Quality Assurance of Hydrocarbon Measurements for the German Tropospheric Research Focus (TFS)

In the German Focus on Tropospheric Research (TFS) independent quality assurance procedures were implemented in order to obtain information on data quality and comparability of the different measurements made in the different field campaigns. This paper describes the results for measurements of hydrocarbons using in-situ gas chromatographictechniques and off line analysis of samples collected in canisters (analysed by two central laboratories CL-1 and CL-2) and samples collected on adsorption tubes. The QA-procedures included comparisons with synthetic standards (prepared by EN 45001 certified laboratories), absolute calibration with a diffusion source, and an instrument/methodology comparison in ambient air. Harmonisation of the ambient measurements was achieved with a complex mixture (NCAR/BERLIOZ) containing 70 commonly observed hydrocarbons at mixing ratios of 0.2 to 10 ppb (mole fraction) in nitrogen, which was calibrated by referencing to hydrocarbon standards of the National Institute for Standards and Technology (NIST).For the certified synthetic standards, the experienced groups agreed to within ± 20% for most compounds. Much larger discrepancies were observed for the new Airmotec HC2010 instruments due to problems with identification, co-elution and blanks/memory effects. The results in ambient air were similar: Reasonable agreement was found for the results from the experienced groups with well characterised in situ instruments andfor the charcoal tubes, whereas larger discrepancies were observed for the results from new groups and instruments. For the latter, only selected compounds met the data quality objectives (DQO). The canister samples analysed by CL-2 were in good agreement with the reference instrument, whereas large deviations were found for a number of compounds in the analysis of the same canisters by CL-1. The results of the comparison provided the final basis for flagging and harmonising the data from all participants prior to their submission to the TFS central data bank.     

Tests of phase center variations of various GPS antennas, and some results

Phase variations of GPS receiving antennas are a significant error component in precise GPS applications. A calibration procedure has been developed by Geo++ and the Institut für Erdmessung, which directly determines absolute phase center variations (PCVs) without any multipath influence by field measurements. The precision and resolution of the procedure allows the determination of reliable azimuthal variations. PCV may affect long-term static GPS differently than real-time GPS, depending on the applications. At the same time, different antenna types are involved. Less investigations have been done on absolute PCV of rover antennas than on geodetic antennas which, however, becomes more important due to the mixed antenna situation in GPS reference networks and RTK networks. The concepts of the absolute PCV field calibration are summarized and emphasis is placed on a variety of absolute PCV patterns of geodetic and rover antennas. Electronic Publication     

Ein Differenzengleichungssystem zur Ermittlung instationärer Bewegungen in einem Meer mit geringer Turbulenzreibung

Zusammenfassung Es wird ein auf Probleme der dynamischen Meteoro-Hydrographie erfolgreich angewandtes Differenzengleichungssystem er?rtert, dessen numerische Stabilit?t, unabh?ngig von der geographischen Breite, auch bei gro?er Tiefe und sehr kleinem Horizontaldiffusionskoeffizienten gew?hrleistet ist. Für Anwendungen auf meridional stark ausgedehnte Ozeane, z. B. bei Gezeitenrechnungen, werden die durch Verwendung von Kugelkoordinaten erforderlichen Erweiterungen abgeleitet.

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A system of finite difference equations for computations of instationary motions in an ocean with small eddy viscosity

Summary A system of finite difference equations successfully applied to some problems of dynamical meteoro-hydrography is discussed. Its numerical stability may also be fitted in cases of very small horizontal eddy diffusity and large depths independend of the latitude. For the purpose of applications to meridionally far extended oceans, for instance when dealing with tidal computations, the necessary completations due to the employment of spherical polar coordinates are derived.

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Un système d'équations aux différences finies permettant le calcul de mouvements non stationnaires dans une mer à faible frottement de turbulence

Résumé On discute d'un système d'équations aux différences finies appliqué avec succès à des problèmes de météoro-hydrographie dynamique. Du fait de sa stabilité numérique, indépendante de la latitude, ce système reste également valable dans le cas des grandes profondeurs et pour de très faibles coefficients de diffusion horizontale. Pour ses applications dans les océans à grande extension méridienne, par exemple aux calculs de marées, on en tire les développements que nécessite l'emploi de coordonnées sphériques.

     

Planktic foraminiferal and 13C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

 The interval spanning the Paleocene–Eocene (P/E) transition in the Possagno section consists of 1 m of red marls, including a 4-cm-thick, dark-red "dissolution" clay, which represents the Paleocene/Eocene boundary event. The Possagno section is much more condensed than other Tethyan and North Atlantic sections previously studied; however, in this section the most significant biotic, isotopic and sedimentological events across the P/E boundary can be recognized. The Possagno section spans the following planktic foraminiferal subzones: upper part of M. gracilis Subzone, A. berggreni Subzone, A. sibaiyaensis Subzone and probably lowermost part of P. wilcoxensis Subzone. The quantitative analysis indicates a major increase of low-latitude acarininids, including compressed tropical acarininids just above the boundary clay. This acarininid incursion begins just below the boundary clay but reaches its maximum just above the clay. The planktic foraminiferal faunal turnover is gradual except for the acarininid incursion. The isotopic results show a negative excursion in ∂¹³C values at the small benthic foraminifera mass extinction event. The acarininid maximum diversity coincides with this isotopic excursion, and reflects an increase in surface seawater temperature. Despite being very condensed, the Possagno section allows us to further confirm that the different biotic, isotopic and sedimentological events recognized in the Spanish sections (Alamedilla, Campo, Caravaca, Zumaya) are not local in nature and allows the establishment of a detailed chronostratigraphic framework to define the P/E boundary stratotype. Received: 8 April 1998 / Accepted: 12 April 1999     

The influence of the solar atmospheric stratification on the structure of the acoustic wave field

We investigate the influence of the solar atmospheric temperature stratification on the amplitude of waves at different heights and its dependence on frequency and wave number. Special interest is taken in the influence of atmospheric layers on the appearence of the recently observed p-mode crossing features and their location in the Fourier domain. We consider four stratification models. One of them is the standard model with convection-zone, VAL-atmosphere and corona. The others are modifications of this model in order to discuss the influence of specific layers of the atmosphere. The changes in the temperature structure significantly influence the velocity amplitude at certain frequency-wave number combinations at certain heights.     

The major features of the crustal structure in north-eastern Venezuela from deep wide-angle seismic observations and gravity modelling

Venezuela is located on the plate boundary zone between the South American continent and the Caribbean plate. A relative movement of 2 cm/year is accommodated by a system of strike–slip faults running from the Andes to the Gulf of Paria. The Interior Range, a moderate-height mountain range, separates the Oriental Basin from the Caribbean. To the south, predominantly Precambrian rocks are outcropping in the Guayana Shield south of the Orinoco River. Results of deep wide-angle seismic measurements for the region were obtained during field campaigns in 1998 (ECOGUAY) for the Guayana Shield and in 2001 (ECCO) for the Oriental Basin. The total crustal thickness decreases from 45 km beneath the Guayana Shield, to 39 km at the Orinoco River, and 36 km close to El Tigre, in the center of the Oriental Basin. The average crustal velocity decreases in the same sense from 6.5 to 5.95 km/s. Detailed information was obtained on the velocity distribution within the Oriental Basin. Velocities are as low as 2.2 km/s for the uppermost 2 km, 4.5 km/s down to 4 km in depth, and a maximum depth of 13 km was derived for material with seismic velocities up to 5.9 km/s, interpreted as the base of the sedimentary basin. A gravimetric model confirms the structures derived from the seismic data. Discrete increases in sedimentary thickness along the basin may be associated to extension processes during the passive margin phase in the Cretaceous, or during earlier extension phases.     

Liquefied vs stratified sediment mobilization processes: Insight from the South of the Barbados accretionary prism

This paper discusses the nature and origin of subsurface sediment mobilization processes in deep marine clay-rich environments. In the studied area of the southern Barbados accretionary prism, new geophysical acquisitions have emphasized the spectacular widespread development of mud volcanoes that are well-developed along ramp anticlines and along sigmoidal rises with trends that are oblique to the axes of the main folds of the accretionary wedge. On some active mud volcanoes, heat-flow measurements show high positive anomalies related to high fluxes of mud transfer. The mobilized solid fraction expelled by the mud volcanoes does not originate from a unique source bed but from various formations pierced by the mud conduits and is driven by the water phase. The area studied also exhibits trends of structures corresponding to sub-circular massive local uplifts of deformed but well-preserved stratified sediments (turbidites and hemipelagics). No piercing shale diapirs have been encountered in this area. Some of these local uplift structures are complicated by the development of collapses, calderas, and superimposed mud volcanoes. Mud volcanism corresponds fundamentally to fluid displacement (water and gas), whereas massive sedimentary uplift corresponds to large vertical displacements of stratified solid levels but for which the deep cause could be partly the intrusion of mud plugs. Both are dynamic phenomena controlled by the development of overpressure at depth, contributing to sedimentary mobilizations.