Zum System der Meeresströmungen in den höheren Breiten     

Wolfgang Krauß 《Ocean Dynamics》1955,8(3):102-111

Zusammenfassung Es wird gezeigt, daß in den höheren Breiten zwischen dem ozeanischen Stromfeld und der Windverteilung beträchtliche Unterschiede bestehen. Daher wird als Ursache des Strömungssystems nicht das Windfeld, sondern die Süßwasserzufuhr vom Festland angesehen, welche als Salzgehaltsstörung das küstennahe Massenfeld beherrscht und entsprechend dem Theorem nach Bjerknes ein Gradientstromsystem bedingt, welches dem beobachteten entspricht.

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A contribution to the system of ocean currents in the higher latitudes

Summary It is demonstrated that in the high latitudes, considerable differences exist between the oceanic current system and the wind distribution. It is, therefore, supposed that it is not the windfield that gives rise to the existing current system but the supply of fresh water from the continent which, as a salinity disturbance, plays a dominant part in the field of mass near the coast. According to Bjerknes' theorem, the disturbance of salinity conditions a gradient current system; this is in good agreement with the observations.

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Sur le système de courants marins par les hautes latitudes

Résumé On montre qu'il existe par les hautes latitudes de différences considérables entre le système de courants océaniques et la distribution des vents. Pour cette raison, on suppose que c'est l'afflux d'eau douce venant du continent et non le champ du vent qui engendre le système de courants dominant, sous la forme d'une perturbation de salinité, le champ de masse près des côtes. D'après le théorème de Bjerknes le système de courants de gradient est la conséquence nécessaire de la perturbation de salinité ce qui est en bon accord avec les observations faites dans ce domaine.

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Ein Brief von C. F. Gauβ     

C. F. Gauß 《Ocean Dynamics》1955,8(1):38-40

Ohne Zusammenfassung  相似文献   

In-flight performance analysis of the CHAMP BlackJack GPS Receiver   总被引：8，自引：1，他引：7  

Oliver?MontenbruckEmail author  Remco?Kroes 《GPS Solutions》2003,7(2):74-86

JPL's BlackJack receiver currently represents the most widely used geodetic grade GPS receiver for space applications. Using data from the CHAMP science mission, the in-flight performance of the BlackJack receiver has been assessed and the impact of various software updates performed during the 2.5 years since launch is described. Key aspects of the study comprise the channel allocation, anomalous data points, and the noise level of the code and carrier data. In addition, it has been demonstrated that the code measurements collected onboard the CHAMP satellite are notably affected by multipath errors in the aft-looking hemisphere, which can be attributed to cross-talk between the occultation antenna string and the primary precise orbit determination antenna. For carrier smoothed 10 s normal points, the code noise itself varies between a minimum of 5 cm at high elevations and 0.5 m (C/A) to 1.0 m (P₁, P₂) at 10° elevation. Carrier-phase data exhibit representative errors of 0.2 to 2.5 mm. The results of the CHAMP GPS data analysis contribute to a better understanding and possible improvement of the BlackJack receiver and support the design of optimal data editing and weighting strategies in precise orbit determination applications.  相似文献   

GIOVE-A initial signal analysis     

Oliver Montenbruck  Christoph Günther  Sebastian Graf  Miquel Garcia-Fernandez  Johann Furthner  Hanspeter Kuhlen 《GPS Solutions》2006,10(2):146-153

In late December 2005 the GIOVE-A test satellite was launched by the European Space Agency (ESA) to secure the frequencies for the Galileo system and to provide a platform for testing the new navigation signals. We performed an initial assessment of these signals using the 30 m deep space antenna of the DLR ground station in Weilheim (Germany). The antenna gain raised the signals above the noise level, thus allowing a detailed analysis even without knowledge of the ranging codes. The present paper covers the analysis of the L1/E1 signals, which includes a discussion of the spectrum, the time domain signal and a decoding of the spreading codes for the Open Service.  相似文献   

Calculation of the Inverse of the Covariance     

Dean S. Oliver 《Mathematical Geology》1998,30(7):911-933

In reservoir characterization, the covariance is often used to describe the spatial correlation and variation in rock properties or the uncertainty in rock properties. The inverse of the covariance, on the other hand, is seldom discussed in geostatistics. In this paper, I show that the inverse is required for simulation and estimation of Gaussian random fields, and that it can be identified with the differential operator in regularized inverse theory. Unfortunately, because the covariance matrix for parameters in reservoir models can be extremely large, calculation of the inverse can be a problem. In this paper, I discuss four methods of calculating the inverse of the covariance, two of which are analytical, and two of which are purely numerical. By taking advantage of the assumed stationarity of the covariance, none of the methods require inversion of the full covariance matrix.  相似文献   

New equipment and processing for magnetotelluric remote reference observations   总被引：2，自引：0，他引：2  

Oliver Ritter  reas Junge  & Graham Dawes 《Geophysical Journal International》1998,132(3):535-548

Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations.  相似文献   

Complex Archean lower crustal structure revealed by COCORP crustal reflection profiling in the Wind River Range,Wyoming     

Scott B. Smithson  Jon A. Brewer  S. Kaufman  J.E. Oliver  R.L. Zawislak 《Earth and Planetary Science Letters》1980,46(2):295-305

A COCORP deep crustal reflection profile across the Wind River uplift crosses exposed Archean rocks and resolves an unusual complex deep crustal structure at a depth of 24–31 km in an area where depth relations in Precambrian rocks can be inferred. The different levels of exposure across the beveled plunge of the Wind River uplift reveal supracrustal rocks at shallower levels with migmatites and pyroxene granulites at deeper levels. For the first time, deep crustal structure from reflection profiling may be interpreted in terms of exposed basement geology. A folded, multilayered deep structure shown by relfection data resembles multiply folded pyroxene granulite interlayered with granitic gneiss exposed in the central Wind River uplift; isoclinal folding is suggested in the folded layered seismic structure. Earlier seismic reflection studies suggested a simpler lower crust. These data indicate that lower crustal structure may have a complexity similar to deeply eroded Precambrian granulite-facies rocks. If this seismic feature represents folded metamorphic rocks, it seems unlikely that this Archean crust could have been thickened by underplating after 2.7 b.y. B.P. and the crust would have to be at least 30 km thich when this structure was formed.  相似文献   

Intercomparison of Tropospheric OH Measurements by Different Laser Techniques during the POPCORN Campaign 1994     

A. Hofzumahaus  U. Aschmutat  U. Brandenburger  T. Brauers  H.-P. Dorn  M. Hausmann  M. Heßling  F. Holland  C. Plass-Dülmer  D. H. Ehhalt 《Journal of Atmospheric Chemistry》1998,31(1-2):227-246

In-situ OH measurements by laser-induced fluorescence (LIF) spectroscopy and folded long-path differential optical absorption spectroscopy (DOAS) were carried out in a rural environment in North-East Germany as part of the field experiment POPCORN in August 1994. The large set of OH data obtained allowed an intercomparison of both techniques based on relative diurnal profiles and simultaneously measured absolute concentrations. Most of the time the two OH instruments encountered the same air and agreed well in the measured relative diurnal variations. Only on a few occasions the measurements significantly disagreed due to a perturbation of the DOAS measurements by a local OH source in the north-western wind sector. Excluding data from this wind direction, the statistical analysis of 137 data pairs yields a correlation coefficient of r = 0.90 and a weighted linear fit with a slope of 1.09 ± 0.12. The correlations are carefully analyzed. The comparison of both instruments is discussed in the light of newly published effective absorption cross-sections for H2O and O2 that affect the calibration of LIF.  相似文献   

The variability of the large-amplitude internal wave field on the Australian North West Shelf     

Paul Van Gastel  Gregory N. Ivey  Michael J. Meuleners  Jason P. Antenucci  Oliver Fringer 《Continental Shelf Research》2009,29(11-12):1373-1383

Observations are presented of large-amplitude internal waves (LAIWs) generated by the steepening of the internal tide on the Australian North West Shelf (NWS) over a 4-month period extending from strongly stratified summer conditions to weakly stratified winter conditions. The observations are from a site in water depth of 124 m where current and temperature measurements were made from a fixed vertical mooring and a benthic L-shaped spatial array. The observations show the LAIWs at this site to be characterized by strong seasonal variability, with energetic LAIWs of depression being dominant during summer and weaker LAIWs of elevation being dominant during the winter months as the stratification weakens, the upper mixed layer deepens, and the thermocline is close to the bottom. Waves were also seen to propagate from a range of directions towards the observation site. Modeling using the Regional Ocean Modeling System (ROMS v2.1) revealed that internal tide generation in the area occurred at water depths of between 400 and 600 m along an arc of approximately 120 km in length, some 70 km to the northwest of our experimental site. The results demonstrate both the 3D nature as well as the seasonal variation of the LAIW field.  相似文献   

Present and Future Observing Trends in Atmospheric Magnetoseismology     

D. Banerjee  R. Erdélyi  R. Oliver  E. O’Shea 《Solar physics》2007,246(1):3-29

With modern imaging and spectral instruments observing in the visible, EUV, X-ray, and radio wavelengths, the detection of oscillations in the solar outer atmosphere has become a routine event. These oscillations are considered to be the signatures of a wave phenomenon and are generally interpreted in terms of magnetohydrodynamic (MHD) waves. With multiwavelength observations from ground- and space-based instruments, it has been possible to detect waves in a number of different wavelengths simultaneously and, consequently, to study their propagation properties. Observed MHD waves propagating from the lower solar atmosphere into the higher regions of the magnetized corona have the potential to provide excellent insight into the physical processes at work at the coupling point between these different regions of the Sun. High-resolution wave observations combined with forward MHD modeling can give an unprecedented insight into the connectivity of the magnetized solar atmosphere, which further provides us with a realistic chance to reconstruct the structure of the magnetic field in the solar atmosphere. This type of solar exploration has been termed atmospheric magnetoseismology. In this review we will summarize some new trends in the observational study of waves and oscillations, discussing their origin and their propagation through the atmosphere. In particular, we will focus on waves and oscillations in open magnetic structures (e.g., solar plumes) and closed magnetic structures (e.g., loops and prominences), where there have been a number of observational highlights in the past few years. Furthermore, we will address observations of waves in filament fibrils allied with a better characterization of their propagating and damping properties, the detection of prominence oscillations in UV lines, and the renewed interest in large-amplitude, quickly attenuated, prominence oscillations, caused by flare or explosive phenomena.  相似文献