Modeling and Fitting of Three-Dimensional Mineral Microstructures by Multinary Random Fields

Mathematical Geosciences - Modeling a mineral microstructure accurately in three dimensions can render realistic mineralogical patterns which can be used for three-dimensional processing...     

A New Tethered Balloon-Borne Payload for Fine-Scale Observations in the Cloudy Boundary Layer

A new scientific payload is introduced for fine-scale measurements of meteorological (wind vector, static air temperature, humidity, and air pressure) and microphysical (aerosol particles and cloud droplets) properties, suspended below a tethered balloon. The high resolution sensors and the tethered balloon are described. Measurements in a lifted fog layer from a first field campaign are presented.The detailed investigation of the fog/haze and the temperature inversion layer demonstrates the damping influence of the fog on temperature fluctuations, while thewind fluctuations are significantly decreased by theevolving temperature inversion, whichwas about 30 m above the fog layer.From spectral analysis the noise floors of the high-resolution sensors are determined to10^-6 kg m^-3 for the LWC (liquid water content) and 4 mK for the fast temperature sensor (UFT-B). The correlation betweentemperature and LWC structures in shallow haze layers is investigated. The release of latent heat and the corresponding warming in the haze of about 0.1 K could be quantified.     

Nd-Sr isotopic and trace element study of rocks and fluids from the continental deep drilling Project (KTB), Germany

Geochemical analyses were interpreted on the dominant lithological units and on a deep crustal fluid from the Continental Deep Drilling Project (KTB) Pilot Hole, situated at the western margin of the Variscan Bohemian Massif. The biotite gneiss (from 384 m depth) shows a rare earth element pattern very similar to the European shale composite with Nd model ages of 940 Ma (CHUR) and 1.4 Ga (DM). The lamprophyre dike in the upper profile (1549 m), a nepheline and olivine normative basalt, is geochemically and isotopically similar to rocks from the Tertiary Central European Volcanic Province. The lower metabasite sequence (3575–4000 m), with an intrusion age of approximately 500 Ma, is made up primarily of highly metamorphosed subalkalic olivine basalts. The geochemical characteristics of the metabasites are a (La/Yb)_N of 5–10, an La concentration of 20–50 times chondrite as well as (⁸⁷Sr/⁸⁶Sr)_i of 0.7035–0.7038 and _Nd(T) of 4–6. These values suggest a depleted mantle source for the igneous precursors, evolving by assimilation-fractional crystallization processes with up to 25% of upper crust into the ultramafic, basaltic, and intermediate rock types of the metabasite sequence. The strong geochemical and chronological similarities between the KTB metabasites and rocks from the Münchberg Massif suggest that these units belong to the same lithological complex. The high salinity as well as the radiogenic ⁸⁷Sr/⁸⁶Sr ratio of 0.709413 in the KTB fluid from 4000 m depth might be the result of migrating fluids reacting with the regional Permo-Mesozoic evaporite deposits, followed by extensive Sr isotopic exchange with the upper crust.     

Efficient Representation of Laguerre Mosaics with an Application to Microstructure Simulation of Complex Ore

Mathematical Geosciences - Laguerre mosaics have been an important modeling approach in astronomy, physics, crystallography, geology and mathematics for several decades. In materials science, they...     

Behaviour Of An Ultrasonic Anemometer Under Cloudy Conditions

The use of ultrasonic anemometers under cloudy weather conditions is often doubted, even rejected or not discussed in the literature. To investigate the influence of liquid water content on the behaviour of sonic anemometers a small intercomparison experiment using an ultrasonic anemometer, a fast response propeller anemometer, and a Particulate Volume Monitor was performed at the German Environmental Research Station Schneefernerhaus near the top of Mt. Zugspitze. The results obtained under different conditions (dry/cloudy) give no significant hint on such an influence.     

Surface Energy Budget Variability: A Case Study over Grass with Special Regard to Minor Inhomogeneities in the Source Area

Summary Eddy correlation measurements of surface energy fluxes above a meadow site are presented and discussed in terms of energy balance closure. The degree of closure changed with time and wind direction, which can be explained by temporal and spatial variations of the surrounding vegetation. More frequently than not, a tendency towards an energy “deficit” was observed, that means, the sum of turbulent fluxes was less than the available energy. As a possible reason, we cautiously suggest that large-scale flux components may have to be taken into account. If so, then a convenient way to obtain fairly accurate total surface energy fluxes would be to correct the turbulent fluxes with an appropriate factor that forces the budget to perfect closure. Received October 14, 1996 Revised October 1, 1998     

Downscaling extreme month-long anomalies in southern South America

We investigate the performance of one stretched-grid atmospheric global model, five different regional climate models and a statistical downscaling technique in simulating 3 months (January 1971, November 1986, July 1996) characterized by anomalous climate conditions in the southern La Plata Basin. Models were driven by reanalysis (ERA-40). The analysis has emphasized on the simulation of the precipitation over land and has provided a quantification of the biases of and scatter between the different regional simulations. Most but not all dynamical models underpredict precipitation amounts in south eastern South America during the three periods. Results suggest that models have regime dependence, performing better for some conditions than others. The models’ ensemble and the statistical technique succeed in reproducing the overall observed frequency of daily precipitation for all periods. But most models tend to underestimate the frequency of dry days and overestimate the amount of light rainfall days. The number of events with strong or heavy precipitation tends to be under simulated by the models.     

A high-resolution 43-year atmospheric hindcast for South America generated with the MPI regional model

An evaluation of the present-day climate in South America simulated by the MPI atmospheric limited area model, REMO, is made. The model dataset was generated by dynamical downscaling from the ECMWF-ERA40 reanalysis and compared to in-situ observations. The model is able to reproduce the low-level summer monsoon circulation but it has some deficiencies in representing the South American Low-Level Jet structure. At upper levels, summer circulation features like the Bolivian High and the associated subtropical jet are well simulated by the model. Sea-level pressure fields are in general well represented by REMO. The model exhibits reasonable skill in representing the general features of the mean seasonal cycle of precipitation. Nevertheless, there is a systematic overestimation of precipitation in both tropical and subtropical regions. Differences between observed and modeled temperature are smaller than 1.5°C over most of the continent, excepting during spring when those differences are quite large. Results also show that the dynamical downscaling performed using REMO introduces some enhancement of the global reanalysis especially in temperature at the tropical regions during the warm season and in precipitation in both the subtropics and extratropics. It is then concluded that REMO can be a useful tool for regional downscaling of global simulations of present and future climates.