The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts   总被引：1，自引：0，他引：1  

Yehouda Enzel  Rivka Amit  Uri Dayan  Onn Crouvi  Ron Kahana  Baruch Ziv  David Sharon   《Global and Planetary Change》2008,60(3-4):165-192

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.  相似文献   

基于数字图像技术的土冻胀试验系统研究   总被引：3，自引：3，他引：0  

王永涛  王大雁  马巍  温智  徐湘田  杜海民 《冰川冻土》2017,39(5):1047-1056

开展土冻胀过程的研究对于认识土冻胀机理具有重要的意义,以往学者多采用建立模型进行数值分析的方法,但是在试验中却不能对模型预测的冷生构造、冰分凝、水分迁移等实时过程进行验证。通过建立包括实时图像采集系统、图像预处理系统以及图像数字化系统为一体的基于数字图像技术的土冻胀试验系统,对青藏粉土的冻胀发展过程和冰分凝过程进行了研究分析。结果显示：试样冻胀后已冻区纵剖面的冷生构造可以分为微薄层状构造区、薄层状构造区以及最暖端厚层状构造区三个部分,其中薄层状构造区下部的冰透镜体的分凝作用是冻胀的主要贡献部分,最暖端厚层状构造区中冰透镜体的分凝作用导致了试样未冻区的固结,试样中冰透镜体的分凝过程与试样的冻胀过程和试后含水率的结果能够相互验证。建立的试验系统可以对土冻胀过程中包括冷生构造发育、冻胀变形、冰分凝等过程进行实时采集和定量分析,为冻胀模型的建立和验证提供了试验方法和技术支撑。  相似文献   

The inter-relationship between coastal sub-aquifers and the Mediterranean Sea, deduced from radioactive isotopes analysis   总被引：3，自引：1，他引：2  

Yoseph Yechieli  Uri Kafri  Orit Sivan 《Hydrogeology Journal》2009,17(2):265-274

Radioactive isotopes were used to estimate the rate of seawater intrusion into the coastal aquifer of Israel, the connection between the different sub-aquifers, and the connection between the sub-aquifers and the sea. This was done by dating both fresh and saline groundwaters from the vicinity of the shoreline, which were analyzed for their ¹⁴C and tritium content together with their chemical and stable isotope composition. The results indicate that the distinct sub-aquifers differ in their water chemistry and age. The saline groundwater in the lower sub-aquifers is older than ca. 10,000 years, as evidenced by the absence of tritium and low ¹⁴C activity (<12 PMC). On the other hand, saline groundwaters in the upper sub-aquifers contain tritium and are thus younger than 50 years, indicating recent intrusion of seawater. The ages of the saline groundwaters become younger upward from the lower sub-aquifers to the upper ones, reflecting the sea-level rise since the last glacial period. The older ages also imply slow groundwater flow in the lower sub-aquifers. The fresh groundwaters in most cases in the lower sub-aquifers were found to be older than ca. 10,000 years and this implies that the flow to the sea is blocked or restricted.  相似文献   

Parametric study of near-wake structure of spherical and cylindrical bodies in the laboratory     

W.A. Oran  N.H. Stone  Uri Samir 《Planetary and Space Science》1974,22(3):379-390

Some aspects of the interaction between metal bodies and streaming rarefied plasmas were studied in a newly constructed Plasma Wind Tunnel as part of an attempt to investigate (via simulation) phenomena relevant to the spacecraft/space plasma interaction. Detailed near-wake ion current profiles for both spherical and cylindrical bodies at different body potentials (φ_S) and at different plasma flow parameters are presented. Various features of the profiles can be correlated, at least qualitatively, with both plasma and body characteristics. For example, the width of the wake zone appears proportional to the Debye length (λ_D) and depends on the potential of the target body although it appears to be relatively insensitive to the ratio $\text{S = V}{}_{\mathrm{<mtext>flow</mtext>}}\text{/(}\text{2kT}{}_{\mathrm{e}}\text{M}{}_{\mathrm{+}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. The amplitude of the ion current peak(s) also appears proportional to λ_D while, for fixed φ_S, the location of the peak is directly related to S and possibly dependent upon body geometry. The general importance of body geometry is qualitatively demonstrated. In addition, a discussion of the relevance of the above studies to previous in situ data obtained from the Ariel I and Gemini/Agena missions is given.  相似文献   

Corrigendum to ‘Lower crustal flow and the role of shear in basin subsidence: An example from the Dead Sea Basin’: [Earth Planet. Sci. Lett. 199 (2002) 67-79]     

Uri S. ten Brink 《Earth and Planetary Science Letters》2002,201(2):447-448

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Stable isotope and Sr2+/Ca2+ evidence of diagenetic dedolomitization in a schizohaline environment: Cenomanian of northern Israel   总被引：1，自引：0，他引：1  

Mordeckai Magaritz  Uri Kafri 《Sedimentary Geology》1981,28(1):29-41

The Cenomanian—Turonian Upper Judea Group of Israel comprises shallow-marine hypersaline dolomites passing laterally into ‘basinal’ limestones and chalks. Chertbearing diagenetic dedolomites characterize the transitional zone. The restriction of dedolomites to a narrow zone, their light δ¹³C (up to ?11%), and their low Sr²⁺ concentration (<16 ppm) all suggest that the dedolomites were formed diagenetically through exposure of this zone to fresh meteoric waters. This type of partly changing environments was referred to as schizohaline by Folk and Siedlecka (1974).  相似文献   

Formation of sequential basins along a strike–slip fault–Geophysical observations from the Dead Sea basin     

Michael Lazar  Zvi Ben-Avraham  Uri Schattner   《Tectonophysics》2006,421(1-2):53-69

The Dead Sea basin is often cited as one of the classic examples for the evolution of pull-apart basins along strike–slip faults. Despite its significance, the internal structure of the northern Dead Sea basin has never been addressed conclusively. In order to produce the first comprehensive, high-resolution analysis of this area, all available seismic data from the northern Dead Sea (lake)–lower Jordan valley (land) were combined. Results show that the northern Dead Sea basin is comprised of a system of tectonically controlled sub-basins delimited by the converging Western and Eastern boundary faults of the Dead Sea fault valley. These sub-basins grow shallower and smaller to the north and are separated by structural saddles marking the location of active transverse faults. The sedimentary fill within the sub-basins was found to be relatively thicker than previously interpreted. As a result of the findings of this study, the “classic” model for the development of pull-aparts, based on the Dead Sea, is revised. The new comprehensive compilation of data produced here for the first time was used to improve upon existing conceptual models and may advance the understanding of similar basinal systems elsewhere.  相似文献   

An evaluation of the role of hurricane Olga (2001) in an extreme rainy event in Israel using dynamic tropopause maps     

S. O. Krichak  P. Alpert  M. Dayan 《Meteorology and Atmospheric Physics》2007,98(1-2):35-53

Summary During the period from end of November to early December 2001, a sequence of extremely intense synoptic developments occurred over the area from the Atlantic to Mediterranean. These included the formation of hurricane Olga, an intensification of the Icelandic Low, strengthening of the subtropical westerly jet stream (STJ) over North Africa, formation of the Red Sea Trough (RST) and Cyprus Low cyclones, which resulted in torrential rains in Israel on December 4–5. The evolution of the synoptic processes over a large area from the Atlantic to Western Europe and the Mediterranean region during November 25–December 2 is investigated here with the help of dynamic tropopause patterns calculated based on reanalysis data. It is shown that the chain of extreme weather events was triggered by the acceleration of a coherent tropopause disturbance (CTD) over the Labrador Sea. Two branches of the process may be distinguished, southern and northern. The southern one was associated with the transformation of a tropical storm into hurricane Olga, strengthening of the STJ and eventually the formation of the RST cyclone. The RST contributed to the intensification of the transport of moist air masses from equatorial Africa to the Mediterranean region. The northern branch was determined by an eastward drift of the CTD, moist air mass transport from the area of the hurricane to the North Atlantic and the European-Mediterranean region, strengthening of the Icelandic Low and formation of an upper troposphere potential vorticity-streamer system over western Scandinavia. Displacement of the streamer to the Mediterranean region and its interaction with the RST system played a major role in the development of the powerful Cyprus Low cyclone over the northeastern Mediterranean region.  相似文献   

主应力轴旋转条件下冻结黏土的动强度特性北大核心CSCD     

张斌龙  王大雁  马巍  雷乐乐  周志伟 《冰川冻土》2022,44(2):448-457

研究冻土动强度对寒区工程和人工冻结工程施工及安全性评价具有重要意义。为了揭示主应力轴旋转对冻结黏土动强度特性的影响,利用空心扭剪仪开展不同围压下冻结黏土动三轴和空心扭剪试验,探讨了主应力轴旋转对冻结黏土动强度、动黏聚力和动内摩擦角变化规律的影响。结果表明:主应力轴旋转导致冻结黏土试样的动强度降低,围压越低主应力轴旋转对动强度影响效果就越明显;随着震动次数的增多,主应力轴旋转条件下冻结黏土动黏聚力衰减速度相对于主应力方向固定时加快;不同于主应力轴方向固定条件下动内摩擦角随震动次数增多而衰减的特点,在主应力轴旋转条件下动内摩擦角随震动次数增多而增大。另外,研究显示主应力轴旋转条件下动强度、动黏聚力和动内摩擦角均与震动次数的对数呈良好的线性关系,用线性方程对其进行了拟合,并给出拟合系数和确定系数。  相似文献   

Epipalaeolithic occupations in Nahal Neqarot Rockshelter,Negev, Israel: Radiocarbon dating and identification of charred wood remains     

Nigel Goring-Morris  Uri Baruch  Anna Belfer-Cohen  Steve Rosen 《Geoarchaeology》1998,13(2):219-232

Recent excavations at Nahal Neqarot Rockshelter in the Central Negev, Israel, revealed 60 cm of in situ sediments. The associated lithic industry is mostly attributable to the Middle Epipalaeolithic Ramonian industry, though there is also evidence for sporadic earlier and later Epipalaeolithic use of the site. This is confirmed by three accelerator ¹⁴C dates, which contribute to a better understanding of the chronological framework for the Epipalaeolithic in the region. Microscopic examination of charred wood remains uncovered with the lithics, revealed the dominance of juniper, which is presently extinct in the nearby contemporaneous vegetation, otherwise composed of still extant taxa. © 1998 John Wiley & Sons, Inc.  相似文献