Advertent/inadvertent changes in the spatial distribution of rainfall in the central coastal plain of Israel   总被引：1，自引：0，他引：1  

Yair Goldreich 《Climatic change》1987,11(3):361-373

Analysis of recent rainfall normals reveals an unusual spatial pattern where the rainfall increases with the distance from the sea over the central coastal plain of Israel. Applying a multiple regression technique separately to rainfall amounts for the two randomized experiments of cloud seeding of seeded days and not seeded days, leads to the conclusion that the inadvertent influence of recent urbanization processes along the coastal plain are the cause of this phenomenon, rather than the advertent artificial cloud seeding. The seeding effect at the target area, on the other hand, seems to increase the inhomogeneity of the spatial structure of the rainfall distribution.  相似文献   

Spatial distribution of surface properties,runoff generation and landscape development in the Zin Valley Badlands,northern Negev,Israel     

Nikolaus J. Kuhn  Aaron Yair  Milica Kasanin Grubin 《地球表面变化过程与地形》2004,29(11):1417-1430

In?ltration tests, soil mapping and soil property analysis were used to assess the effect of within‐storm rainfall conditions on spatial patterns of surface characteristics relevant for runoff generation, continuity and erosion in the Zin Valley Badlands. Runoff and erosion differ strongly between ridges and slopes. Soils at both locations are susceptible to sealing, but on the sideslopes deep desiccation cracks inhibit continuous ?ow, even during high magnitude rainstorms. The discontinuous nature of runoff has a feedback on surface conditions. Erosion on the ridges maintains shallow soils prone to sealing while in?ltration and deposition on the sideslopes enhance soil depth, a prerequisite for stable desiccation cracks. Some runoff generated on the ridges is transmitted to the valley via rills. On straight sideslopes, rills are single and often discontinuous, indicating limited frequency of continuous runoff. Along concave valley heads, rill systems are well integrated and continuous, concentrating runoff and reducing in?ltration losses along slopes. The longitudinal, V‐shaped valley morphology of small catchments in the Zin Valley Badlands re?ects the long‐term effect of different erosion rates in valley heads and on sideslopes. Over time, valley incision lengthened the sideslopes, reducing the portion of annual rainfall that was runoff‐effective. Once sideslopes reached a critical length that inhibited frequent continuous ?ow, a colluvium with an increased in?ltration capacity developed, reducing runoff frequency even further. Consequently, erosion on the valley sideslopes decreased. Continuous ?ow from ridges to the valley channel remained more common in integrated rill systems in concavities and valley heads, leading to more erosion and retreat of the valley heads. The spatial patterns of runoff and erosion in the Zin Valley Badlands demonstrate that landscape development is strongly affected by processes that lead to differentiation of soil properties on hillslopes with uniform lithology. The patterns of surface characteristics and their role in landscape development are strongly dependent on rainfall conditions, highlighting the need for geomorphologists to identify the dynamic spatial and temporal scales relevant for landscape development. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Geochemical characteristics from tests of four modern planktonic foraminiferal species in the Indonesian Throughflow region and their implications     

Peng Zhang  Rina Zuraida  Yair Rosenthal  Ann Holbourn  Wolfgang Kuhnt  Jian Xu 《地学前缘(英文版)》2019,10(2):505-516

Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ¹⁸O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ¹⁸O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.  相似文献   

Indication for circular organization of column sprite elements associated with Eastern Mediterranean winter thunderstorms     

Elyakom Vadislavsky  Yoav Yair  Carynelisa Erlick  Colin Price  Eran Greenberg  Roy Yaniv  Baruch Ziv  Nàama Reicher  Adam Devir 《Journal of Atmospheric and Solar》2009,71(17-18):1835-1839

We report synchronized optical observations of sprites in Israel during the winters of 2006/7–2007/8. Based on several events, we suggest that the elements of columniform sprites are organized in spaced intervals on the circumference of a circle centered directly above, or a little offset, to the vertical direction from the parent lightning. In 2D images most of the cases show columns to be arranged in highly eccentric elliptical forms or in straight rows. The analysis of the optical images provided the geometrical dimensions of the columns and their spatial organization. We used an electrostatic model of the QE field with reasonable assumptions on the location and magnitude of the cloud charge center, constrained by ELF evaluation of the Charge Moment Change in the parent flash, to show that the observed diameter of the columnar arrangement closely matches the conventional breakdown field line contour at the same altitude.  相似文献   

北京地区闪电活动与气溶胶浓度的关系研究   总被引：1，自引：0，他引：1       下载免费PDF全文

孙萌宇  郄秀书  刘冬霞  Yoav Yair  夏祥鳌  袁善锋  王东方  卢晶雨  Abhay Srivastava  Didier Ntwali 《地球物理学报》2020,63(5):1766-1774

基于2015—2017年北京闪电定位网(BLNET)总闪资料与35个自动空气质量监测站PM2.5数据,分析了北京地区(39.5°N—41.0°N,115.0°E—117.5°E)夏季(6—8月)闪电活动与PM2.5的时空分布特征,同时针对117次雷暴天气,探讨了气溶胶浓度变化对闪电活动的可能影响.结果表明:PM2.5浓度及总闪密度均呈现自西北向东南升高的空间分布特征.闪电峰值在污染背景下出现的时间(19∶00LT)晚于清洁背景下(15∶00LT)约4h,且总闪百分比(～20%)可达清洁背景下(～9%)的两倍.对雷暴前1～4h的PM2.5浓度与时间窗(12∶00—22∶00LT)内总闪数目的中位数进行相关分析,发现PM2.5浓度低于130μg·m-3时,PM2.5与总闪数存在明显正相关,此时气溶胶可能通过影响云微物理过程进而影响雷暴的对流发展,增强闪电活动;PM2.5大于150μg·m-3时,总闪数随PM2.5浓度的增加呈减少趋势,可能的原因是高气溶胶浓度下地面太阳辐射显著下降,对流活动受到抑制,导致闪电活动减少.当PM2.5浓度在130～150μg·m-3时,两者关系不明显.  相似文献   

Rainfall–runoff relationship over encrusted dune surfaces,Nizzana, Western Negev,Israel     

G. J. Kidron  A. Yair 《地球表面变化过程与地形》1997,22(12):1169-1184

A thin microbial crust covers the lower part of longitudinal dunes in the western Negev, where average annual rainfall is 95 mm. In order to study the effect of the microbial crust on rainfall–runoff relationships under natural rainfall conditions, runoff plots equipped with pressure gauges were established on opposite north- and south-facing slopes that differ in their vegetal cover and crust properties. The study covered four years (1990–94). The first two years were wet and the following two years relatively dry. One to five flow events were recorded per year. No correlation was found between runoff yield, rain amount and rain intensity. Unlike many microbial crusts reported in the literature, the microbial crust in the western Negev is not hydrophobic. Infiltration rate is high under dry surface conditions and of the order of 9–12 mm h⁻¹ when the crust is saturated. The high final infiltration rate is explained by the occurrence of large pores that do not seal when the crust is saturated. Typical hydrographs have very steep rising and falling limbs, pointing at a limited contributing area. Most flows last less than 10 min and runoff volumes collected are, on the whole, very small. Owing to differences in crust properties, runoff is higher on north- than on south-facing slopes. © 1997 John Wiley & Sons, Ltd.  相似文献   

Weighting the Effects of Spatial Cognition and Activity Anchors on Time–Space Activity     

A. Yair Grinberger 《The Professional geographer》2019,71(1):52-64

Many elements are known to affect the decision-making procedures that underlie time–space activity patterns. Yet, knowledge regarding the relations between these elements is lacking. In this article, a hierarchical structure of external and cognitive time–space behavioral influences is proposed based on the results of a field experiment. The experiment relied on an in situ sampling of stated and overt behaviors of visitors to a touristic site in northern Israel, using questionnaires and Global Positioning System loggers. Two experimental treatments were simultaneously applied during sampling, dividing the sample into four groups: Each participant received on entry one of two maps, designed according to different cartographical–cognitive approaches; new activity stations were placed during half of the sampling days, meaning that each participant was exposed to one of two possible spatial layouts. The behavioral patterns recorded expose each treatment's distinct behavioral effect along with its relative weight within the decision-making process, thus pointing toward a hierarchical structure.  相似文献   

Short and long term effects of bioturbation on soil erosion, water resources and soil development in an arid environment     

A. Yair 《Geomorphology》1995,13(1-4)

The importance of vegetal cover on soil erosion processes has been recognized for a long time. However, the short and long term effects of faunal activity on soil erosion and soil development had been largely overlooked by geomorphologists. The study of runoff and erosion processes in the Negev desert indicated pronounced systematic differences in sediment concentration and soil erosion rates between rocky and colluvial surfaces. Erosion rates were always higher on the former than on the latter. Field observations drew attention to an intense burrowing and digging activity conducted mainly by Isopods and Porcupines. The monitoring of this activity, based on a grid system, which consists of rows 5 m wide, lasted ten consecutive years. Data obtained suggest the existence of a strong link between the spatial pattern of bioturbation and that of soil erosion. The study also examines, through feedback processes, the regulatory role of bioturbation on the spatial distribution of water availability; soil moisture and soil forming processes. Due to bioturbation two distinct environments were recognised. The rocky environment which is characterized by a positive feedback with a high water availability and low soil salinity; and the soil covered areas where a negative feedback results in low water availability and a high soil salinity.  相似文献   

Magnetotelluric profile across the Dead Sea rift in Northern Israel     

Y. Rotstein  S. Goldberg 《Tectonophysics》1981,80(1-4):147-164

A series of magnetotelluric soundings were carried out in and on both sides of the Dead Sea rift in northern Israel. The more interesting result of this survey is the discovery of a high-conductivity layer within the crust and at a depth of probably less than 15 km. The depth to this layer is shallower than found elsewhere in Israel for the same layer. The high conductivity is not influenced by the presence of the rift and no indication was found for changes in the deep crustal structure across the rift. Information about the characteristics of the resistivity of the sedimentary layer is presented but is less certain. Determination of high-resistivity basement in the rift and the Golan Heights indicates a throw of about 2000 m on the rift eastern fault in this region.  相似文献   

The closing of a seaway: ocean water masses and global climate change     

Caroline H. Lear  Yair Rosenthal  James D. Wright 《Earth and Planetary Science Letters》2003,210(3-4):425-436

The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic δ¹³C, δ¹⁸O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1–2°C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by 1°C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of 3.5°C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of ‘warm’ proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio–Pleistocene.  相似文献