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71.
Remarks on the Definition and Estimation of Friction Velocity 总被引:3,自引:1,他引:2
Rudolf O. Weber 《Boundary-Layer Meteorology》1999,93(2):197-209
One of the mainscaling parameters in similarity theory of the atmospheric boundary layer is friction velocity. Unfortunately, several definitions of friction velocity exist in the literature. Some authors use the component of the horizontal Reynolds stress vector in the direction of the mean wind vector to define friction velocity. Others define the friction velocity by means of the absolute value of the horizontal Reynolds stress vector. The two definitions coincide only if the direction of the mean wind vector is parallel to the horizontal Reynolds stress vector. In general, the second definition gives larger values for the friction velocity. Over complex terrain the situation is further complicated by the fact that the terrain following flow is not necessarily horizontal. Thus, several authors have proposed to use terrain following coordinate systems for the definition of friction velocity. By means of a large dataset of fast-response wind measurements with an ultrasonic anemometer the friction velocities resulting from the different definitions are compared. Furthermore, it is shown that friction velocity can be well estimated from horizontal wind speed, and even better from simple horizontal or vertical turbulence parameters. 相似文献
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GPCC's new land surface precipitation climatology based on quality-controlled in situ data and its role in quantifying the global water cycle 总被引:10,自引:3,他引:10
Udo Schneider Andreas Becker Peter Finger Anja Meyer-Christoffer Markus Ziese Bruno Rudolf 《Theoretical and Applied Climatology》2014,115(1-2):15-40
In 1989, the need for reliable gridded land surface precipitation data sets, in view of the large uncertainties in the assessment of the global energy and water cycle, has led to the establishment of the Global Precipitation Climatology Centre (GPCC) at Deutscher Wetterdienst on invitation of the WMO. The GPCC has calculated a precipitation climatology for the global land areas for the target period 1951–2000 by objective analysis of climatological normals of about 67,200 rain gauge stations from its data base. GPCC's new precipitation climatology is compared to several other station-based precipitation climatologies as well as to precipitation climatologies derived from the GPCP V2.2 data set and from ECMWF's model reanalyses ERA-40 and ERA-Interim. Finally, how GPCC's best estimate for terrestrial mean precipitation derived from the precipitation climatology of 786 mm per year (equivalent to a water transport of 117,000 km3) is fitting into the global water cycle context is discussed. 相似文献
74.
Geomechanics of hazardous landslides 总被引:1,自引:1,他引:0
POISEL Rainer BEDNARIK Martin HOLZER Rudolf LISCAK Pavel 《山地科学学报》2005,2(3):211-217
A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass (deformation and strength parameters), is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models. 相似文献
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Rudolf A. Treumann 《Astrophysics and Space Science》1992,198(1):71-77
We examine the hypothesis of the connection between quasars and galaxies from the point of view of the theory of nonlinear dynamics of highly complex systems. It is found that complexity and nonlinearity of systems which are informationally disconnected may lead to different intrinsic time-scales of the systems. Systems with different intrinsic time-scales age at different rates. This kind of aging can be measured by observing their different redshifts. On interpreting strongly differing redshifts of astrophysically closely related objects as informational redshifts, we are in the position to determine their maturity ratios which are measures of the different nonlinear stages of the objects on the cosmological time-scale. 相似文献
78.
Radiation-induced defects in quartz. II. Single-crystal W-band EPR study of a natural citrine quartz 总被引:1,自引:1,他引:0
Yuanming Pan Mark J. Nilges Rudolf I. Mashkovtsev 《Physics and Chemistry of Minerals》2008,35(7):387-397
Single-crystal electron paramagnetic resonance (EPR) spectra of a natural citrine quartz without any artificial irradiation,
measured at W-band frequencies (∼94 GHz) and temperatures of 77, 110 and 298 K, allow better characterization of three previously-reported
Centers (#6, #7 and B) and discovery of three new defects (B′, C′ and G′). The W-band EPR spectra reveal that Centers #6 and
#7 do not reside on twofold symmetry axes, contrary to results from a previous X-band EPR study. The W-band spectra also show
that the previously reported Center B is a mixture of two defects (B and B′) with similar g matrices but different-sized 27Al hyperfine structures. Center C′ has similar principal g values to the previously reported Center C but is distinct from the latter by a larger 27Al hyperfine structure with splittings from 0.10 to 0.22 mT. Also, Center G′ has a similar g matrix to the previously reported Center G but a different 27Al hyperfine structure with splittings from 0.41 to 0.53 mT. These spin-Hamiltonian parameters, together with observed thermal
properties and microwave-power dependence, suggest that Centers #6 and #7 probably represent O23− type defects. Centers B and B′ are probably superoxide radicals (O2−) with the unpaired spin localized on the same pair of oxygen atoms around a missing Si atom but linked to a substitutional
Al3+ ion each at different neighboring tetrahedral sites. Similarly, Centers G and G′ are most likely superoxide radicals with
the unpaired spin localized on another pair of oxygen atoms around a missing Si atom and linked to a substitutional Al3+ ion each at different neighboring tetrahedral sites. Center C′ is probably an ozonide radical associated with a missing Si
atom and linked to a substitutional Al3+ ion at the neighboring tetrahedral site. This study exemplifies the value of high-frequency EPR for discrimination of similar
defect centers and determination of small local structural distortions that are often difficult to resolve in conventional
X- and Q-band EPR studies. 相似文献
79.
Brázdil Rudolf Szabó Péter Dobrovolný Petr Řezníčková Ladislava Kotyza Oldřich Suchánková Silvie Valášek Hubert 《Theoretical and Applied Climatology》2017,129(1-2):623-632
Theoretical and Applied Climatology - This paper addresses the course, extent, and impacts of a windstorm that occurred on 20–21 December 1740, in the Czech Lands. The analysis is based on... 相似文献
80.