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21.
T. Ben-Gai A. Bitan A. Manes P. Alpert Y. Kushnir 《Theoretical and Applied Climatology》2001,69(3-4):171-177
Summary
Teleconnections associated with changing patterns of temperature and pressure anomalies over Israel during the second half
of the 20th century are investigated. Relatively high, statistically significant, correlation coefficients of −0.8 and +0.9
were found between the North Atlantic Oscillation (NAO) Index anomalies and smoothed (5 year running mean) cool season temperature
and surface pressure anomalies in Israel, respectively.
A relatively high positive correlation, (r = 0.8) was also found between the NAO Index anomalies and smoothed geopotential height of the 1000 hPa pressure level, during
the cool season at Bet Dagan radiosonde station located on the Israel Mediterranean coastal plain. Correlation coefficients
between NAO Index anomalies and the higher standard pressure levels, 850 and 700 hPa, decrease gradually and become negative
(not statistically significant) for the 500 hPa level.
Received January 25, 2000/Revised March 6, 2001 相似文献
22.
V. M. Kushnir 《Physical Oceanography》1992,3(2):105-113
A non-linear equation is derived for the hydrophysical probe's angular oscillations induced by tension fluctuations of the cable and by the influence of the horizontal and vertical current velocity components on the probe. The amplitude-frequency and phase-frequency characteristics of the angular oscillations are calculated for minor disturbances. Results of the analysis are shown to be consistent with the experimental data.Translated by V. Puchkin. 相似文献
23.
The paper discusses a method for the statistical evaluation of the vertical current velocity componentV
z(z) using data provided by profilers. The calculation of theV
z(z) profiles involves the determination of the root-mean-square deviation of the error of determination of the vetical current
velocity component at each level and the RMS deviation of the sample statistical variability of this quantity's estimates.
ProfilesV
z(z) have been computed for the north-western Black Sea using three surveys, with the involvement of an OLT profiler. The computations
have shownV
z(z) to have a two-layer structure, with zero being crossed in the main pycnocline. Such structure of the current velocity
vertical component is consistent with the hydrodynamic model of the field of currents induced by buoyancy fluxes through the
lateral boundaries of the basin. The availability of the zero values of the vertical current velocity in the pycnocline yields
a tool for gaining insight into the mechanism controlling the emergence of the oxic/anoxic interface and areas with sharp
vertical gradients of chemical and hydro-optical characteristics.
Translated by Vladimir A. Puchkin. 相似文献
24.
On the basis of the results derived by theoretical analysis [1] and laboratory physical modelling [2] of the circulation seawater
and stratification, induced by buoyancy fluxes, the suggestion has been made that, possibly, the Black Sea currents system
is three-layered. It has been supposed that an anticyclonic current flows in the basin.
To verify this deduction, the data from MHI's archived dataset have been treated, and results from twoad hoc expeditions are submitted here. Analysis of the vertical structure of currents, based on thein situ velocity measurements, using various means and calculations of the geostrophic circulation, has confirmed that a flow with
the theoretically predicted parameters may exist in the Black Sea.
Translated by Vladimir A. Puchkin. 相似文献
25.
V. M. Kushnir 《Physical Oceanography》1996,7(2):149-157
This paper considers the theoretical grounds for designing a new multi-component current velocity meter with a comprehensive
beam pattern and minimum impact of structural elements on the measurement data. The effect of technological error on the sensor's
ability to transmit acoustic signals is assessed. Information about the practical realization of the acoustic current velocity
meter is provided, together with the results of its metrological tests.
Translated by Vladimir A. Puchkin. 相似文献
26.
V. M. Kushnir E. Hansen L. A. Petrenko V. K. Pavlov A. N. Morozov S. V. Stanichnyi S. V. Fedorov 《Physical Oceanography》2007,17(5):278-295
The numerical analysis of the stationary field of current velocity on the upper boundary of the bottom boundary layer in the
Barents Sea is performed on the basis of a simplified model taking into account the fields of wind velocity and density of
water for the principal periods of the seasonal cycle and the bottom topography. The analysis is based on the climatic BarKode database and the data on the wind velocity over the Barents Sea for the last 50 yr. The numerical results demonstrate that
the field of bottom currents is fairly nonuniform and the current velocities vary from several fractions of 1 cm/sec to 5
cm/sec in the zones with noticeable slopes of the bottom. The estimates of the thickness of the bottom boundary layer are
obtained for the constant coefficient of bottom friction C
f
= 0.04. In the major part of the water area of the Barents Sea, the thickness of the bottom boundary layer is close to 1
m. In the regions with significant slopes of the bottom, it increases to 2–2.5 m and, in the two zones of intensification
of the bottom currents, becomes as large as 5 m. The maximum estimate of the coefficient of turbulent viscosity is close to
5 cm2/sec. The mean value of the coefficient of vertical density diffusion K
S
is equal to 2.34 cm2/sec and its standard deviation is equal to 1.52 cm2/sec.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 31–49, September–October, 2007. 相似文献
27.
The analysis of the thermochaline (double-diffusive) convection in the edge-ice zone of the Barents Sea to the east of Spitsbergen was performed by using the data of two hydrological surveys of the Norwegian Polar Institute in 1999 and 2000. The Turner's model, where the critical Rayleigh number is determined by using the empirical relationship between the Nusselt number and the Rayleigh number normalized to its critical value, was used for analysis. The results of calculation of thickness of the convective layer were compared with the data of supervision. The estimates of the vertical convective velocity were obtained. 相似文献
28.
Variation of the North Atlantic subtropical high western ridge and its implication to Southeastern US summer precipitation 总被引：1，自引：0，他引：1
Variations of the North Atlantic subtropical high (NASH) western ridge and their implication to the Southeastern United States (SE US) summer precipitation were analyzed for the years 1948–2007. The results show that the movement of the NASH western ridge regulates both moisture transport and vertical motion over the SE US, especially in the last three decades, during which the ridge moved westward towards the American continent. When the NASH western ridge is located southwest (SW) of its mean climate position, excessive summer precipitation is observed due to an enhanced moisture transport. In contrast, when the western ridge is located in the northwest (NW), a precipitation deficit prevails as downward motion dominates the region. Composite analysis indicates that SW ridging results mainly from the NASH center’s intensification; whereas NW ridging is likely caused by stationary wave propagation from the eastern Pacific/US western coast. In recent decades, both the SW and NW ridge positions have been observed to increase in frequency. Our results suggest that the increase in the SW ridging consistently follows the NASH’s intensification associated with anthropogenic forcing as projected by coupled climate models. However, the increased frequency of NW ridging tends to follow the positive Pacific decadal oscillation (PDO) index. Thus, the enhanced variability in the SE US summer precipitation in recent decades might be a combined result of anthropogenic forcing and internal variability of the climate system. Results suggest that, as anthropogenic forcing continues to increase, the SE US will experience more frequent wet summers and an increase in the frequency of dry summers during positive PDO phases. 相似文献
29.
V. M. Kushnir 《Physical Oceanography》1990,1(5):377-382
The relations for calculating the dynamic error in the angular coordinate measurements of hydrophysical instruments have been derived (non-linear terms being considered) through the analysis of an equation for the oscillations of a pendulum mounted on a mobile base. Some examples of calculating the errors encountered in some meters widely used in today's oceanographic measuring sets are given.Translated by Vladimir A. Puchkin. 相似文献
30.
Jacob Kushnir 《Geochimica et cosmochimica acta》1982,46(3):433-446
The coprecipitation of Sr, Mg, Na and K with anhydrite during the dehydration of gypsum was studied in laboratory experiments. The partition coefficients of Mg and Sr between anhydrite and solution decrease with increasing temperature. The partition coefficients of the alkali-ions do not depend upon temperature, but are affected by the brine composition.The mechanism of the phase transformation gypsum → anhydrite occurs via dissolution and precipitation, when the coprecipitated-ions are repartitioned between the new phase and the solution. The partition coefficients established in this study are applicable also for primary anhydrite.During the dehydration of gypsum at elevated temperatures metastable bassanite may form as an intermediate stage. The amount of cations coprecipitated with bassanite is much larger than the amount coprecipitated with anhydrite or gypsum. This phenomenon may have an influence on the partitioning of cations during the dehydration of gypsum, particularly on Sr.The partition coefficients of seawater cations between anhydrite and the brine are similar to those between gypsum and the brine. For this reason the coprecipitated-ions are not expected to be good indicators to distinguish between primary and secondary calcium sulfate minerals.The temperature effect on the coprecipitation of Mg and Sr with anhydrite makes these ions possible indicators for the temperature at which the phase transformation occurred. This temperature corresponds to the depth of burial of the gypsum at the stage of dehydration.The coprecipitation of seawater cations with anhydrite in the natural environment was studied in two systems: A small Pleistocene evaporite lens from the Sinai Peninsula and the Triassic anhydrite of the Mohilla Formation, Israel. The coprecipitated-ion composition of these samples was used to derive the conditions under which the anhydrite was formed. 相似文献