OH-initiated degradation of several hydrocarbons in the atmosphere simulation chamber SAPHIR

Degradation of isoprene, m-xylene, n-octane, propene, and methacrolein by hydroxyl radicals has been studied in the simulation chamber SAPHIR under burden of trace gases as they are typical for the moderately polluted planetary boundary layer. Measured time series of the hydrocarbon mixing ratios and the OH concentrations were used to determine the rate constants. The hydrocarbons were measured with gas chromatography and proton transfer reaction mass spectrometry. OH was measured with the Jülich DOAS (differential optical absorption spectroscopy) instrument. In all cases except methacrolein good agreement was found with the reference rate constants taken from the Master Chemical Mechanism (MCM3.1). The data for methacrolein are consistent with the results of Karl et al. (J. Atmos. Chem 55, 2006, doi:) who reported a 12% smaller value. The degradation of hydrocarbons provides an independent method to analyse precision and accuracy of the OH measurements. A precision of better than 4% over a period of nearly 4 months was found. The accuracy is within the limitations given by the light absorption cross section of OH. Both results are consistent with earlier results by Hausmann et al. (J. Geophys. Res. 102:16011–16022, 1997).     

Determination of the material damping ratio and the shear wave velocity with the Seismic Cone Penetration Test

The Seismic Cone Penetration Test (SCPT) is used to determine the variation with depth of the shear (and longitudinal) wave velocity at various sites in Belgium. The cross correlation technique together with a posteriori increase of the sampling frequency proves to be a reliable method to determine wave velocities by the SCPT. Additionally, the Spectral Ratio Slope (SRS) method is applied to Fourier transforms of the measured response to determine the variation of the material damping ratio with depth. This method is applied to synthetic signals computed for three different soil profiles with known characteristics and to the horizontal acceleration time histories that have been measured during SCPT on two sites. The influence of some signal processing techniques commonly applied in the SRS method is studied. A remarkable influence of the window length, applied on the predicted signals, on the computed material damping ratio is found, especially its scattering. It is therefore concluded that the use of a window function should be avoided wherever possible. On one of the two test sites, results of Resonant Column Tests and Free Torsion Pendulum Tests on undisturbed soil samples have been used to evaluate the values of the shear wave velocity and the material damping ratio as obtained in the in situ test.     

Orogenic structure of the Eastern Alps, Europe, from TRANSALP deep seismic reflection profiling

The TRANSALP Group, comprising of partner institutions from Italy, Austria and Germany, acquired data on a 340 km long deep seismic reflection line crossing the Eastern Alps between Munich and Venice. Although the field work was split into four campaigns, between fall 1998 and summer 2001, the project gathered for the first time a continuous profile across the Alps using consistent field acquisition and data processing parameters. These sections span the orogen itself, at its broadest width, as well as the editor Fred Davey and the two adjacent basins. Vibroseis and explosion data, complementary in their depth penetration and resolution characteristics, were obtained along with wide-angle and teleseismic data. The profile shows a bi-vergent asymmetric structure of the crust beneath the Alpine axis which reaches a maximum thickness of 55 km, and 80–100 km long transcrustal ramps, the southward dipping ‘Sub-Tauern-Ramp’ and the northward-dipping ‘Sub-Dolomites-Ramp’. Strongly reflective patterns of these ramps can be traced towards the north to the Inn Valley and towards the south to the Valsugana thrust belt, both of which show enhanced seismicity in the brittle upper crust. The seismic sections do not reveal any direct evidence for the presence of the Periadriatic Fault system, the presumed equivalent to the Insubric Line in the Western Alps. According to our new evolutionary model, the Sub-Tauern-Ramp is linked at depth with remnants of the subducted Penninic Ocean. The ‘crocodile’-type model describes an upper/lower crustal decoupling and wedging of both the European and the Adriatic–African continents.     

Helmet Streamers with Triple Structures: Weakly Two-Dimensional Stationary States

Recent observations of the solar corona with the LASCO coronagraph on board the SOHO spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum, which occasionally go unstable and give rise to particularly huge coronal mass ejections. We present a method to calculate (semi-)analytically self-consistent stationary configurations of triple helmet streamers which can serve as input for stability considerations and dynamical calculations. The method is based on an asymptotic expansion procedure using the elongated structure of the streamers. The method is very flexible and can be used in both Cartesian and spherical geometry. We discuss the effects of magnetic shear, gravity and field-aligned flow on open field lines. Example solutions illustrating the influence of each of these features on the solution structure are presented.     

On the quantitative importance of heterotrophic microplankton in the northern German Wadden Sea

To assess the importance of heterotrophic microplankton in the Wadden Sea, seasonal distribution and biomass of the main subgroups, that is, heterotrophic dinoflagellates, (separated into thecate and athecate forms), tintinnids, and aloricate ciliates, were studied in 1989 and 1990 in a total of six surveys covering the whole area of the northern German Wadden Sea. Heterotrophic microplankton biomass exhibited high spatial and temporal variation, ranging from 0 μg Cl^?1 to 66 μg Cl^?1, with maximum concentrations in spring., Mean stocks were lowest in winter (1.6 μg Cl^?1) and highest in spring (11.7 μg Cl^?1); intermediate concentrations were found in summer (8.5 μg Cl^?1). In winter, the heterotrophic microplankton was dominated by tintinnids. In spring and summer, aloricate ciliates and dinoflagellates made up the largest part of the biomass. A pronounced feature was a shift within the dinoprotist group from athecate to thecate forms in summer. In spring, maxima of athecate dinoflagellate carbon were associated with blooms ofPhaeocystis globosa, indicating a close trophic relationship. From rough estimates of the daily grazing potential, based on microheterotrophic biomass and conversion factors from the literature, it may be concluded that heterotrophic microplankton temporarily share a main role in the transfer of food and energy to higher trophic levels within the pelagic system of the Wadden Sea.     

Population and rangelands in Central Tibet: a GIS-Based Approach

This study focuses on the meso-regional pattern of rangeland ecotypes in Central Tibet in relation to population density. Data on rangelands derive from a recent land-cover GIS database of China based on the 1:1,000,000 Land Use Map of China. Specific kinds of grassland and steppe are analyzed in relation to 466 township-level enumeration units selected from China's 1990 census in the Tibetan Autonomous Region. This methodology offers a finer geographic resolution than in all other available research reports, and results in a more detailed understanding of the kinds of rangeland resources available to Central Tibetan communities. Systemic land cover patterns are mapped, and reveal the importance of local interactions between population and rangeland ecotypes. Alpine meadow and alpine steppe predominate above the cultivation limit at approximately 4,200 m. In the densely settled valleys below this limit, dry steppe and scrub grassland predominate.     

The use of teleseismic P-wave complexity for seismic event screening – results determined from GRF and GERESS array data

Seismic data recorded at the broad-band teleseismic GRF array and theshort-period regional GERESS array, which is a designated IMS primarystation, are analyzed to determine the effectiveness of teleseismic P-wave complexity for the purpose of seismic event screening within theframework of Comprehensive Nuclear-Test-Ban Treaty verification. For theGRF array, seismic waveform data from nearly 200 nuclear explosions havebeen recorded since its installation in the late 1970's, which were studiedalong with several thousand earthquakes from the last few years.Additionally, we investigated teleseismic P wave complexity for a similarnumber of earthquakes recorded at GERESS. However, owing to itsoperation starting in 1991, only a limited number of nuclear explosionseismograms are available for study.For nuclear explosions, complexity does not exceed levels of 0.3 except fora number of events from the Nevada Test Site recorded only at the GRFarray and located at a large distance where PcP may interfere with the initialP wavelet. Since all events with complexity at GRF larger than 0.3 areexclusively located on Pahute Mesa within the Nevada Test Site,near-source geology or topography must play a dominant role for theseincreased complexity values, while PcP may not contribute significantly tothe high-frequency energy measured by the complexity parameter.Although many earthquakes show complexities below this level, for morethan 25% of the earthquakes investigated the complexities determined arelarger than 0.7, thus showing distinctly larger values than nuclearexplosions. Therefore, this percentage may be screened as earthquakes fromall seismic events detected. As currently only about half of the eventsdetected by the global IMS network are screened out based on focal depthand the m _b :M _s criterion, teleseismic P-wavecomplexity may contribute significantly to the task of seismic eventscreening.     

Neue Beobachtungen zur Paläogeographie des Devon auf dem brasilianischen Block

Zusammenfassung Neuere Beobachtungen im Jatobá-Becken (Pernambuco — Brasilien), dem nördlichsten Ausläufer der Reconcavo-Zone von Bahia haben überraschenderweise dort eine Vertretung von Unterdevon und unterstem Unterkarbon ergeben. Das Cariri-Konglomerat im Liegenden der kretacischen Araripe-Serie (West-Pernambuco) muß nach neuen Beobachtungen ebenfalls ins Unterdevon eingereiht werden. Gleiches gilt für den stratigraphisch bisher in der Luft hängenden Tombador-Sandstein im zentralen Bahia, dessen Profil weitgehend dem Unterdevon-Profil von Piaui entspricht. Die Devondecke auf dem nordöstlichen Teil des brasilianischen Blockes war ursprünglich viel ausgedehnter als bisher vermutet werden konnte. Eigenartig ist die auf die weiten Entfernungen gleichförmige grobklastische Fazies auch in offensichtlich küstenferneren Bereichen, die kaum eine andere Deutung als driftglaziale Einflüsse im Unterdevon-Meer zuläßt, was früher auch schonMaack für das Unterdevon in Paraná vermutet hatte. Die aus paläomagnetischen Messungen erschlossene Lage des brasilianischen Blockes während des Devon stimmt damit gut überein.

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Recent observations in the basin of Jatobá (Pernambuco — Brasil), the extreme northern end of the Reconcavo-Zone of Bahia, resulted in the surprising discovery of Subdevonian and lowest Carboniferous. Recent studies also found out that the Cariri-conglomerat in the underlying bed of the cretaceous Araripe-series (West-Pernambuco) must also be classified in the Subdevonian, as well as the Tombador sandstone in central Bahia, whose profil resembles that of the Subdevonian of Piaui. The Devonian nappe on the north-eastern part of the Brasilian block was originally much larger than it has been assumed. The clastic facies even in regions far from the coast, is very strange. It can only be interpreted as glacial deposits in the subdevonian ocean, a suggestion which has already been made byMaack for the Subdevonian in Paraná. This agrees with the situation of the Brasilian block during the Devonian, infered from paleomagnetic measurements.

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Resumen Conforme as observações mais recentes há uma representação do Devoniano inferior e do Carbonífere mais inferior na bacia de Jatobá (Pernambuco — Brasil), a extremidade setentrional da zone de Revoncavo. O conglomerado de Cariri na lapa da série Araripe, deve ser atribuido ao Devoniano inferior conforme observações recentes. O arenito Tombador da Bahia, cujo perfil corresponde muito bem ao do Devoniano inferior de Piaui, tern a mesma posição estratigráfica. No bloco brasileiro, a capa, devoniana era originalmente muito mais extensa do que se supôs até agora. A fácies clástica, muito monótona por todas estas amplas áreas, é um fenomeno muito estranho que pode ser interpretado só pela idéia que no mar devoniano houve gelo flutuante. No Devoniano do Paraná, R.Maack pronunciou a mesma idéia. As medições paleomagnéticas indicam uma posição do bloco brasileiro durante o Devoniano, que bem corresponde a esta interpretação.

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