(SRH),主要差异是强龙卷的深层和低层垂直风切变与SRH更大;相似台风路径下,有/无龙卷环境条件的明显差异在于0～1 km低层垂直风切变和SRH,两值越大出现超级单体或中气旋的可能性越大,龙卷发生概率也就越高。台风龙卷风暴母体属于低质心的微型超级单体风暴;低层有强或中等强度中气旋,有时强中气旋中心伴有龙卷涡旋特征(TVS);龙卷出现在钩状回波顶端或TVS附近。与西风带超级单体龙卷相比,台风龙卷中气旋的尺度更小、垂直伸展高度更低。  相似文献