低温热年代学数据对龙门山推覆构造带南段新生代构造活动的约束   总被引：3，自引：2，他引：1  

谭锡斌  李元希  徐锡伟  陈玟禹  许冲  于贵华 《地震地质》2013,35(3)

龙门山位于青藏高原东边缘,地形陡变,剥蚀作用强烈.近年来先后经历了2008年汶川MW7.9地震和2013年芦山MS7.0地震,多位学者对龙门山地区做了大量的低温热年代学研究.文中在研究程度相对薄弱的龙门山南段补充了4个锆石裂变径迹年龄和4个磷灰石裂变径迹年龄,结合前人的低温热年代学数据结果得出,宝兴杂岩从新生代早期开始快速冷却,降温幅度超过225℃,而龙门山中段的彭灌杂岩降温幅度为185 ～225℃.宝兴杂岩的4个裂变径迹年龄分布在2.7 ～5Ma,相对彭灌杂岩较年轻,表明晚新生代以来宝兴杂岩的冷却速率要高于彭灌杂岩.在地表温度为15℃和古地温梯度为30℃/km的假设下,宝兴杂岩距今3～5Ma以来的平均剥露速率为0.63 ～ 1.17mm/a.低温热年代学数据揭示出龙门山中段的差异剥蚀集中在北川-映秀断裂和江油-灌县断裂上,而南段的差异剥蚀分散在更宽范围内的双石-大川断裂(南、北2个分支)及其东侧的断层和褶皱.  相似文献   

波浪作用下饱和砂质海床土体与管线相互作用规律研究     

王小雯  张建民  李焯芬 《岩土力学》2018,39(7):2499-2508

针对波浪引起的饱和砂质海床土体和管线相互作用问题,将Biot动力固结理论与笔者课题组提出的砂土液化变形弹塑性本构模型相耦合,较为合理地再现了简谐波浪作用下较浅饱和砂质海床中管线周围可液化海床土体的超静孔隙水压力瞬态累积变化规律与液化过程。数值计算结果与Sumer等的试验规律一致。结果表明：由于管线的存在,改变了饱和砂质海床液化区域的空间分布。液化首先由管线下部土体开始产生,随着波浪荷载的持续作用,液化区域沿着管线外壁向上演化;同时海床表层土体产生液化并向深层发展,最终管线周围土体都发生液化,这是导致空管上浮的主要原因。当饱和砂质海床中存在管线时,管线附近海床土体液化深度明显变深。超静孔压累积和渗透力变化的耦合作用是导致饱和砂质海床土体产生液化的原因。与将海床土体视为饱和弹性多孔介质相比,可考虑液化全过程的弹塑性动力分析能更为合理地揭示实际波浪作用下饱和砂质海床土体的渗流场和应力场的瞬态时空演变规律。  相似文献   

Late Quaternary Paleoclimatic Change in the Ulleung Basin, East Sea, Korea     

Young-Suk BAK  Young-Up LEE 《《地质学报》英文版》2017,91(1):263-269

Paleoclimatic changes in the late Quaternary sediments deposited in the East Sea were analyzed by studying diatoms. A total of 95 species belonging to 47 genera were identified from the Core02GHP-02 of the Ulleung Basin in the East Sea, Korea. In the Core 02GHP-02, U-Oki(169–181 cm; 9.3 ka), AT(464–465.5 cm; 22 ka) and U–Ym(556–559 cm; 33 ka) tephra layers were recognized. The chronological divisions of 02GHP-02 may be correlated with the climatic changes from the glacial interval(730–620 cm; MIS3), to interstadial(620–500 cm; MIS3), to the last glacial maximum(500–390 cm; MIS 2), to the deglaciation(390–290 cm; MIS 2), to the late glacial(290–190 cm; MIS 1), and to the Holocene(190–10 cm; MIS 1). It is speculated that diatoms were rarely found during the glacial interval when the 02GHP-02 core was deposited; during the interstadial(MIS 3) and deglaciation, a mixture of warm-water and cold-water species were found. In particular, Fragilariopsis doliolus seems to have appeared in the East Sea after 8 ka BP. In the lower layers of the Holocene deposits, cold-water species such as Neodenticula seminae were frequently found, while in the upper layers, warm-water species such as Hemidiscus cuneiformis were found in relatively large abundance. Therefore, the findings indicate that the climate became warmer during the transition from the lower layer to the upper layer of the Holocene deposits.  相似文献   

Radar Data Assimilation for the Simulation of Mesoscale Convective Systems     

Jo-Han LEE  Dong-Kyou LEE  Hyun-Ha LEE  Yonghan CHOI  Hyung-Woo KIM 《大气科学进展》2010,27(5):1025-1042

A heavy rainfall case related to Mesoscale Convective Systems (MCSs) over the Korean Peninsula was selected to investigate the impact of radar data assimilation on a heavy rainfall forecast. The Weather Research and Forecasting (WRF) three-dimensional variational (3DVAR) data assimilation system with tuning of the length scale of the background error covariance and observation error parameters was used to assimilate radar radial velocity and reflectivity data. The radar data used in the assimilation experiments were preprocessed using quality-control procedures and interpolated/thinned into Cartesian coordinates by the SPRINT/CEDRIC packages. Sensitivity experiments were carried out in order to determine the optimal values of the assimilation window length and the update frequency used for the rapid update cycle and incremental analysis update experiments. The assimilation of radar data has a positive influence on the heavy rainfall forecast. Quantitative features of the heavy rainfall case, such as the maximum rainfall amount and Root Mean Squared Differences (RMSDs) of zonal/meridional wind components, were improved by tuning of the length scale and observation error parameters. Qualitative features of the case, such as the maximum rainfall position and time series of hourly rainfall, were enhanced by an incremental analysis update technique. The positive effects of the radar data assimilation and the tuning of the length scale and observation error parameters were clearly shown by the 3DVAR increment.  相似文献   

Determination of probability distributions for Strahler stream lengths based on Poisson process and DEM     

MING-SANG YANG  KWAN TUN LEE 《水文科学杂志》2013,58(5):813-824

Abstract

One of the basic tasks in geomorphologic analysis is to know the probability distributions of the stream lengths of different orders. In practical applications, this information is useful for basin rainfall-runoff modelling. The objective of this study is to determine the length distributions of the Strahler streams. A Poisson process was used to derive the theoretical distributions. The result showed that the length distribution of the first-order stream is an exponential distribution and the second-order or higher order stream length is a gamma distribution. In order to verify the theoretical distributions, a digital elevation model (DEM) was adopted to calculate the stream lengths of four basins in Taiwan. Kolmogorov-Smirnov and chi-square tests were used to test the goodness-of-fit of the data. Results showed that the length distributions of the first- and second-order streams analysed by using DEM correspond with those from the derived distribution method.  相似文献   

Stable carbon isotopic evidence for climate change across the late Pleistocene to early Holocene from Lesotho,southern Africa     

P. ROBERTS  J. A. LEE‐THORP  P. J. MITCHELL  C. ARTHUR 《第四纪科学杂志》2013,28(4):360-369

  相似文献   

Observational Study of Surface Wind along a Sloping Surface over Mountainous Terrain during Winter     

Young-Hee LEE  Gyuwon LEE  Sangwon JOO  Kwang-Deuk AHN 《大气科学进展》2018,35(3):276-284

The 2018 Winter Olympic and Paralympic Games will be held in Pyeongchang, Korea, during February and March. We examined the near surface winds and wind gusts along the sloping surface at two outdoor venues in Pyeongchang during February and March using surface wind data. The outdoor venues are located in a complex, mountainous terrain, and hence the near-surface winds form intricate patterns due to the interplay between large-scale and locally forced winds. During February and March, the dominant wind at the ridge level is westerly; however, a significant wind direction change is observed along the sloping surface at the venues. The winds on the sloping surface are also influenced by thermal forcing,showing increased upslope flow during daytime. When neutral air flows over the hill, the windward and leeward flows show a significantly different behavior. A higher correlation of the wind speed between upper-and lower-level stations is shown in the windward region compared with the leeward region. The strong synoptic wind, small width of the ridge, and steep leeward ridge slope angle provide favorable conditions for flow separation at the leeward foot of the ridge. The gust factor increases with decreasing surface elevation and is larger during daytime than nighttime. A significantly large gust factor is also observed in the leeward region.  相似文献   

Collating Historic Weather Observations for the East Asian Region:Challenges,Solutions,and Reanalyses     

Fiona WILLIAMSON  Rob ALLAN  Guoyu REN  Tsz-cheung LEE  Wing-hong LUI  Hisayuki KUBOTA  Jun MATSUMOTO  Jürg LUTERBACHER  Clive WILKINSON  Kevin WOOD 《大气科学进展》2018,35(8):899-904

正1.Introduction Historic instrumental weather observations,made on land or at sea from as early as the 17th century(e.g.,Camuffo et al.,2010),are integral to extending our understanding of the decadal and centennial variations of Earth’s climate and for comparison with paleo-proxy data.The potential of such data is shown to best effect when used in dynamical 4D global  相似文献   

《坤輿万国全图》与《利玛窦中国札记》中外译本考疑   总被引：1，自引：0，他引：1  

李兆良 《测绘科学》2017,42(5)

金尼阁编译的《利玛窦中国札记》多种欧洲文字版本之间存在翻译差异,而300年后出版的英译本和中译本与原文存在严重错漏。600页的札记,利玛窦只用不到两页的篇幅叙述测绘《坤輿万国全图》一事,连实际比例尺的描述也不清楚。利玛窦承认没有见过其他的版本,"六幅版"地图出现在南京或北京,个别欧洲文字翻译版本不一,《坤輿万国全图》究竟是在南京还是北京完成的也有疑问。《利玛窦中国札记》用的是中国传统的测绘术语,指出地图的错误是针对西方地图而不是中国地图。《坤輿万国全图》中一半的中文地名,当时欧洲地图没有对应。1593年,利玛窦尚未制作《坤輿万国全图》,"六幅版"中文世界地图已出现在南京。因此,《坤輿万国全图》原本早已存在,《坤輿万国全图》应是郑和时代(1405—1433)大航海的成果,中国的地图学,不是西学东渐,甚至有可能是中国的世界地理与地图学流传到西方。世界地图史应该还原中国对地理大发现与地图学的贡献。  相似文献   

Cloud Radiative Effects and Changes Simulated by the Coupled Model Intercomparison Project Phase 5 Models     

Sun-Hee SHIN  Ok-Yeon KIM  Dongmin KIM  Myong-In LEE 《大气科学进展》2017,34(7):859-876

Using 32 CMIP5(Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects(CREs) in the historical run driven by observed external radiative forcing for 1850–2005, and their future changes in the RCP(Representative Concentration Pathway) 4.5 scenario runs for2006–2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models—ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K~(-1)and net radiative warming of 0.46 W m~(-2)K~(-1), suggesting a role of positive feedback to global warming.  相似文献