Eddy-Covariance Flux Measurements in the Complex Terrain of an Alpine Valley in Switzerland

We measured the surface energy budget of an Alpine grassland in highly complex terrain to explore possibilities and limitations for application of the eddy-covariance technique, also for CO₂ flux measurements, at such non-ideal locations. This paper focuses on the influence of complex terrain on the turbulent energy measurements of a characteristic high Alpine grassland on Crap Alv (Alp Weissenstein) in the Swiss Alps during the growing season 2006. Measurements were carried out on a topographic terrace with a slope of 25^◦ inclination. Flux data quality is assessed via the closure of the energy budget and the quality flag method used within the CarboEurope project. During 93% of the time the wind direction was along the main valley axis (43% upvalley and 50% downvalley directions). During the transition times of the typical twice daily wind direction changes in a mountain valley the fraction of high and good quality flux data reached a minimum of ≈50%, whereas during the early afternoon ≈70% of all records yielded good to highest quality (CarboEurope flags 0 and 1). The overall energy budget closure was 74 ± 2%. An angular correction for the shortwave energy input to the slope improved the energy budget closure slightly to 82 ± 2% for afternoon conditions. In the daily total, the measured turbulent energy fluxes are only underestimated by around 8% of net radiation. In summary, our results suggest that it is possible to yield realistic energy flux measurements under such conditions. We thus argue that the Crap Alv site and similar topographically complex locations with short-statured vegetation should be well suited also for CO₂ flux measurements.     

The Cretaceous of the Eastern Bangong-Nujiang Suture Zone (Tibet):Tectono-Sedimentation

1IntroductionThe Tibet plateau consists of terranes which were accreted in a southward-younging succession from Late Permian to Mid-Eocene (Dewey etal., 1988; Mattern etal., 1998; Mattern and Schneider, 2000). The Songpan-Ganzi terrane was accreted to the Kunlun during Late Permian along Kunlun-Qin-ling suture. The Qiangtang block was added onto the Songpan-Ganzi terrane at the Jinsha suture dur-ing Late Triassic-Early Jurassic. The Lhasa block became attached to the Qia…     

Deep versus shallow origin of gravity anomalies, topography and volcanism on Earth, Venus and Mars

The relation between gravity anomalies, topography and volcanism can yield important insights about the internal dynamics of planets. From the power spectra of gravity and topography on Earth, Venus and Mars we infer that gravity anomalies have likely predominantly sources below the lithosphere up to about spherical harmonic degree l=30 for Earth, 40 for Venus and 5 for Mars. To interpret the low-degree part of the gravity spectrum in terms of possible sublithospheric density anomalies we derive radial mantle viscosity profiles consistent with mineral physics. For these viscosity profiles we then compute gravity and topography kernels, which indicate how much gravity anomaly and how much topography is caused by a density anomaly at a given depth. With these kernels, we firstly compute an expected gravity-topography ratio. Good agreement with the observed ratio indicates that for Venus, in contrast to Earth and Mars, long-wavelength topography is largely dynamically supported from the sublithospheric mantle. Secondly, we combine an empirical power spectrum of density anomalies inferred from seismic tomography in Earth’s mantle with gravity kernels to model the gravity power spectrum. We find a good match between modeled and observed gravity power spectrum for all three planets, except for 2?l?4 on Venus. Density anomalies in the Venusian mantle for these low degrees thus appear to be very small. We combine gravity kernels and the gravity field to derive radially averaged density anomaly models for the Martian and Venusian mantles. Gravity kernels for l?5 are very small on Venus below ≈800 km depth. Thus our inferences on Venusian mantle density are basically restricted to the upper 800 km. On Mars, gravity anomalies for 2?l?5 may originate from density anomalies anywhere within its mantle. For Mars as for Earth, inferred density anomalies are dominated by l=2 structure, but we cannot infer whether there are features in the lowermost mantle of Mars that correspond to Earth’s Large Low Shear Velocity Provinces (LLSVPs). We find that volcanism on Mars tends to occur primarily in regions above inferred low mantle density, but our model cannot distinguish whether or not there is a Martian analog for the finding that Earth’s Large Igneous Provinces mainly originate above the margins of LLSVPs.     

Properties of atmospheres and winds of H-deficient central stars and related objects

According to latest results presented at this workshop, it appears that thesurface chemistry of hydrogen-deficient post-AGB stars can now be explained byevolutionary calculations involving a late He-shell flash. A quantitativecomparison of theoretical predictions with observed element abundances caneventually constrain details of this evolutionary scenario. I will emphasizehere the diverse chemical compositions observed in H-deficient post-AGB stars,which call for an explanation. The abundance patterns vary from almost purehelium atmospheres to hydrogen- and helium-free atmospheres, with a richchoice of compositions in between, involving rather different mixtures of H,He, and CNO.     

Der offene Sternhaufen M6 (NGC 6405)

The open star cluster M6 (NGC 6405) is investigated by strip counts on reproductions of the chart of Vleeming (1974). The results are collected in Part 3.

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Mitteilungen Serie A.     

UV spectroscopy of the hot bare stellar core H1504+65 with the HST Cosmic Origins Spectrograph

We present new ultraviolet spectra of the hottest known, peculiar white dwarf H1504+65, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. H1504+65 is the hottest known white dwarf (T _eff=200 000 K) and has an atmosphere mainly composed by carbon and oxygen, augmented with high amounts of neon and magnesium. This object is unique and the origin of its surface chemistry is completely unclear. We probably see the naked core of either a C–O white dwarf or even a O–Ne–Mg white dwarf. In the latter case, this would be the first proof that such white dwarfs can be the outcome of single-star evolution. The new observations were performed to shed light on the origin of this mysterious object.     

World space observatory-ultraviolet among UV missions of the coming years

Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity imaging and high/low resolution spectroscopy from the middle of the decade.     

Experimental hydrothermal alteration of basaltic glass with relevance to Mars

Phyllosilicates, carbonates, zeolites, and sulfates on Mars give clues about the planet's past environmental conditions, but little is known about the specific conditions in which these minerals formed within the crust and at the surface. The aim of the present study was to gain increased understanding on the formation of secondary phases by hydrothermal alteration of basaltic glass. The reaction processes were studied under varying conditions (temperature, pCO₂, water:rock ratio, and fluid composition) with relevance to aqueous hydrothermal alteration in fully and partly saturated Martian basalt deposits. Analyses made on reaction products using X‐ray diffraction (XRD) and scanning electron microscope (SEM) were compared with near infrared spectroscopy (NIR) to establish relative detectability and spectral signatures. This study demonstrates that comparable alteration minerals (phyllosilicates, carbonates, zeolites) form from vapor condensing on mineral surfaces in unsaturated sediments and not only in fully water‐saturated sediments. In certain environments where water vapor might be present, it can alter the basaltic bedrock to a suite of authigenic phases similar to those observed on the Martian surface. For the detection of the secondary phases, XRD and SEM‐EDS were found to be superior to NIR for detecting and characterizing zeolites. The discrepancy in detectability of zeolites between NIR and XRD/SEM‐EDS might indicate that zeolites on Mars are more abundant than previously thought.     

Late Miocene paleoenvironment of the Lambert Graben embayment, East Antarctica, evident from: Mollusc paleontology, sedimentology and geochemistry

The Upper Miocene (10.7–9.0 Ma) Battye Glacier Formation was deposited 250 km inland from the modern Amery Ice Shelf edge in Prydz Bay, East Antarctica. The composition of clay minerals distinguishes a Lower Member, which reflects regional erosion of Precambrian metamorphic basement, from an Upper Member, which records increased erosion of local Permian–Triassic Amery Group strata. The Upper Member was deposited in an ice-proximal environment akin to the modern fjords of East Greenland, with substantial diamict deposition resulting from melting iceberg discharge. The Lower Member was deposited in an ice-distal environment and included the accumulation of the fossil-bearing McLeod Beds. The McLeod Beds contain much siliceous biogenic sediment (≤ 15% opal), which is rare to absent in the predominantly hemipelagic mud of modern East Greenland fjords. The McLeod Beds also contain largely monospecific in situ Hiatella sp. mollusc assemblages suggestive of environmental stress, potentially caused by low salinity melt-water and a high input of terrigenous sediment, which excluded most other benthic taxa. Geochemical results from primary aragonite in Hiatella shells imply large freshwater input into the marine environment during mollusc growth, causing low δ¹⁸O, Na, Mg and high Fe values. The present study indicates that iceberg melt-water influence entering the marine environment was greater during the Late Miocene than today around Antarctica, and documents the paleoenvironment associated with a discrete period of ice margin retreat and marine incursion into the Lambert embayment.