A late Holocene winter monsoon record inferred from the palaeo-aeolian sand dune in the southeastern Mu Us Desert, northern China     

Bing Liu  HeLing Jin  Fan Yang 《寒旱区科学》2016,8(5):388-399

The variation of the Asian winter monsoonal strength has seriously affected the climate and environmental conditions in the Asian monsoonal region, and even in marginal islands and the ocean in the East Asian region. However, relevant understanding remains unclear due to the lack of suitable geological materials and effective proxies in the key study areas. Here, we present a grain-size record derived from the palaeo-aeolian sand dune in the southeastern Mu Us Desert, together with other proxies and OSL dating, which reflect a relatively detailed history of the winter monsoon and abrupt environmental events during the past 4.2 ka. Our grain-size standard deviation model indicated that >224 μm content can be considered as an indicator of the intensity of Asian winter monsoon, and it shows declined around 4.2-2.1 ka, enhanced but unstable in 2.1-0.9 ka, and obviously stronger since then. In addition, several typical climate events were also documented, forced by the periodic variation of winter monsoonal intensity. These include the cold intervals of 4.2, 2.8, 1.4 ka, and the Little Ice Age (LIA), and relatively warm sub-phases around 3.0, 2.1, 1.8 ka, and the Medieval Warm Period (MWP), which were roughly accordant with the records of the aeolian materials, peat, stalagmites, ice cores, and sea sediments in various latitudes of the Northern Hemisphere. Combined with the previous progresses of the Asian summer monsoon, we preliminarily confirmed a millennial-scale anti-correlation of Asian winter and summer monsoons in the Late Holocene epoch. This study suggests that the evolution of the palaeo-aeolian sand dune has the potential for comprehending the history of Asian monsoon across the desert regions of the modern Asian monsoonal margin in northern China.  相似文献   

Mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradation   总被引：2，自引：0，他引：2  

Xiao-yi Fan  Shu-jun Tian  You-yi Zhang 《山地科学学报》2016,13(2):234-245

The mass-front velocities of granular flows results from the joint action of particle size gradations and the underlying surfaces.However,because of the complexity of friction during flow movement,details such as the slope-toe impedance effects and momentum-transfer mechanisms have not been completely explained by theoretical analyses,numerical simulations,or field investigations.To study the mass-front velocity of dry granular flows influenced by the angle of the slope to the runout plane and particle size gradations we conducted model experiments that recorded the motion of rapid and long-runout rockslides or avalanches.Flume tests were conducted using slope angles of 25°,35°,45°,and 55° and three particle size gradations.The resulting mass-front motions consisted of three stages:acceleration,velocity maintenance,and deceleration.The existing methods of velocity prediction could not explain the slowing effect of the slope toe or the momentum-transfer steady velocity stage.When the slope angle increased from 25° to 55°,the mass-front velocities dropped significantly to between 44.4% and59.6% of the peak velocities and energy lossesincreased from 69.1% to 83.7% of the initial,respectively.The velocity maintenance stages occurred after the slope-toe and mass-front velocity fluctuations.During this stage,travel distances increased as the angles increased,but the average velocity was greatest at 45°.At a slope angle of 45°,as the median particle size increased,energy loss around the slope toe decreased,the efficiency of momentum transfer increased,and the distance of the velocity maintenance stage increased.We presented an improved average velocity formula for granular flow and a geometrical model of the energy along the flow line.  相似文献   

Constraining the groundwater flow system and aquifer properties using major ions,environmental traces and a simple physical model in China’s Jilantai Basin     

Guoxiao Wei  Xifeng Zhu  Ning Yue  Yuxin Fan  Jun Dong  Huihui Dang 《Environmental Earth Sciences》2016,75(6):459

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基于无人船的大洋中尺度涡观测系统展望     

范聪慧  于非  南峰  魏传杰  任强 《海洋科学集刊》2016,51(51):49-57

中尺度涡在大洋中普遍存在,研究发现其能量比大尺度海洋环流的能量大一个量级,在海洋物质能量输运和全球气候变化中起着重要的作用。受观测条件限制,目前对中尺度涡的观测主要通过卫星高度计实现,只能从海面高度来推算中尺度涡大小、分布、强度及其伴随的水体和能量输送,而卫星高度计对中尺度涡垂直结构特征认识不足,也导致了对中尺度涡所引起的上层海洋能量、热量输送估计误差偏大。目前对中尺度涡三维结构观测认识不足,展望未来将会出现基于无人船平台的大洋中尺度涡三维结构自动观测系统,该平台将集成自动水下剖面观测功能等先进技术,以便观测中尺度涡的垂直结构特征及其时空变化特征,进而可对中尺度涡带来的物质和能量输送进行系统认识。  相似文献   

Seasonal variation and principle of cyanobacterial biomass and forms in the water source area of Chaohu City,China     

徐宪根  柯凡  李文朝  冯慕华  尚丽霞  范帆  何延召 《中国海洋湖沼学报》2016,34(1):34-43

We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population(M. aeruginosa) and their correlation with environmental factors in the water source area of Chaohu City,China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass,and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June,and the biomass of cyanobacteria reached a maximum in August. From February to March 2012,the main form of M.aeruginosa was the single-cell form; M.aeruginosa colonies began to appear from April,and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July,and then gradually decreased from August. The diameter range of M. aeruginosa colonies was 18.37–237.77 μm,and most of the colonies were distributed in the range 20–200 μm,comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobacterial growth was in the range of 15–30°C. In natural water bodies,photosynthetically active radiation had a significant positive influence on the colonial diameter of M.aeruginosa(P0.01).  相似文献   

From sequential to parallel growth of cities: Theory and evidence from Canada     

Kerong Sheng  Jie Fan  Wei Sun  Hailong Ma 《中国地理科学(英文版)》2016,26(3):377-388

This paper examines city growth patterns and the corresponding city size distribution evolution over long periods of time using a simple New Economic Geography(NEG) model and urban population data from Canada. The main findings are twofold. First, there is a transition from sequential to parallel growth of cities over long periods of time: city growth shows a sequential mode in the stage of rapid urbanization, i.e., the cities with the best development conditions will take the lead in growth, after which the cities with higher ranks will become the fastest-growing cities; in the late stage of urbanization, city growth converges according to Gibrat′s law, and exhibits a parallel growth pattern. Second, city size distribution is found to have persistent structural characteristics: the city system is self-organized into multiple discrete size groups; city growth shows club convergence characteristics, and the cities with similar development conditions eventually converge to a similar size. The results will not only enhance our understanding of urbanization process, but will also provide a timely and clear policy reference for promoting the healthy urbanization of developing countries.  相似文献   

Subduction/obduction rate in the North Pacific diagnosed by an eddy-resolving model     

刘玲玲  黄瑞新  王凡 《中国海洋湖沼学报》2016,34(4):835-846

Ventilation in the North Pacifi c is examined using data from the eddy-resolving 1/12° global HYbrid Coordinate Ocean Model(HYCOM) and Quik SCAT wind stress data. For the period January 2004 to December 2006 and area 20°–40°N, the total annual subduction rate is estimated at 79 Sv, and the obduction rate 41 Sv. Resolving the small-scale and high-frequency components of the eddy fi eld can increase the subduction rate by 42 Sv, and obduction by 31 Sv. Lateral induction is the dominant contributor to enhancement of subduction/obduction, and temporal change of mixed layer depth has a secondary role. Further analysis indicates that the high-frequency components of the eddy fi eld, especially those with timescale shorter than 10 days, are the most critical factor enhancing subduction/obduction.  相似文献   

New Zircon U‐Pb Age of Granodiorite in Chifeng at the Northern Margin of North China Craton and Constraints on Plate Tectonic Evolution     

CHEN Jingsheng  LI Bin  YANG Hao  LIU Miao  YANG Fan  LI Wei  WANG Yan  CUI Tianri 《《地质学报》英文版》2018,92(1):410-413

正Objective The North China Craton(NCC)is one of the oldest cratons in the world.The accretionary belt at its northern margin has been the focus of scholars both at home and abroad(Zhu Junbing and Ren Jishun,2017).In recent years,a series of Late Paleozoic–Mesozoic intrusions trending E–W have been discovered within the northern margin of the NCC,forming a magmatic belt.The study  相似文献   

Identification and determination of the boundary between the Cathaysian and Yangtze blocks: a preliminary understanding of gravity and magnetic fields     

Jiayong Yan  Kun Zhang  Guangming Fu  Fan Luo  Hao Wang  Guang Qi 《《地质学报》英文版》2018,92(Z1):222-225

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Elastic properties of orthoenstatite and its high-pressure phase and implications for the origin of low VP/VS zones and the X discontinuity     

Wangsheng Qian  Wengzhong Wang  Fan Zou  Zhongqing Wu 《《地质学报》英文版》2018,92(Z1):133-133

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