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By BERND HEINOLD INA TEGEN MICHAEL ESSELBORN KONRAD KANDLER PETER KNIPPERTZ DETLEF MÜLLER ALEXANDER SCHLADITZ MATTHIAS TESCHE BERNADETT WEINZIERL ALBERT ANSMANN DIETRICH ALTHAUSEN BENOIT LAURENT REAS MASSLING THOMAS MÜLLER REAS PETZOLD KERSTIN SCHEPANSKI ALFRED WIEDENSOHLER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):307-324
The regional dust model system LM-MUSCAT-DES was developed in the framework of the SAMUM project. Using the unique comprehensive data set of near-source dust properties during the 2006 SAMUM field campaign, the performance of the model system is evaluated for two time periods in May and June 2006. Dust optical thicknesses, number size distributions and the position of the maximum dust extinction in the vertical profiles agree well with the observations. However, the spatio-temporal evolution of the dust plumes is not always reproduced due to inaccuracies in the dust source placement by the model. While simulated winds and dust distributions are well matched for dust events caused by dry synoptic-scale dynamics, they are often misrepresented when dust emissions are caused by moist convection or influenced by small-scale topography that is not resolved by the model. In contrast to long-range dust transport, in the vicinity of source regions the model performance strongly depends on the correct prediction of the exact location of sources. Insufficiently resolved vertical grid spacing causes the absence of inversions in the model vertical profiles and likely explains the absence of the observed sharply defined dust layers. 相似文献
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KERSTIN KOLDITZ OLAF DELLWIG JAN BARKOWSKI RAINER BAHLO THOMAS LEIPE HOLGER FREUND HANS‐JÜRGEN BRUMSACK 《Sedimentology》2012,59(2):337-355
The barrier islands of the southern North Sea were formed during the Holocene sea‐level rise. These islands form part of a highly dynamic environment whose evolution continues today. Subjected to sea‐level changes, tides and storm events, the sedimentary record reflects processes occurring under varying energy conditions. This article presents geochemical, mineralogical and diatom investigations carried out in the salt marsh of the East Frisian barrier island of Langeoog, which is re‐exposed to a rising sea‐level due to de‐embankment. The major aim of this study is to improve the knowledge of the sedimentological and geochemical development of these deposits under the influence of sea‐level rise, with a special focus on the geochemistry and distribution of heavy mineral‐associated elements. Correlation diagrams between FeO, TiO2 and MnO, as well as ternary plots (Al2O3–SiO2–Zr or TiO2), clearly indicate the variable appearance of heavy minerals in different lithological facies, comprising marsh soil, mixed and sand flat, and relocated beach sands. A dominating abundance of ilmenite followed by zircon, garnets and some other heavy minerals is evidenced by Scanning Electron Microscope‐Energy Dispersive X‐ray measurements. The data presented here suggests that these geochemical proxies are useful tools for characterizing depositional energy conditions. Increasing depositional energy is evident for the lithological units in the following order: marsh soil, mixed flat, sand flat and relocated beach sand. The energetic conditions during sediment deposition, as well as the sedimentary history, are confirmed by diatom analyses as an additional independent indicator. Depending on source rock composition, the geochemical parameters used in this study may also help to investigate depositional energy regimes of other siliciclastic sedimentary systems. 相似文献
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Dust mobilization and transport in the northern Sahara during SAMUM 2006 – a meteorological overview
By PETER KNIPPERTZ ALBERT ANSMANN DIETRICH ALTHAUSEN DETLEF MÜLLER MATTHIAS TESCHE EIKE BIERWIRTH TILMAN DINTER THOMAS MÜLLER WOLFGANG VON HOYNINGEN-HUENE KERSTIN SCHEPANSKI MANFRED WENDISCH BERND HEINOLD KONRAD KANDLER REAS PETZOLD LOTHAR SCHÜTZ INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):12-31
The SAMUM field campaign in southern Morocco in May/June 2006 provides valuable data to study the emission, and the horizontal and vertical transports of mineral dust in the Northern Sahara. Radiosonde and lidar observations show differential advection of air masses with different characteristics during stable nighttime conditions and up to 5-km deep vertical mixing in the strongly convective boundary layer during the day. Lagrangian and synoptic analyses of selected dust periods point to a topographic channel from western Tunisia to central Algeria as a dust source region. Significant emission events are related to cold surges from the Mediterranean in association with eastward passing upper-level waves and lee cyclogeneses south of the Atlas Mountains. Other relevant events are local emissions under a distinct cut-off low over northwestern Africa and gust fronts associated with dry thunderstorms over the Malian and Algerian Sahara. The latter are badly represented in analyses from the European Centre for Medium–Range Weather Forecasts and in a regional dust model, most likely due to problems with moist convective dynamics and a lack of observations in this region. This aspect needs further study. The meteorological source identification is consistent with estimates of optical and mineralogical properties of dust samples. 相似文献
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The genesis of nodular limestones in the Ordovician and Silurian of the Oslo Region (Norway) 总被引:1,自引:0,他引:1
Nodular limestones have been studied from the Lower Chasmops Shale (Middle Ordovician) and the Rytteráker Formation (Lower Silurian). Observations on nodule-host-rock relations and variations of ferroan/non-ferroan calcite cements help explain the role of precipitation, dissolution and redistribution of carbonate. Distribution and frequency of nodules depends on environmental parameters such as carbonate/clay ratio, grain size distribution and bioturbation, though final shapes are the result of pressure-dissolution and cleavage. 相似文献
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