Deriving characteristic parameters of the convective boundary layer from sodar measurements of the vertical velocity variance     

Petra Seibert  Matthias Langer 《Boundary-Layer Meteorology》1996,81(1):11-22

This paper deals with the derivation of the convective mixing height and the characteristic convective velocity w _* from profiles of _w measured by sodar. The parameters were obtained by fitting an analytical profile to the observed data. Results were compared with values obtained by the meteorological preprocessor of a dispersion model and from noon radiosoundings. In addition, a Monte Carlo method was applied to study the influence of measurement errors. It turned out that it is inherently difficult to determine the depth of deep mixed layers from sodar measurements with a limited range, although the determination of w _* should be possible. However, a significant underestimation of _w , and thus w _*, was found, which is probably due to disproportional sampling of updrafts and downdrafts.  相似文献   

A Simplified Analytical Procedure for the Determination of Organically Bound Halogens in Salt‐containing Water Samples     

Helko Borsdorf  Petra Fiedler  Dorit Wilke  Holger Weiß 《洁净——土壤、空气、水》2003,31(1):19-24

A method was developed for the determination of organic halogens in water samples with the aim of minimizing matrix effects and simplifying the sample preparation technique commonly used. The method is based on the adsorption of organic halogens in modified hydrophilic divinylbenzene polymer columns and their elution with methanol. The adsorbent used enables rapid adsorption and desorption due to comparatively high operating flow rates and minimized solvent amounts. Furthermore, no additional reconcentration steps are needed. The methanol extract obtained is combusted with a standard EOX (extractable organic halogen) analyzer and the concentration of organically bound halogens is determined by microcoulometric analysis. The matrix effects are considerably reduced compared to the standard procedure (EN 1485) commonly used. A detection limit of 13 μg/L was established.  相似文献   

Thermodynamic mixing properties of Mg(Al,Cr)2O4 spinel crystalline solution at high temperatures and pressures     

Yastami Oka  Petra Steinke  Niranjan D. Chatterjee 《Contributions to Mineralogy and Petrology》1984,87(2):196-204

Three Al-Cr exchange isotherms at 1,250°, 1,050°, and 796° between Mg(Al, Cr)₂O₄ spinel and (Al, Cr)₂O₃ corundum crystalline solutions have been studied experimentally at 25 kbar pressure. Starting from gels of suitable bulk compositions, close approach to equilibrium has been demonstrated in each case by time studies. Using the equation of state for (Al, Cr)₂O₃ crystalline solution (Chatterjee et al. 1982a) and assuming that the Mg(Al, Cr)₂O₄ can be treated in terms of the asymmetric Margules relation, the exchange isotherms were solved for Δ G ^*, and . The best constrained data set from the 1,250° C isotherm clearly shows that the latter two quantities do not overlap within three standard deviations, justifying the choice of asymmetric Margules relation for describing the excess mixing properties of Mg(Al, Cr)₂O₄ spinels. Based on these experiments, the following polybaric-polythermal equation of state can be formulated: , P expressed in bars, T in K, G _m ^ex and W _G,i ^Sp in joules/mol. Temperature-dependence of G _m ^ex is best constrained in the range 796–1,250° C; extrapolation beyond that range would have to be done with caution. Such extrapolation to lower temperature shows tentatively that at 1 bar pressure the critical temperature, T _c, of the spinel solvus is 427° C, with dT_c/dP≈1.3 K/kbar. The critical composition, X _c, is 0.42 , and changes barely with pressure. Substantial error in calculated phase diagrams will result if the significant positive deviation from ideality is ignored for Al-Cr mixing in such spinels.  相似文献   

Supporting large-scale hydrogeological monitoring and modelling by time-variable gravity data   总被引：1，自引：0，他引：1  

Andreas Güntner  Roland Schmidt  Petra Döll 《Hydrogeology Journal》2007,15(1):167-170

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Auswirkungen des Ablassens von Hochwasserrückhaltebecken auf deren Limnochemie und Phytoplankton-Biozönose     

Susanne Maier  Klaus Zintz  Jürgen Bhmer  Petra Sterk  Hinrich Rahmann 《Limnologica》2001,31(3):239

Reservoirs have to be released when repairing of the dams is necessary. In 1995, two reservoirs in Baden-Württemberg (Germany) of similar age and volume (Lake Herrenbach near Göppingen, 1.0 Mio. m³ and Lake Breitenau near Heilbronn, 2.3 Mio. m³) were emptied. This allowed the singular possibility to investigate the effects of drainage and refilling on the limnochemistry and the phytoplankton biocoenosis of such artificial lakes.Before the drainage of the reservoirs, both lakes showed phosphorus release from the sediment during summer stagnation. Phosphorus values of Lake Herrenbach were regularly higher than those of Lake Breitenau (Lake Herrenbach 88 μg/l, Lake Breitenau 33 μg/l). During release, both lakes indicated higher phosphorus and chlorophyll concentrations as well as rising biomasses. Remarkable differences were observed during refilling of the reservoirs: while Lake Herrenbach showed higher transparency and lower phosphorus concentrations, Lake Breitenau progressed towards eutrophication (total phosphorus during summer 1996: Lake Herrenbach 30 μg/l, Lake Breitenau 55 μg/l). One reason for the reaction of Lake Breitenau was the reduced ground drainage during the refilling, which caused an accumulation of nutrients in the hypolimnion. Another reason was the mineralisation of vegetation which covered great parts of the dry lake sediment. The limnological change of Lake Herrenbach was not as clear but could be caused by the restauration of the pre-reservoir which was drainaged and dredged before the emptying of the main reservoir started as well as many other facts which differed Lake Herrenbach from Lake Breitenau.  相似文献   

The Little Ice Age climate of New Zealand reconstructed from Southern Alps cirque glaciers: a synoptic type approach   总被引：2，自引：1，他引：1  

Andrew Lorrey  Nicolas Fauchereau  Craig Stanton  Petra Chappell  Steven Phipps  Andrew Mackintosh  James Renwick  Ian Goodwin  Anthony Fowler 《Climate Dynamics》2014,42(11-12):3039-3060

Little Ice Age (LIA) austral summer temperature anomalies were derived from palaeoequilibrium line altitudes at 22 cirque glacier sites across the Southern Alps of New Zealand. Modern analog seasons with temperature anomalies akin to the LIA reconstructions were selected, and then applied in a sampling of high-resolution gridded New Zealand climate data and global reanalysis data to generate LIA climate composites at local, regional and hemispheric scales. The composite anomaly patterns assist in improving our understanding of atmospheric circulation contributions to the LIA climate state, allow an interrogation of synoptic type frequency changes for the LIA relative to present, and provide a hemispheric context of the past conditions in New Zealand. An LIA summer temperature anomaly of ?0.56 °C (±0.29 °C) for the Southern Alps based on palaeo-equilibrium lines compares well with local tree-ring reconstructions of austral summer temperature. Reconstructed geopotential height at 1,000 hPa (z1000) suggests enhanced southwesterly flow across New Zealand occurred during the LIA to generate the terrestrial temperature anomalies. The mean atmospheric circulation pattern for summer resulted from a crucial reduction of the ‘HSE’-blocking synoptic type (highs over and to the west of NZ; largely settled conditions) and increases in both the ‘T’- and ‘SW’-trough synoptic types (lows passing over NZ; enhanced southerly and southwesterly flow) relative to normal. Associated land-based temperature and precipitation anomalies suggest both colder- and wetter-than-normal conditions were a pervasive component of the base climate state across New Zealand during the LIA, as were colder-than-normal Tasman Sea surface temperatures. Proxy temperature and circulation evidence were used to corroborate the spatially heterogeneous Southern Hemisphere composite z1000 and sea surface temperature patterns generated in this study. A comparison of the composites to climate mode archetypes suggests LIA summer climate and atmospheric circulation over New Zealand was driven by increased frequency of weak El Niño-Modoki in the tropical Pacific and negative Southern Annular Mode activity.  相似文献   

Deep seismic reflectivity patterns in specific tectonic units of Western and Central Europe   总被引：2，自引：0，他引：2  

Petra Sadowiak  Thomas Wever  Rolf Meissner 《Geophysical Journal International》1991,105(1):45-54

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Results of the DEKORP 1 (BELCORP-DEKORP) deep seismic reflection studies in the western part of the Rhenish Massif   总被引：1，自引：0，他引：1  

DEKORP Research GroupH.-J. Anderle  R. Bittner  R. Bortfeld  J. Bouckaert  G. Büchel  G. Dohr  H.-J. Dürbaum  H. Durst  W. Fielitz  E. Flüh  T. Gundlach  L. Hance  A. Henk  F. Jordan  D. Kläschen  M. Klöckner  R. Meissner  W. Meyer  O. Oncken  C. Reichert  K.-H. Ribbert  P. Sadowiak  H.-U. Schmincke  J. Schmoll  R. Walter  K. Weber  U. Weihrauch  Th. Wever 《Geophysical Journal International》1991,106(1):203-227

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Continental collisions and seismic signature   总被引：6，自引：0，他引：6  

R. Meissner  Th. Wever  P. Sadowiak 《Geophysical Journal International》1991,105(1):15-23

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Freshwater geographies: Experimenting with knowing and doing geography differently   总被引：1，自引：0，他引：1  

Brendon Blue  Claire Gregory  Kiely McFarlane  Marc Tadaki  Petra van Limburg‐Meijer  Nick Lewis 《New Zealand geographer》2012,68(1):62-66

The fair and effective governance of freshwater is an increasingly prominent issue in New Zealand. Emerging from a complex of cultural, economic and biophysical narratives, freshwater geographies are multiple, varied and increasingly acknowledged as worthy of interdisciplinary scrutiny. In this commentary, we reflect on a series of generative spaces that we – as group of postgraduate geographers (plus supporting staff) – created to engage with the multiplicity of freshwater meanings both within and beyond the academy. Through this evolving epistemic‐political project, we significantly reframed our own understandings about what freshwater ‘is’ and how it ought to be governed. By pursuing a deeper understanding of how the world gets made, we expand our ability to know and make it differently.  相似文献