A STATISTICAL ANALYSIS ON THE DIFFERENT FEATURES OF TC EXTRATROPICAL TRANSITION OVER LAND AND OCEAN     

钟霖浩  华丽娟  冯士德 《热带气象学报(英文版)》2012,18(2):228-241

The extratropical transitions(ETs)of tropical cyclones(TCs)over China and the ocean east to 150°E are investigated by the use of best-track data and JRA-25 reanalysis spanning 1979-2008.The ET events occurring north of 25°N and in the warm season(from May to October)are extracted from the reanalysis to emphasize the interaction between TC and midlatitude circulation.Statistical analysis shows that 18.5%of the warm-season TCs go through land ETs north of 25°N in the western North Pacific.And 20.5%of the ET events occur over the ocean east of 150°E.Most(62.2%)ET TCs over China gradually die out after ET,but more(70.7%)ocean ET cases have post-ET reintensification.The evolutions in cyclone phase space and the composite fields for land and ocean ETs,as well as the ET cases with and without post-ET reintensification,are further analyzed.It is found that most TCs with ET over China and those without post-ET reintensification evolve along the typical ET phase path as follows:emergence of thermal asymmetry→losing upper-level warm core→losing lower-level cold core→evolving as extratropical cyclone.The TCs undergoing ETs over ocean and those with post-ET reintensification form a high-level cold core before the ET onset.The TCs with land ET have long distance between the landing TC and a high-level trough.That makes the TC maintain more tropical features and isolates the TC flow from the upstream and downstream jets of the midlatitude trough.The structure of circulation leads to weak development of baroclinicity in land ET.On the contrary,shorter distance between ocean TC and high-level trough makes the high-level trough absorb the TC absolutely.Under that baroclinicity-favorable environment,strong cold advection makes the TC lose its high-level warm core before ET onset.The composite fields confirm that the TC with ocean ET has stronger baroclinic features.Generally,the TC at land ET onset is located to the south of the ridge of the subtropical high,which tends to prevent the TCs from interacting with midlatitude circulation.But for the ocean ET,the situation is just the opposite.Similar analyses are also carried out for the TCs with and without post-ET reintensification over both land and ocean east of 150°E.The results further prove that the TC with stronger baroclinic characteristics,especially in the circumstance favorable to its interaction with high-level midlatitude systems,has more opportunity to reintensify as an extratropical cyclone after ET.  相似文献   

侵入下马岭组的基性岩床的锆石和斜锆石U-Pb精确定年——对华北中元古界地层划分方案的制约   总被引：46，自引：2，他引：44  

李怀坤  陆松年  李惠民  孙立新  相振群  耿建珍  周红英 《地质通报》2009,28(10):1396-1404

华北克拉通马兰峪隆起北侧的下马岭组页岩中广泛发育辉绿岩床。分别利用高灵敏度、高精度的离子探针质谱法和同位素稀释热电离质谱法,测定了辉绿岩中锆石和斜锆石的U-Pb同位素年龄,获得了辉绿岩的侵位年龄1320Ma±6Ma。该年龄数据的获得制约了下马岭组的上限年龄不老于1320Ma。将下马岭组置于1400~1350Ma的区间内。综合已有的测年成果,对华北克拉通燕辽裂陷槽内中元古界的划分方案进行了厘定,提出了一个新的中元古界划分方案。建议方案中长城系包括常州沟组、串岭沟组、团山子组和大红峪组,时限为1800~1600Ma;蓟县系包括高于庄组、杨庄组、雾迷山组、洪水庄组和铁岭组,时限为1600~1400Ma;蓟县系之上1400~1000Ma期间的地层为待建系,亟需进一步研究。  相似文献   

渤张断裂带的构造机制及其地质意义   总被引：10，自引：1，他引：9       下载免费PDF全文

侯贵廷  叶良新 《地质科学》1999,34(3):375-380

渤张断裂带形成于中生代,为剪张性断裂带。中新生代以来渤张断裂带一直活动,并控制中新生代沉积和火山活动。中生代至老第三纪早期(42Ma 之前)渤张断裂带为右旋走滑的剪张性断裂带,而老第三纪中晚期以来(42Ma 以来)渤张断裂带转为左旋走滑的剪张性断裂带,并控制了渤海盆地的油气分布和现代的地震活动。近期,沿渤张断裂带地震活动频繁,说明渤张断裂带仍在活动。  相似文献   

Holocene palaeoceanographic changes in Barrow Strait,Canadian Arctic: foraminiferal evidence     

Thomas R. Gregory  Christopher W. Smart  Malcolm B. Hart  Guillaume Massé  Lindsay L. Vare  Simon T. Belt 《第四纪科学杂志》2010,25(6):903-910

Holocene changes in the benthic and planktic foraminiferal fauna (>63 µm) from a marine sediment core (ARC‐3 Canadian Arctic Archipelago, 74° 16.050′ N, 91° 06.380′ W, water depth 347 m) show that significant environmental and palaeoceanographic variations occurred during the last 10 ka. Foraminiferal assemblages are restricted to the ca. 4.5–10 ka interval as younger samples are mostly barren of foraminifera due to intense carbonate dissolution after ca. 4.5 ka. Foraminiferal assemblages in the ca. 4.5–10 ka interval are dominated by the benthic species Islandiella helenae and Cassidulina reniforme (57% of total), with Elphidium clavatum, Cibicides lobatulus and Buccella frigida also being common in this interval. The dominance of these species indicates a seasonal sea ice regime which is consistent with the occurrence of the sea ice diatom‐derived organic geochemical biomarker IP₂₅ throughout the core. The abundances of C. reniforme and E. clavatum decline upcore; consistent with more frequent mixing of the Barrow Strait water column during the early Holocene. It is likely that the influence of CO₂‐rich Arctic surface water masses have caused an increase in bottom water corrosivity after ca. 8.5 ka, and dissolution has been further enhanced by sea ice‐related processes after ca. 6 ka, concomitant with increased IP₂₅ fluxes. Dissolution is strongest when IP₂₅ fluxes are highest, suggesting a link between the sea ice and benthic systems. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Late Permian-Triassic granitic rocks of Vietnam: the Muong Lat example     

《International Geology Review》2012,54(15):1823-1841

ABSTRACT

The Song Ma zone in Northwestern Vietnam is considered as a suture of the South China and Indochina blocks, and plays an important role in understanding the tectonic evolution in Southeast Asia and surrounding areas. Granitic rocks of the Muong Lat complex are distributed in the Song Ma suture, consisting mainly of monzogranite and granodiorite. The rocks are sub-alkaline in affinity with high K contents and characteristics of S-type granite. They have high SiO₂, total Na₂O + K₂O, and Zr contents and high aluminium saturation index values (0.97 to 1.29 with an average of 1.14). All these geochemical signatures, together with high (⁸⁷Sr/⁸⁶Sr)_i ratios (0.71391 to 0.74568), and low whole rock ε_Nd(t) and zircon ε_Hf(t) values (?13.1 to ?9.4) suggested an origin from partial melting of crustal source rocks. Primitive mantle normalized trace element contents exhibit positive anomalies of Rb, Th, U and Pb, but negative anomalies of Nb, Ta, and Ti, indicating a collision-related environment. The depleted Nd and Hf zircon model ages from investigated samples, in combination with inherited zircon ages, suggest the existence of Precambrian basement in the study region. S-type granites of the late Permian-early Triassic (the Muong Lat, Phia Bioc and Hai Van complexes) in Vietnam were formed by the subduction-collision of the South China and Indochina blocks.  相似文献   

用1/2.5万不规则网直接查证1/20万化探异常的尝试     

刘俊斌 《吉林地质》2012,31(2):80-83

尝试地运用1/2.5万不规则网土壤地球化学测量方法,对吉林省珲春市小西南岔金铜矿外围某勘查区的1/20万区域化探直接进行了查证,圈出两处地球化学综合异常,异常主成矿元素Au、Cu异常连续,浓集中心突出,浓度分带清晰,与伴生的As、Bi、Pb、Ag、Zn等元素异常套合较好,具有指导找矿作用。  相似文献   

塔河油田稠油中25-降苯并藿烷的检出及其意义     

李敏  ;田辉  ;肖贤明  ;张水昌  ;相明辉  ;盖海峰  ;程鹏  ;傅家谟 《地球化学》2014,(5):453-459

与苯并藿烷相比,25-降苯并藿烷的研究较少,目前这类化合物仅检出于加拿大和我国川西北的降解沥青中。本研究在塔河油田井下奥陶系储层稠油中检测到了完整系列的25-降苯并藿烷（C31-C34）,发现25-降苯并藿烷与苯并藿烷的比值与现有的生物降解评价参数有较好的可比性,且该参数在不同降解程度原油中的差别比其他参数更大,故今后有必要对其开展更深入的研究,以便更精细地评价原油的生物降解程度。  相似文献   

A search for H i in some peculiar faint dwarf galaxies     

Ayesha Begum  Jayaram N. Chengalur 《Monthly notices of the Royal Astronomical Society》2005,362(2):609-611

We present a deep Giant Metrewave Radio Telescope (GMRT) search for H  i 21-cm emission from three dwarf galaxies, viz. POX 186, SC 24 and KKR 25. Based, in part, on previous single-dish H  i observations, these galaxies have been classified as a blue compact dwarf (BCD), a dwarf irregular and a transition galaxy, respectively. However, in conflict with previous single-dish detections, we do not detect H  i in SC 24 or KKR 25. We suggest that the previous single-dish measurements were probably confused with the local Galactic emission. In the case of POX 186, we confirm the previous non-detection of H  i but with substantially improved limits on its H  i mass. Our derived upper limits on the H  i mass of SC 24 and KKR 25 are similar to the typical H  i mass limit for dwarf spheroidal (dSph) galaxies, whereas in the case of POX 186, we find that its gas content is somewhat smaller than is typical of BCD galaxies.  相似文献   

100Ma来海水的锶同位素组成演化及主要控制因素   总被引：1，自引：1，他引：0  

黄成刚  黄思静  吴素娟  陈启林 《地球科学与环境学报》2006,28(2):19-24

讨论了100 Ma以来海水锶同位素比值的变化趋势及控制因素。100~40 Ma期间,海水锶同位素比值有多次升降,总体上变化幅度较小;40 Ma以来,海水锶同位素比值显著增加,并呈现出单调上升的总体特征。100 Ma以来海水锶同位素的变化主要可能与星外物体对地球的撞击作用;全球海平面变化及洋中脊扩张速度的改变;喜马拉雅—青藏高原的隆升;玄武岩喷发和冰川作用因素有关。在各种因素中,喜马拉雅—青藏高原的隆升对40 Ma以来海水锶同位素演化具有最重要的控制作用。喜马拉雅—青藏高原的隆升可能始于40 Ma左右,隆升速度最快的时期在20~15 Ma。  相似文献   

Sephadex G-25用于YML-1脱盐条件优化   总被引：1，自引：0，他引：1  

廖铭能  苏伟明  于立坚  马润娣 《广东海洋大学学报》2006,26(4):94-95

凝胶过滤(或称分子筛)层析是一种由限制分子通过多孔基质,按分子大小分离混合分子的技术[1]。凝胶过滤方法常用于生物样品脱盐,其操作简便易行,脱盐效果可靠[2]。由于可通过紫外和电导检测器监控整个层析过程、产品的纯度和回收率,又可连续自动进样和收集样品,自动化程度高,容易放大[3],所以,自上世纪60年代初始,随着层析介质技术的发展,Sephadex G-25系列凝胶过滤介质常用于实验室乃至工业规模的脱盐、小分子物质去除及缓冲液的置换。一般实验室脱盐常用透析方法,但其耗费时间长、缓冲液消耗量大,又易损失宝贵样品。笔者采用凝胶过滤法研…  相似文献