“A brief response to our critics”     

Oren Yiftachel Haim Yacobi 《Geoforum》2002,33(3):287

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Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall     

Yehouda Enzel  Revital Bookman  David Sharon  Haim Gvirtzman  Uri Dayan  Baruch Ziv  Mordechai Stein 《Quaternary Research》2003,60(3):263-273

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.  相似文献   

Salt accumulation in the loessial sequence in the Be'er Sheva Basin,Israel     

Mordeckai Magaritz  Haim Gvirtzman  Arie Nadler 《Environmental Geology》1988,11(1):27-33

Evidence of climatic changes is recorded in the salt content of the surface sediments in arid zones. In wetter periods airborne salts are removed downward by leaching to the groundwater, whereas in drier periods they accumulate. The period of salt accumulation in the loessial sediments of the northern Negev is about 10,000 yr. This period represents the recent aridification phase. The beginning of this stretch of time followed the last humid period in the region. Top paleo soil (calcic horizon) found in the region and dated 12,000 yr B.P. is an indicator of this humid period. This article is a contribution from the Agricultural Research Organization, The Volcani Center, Bet Datan, Israel, No. 1751E, 1986 series.  相似文献   

Extended free net adjustment constraints     

Haim B. Papo 《Journal of Geodesy》1985,59(4):378-390

The contribution of geodetic measurements to the establishment of a control network can be partitioned into global and local (individual) components. The global component epitomized in a number of geometrically meaningful parameters can be estimated together with the individual point coordinates. The additional rank defect created by the extension of the parameter list is corrected by free net adjustment constraints which are extended beyond those needed for a solution of the network datum problem. Two applications of extended free net adjustment are outlined and illustrated by elementary numerical examples. A non-Cartesian (skew) reference system discussed in the Appendix provides an exotic interpretation of the estimated global and individual parameters. Prepared during a grant period (September 1984 through February 1985) while serving as a Visiting Senior Scientist in Geodesy, National Research Council, National Academy of Sciences, Washington, D.C.  相似文献   

Calibration of regional pollen data to construct maps of former forest types in southern Sweden     

Gisela Björse  Richard H. W. Bradshaw  Daniel B. Michelson 《Journal of Paleolimnology》1996,16(1):67-78

A method was developed to construct maps of former forest types based on regional pollen data in southern Sweden. The considered species were Alnus, Betula, Carpinus, Corylus, Fagus, Fraxinus, Juniperus, Picea, Pinus, Populus, Quercus, Salix, Tilia and Ulmus. A network of 37 regional pollen sites with high data quality from lakes and peat deposits were selected from Sweden south of 60 ° N. Pollen percentage values were calculated and converted into estimates of tree composition. For controlling the reliability of the reconstruction, the estimates from the core-tops were compared with present day forest inventory data, and local pollen diagrams were compared with the regional pollen diagrams. An inverse distance weighted interpolation algorithm was used to generate maps for each tree species distribution at 2000 BP, 1500 BP, 1000 BP, 500 BP and 0 BP. A supervised classification routine was implemented to generate nine different forest types common to the five studied time intervals. The maps show that the amounts and patterns of distribution of the species and the forest types have varied in a significant but systematic manner through time. The changes are due to human activities, migrational patterns and changes in climate. These maps will be of value as a basis for future landscape planning, forestry and conservation of biodiversity.This is the 20th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.  相似文献   

Considered parameters in a least squares adjustment process     

Haim B. Papo 《Journal of Geodesy》1973,47(1):89-95

Least squares adjustment processes occasionally utilize constants with a known degree of uncertainty. If the covariance matrix of the adjusted parameters is estimated without considering those uncertainties the resulting estimate is invariably too optimistic. A method is proposed by which without altering the values of the adjusted parameters their a posteriori (after the adjustment) covariance matrix can be improved by the inclusion of the effect of uncertainties in the constants.  相似文献   

Resolution of tidal high water anomaly     

Irving Michelson 《Pure and Applied Geophysics》1965,61(1):149-151

Summary As a preliminary calculation of the Equilibrium Theory of Tides, a fictitious Earth-Moon configuration is analyzed byThomson andTait [1]²), in which non-sphericity of oceans is attributed to the attraction exerted by a stationary Moon. A rise of level is found at the which Earth-Moon orbital motion is accounted. This feature, which is utterly contradictory to fact according toG. H. Darwin [2] prompted him to remark that the equilibrium theory is nearly as much wrong as possible, in respect to the time of high water. An elementary analysis is given which, in demonstrating an exactly opposite finding, suggests a manner of removing one of the long-standing obscurities of the Laplace theory, remarked upon byHough andAiry, and in recent times byC. Eckart [3].  相似文献   

GLAST large area telescope multiwavelength planning     

O. Reimer  P. F. Michelson  R. A. Cameron  S. W. Digel  D. J. Thompson  K. S. Wood 《Astrophysics and Space Science》2007,309(1-4):523-526

Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-band blazar monitoring; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification and characterization. Several of these activities are needed to be in place before launch.   相似文献   

Estimating ground water recharge using flow models of perched karstic aquifers   总被引：3，自引：0，他引：3  

Weiss M  Gvirtzman H 《Ground water》2007,45(6):761-773

The fraction of rain that is annually recharged to ground water is a function of the transient quantities of precipitation (wet vs. dry years) as well as other meteorological and geologic factors, and thus it is very difficult to estimate. In this study, we have used long records (20 to 30 years) of precipitation and spring discharge to reconstruct the transient character of yearly recharge. These data sets were used to calibrate numerical ground water flow models on the less than 3 km(2) scale for four separate perched karstic aquifers in the Judean and Samarian Mountains of Israel. The stratification and karstic character of the local carbonate rock aquifers cause ground water to flow through discrete dissolution channels and to discharge at isolated springs. An innovative, dual-porosity approach was used where a finite-difference solution simulates flow in the rock matrix, while the karstic channels are simulated using computationally simple drains. Perched conditions are also simulated innovatively using MODFLOW by treating the bottom unsaturated layer as if it is saturated, but by assuming zero pressure head throughout the "unsaturated" layer. Best fitting between measured and computed spring hydrograph data has allowed us to develop a set of empirical functions relating measured precipitation to recharge to the aquifer. The generic methodology presented gives insight into the suspected changes in aquifer recharge rates between particularly wet or dry years.  相似文献   

Spatial and Temporal Characteristics of Saline Springs: Sea of Galilee, Israel   总被引：1，自引：0，他引：1  

Alon Rinimer  Shaul Hurwitz  Haim Gvirtzman 《Ground water》1999,37(5):663-673

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