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131.
Dominik van Pinxteren Erika Brüggemann Thomas Gnauk Konrad Müller Christian Thiel Hartmut Herrmann 《Journal of Atmospheric Chemistry》2010,67(1):1-28
A new method has been developed to combine back trajectory statistics with a detailed land cover analysis. It provides numeric
proxies for the residence times of sampled air masses above certain land cover classes (marine, natural vegetation, agricultural
lands, urban areas, and bare areas), as well as further meteorological parameters (mean trajectory length, solar radiation
along trajectory, and local height of the boundary mixing layer). The method has been implemented into a GIS-enabled database
system to allow for an efficient processing of large datasets with low computational demands. A principal component analysis
was performed on a dataset including the modelled residence times, the modelled meteorological parameters, some measured meteorological
parameters (wind speed and temperature), and the concentrations of 10 particle constituents (inorganic ions and organic and
elemental carbon) in 5 particle size ranges for 29 winter- and summertime samples at an urban background site in Leipzig,
Germany. Six principal components could be extracted which together explained about 80% of the total variance in the dataset.
The factors could be attributed to the influence of meteorology to continental background pollution, secondary formation processes
in polluted air masses, wood burning, aged sea-salt, local traffic, and long-range transported crustal material. The modelled
residence times and the meteorological parameters were generally consistent with the existing knowledge of specific particle
sources and thereby facilitated and strengthened the interpretation of the factors. Moreover, they allowed for a clear distinction
between continental background pollution and secondary formation processes, which has not been possible in previous source
apportionment studies. The results demonstrate that the combined usage of back trajectory, land cover, and meteorological
data by the presented method yields valuable additional information on the history of sampled air masses, which can improve
the quality of source apportionment of atmospheric aerosol constituents. 相似文献
132.
How to improve the representation of hydrological processes in SWAT for a lowland catchment – temporal analysis of parameter sensitivity and model performance
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Model diagnostic analyses help to improve the understanding of hydrological processes and their representation in hydrological models. A detailed temporal analysis detects periods of poor model performance and model components with potential for model improvements, which cannot be found by analysing the whole discharge time series. In this study, we aim to improve the understanding of hydrological processes by investigating the temporal dynamics of parameter sensitivity and of model performance for the Soil and Water Assessment Tool model applied to the Treene lowland catchment in Northern Germany. The temporal analysis shows that the parameter sensitivity varies temporally with high sensitivity for three groundwater parameters (groundwater time delay, baseflow recession constant and aquifer fraction coefficient) and one evaporation parameter (soil evaporation compensation factor). Whereas the soil evaporation compensation factor dominates in baseflow and resaturation periods, groundwater time delay, baseflow recession constant and aquifer fraction coefficient are dominant in the peak and recession phases. The temporal analysis of model performance identifies three clusters with different model performances, which can be related to different phases of the hydrograph. The lowest performance, when comparing six performance measures, is detected for the baseflow cluster. A spatially distributed analysis for six hydrological stations within the Treene catchment shows similar results for all stations. The linkage of periods with poor model performance to the dominant model components in these phases and with the related hydrological processes shows that the groundwater module has the highest potential for improvement. This temporal diagnostic analysis enhances the understanding of the Soil and Water Assessment Tool model and of the dominant hydrological processes in the lowland catchment. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
133.
A rapid removal of Chernobyl137Cs from a number of large lakes has been previously reported. Our measurements of137Cs in water, sediments and pore water in the mono- and meromictic basins of Lake Lugano (Lago di Lugano) reveal generally slower half-removal times of 1.2 and 6.7 yrs, respectively. In the seasonally anoxic southern basin, this is most probably related to an intensive recycling of137Cs between water and sediments. In the permanently stratified northern basin the removal rate is much slower due to an important inventory build up in the deep anoxic part of the basin. 相似文献
134.
Dominik Pawłowski Beata Gruszka Hanna Gallas Joanna Petera-Zganiacz 《Journal of Paleolimnology》2013,49(4):679-696
Upper Saalian (Illinoian) glaciolacustrine deposits in central Poland, preserved in a tectonic graben, were exposed in an opencast lignite mine and investigated using sedimentological and micro-paleontological methods. The extraglacial lake sediments provide the first records of late Saalian cladoceran communities in central Europe, recovered from glaciolacustrine deposits. Sedimentation was dominated by a supply of clastics that fluctuated with the seasons, forming rhythmites. In addition to seasonal cyclicity, sedimentary and environmental conditions changed every several years to decades, with periods of increased inflow to the lake delivering sandy material, and periods of almost stagnant water dominated by suspension settling. The sediments contain Cladocera assemblages that indicate the lake was initially deep, oligotrophic, and filled with moderately cold water. Changes in Cladocera community composition and abundance were perhaps responses to climate seasonality. Zones without Cladocera were associated with seasons of higher inflow and sediment supply, and directly or indirectly, with tectonic activity in the graben. Earthquakes, documented by the presence of seismites, caused not only deformation of unconsolidated lake-bottom sediments, but possibly also changes in habitat characteristics. Combined sedimentological and biological data were used to infer the lake’s history and show that deposits of glaciolacustrine lakes can be used as indicators of past ecological and climate changes. 相似文献
135.
We discuss the composition and size distribution of the dust in the coma of Comet Hale-Bopp. We do this using a model fit for the infrared emission measured by the Infrared Space Observatory (ISO) and the measured degree of linear polarization of scattered light at various phase angles and wavelengths. The effects of particle shape on the modeled optical properties of the dust grains are taken into account. Both the short wavelength (7-44 μm) and the long wavelength (44-120 μm) infrared spectrum are fitted using the same dust parameters, as well as the degree of linear polarization at twelve different wavelengths in the optical to near-infrared domains. We constrain our fit by forcing the abundances of the major rock forming chemical elements to be equal to those observed in meteorites. The infrared spectrum at long wavelengths reveals that large grains are needed in order to fit the spectral slope. The size and shape distribution we employ allows us to estimate the sizes of the crystalline silicates. The ratios of the strength of various forsterite features show that the crystalline silicate grains in Hale-Bopp must be submicrometer-sized. On the basis of our analysis the presence of large crystalline silicate grains in the coma can be excluded. Because of this lack of large crystalline grains combined with the fact that we do need large amorphous grains to fit the emission spectrum at long wavelengths, we need only approximately 4% of crystalline silicates by mass (forsterite and enstatite) to reproduce the observed spectral features. After correcting for possible hidden crystalline material included in large amorphous grains, our best estimate of the total mass fraction of crystalline material is ∼7.5%, which is significantly lower than deduced in previous studies in which the typical derived crystallinity is ∼20-30%. The implications of this low abundance of crystalline material on the possible origin and evolution of the comet are discussed. We conclude that the crystallinity we observe in Hale-Bopp is consistent with the production of crystalline silicates in the inner Solar System by thermal annealing and subsequent radial mixing to the comet forming region (∼30 AU). 相似文献
136.
M. Dominik 《Monthly notices of the Royal Astronomical Society》2006,367(2):669-692
A comprehensive new approach is presented for deriving probability densities of physical properties characterizing the lens and source that constitute an observed galactic microlensing event. While previously encountered problems are overcome, constraints from event anomalies and model parameter uncertainties can be incorporated into the estimates. Probability densities for given events need to be carefully distinguished from the statistical distribution of the same parameters among the underlying population from which the actual lenses and sources are drawn. Using given model distributions of the mass spectrum, the mass density, and the velocity distribution of Galactic disc and bulge constituents, probability densities of lens mass, distance, and the effective lens–source velocities are derived, where the effect on the distribution that arises from additional observations of annual parallax or finite-source effects, or the absence of significant effects, is shown. The presented formalism can also be used to calculate probabilities for the lens to belong to one or another population and to estimate parameters that characterize anomalies. Finally, it is shown how detection efficiency maps for binary-lens companions in the physical parameters, such as companion mass and orbital semimajor axis, arise from values determined for the mass ratio and dimensionless projected separation parameter, including the deprojection of the orbital motion for elliptical orbits. Compared to the naive estimate based on 'typical values', the detection efficiency for low-mass companions is increased by mixing in higher detection efficiencies for smaller mass ratios (i.e. smaller masses of the primary). 相似文献
137.
138.
Katharopoulos Ioannis Brunner Dominik Emmenegger Lukas Leuenberger Markus Henne Stephan 《Boundary-Layer Meteorology》2022,185(1):129-160
Boundary-Layer Meteorology - Lagrangian particle dispersion models (LPDMs) are frequently used for regional-scale inversions of greenhouse gas emissions. However, the turbulence parameterizations... 相似文献
139.
Zoltán Püspöki Philip L. Gibbard László Ferenc Kiss Richard W. McIntosh Edit Thamó-Bozsó Zita Krassay Bálint Szappanos Vera Maigut Péter Kovács Dominik Karácsony Ferenc Stercel Ferenc Visnovitz Krisztina Demény László Bereczki Teodóra Szőcs Ágnes Rotár-Szalkai Tamás Fancsik 《Boreas: An International Journal of Quaternary Research》2023,52(3):402-426
Magnetic susceptibility (MS) of the Quaternary long-term mid-latitude Maros fluvial fan (Pannonian Basin) was recorded to understand the stratigraphical features of source-proximal fluvial depositional settings. Three fully cored 500-m-deep boreholes were sampled at 0.5-m intervals; low-field and frequency dependent MS were measured, and complementary hysteresis and SEM-EDAX investigations were performed on selected samples. Logged susceptibility data were also used to log correlations established by a simultaneous comparison of wireline log and laboratory measurements. Time-series analyses of the susceptibility records reveal a ~41-ka and ~100-ka cyclicity. Towards the source-distal sections the intensity of the ~41-ka cycles decreases, while that of the ~100-ka cycles remains strong. Stratigraphical and spectral similarities were observed between the Maros fluvial fan and Chinese loess records; however, based on complementary magnetic data, the magnetic phase of the Maros Fan sections is related to the detrital magnetite that originates from the catchment during early postglacial permafrost degradations. The amplification of the ~41-ka cycles can be attributed to the very high susceptibility values in source-proximal settings and to the special stratigraphical feature of the distributive fluvial systems. This comprises the increased avulsion frequency on the fluvial fans in ‘glacial recession periods’, in concert with the ‘early postglacial’ occurrence of the permafrost-related magnetite originating from the catchment. As a local phenomenon, this is significant since it records the obliquity-driven variations in permafrost development in a catchment. However, fluvial and alluvial fans are widespread depositional landforms within the Eurasian mountain range and were possibly the same during the Quaternary deglaciations. Thus, obliquity-driven magnetic susceptibility variations in source-proximal fan deposits attached or adjacent to regions of loess deposition should also be considered when scanning for potential source material of aeolian deposits. 相似文献
140.