An Automatic Well Planner for Complex Well Trajectories

Mathematical Geosciences - A data-driven automatic well planner procedure is implemented to develop complex well trajectories by efficiently adapting to near-well reservoir properties and geometry....     

Estimation of daytime downward longwave radiation at the surface from satellite and grid point data

Summary A hybrid method is developed for the estimation of the daytime downward longwave radiation flux (DLF) at the surface. The method makes use of the grid point thermodynamic fields at the surface and at the 1000 and 850 hPa levels. The cloud parameters are derived from the infrared and visible image data of the satellite METEOSAT-2. The calculation of the DLF is split into a clear-sky contribution, which is calculated from empirical formulae, and a cloud contribution which depends on cloud amount, cloud base height, and temperature.A sensitivity test to perturbations in the relevant parameters resembles closely the response of a multispectral radiation scheme, however the humidity dependence under clear sky has been identified as a weak point. A comparison of the method using observed input parameters with simultaneous measurements of the DLF yields an RMS error of 12.2 W/m².The method is applied for mapping the DLF over western Europe and the Mediterranean using satellite images for two days near midday and ancillary grid point data obtained during the ALPEX experiment. A comparison with ground measurements of 4 stations in West Germany shows a mean deviation of 3.9 W/m² and an RMS error of 11.6 W/m². The method is a first attempt to estimate the DLF at regional scales from satellite data on the cloud field and grid point analysis data on the thermodynamic field.

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Zusammenfassung Zur Schätzung des abwärts gerichteten langwelligen Strahlungsflusses (DLF) während des Tages an der Erdoberfläche wird eine Hybridmethode entwickelt. Die Methode verwendet Gitterpunkt-thermodynamische Felder am Boden und auf den 1000 und 850 h Pa-Flächen. Die Wolkenparameter stammen von den Bilddaten im infraroten und sichtbaren Bereich des Satelliten METEOSAT-2. Die Berechnung des DLF teilt sich in einen, aus empirischen Formeln berechneten Beitrag des wolkenlosen Himmels und einen Beitrag durch Wolken, welcher von der Wolkenmenge, von der Höhe der Wolkenbasis und der Temperatur abhängt.Ein Test der Empfindlichkeit auf Störungen in den relevanten Parametern ist der Reaktion eines multispektraligen Strahlungsschemas sehr ähnlich, obwohl die Feuchtigkeitsabhängigkeit unter wolkenlosem Himmel als Schwachpunkt herausgefunden wurde. Ein Vergleich der Methode unter Verwendung beobachteter Inputparameter bei gleichzeitigen Messungen des DLF ergibt einen RMS-Fehler von 12.2 W/m².Diese Methode wird für die Kartierung des DLF über Westeuropa und dem Mittelmeer angewendet. Dazu werden Satellitenbilder von zwei Tagen um Mittag und zusätzliche Gitterpunktdaten, die während des ALPEX-Experiments gewonnen wurden, verwendet. Ein Vergleich mit Bodenmessungen von 4 Stationen in West-deutschland zeigt eine mittlere Abweichung von 3.9 W/m² und einen RMS-Fehler von 11.6 W/m². Diese Methode ist ein erster Versuch, den DLF im regionalen Bereich aus Satellitendaten des Wolkenfeldes und Gitterpunkt-Analysedaten des thermodynamischen Feldes zu schätzen.

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With 10 Figures     

Derivation Of Refractive Index And Temperature Gradients From Optical Scintillometry To Correct Atmospherically Induced Errors For Highly Precise Geodetic Measurements

Refraction effects of optical beams are generally caused by an inhomogeneous propagation medium and are a major source of systematic errors in the precise optical determination of angles and distances in the atmospheric surface layer. In this contribution a method for deriving vertical temperature and refractive index gradients from optical scintillation is presented. Knowledge of these gradients is required for the compensation of atmospherically induced errors for highly precise terrestrial geodetic measurements, like direct transfer and levelling. The advantage of the present optical method is, that temperature and refractive index gradients can be derived as line-averaged values over the propagation path, which is not possible by meteorological point measurements. Field observations have been carried out with a displaced-beam scintillometer over flat terrain and under different atmospheric conditions in order to verify this method. The experiments show, that this method allows to derive accurate correction values for precise terrestrial geodetic measurements.     

Processing and quality control of flux data during LITFASS-2003

Different aspects of the quality assurance and quality control (QA/QC) of micrometeorological measurements were combined to create a comprehensive algorithm which was then applied to experimental data from LITFASS-2003 (Lindenberg Inhomogeneous Terrain—Fluxes between Atmosphere and Surface: a long term Study). Eddy-covariance measurements of the latent heat flux were the main focus of the QA/QC efforts. The results of a turbulence sensor intercomparison experiment showed deviations between the different eddy-covariance systems on the order of 15%, or less than 30 W m⁻², for the latent heat flux and 5%, or less than 10 W m⁻², for the sensible heat flux. In order to avoid uncertainties due to the post-processing of turbulence data, a comprehensive software package was used for the analysis of experimental data from LITFASS-2003, including all necessary procedures for corrections and quality control. An overview of the quality test results shows that for most of the days more than 80% of the available latent heat flux data are of high quality so long as there are no instrumental problems. The representativeness of a flux value for the target land-use type was analysed using a stochastic footprint model. Different methods to calculate soil heat fluxes at the surface are discussed and a sensitivity analysis is conducted to select the most robust method for LITFASS-2003. The lack of energy balance closure, which was found for LITFASS-2003, can probably be attributed to the presence of low-frequency flux contributions that cannot be resolved with an averaging time of 30 min. Though the QA/QC system has been developed for the requirements of LITFASS-2003, it can also be applied to other experiments dealing with similar objectives.     

The effect of mountainous topography on moisture exchange between the “surface” and the free atmosphere

Typical numerical weather and climate prediction models apply parameterizations to describe the subgrid-scale exchange of moisture, heat and momentum between the surface and the free atmosphere. To a large degree, the underlying assumptions are based on empirical knowledge obtained from measurements in the atmospheric boundary layer over flat and homogeneous topography. It is, however, still unclear what happens if the topography is complex and steep. Not only is the applicability of classical turbulence schemes questionable in principle over such terrain, but mountains additionally induce vertical fluxes on the meso-γ scale. Examples are thermally or mechanically driven valley winds, which are neither resolved nor parameterized by climate models but nevertheless contribute to vertical exchange. Attempts to quantify these processes and to evaluate their impact on climate simulations have so far been scarce. Here, results from a case study in the Riviera Valley in southern Switzerland are presented. In previous work, measurements from the MAP-Riviera field campaign have been used to evaluate and configure a high-resolution large-eddy simulation code (ARPS). This model is here applied with a horizontal grid spacing of 350 m to detect and quantify the relevant exchange processes between the valley atmosphere (i.e. the ground “surface” in a coarse model) and the free atmosphere aloft. As an example, vertical export of moisture is evaluated for three fair-weather summer days. The simulations show that moisture exchange with the free atmosphere is indeed no longer governed by turbulent motions alone. Other mechanisms become important, such as mass export due to topographic narrowing or the interaction of thermally driven cross-valley circulations. Under certain atmospheric conditions, these topographical-related mechanisms exceed the “classical” turbulent contributions a coarse model would see by several times. The study shows that conventional subgrid-scale parameterizations can indeed be far off from reality if applied over complex topography, and that large-eddy simulations could provide a helpful tool for their improvement.     

Plastic debris as nesting material in a Kittiwake-(Rissa tridactyla)-colony at the Jammerbugt, Northwest Denmark

This paper continues the investigations of Clemens and Hartwig from 1992 on the proportion of garbage used as nesting material in the Kittiwake colony at Bulbjerg in the Jammerbugt in Northwest Denmark. Whereas in the year 1992 plastic garbage items were included in 39.3% of 466 Kittiwake nests in the Bulbjerg colony, in 2005 57.2% of 311 nests contained plastic debris. Although it has been forbidden to dispose of plastic garbage into the marine environment since the implementation of the MARPOL 73/78-Agreement/Annex V (Regulation for the Prevention of Pollution by Ship Waste) of 1989 and especially since the declaration of the North Sea as a MARPOL-Special Area for garbage in 1991, the pollution of the oceans and the North Sea is still an ubiquitous problem, particularly with regard to plastic waste. Plastic waste is presumably not used preferentially for nest-building, but in the context of available nesting material in the waters surrounding the breeding colony. Therefore the share of garbage parts in nests of certain species of birds is an indicator of the amount of waste in the natural environment in the vicinity of their breeding site.     

Climatic factors controlling plant sensitivity to warming

Plant sensitivity to warming can be expressed as β or the number of days of advance in leafing or flowering events per 1 °C of Mean Annual Temperature (MAT) change. Many local studies demonstrate that β estimates for spring flowering species are usually larger than estimates for plants flowering in summer or fall. Until now, however, neither observational nor experimental estimates of this parameter were considered to be climate or geographically dependent. Here we question this paradigm through reanalysis of observational β estimates and mathematical modeling of the seasonal warming signal. Statistical analysis of a large number of bulk (averaged over species) estimates of β derived from the Pan European Phenology Data network (PEP725) revealed a positive spatial correlation with MAT, as well as a negative correlation with the Seasonal Temperature Range (STR). These spatial correlations of bulk β values as well as interseasonal variability in β were explained using a simple deterministic model of the Thermal Growing Season (TGS). More specifically, we found that the geographic distribution of bulk plant sensitivity to warming as well as the seasonal decline of β were controlled by the seasonal patterns in the warming signal and by average soil thermal properties. Thus, until recently, plants managed to keep pace with climate warming by shifting their leafing and flowering events by the same number of days as the length of the period of weather suitable for their growth. Our model predicts, however, an even greater increase in the TGS for subsequent increases in MAT. Depending on how they interact with other factors such as changes in precipitation and increased temperature variability, these longer thermal growing seasons may not be beneficial for plant growth.     

Using Multiple-Point Geostatistics for Tracer Test Modeling in a Clay-Drape Environment with Spatially Variable Conductivity and Sorption Coefficient

This study investigates the effect of fine-scale clay drapes on tracer transport. A tracer test was performed in a sandbar deposit consisting of cross-bedded sandy units intercalated with many fine-scale clay drapes. The heterogeneous spatial distribution of the clay drapes causes a spatially variable hydraulic conductivity and sorption coefficient. A fluorescent tracer (sodium naphthionate) was injected in two injection wells and ground water was sampled and analyzed from five pumping wells. To determine (1) whether the fine-scale clay drapes have a significant effect on the measured concentrations and (2) whether application of multiple-point geostatistics can improve interpretation of tracer tests in media with complex geological heterogeneity, this tracer test is analyzed with a local three-dimensional ground-water flow and transport model in which fine-scale sedimentary heterogeneity is modeled using multiple-point geostatistics. To reduce memory needs and calculation time for the multiple-point geostatistical simulation step, this study uses the technique of direct multiple-point geostatistical simulation of edge properties. Instead of simulating pixel values, model cell edge properties indicating the presence of irregularly shaped surfaces are simulated using multiple-point geostatistical simulations. Results of a sensitivity analysis show under which conditions clay drapes have a significant effect on the concentration distribution. Calibration of the model against measured concentrations from the tracer tests reduces the uncertainty on the clay-drape parameters. The calibrated model shows which features of the breakthrough curves can be attributed to the geological heterogeneity of the aquifer and which features are caused by other processes.     

The myth of the brackish Sarmatian Sea

The biota of the 1.5 Ma period of the Middle Miocene Sarmatian of the Central Paratethys lack stenohaline components. This was the reason to interpret the Sarmatian stage as transitional between the marine Badenian and the lacustrine Pannonian stages. However, our new data indicate that brackish water conditions could not have prevailed. Sarmatian foraminifera, molluscs, serpulids, bryozoans, dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire Sarmatian. During the Lower Sarmatian, however, a sea-level lowstand forced the development of many marginal marine environments. During the Late Sarmatian a highly productive carbonate factory of oolite shoals, mass-occurrences of thick-shelled molluscs and larger foraminifera, as well as marine cements clearly point to normal marine to hypersaline conditions. This trend is not restricted to the western margin of the Pannonian Basin System but can be observed in the entire Central and even Eastern Paratethys.