Study of vertical structure of aerosol optical properties with sun photometers and ceilometer during the MACRON campaign in 2007

This paper presents the measurements of a vertical structure of aerosol optical properties performed during the MACRON (Maritime Aerosol, Clouds and Radiation Observation in Norway) campaign, which took place in July and August 2007 at ALOMAR observatory on Andøya island (69.279°N, 16.009°E, elevation 380 m a.s.l.). The mean value of the aerosol optical thickness (AOT) at 500 nm during campaign was 0.12. Significant increase of the AOT above longtime mean value was observed on 7 and 8 August 2007 when the AOT exceeded 0.4 at 500 nm. Analyses of back trajectories show the aerosol transported from over Africa and Central Europe. The aerosol extinction coefficient obtained from the synergy of ceilometer and sun photometer observations reached 0.05–0.08 km^?1 (at 1064 nm) in the dust layer. The single scattering albedo at the ALOMAR observatory decreased during the dust episode to 0.93–0.94, which indicates some absorptive aerosols in the lower PBL.     

Cytochrome P450 1A1 expression in cetacean skin biopsies from the Indian Ocean

The study describes cytochrome P450 1A1 (CYPA1) expression in the skin of different cetacean species (Megaptera novaeangliae, n = 15; Stenella attenuata, n = 7 and Stenella longirostris, n = 24) from the Mozambique Channel island of Mayotte. Immunohistochemical examination was performed with a monoclonal antibody against scup cytochrome CYPA1. The sex was determined using a molecular approach consisting in the genotyping sex-specific genes. CYPA1 was detected at the junction between epidermis and blubber on dolphins only, mostly in the endothelial cells. Similar observation was obtained in the dermis of one M. novaeangliae. Immunohistochemical slides were scored to evaluate the expression of the CYPA1 and a higher expression was observed in S. longirostris, suggesting a higher exposure to pollutants for this species. The difference of expression between sexes was not significant.     

Size-dependent uptake of nitrate and ammonium as a function of light in well-mixed temperate coastal waters

The effect of light on nitrate (NO₃⁻) and ammonium (NH₄⁺) uptake by natural communities was investigated in relation to cell size (<10 and >10 μm) in the well-mixed coastal waters of the English Channel. Nitrogen (N) uptake kinetics as a function of irradiance were assessed using ¹⁵N tracer techniques, for a seasonal cycle of populations collected at 50% and 1% light penetration depth. The nitrogen uptake responses to irradiance can be represented by the formulation used to describe the photosynthesis versus irradiance relationships and modified by the addition of a dark uptake parameter. The response curves of two size fractions of phytoplankton collected at 50% and 1% of incident light did not differ significantly, which suggested that the physiological characteristics of N uptake were not affected by the light intensity at which the phytoplankton assemblages were sampled. The kinetics parameters indicated that the NO₃⁻ uptake system was more strongly dependent on light than the NH₄⁺ uptake system. They also showed that N uptake was less limited by the light intensity in the small size fraction than it was in the large size fraction. At the mean light intensity in the water column, kinetics analysis predicted a NH₄⁺ uptake that was on average 1.8 (±0.6) and 2.4 (±1.0) times greater than the NO₃⁻ uptake, for <10 and >10 μm size fractions, respectively. The kinetics also predicted, at the in situ mean light intensity, that the mean ability to take up nitrogen was twice as high (1.8±0.5) for the small than for the large cells when the N substrate was NH₄⁺ and more than twice as high (2.6±1.5) when the substrate was NO₃⁻. These results added to our understanding of the light effect on N uptake processes in well-mixed waters, and can largely explain the phytoplankton production, mainly regenerated and dominated by small cells, that has been observed in these waters.     

Anisotropy of magnetic susceptibility as an indicator for palaeocurrent analysis in folded turbidites (Outer Western Carpathians,Poland)

The anisotropy of magnetic susceptibility is a well-known geological proxy in revealing the directional tectonic and sedimentological features of rocks, although it can be ambiguous in situations where these two factors co-occur. This paper demonstrates the usefulness of the anisotropy of magnetic susceptibility in determining palaeotransport directions in turbiditic rocks that underwent subsequent thrusting and folding. This study demonstrates that the magnetic lineation is largely unsuitable as a palaeocurrent direction proxy, and suggests that the imbrication of magnetic foliation is better in such cases. Moreover, the anisotropy of magnetic susceptibility results were analyzed in reference to a joint and fold study within the framework of the regional structural geology. Magnetic fabric investigations were conducted in the eastern part of the Outer Western Carpathians (south-east Poland). During the study, a total of 191 oriented palaeomagnetic samples were collected from three outcrops (Nasiczne, Dwernik and Hoczew) in the Krosno Beds, Silesian Unit. For the purpose of sedimentological analysis, 121 m of turbidite successions were documented and 126 directional sedimentary structures were measured. The magnetic anisotropy of sandstones revealed typical sedimentary fabrics, often overprinted by variably intense tectonic deformation. Oblate susceptibility ellipsoids from Nasiczne showed tilt coherent with the palaeoflow direction, whereas the rocks from Dwernik and Hoczew contained triaxial magnetic fabric developed during compressional palaeostress. This paper suggests that medium-grained and coarse-grained sandstones, preferably with high mica content, are the most suitable for palaeotransport reconstructions among the studied lithologies.     

Fluid inclusion and stable isotope (O, H, C, and S) constraints on the genesis of the Serrinha gold deposit, Gurupi Belt, northern Brazil

The Serrinha gold deposit of the Gurupi Belt, northern Brazil, belongs to the class of orogenic gold deposits. The deposit is hosted in highly strained graphitic schist belonging to a Paleoproterozoic (∼2,160 Ma) metavolcano-sedimentary sequence. The ore-zones are up to 11 m thick, parallel to the regional NW–SE schistosity, and characterized by quartz-carbonate-sulfide veinlets and minor disseminations. Textural and structural data indicate that mineralization was syn- to late-tectonic and postmetamorphic. Fluid inclusion studies identified early CO₂ (CH₄-N₂) and CO₂ (CH₄-N₂)-H₂O-NaCl inclusions that show highly variable phase ratios, CO₂ homogenization, and total homogenization temperatures both to liquid and vapor, interpreted as the product of fluid immiscibility under fluctuating pressure conditions, more or less associated with postentrapment modifications. The ore-bearing fluid typically has 18–33mol% of CO₂, up to 4mol% of N₂, and less than 2mol% of CH₄ and displays moderate to high densities with salinity around 4.5wt% NaCl equiv. Mineralization occurred around 310 to 335°C and 1.3 to 3.0 kbar, based on fluid inclusion homogenization temperatures and oxygen isotope thermometry with estimated oxygen fugacity indicating relatively reduced conditions. Stable isotope data on quartz, carbonate, and fluid inclusions suggest that veins formed from fluids with δ¹⁸O_H2O and δD_H2O (310–335°C) values of +6.2 to +8.4‰ and −19 to −80‰, respectively, which might be metamorphic and/or magmatic and/or mantle-derived. The carbon isotope composition (δ¹³C) varies from −14.2 to −15.7‰ in carbonates; it is −17.6‰ in fluid inclusion CO₂ and −23.6‰ in graphite from the host rock. The δ³⁴S values of pyrite are −2.6 to −7.9‰. The strongly to moderately negative carbon isotope composition of the carbonates and inclusion fluid CO₂ reflects variable contribution of organic carbon to an originally heavier fluid (magmatic, metamorphic, or mantle-derived) at the site of deposition and sulfur isotopes indicate some oxidation of the originally reduced fluid. The deposition of gold is interpreted to have occurred mainly in response to phase separation and fluid-rock interactions such as CO₂ removal and desulfidation reactions that provoked variations in the fluid pH and redox conditions.     

Flood Forecasting and Warning at the River Basin and at the European Scale

Application of recent advances in numerical weather prediction (NWP) has the potential of allowing delivery of flood warning to extend well beyond the typical lead times of operational flood warning at the river basin scale. A prototype system, a European Flood Forecasting System (EFFS) developed to deliver such pre-warnings, aiming at providing a pre-warning at lead times of between 5 and 10 days is described. Considerable uncertainty in the weather forecast at these lead times, however, means that resulting forecasts must be treated probabilistically, and although probabilistic forecasts may be easy to disseminate, these are difficult to understand. This paper explores the structure of operational flood warning, and shows that integration in the flood warning process is required if the pre-warning is to fulfil its potential. A simple method of summarising the information in the pre-warning is presented, and the system in hindcast mode is shown to give clear indication of an upcoming major event in the Rhine basin up to 10 days before the actual event. Finally recommendations on the use of data assimilation to embed the EFFS system within an operational environment are given.     

Construction of the casa grande by sequential high precision C-14 dating

Two composite radiocarbon dates on wood beams from a unique, prehistoric building in southern Arizona are the result of growth series subsampling of the beams and statistical evaluation of radiocarbon dates on the subsamples. This procedure avoids some of the problems caused by secular variations in the biospheric ¹⁴C activity and by the dating of specimens grown over a range of years. This procedure yields results similar to more precise tree-ring dates from other sites in the southwestern United States. The procedure illustrated here is applicable to any archaeological tree specimen consisting of at least the last 40 growth rings.     

Effects Of Changing Surface Heat Flux On Atmospheric Boundary-Layer Flow Over Flat Terrain

We examine the unsteady response of a neutral atmospheric boundary layer (ABL) of depth h and friction velocity u _* when a uniform surface heat flux is applied abruptly or decreased rapidly over a time scale t<inf>θ</inf> less than about h /(10u _*). Standard Monin–Obukhov (MO) relationships are used for the perturbed eddy viscosity profile in terms of the changes to the heat flux and mean shear. Analytical solutions for changes in temperature, mean wind and shear stress profile are obtained for the surface layer, when there are small changes in h /|L_MO| over the time scale t_MO~|L _MO|/(10u_*) (where L _MO and t _MO are the length and time scales, respectively). They show that a maximum in the wind speed profile occurs at the top of the thermal boundary layer for weak surface cooling, i.e. a wind jet, whereas there is a flattening of the profile and no marked maximum for weak surface heating. The modelled profiles are approximately the same as those obtained from the U.K. Met Office Unified Model when operating as a mesoscale model at 12-km horizontal resolution. The theoretical model is modified when strong surface heating is suddenly applied, resulting in a large change in h /|L _MO| (>>1), over the time scale t _MO. The eddy structure is predicted to change significantly and the addition of convective turbulence increases the shear turbulence at the ground. A low-level wind jet can form, with convective turbulence adding to the mean momentum of the flow. This was verified by our laboratory experiment and direct numerical simulations. Additionally, it is shown that the effects of Coriolis acceleration diminish (rather than as suggested in the literature, amplify) the formation of the wind jets in the situations considered here. Hence, only when the surface heat flux changes over time scales greater than 1/f (where f is the Coriolis parameter) does the ABL adjust monotonically between its equilibrium states. These results are also applicable to the ABL passing over spatially varying surface heat fluxes.     

On the current profile in the German Bight: A two-month BroadBand ADCP time series of high vertical resolution

Summary A bottom mounted BroadBand ADCP was deployed for about two months in the German Bight (54° 15.3′, N, 7° 35.5′ E) at 40 m depth. The ADCP recorded current data and echo intensity between 3 and 38m depth with a vertical resolution of 1 m. The data, which provide continuous vertical current profiles, are investigated with regard to the vertical variations of residual and tidal currents and kinetic energies. To investigate the temporal variability of the current profiles, the time series are subdivided into 8-day intervals. Furthermore, the data are compared with historical data. According to the ADCP profiles, the water column can be subdivided into three layers: A primarily wind-driven near-surface layer (∼10m), a middepth layer with great directional variability, and a near-bottom layer of about 10 m thickness with a strictly logarithmic current profile.

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über das Stromprofil in der Deutschen Bucht: Eine zweimonatige BroadBand ADCP Zeitserie mit hoher vertikaler Aufl?sung

Zusammenfassung Ein am Boden stehender BroadBand ADCP wurde für zwei Monate in der Deutschen Bucht (54° 15.3′ N, 7° 35.5′ E) in 40 m Wassertiefe eingesetzt. Er registrierte Str?mungsdaten und Echointensit?t zwischen 3 und 38 m Wassertiefe mit einer vertikalen Aufl?sung von 1 m. Dieser Datensatz, der kontinuierliche vertikale Stromprofile liefert, wird hinsichtlich der vertikalen Variation von Rest- und Gezeitenstr?men und kinetischer Energie analysiert. Zur Untersuchung der zeitlichen Variabilit?t der Stromprofile wird die Gesamtzeitserie in 8-Tage-Intervalle unterteilt. Ferner werden die Ergebnisse mit historischen Messungen verglichen. Aus den ADCP-Profilen ergibt sich eine prinzipielle Dreiteilung der Wassers?ule: Eine vorwiegend windgetriebene oberfl?chennahe Schicht (∼10m), eine mittlere Schicht mit hoher Richtungsvariabilit?t und eine etwa 10 m m?chtige Bodenschicht mit streng logarithmischem Stromprofil.

     

Dynamic soil–structure interaction of coupled shear walls by boundary element method

For a class of civil engineering structures, that can be accurately represented by ‘coupled shear walls’ (CSWs), a discrete model for the analysis of the dynamic interaction with the underlying soil is proposed. The CSWs, with one or more rows of openings, rest on a rigid foundation embedded in the elastic or viscoelastic half-space. A hierarchical finite element model based on an equivalent continuum approach is adopted for the structure. A frequency-domain boundary element method is used to represent the half-space. Finally, the set of equations governing the response of the coupled soil-structure system to harmonic lateral loads acting on the structure is also given. The frequency deviation effect with respect to the fixed-base structure and the effects of radiation and material damping in the soil are presented for different characteristics of the structure and different soil properties.