1998年与1954年夏季大尺度环流特征的对比分析   总被引：7，自引：0，他引：7  

晁淑懿  李月安 《气象》2000,26(1):38-42

对比分析夏季发生在长江全流域两次特大洪涝的１９５４年和１９９８年大尺度环充的特征。指出１９５４年西北太平洋副热带高压第二次季节性北跳明显偏迟,出现在８月初,６～７月副高位置持续偏南,８月副高位置偏北;而１９９８年副高第二次季节性北跳偏早,出现在７月上旬中期,但盛夏７月下旬～８月底副高位持续偏南,这两年夏季亚洲西凤带阻塞高压活动都十分频率,１９９８年更甚。夏季赤道辐合带１９９８年明显弱于１９５４年。  相似文献   

Petrotectonic evolution of the high- to ultrahigh-pressure Maksyutov Complex, Karayanova area, south Ural Mountains: structural and oxygen isotope constraints     

Mary L. Leech  W. G. Ernst 《Lithos》2000,52(1-4):235-252

The Maksyutov Complex consists of three fault-bounded lithologic units: a quartzofeldspathic gneiss containing mafic eclogite boudins (Unit #1); a metasedimentary blueschist-facies (Yumaguzinskaya) unit; and a meta-ophiolitic mélange (Unit #2). The geologic history of the high- to ultrahigh-pressure (HP–UHP) assembly of the Maksyutov Complex is complicated by several stages of prolonged retrograde metamorphism and deformation. The Sakmara River exposes all three units near the former village of Karayanova. A structural/petrologic cross-section through the area yields new quantitative data for the complex and, regionally, for the south Urals. Analysis of the Karayanova area has identified the major structures. Regional folding within the complex is parallel to the dominant foliation trending northeast–southwest. Stereonet data show that, during exhumation, this large-scale folding was refolded about axes trending southeast. Unit #1 and the Yumaguzinskaya are tectonically and petrologically distinct units juxtaposed by west-vergent thrusting and recrystallization within the same subduction zone. A shear zone developed later between Unit #2 and the Unit #1+Yumaguzinskaya tectonic package accompanying exhumation. Field relations and petrofabric demonstrate that blueschist-facies recrystallization overprinted an earlier eclogite-facies metamorphism. Thermobarometric measurements yield P–T values of 594–637°C, 1.5–1.7 GPa for eclogite, but these conditions may reflect annealing during the early-stage exhumation at 375 Ma. Cuboid graphite aggregates testify to precursor conditions for Unit #1 within the diamond stability field, if such textures are correctly interpreted. Measured ¹⁸O/¹⁶O partitioning between pairs of coexisting phases yield three main recrystallization temperature ranges: (1) 678±83°C, attending Unit #1 eclogite-facies metamorphism; (2) 453±17°C, during transitional blueschist/greenschist-facies metamorphism for the amalgamated Unit #1+Yumaguzinskaya+Unit #2 assembly; and (3) 250±68°C, reflecting late-stage hydrothermal alteration and exhumation. Oxygen isotope data for Units #1 and #2 indicate that garnet, blue amphibole, and pyroxene crystallized in isotopic equilibrium, validating previous thermobarometric calculations for a Unit #1 retrograde metamorphic event. Variations in δ¹⁸O values for phengites suggest the possibility of late metamorphic fluid infiltration. Retrograde recrystallization at high pressure in the presence of fluids and a calculated slow exhumation rate for the Maksyutov Complex account for the fact that inferred UHP coesite and diamond were completely back-reacted during decompression.  相似文献   

Wave-Breaking Features of Blocking over Central Siberia and Its Impacts on the Precipitation Trend over Southeastern Lake Baikal     

Dorina CHYI  Zuowei XIE  Ning SHI  Pinwen GUO  Huijun WANG 《大气科学进展》2020,37(1):75-89

Precipitation over southeastern Lake Baikal features a significant decreasing trend in July and August over 1979–2018 and is closely related to blocking occurrence over central Siberia(45°–70°N,75°–115°E).This study investigates the formation and maintenance of anticyclonic and cyclonic wave-breaking(AWB and CWB)blocking events and their climate impacts on precipitation in the southeastern Lake Baikal area.Both AWB and CWB blocking events are characterized by a cold trough deepening from the sub-Arctic region and a ridge amplifying toward its north over central Siberia,as well as an evident Rossby wave train over midlatitude Eurasia.For AWB blocking events,the ridge and trough pair tilts clockwise and the wave train exhibits a zonal distribution.In contrast,ridge and trough pair associated with CWB blocking events leans anticlockwise with larger-scale,meridional,and more anisotropic signatures.Moreover,the incoming Rossby wave energy associated with CWB blocking events is more evident than for AWB blocking events.Therefore,CWB blocking events are more persistent.AWB blocking events produce more extensive and persistent precipitation over the southeastern Lake Baikal area than CWB blocking events,in which moderate above-normal rainfall is seen in the decaying periods of blockings.A significant decreasing trend is found in terms of AWB blocking occurrence over central Siberia,which may contribute to the downward trend of precipitation over southeastern Lake Baikal.  相似文献   

中高纬大气ISO对夏季鄂海阻高形成和维持的调节作用          下载免费PDF全文

杨双艳  李天明 《大气科学学报》2020,43(1):104-115

运用1979—2015年的逐日NCEP-DOE再分析资料,探讨了夏季鄂霍次克海阻塞高压(简称“鄂海阻高”)与中高纬大气季节内振荡(简称“ISO”)之间的可能联系。研究发现,ISO扰动与夏季鄂海阻高在关键区(130°~160°E,60°~75°N)有最好的耦合关系,且关键区位势高度表现出显著的10~30 d的振荡周期。超前滞后合成分析表明,与鄂海阻高相联系的ISO扰动具有明显的向西传播的特征。波活动通量分析结果显示,波能量在中高纬140°W附近累积,因此西传的ISO扰动可能源自中高纬140°W附近。对位势倾向方程的诊断结果显示,动力作用对关键区位势高度的时间变化起主要作用。进一步运用尺度分析表明,在夏季鄂海阻高发生和维持的过程中,ISO经向风引导的平均涡度平流对位势高度的时间变化起主导作用。  相似文献   

一种新型微泡套铣冲砂液的研制     

任奕  张茂  王冬  任强  朱亮 《海洋地质译丛》2013,(4):52-56

针对渤海油田在大修井过程中出现的地层漏失严重、井下工具打捞困难、套铣进尺缓慢等问题,根据泡沫钻井的理论知识及其应用特点,研究开发了一种新型的环保型的套铣冲砂液,与传统的暂堵液相比,其黏度低、切力小、携砂能力好,润滑系数低、循环摩阻小,易于溶解,不会结块憋泵,后期不需要破胶等等.其主要配比为：0.5％BH-VIS＋3％FPJ-12＋3％XJW-1 ＋2％YS-A.它主要以微泡作为分散相,低黏胶液作为连续相,依靠泡沫承托能力强以及泡沫和生物聚合物的双层封堵的特点,达到一种良好的冲砂、降漏失效果.该技术在渤海油田得到了成功的应用,保证了大修作业的顺利进行.  相似文献   

内蒙古曹四夭钼矿复杂地层深孔钻探技术     

郑思光  刘继东 《探矿工程》2013,40(5):17-22

针对内蒙古兴和县曹四夭钼矿区构造发育,地层坚硬、岩心破碎,以及钻孔缩径、漏失、坍塌、掉块等复杂情况,总结了该矿区“硬、脆、碎”复杂地层绳索取心深孔钻探施工技术经验,从钻孔结构、泥浆配置和冲洗液选取以及钻探设备、新型SYZX75 2（77）型绳索取心液动锤钻具等方面采取措施,解决了破碎漏失、坍塌掉块及坚硬“打滑”地层的难题。着重阐述了高强度快失水堵漏技术试验,改善了复杂地层的深孔钻进环境,提高了钻探生产效率,保证了钻孔的安全终孔。  相似文献   

Application of Conditional Nonlinear Optimal Perturbation to Targeted Observation Studies of the Atmosphere and Ocean          下载免费PDF全文

MU Mu  WANG Qiang  DUAN Wansuo  JIANG Zhina 《Acta Meteorologica Sinica》2014,28(5):923-933

This paper reviews progress in the application of conditional nonlinear optimal perturbation to targeted observation studies of the atmosphere and ocean in recent years, with a focus on the E1 Nifio-Southern Oscillation （ENSO）, Kuroshio path variations, and blocking events. Through studying the optimal precursor （OPR） and optimally growing initial error （OGE） of the occurrence of the above events, the similarity and localization features of OPR and OGE spatial structures have been found for each event. Ideal hindcasting experiments have shown that, if initial errors are reduced in the areas with the largest amplitude for the OPR and OGE for ENSO and Kuroshio path variations, the forecast skill of the model for these events is significantly improved. Due to the similarity between patterns of the OPR and OGE, additional observations implemented in the same sensitive region would help to not only capture the precursors, but also reduce the initial errors in the predictions, greatly increasing the forecast abilities. The similarity and localization of the spatial structures of the OPR and OGE during the onset of blocking events have also been investigated, but their application to targeted observation requires further study.  相似文献   

一起测井仪遇卡孔内事故的处理与教训          下载免费PDF全文

胥刚 《探矿工程》2012,39(1):50-52

煤田钻孔终孔测井前大幅度调整泥浆性能,用稀泥浆循环冲孔,破坏了原孔壁的稳定性,引发破碎岩石掉块,造成测井探管遇卡,如果处理方法不当将造成事故的复杂化。通过实例叙述了探管遇卡的经过,分析了遇卡原因,从处理方案的确定到处理过程,总结事故处理经验与教训,为今后在施工中遇到类似情况提供可借鉴的经验。  相似文献   

Middle‐Late Pleistocene Glacial Lakes in the Grand Canyon of the Tsangpo River,Tibet   总被引：1，自引：0，他引：1  

ZHU Song  WU Zhenhan  ZHAO Xitao  LI Jianping  WANG Hua 《《地质学报》英文版》2012,86(1):266-283

Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691~505 kaBP middle Pleistocene ice age, 75–40 kaBP the early stage of last glacier, 27–8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn’t erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn’t form stable lake.  相似文献   

The Anomalous European Climates Linked to Different Euro-Atlantic Blocking          下载免费PDF全文

YAO Yao  LUO De-Hai 《大气和海洋科学快报》2014,(4):309-313

The impact on temperature and precipitation anomalies over the European continent of the different action centers of blocking events in the Euro-Atlantic sector was investigated. It was found that the position of the blocking action center in the Euro-Atlantic region seems to dominate European climates. When the center of the blocking action is in the Greenland region, there is a strong negative temperature anomaly over Central and Northern Europe, as well as a strong positive precipitation anomaly over southern Europe. However, there tends to be a strong negative temperature anomaly in the west （east） part of Europe when the center of the blocking action is shifted to the Eastern Atlantic and west Europe （east Europe）. In particular, when the blocking action center is closer to the European continent, the fall in temperature becomes more evident over Central and south Europe than over other regions. Moreover, it was found that when the region where the blocking action center exists changes from the Eastern Atlantic and west Europe region to the east Europe region, the existing region of dominant positive precipitation anomalies varies from southwest Europe to southeast Europe and the Middle East.  相似文献