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1.
Markku Pirttijärvi Risto Pietilä Aimo Hattula Sven-Erik Hjelt 《Geophysical Prospecting》2002,50(5):425-440
This paper presents a computational method for the interpretation of electromagnetic (EM) profile data in the frequency domain using a thin plate model within a two-layer earth. The modelling method is based on an integral equation formulation, where the conductor is represented by a lattice structure composed of two-dimensional surface elements. Several approximations are used to simplify the theoretical basis and to decrease the computation time. The simple parametric model allows efficient use of optimization methods. We employ a linearized inversion scheme based on singular value decomposition and adaptive damping. The new forward computation method and the parameter optimization are combined in the computer program, emplates . The modelling examples demonstrate that the approximate method is capable of describing the characteristic behaviour of the EM response of a thin plate-like conductor in conductive surroundings. The efficacy of the inversion is demonstrated using both synthetic and field data. An optional depth compensation method is used to improve the interpreted values of the depth of burial. The results show that the method is cost effective and suitable for interactive interpretation of EM data. 相似文献
2.
Hannu Savijärvi 《Surveys in Geophysics》1994,15(6):755-773
The thermodynamics, dynamics, weather and general circulation (climate) of the atmospheres of Venus, Earth and Mars is reviewed, in the light of present knowledge. These three terrestrial planets each have a gaseous sunlit envelope, but the realizations of motions in them are quite different. This makes comparisons of their meteorology very interesting and challenging. 相似文献
3.
Leena Järvi Ari-Juhani Punkka David M. Schultz Tuukka Petäjä Harri Hohti Janne Rinne Toivo Pohja Markku Kulmala Pertti Hari Timo Vesala 《Boundary-Layer Meteorology》2007,125(2):343-359
On the afternoon of 3 July 2004 in Hyytiälä (Juupajoki, Finland), convective cells produced a strong downburst causing forest damage. The SMEAR II field station, situated near the damage site, enabled a unique micrometeorological analysis of a microburst with differences above and inside the canopy. At the time of the event, a squall line associated with a cold front was crossing Hyytiälä with a reflectivity maximum in the middle of the squall line. A bow echo, rear-inflow notch, and probable mesovortex were observed in radar data. The bow echo moved west-north-west, and its apex travelled just north of Hyytiälä. The turbulence data were analysed at two locations above the forest canopy and at one location at sub-canopy. At 1412 EET (Eastern European Time, UTC+2), the horizontal and vertical wind speed increased and the wind veered, reflecting the arrival of a gust front. At the same time, the carbon dioxide concentration increased due to turbulent mixing, the temperature decreased due to cold air flow from aloft and aerosol particle concentration decreased due to rain scavenging. An increase in the number concentration of ultra-fine particles (< 10 nm) was detected, supporting the new particle formation either from cloud outflow or due to rain. Five minutes after the gust front (1417 EET), strong horizontal and downward vertical wind speed gusts occurred with maxima of 22 and 15 m s?1, respectively, reflecting the microburst. The turbulence spectra before, during and after the event were consistent with traditional turbulence spectral theory. 相似文献
4.
Use of biliary PAH metabolites as a biomarker of pollution in fish from the Baltic Sea 总被引：2，自引：0，他引：2
Vuorinen PJ Keinänen M Vuontisjärvi H Barsiene J Broeg K Förlin L Gercken J Kopecka J Köhler A Parkkonen J Pempkowiak J Schiedek D 《Marine pollution bulletin》2006,53(8-9):479-487
During field campaigns of the BEEP project (Biological Effects of Environmental Pollution in Marine Coastal Ecosystems) in 2001-2002, metabolites of polycyclic aromatic hydrocarbons (PAHs) were determined in bile samples from three fish species, flounder (Platichthys flesus), perch (Perca fluviatilis) and eelpout (Zoarces viviparus), from four separate areas in the Baltic Sea. Two determination methods were applied: fixed wavelength fluorescence (FF) for pyrene-type metabolites and high-performance liquid chromatography with fluorescence detection (HPLC). There was a good correlation between the FF method and 1-OH pyrene determined by HPLC. Normalisation of the FF data for absorbance at 380 nm or bile protein concentrations greatly increased variance in one third and decreased it in two thirds of the cases and resulted in a loss of significant differences (protein normalisation) between the sampling stations, but normalisation of the HPLC data had little effect on the results. The biliary PAH metabolite content was usually higher in males than in females. In perch and eelpout the biliary PAH contents were at similar levels, whereas in flounder the levels were lower. The sampling areas arranged in decreasing order of biliary PAH contents were: Wismar Bay > Gulf of Gdansk > Lithuanian coast > Kvadofj?rden (reference area). It is concluded that FF with un-normalised data is a reliable and simple method for monitoring purposes and only one sex of a selected species should be used. 相似文献
5.
David Hodgkinson Hakim Benabderrahmane Mark Elert Aimo Hautojärvi Jan-Olof Selroos Yasuharu Tanaka Masahiro Uchida 《Hydrogeology Journal》2009,17(5):1035-1049
An overview is presented of a 4-year study by the Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes, whose primary aim was to build a bridge between the approaches used for site characterisation (SC) and performance assessment (PA) associated with nuclear waste repositories. Eleven modelling teams representing six national radioactive waste organisations participated in eight modelling exercises whose objectives were: to assess simplifications used in PA models; to determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models; to support the design of SC programmes to assure that the results have optimal value for PA calculations; and to improve the understanding of site-specific flow and transport behaviour at different scales using SC models. The modelling tasks were concerned with flow and transport through single and multiple near-planar features on SC and PA timescales, including the diffusion of solutes into multiple immobile zones adjacent to fracture surfaces. In general, tracer tests provide only limited quantitative constraints on retention parameter values relevant to PA but nevertheless provide insight about the flow and transport processes, which is a key element of the bridge between SC and PA. 相似文献
6.
Aspects of the Fine-Scale Climatology Over Lake Tanganyika as Resolved by a Mesoscale Model 总被引：1，自引：0，他引：1
Summary An hourly averaged climatology at 0.05 ° horizontal resolution over the Lake Tanganyika region was created by making simulations
with a mesoscale model (HIRLAM) using a high resolution physiography to represent the surface. Initial and boundary values
were interpolated from ECMWF analyses. Climatologies for a typical dry season month (July 1994) and wet season month (March
1994) were created by 7-day segmenting. Model results were validated by utilizing a special coastal observation network. A
number of experiments were made with changes to the physiography (mountains/no mountains, lake/no lake).
The results reveal local channelling and blocking effects of the near-surface southeasterly trade winds by the high mountain
chains in the region of the East African rift. Furthermore, surface winds display regular diurnal cycles in many places, due
to slope winds over hills and lake-land-type breezes near the coast. The diurnal coastal winds (defined by the observation
network) are reasonably well simulated. Precipitation patterns display the semi-annual march of the ITCZ across the area,
plus considerable topographic effects. There is high evaporation from lakes and wetlands during the windy dry season, while
evaporation from the moist land surface dominates the rainy season.
Received October 15, 1998/Revised September 2, 1999 相似文献
7.
Barsiene J Lehtonen KK Koehler A Broeg K Vuorinen PJ Lang T Pempkowiak J Syvokiene J Dedonyte V Rybakovas A Repecka R Vuontisjärvi H Kopecka J 《Marine pollution bulletin》2006,53(8-9):422-436
During the EU project BEEP a battery of biomarkers was applied in flounder (Platichthys flesus) and the blue mussel (Mytilus edulis) collected at three locations off the Lithuanian coast (Baltic Sea) in June and September 2001 and 2002. The elevated biomarker responses in specimens sampled in September 2001 were apparently related to the extensive dredging activities in the Klaipeda port area and subsequent dumping of contaminated sediments. High concentrations of organic pollutants (organochlorines and PBDEs) were also measured in the tissues of both indicator species. In addition, response levels of genotoxicity, cytotoxicity, immunotoxicity as well as concentrations of PAH metabolites in the bile of flounder showed elevations in 2002 after an oil spill in the Būtinge oil terminal in November 2001. In flounder, biomarker measurements 10 months after the spill indicated recovery processes but in mussels a high level of genotoxicity could still be observed 22 months later. The present study illustrates the usefulness of the multi-biomarker approach in the detection of biological effects of pollution in this region of the Baltic Sea. 相似文献
8.
Th. G. Sahama Martti Lehtinen Pentti Rehtijärvi 《Contributions to Mineralogy and Petrology》1973,39(2):171-174
Single crystals of boehmite, up to 0.1 mm in size, were found in open cavities inside a corundum crystal from the Ratnapura area gem gravels in Ceylon. The unit cell parameters are (X-ray powder pattern): a
0=3.695 Å b
0=12.212 Å, c
0=2.867 Å. The crystallographic orientation is based on X-ray single-crystal precession photographs. The crystals show the faces (it010), (001), (101), and (221). Systematic extinctions agree with the space group Amam. Optical orientation: a, b, c. Refractive indices are given. The mineral is optically positive with a large optic axial angle. 相似文献
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10.
The Sundqvist parameterization for warm rain production by autoconversion processes as the function of cloud liquid water mixing ratio m is tested by defining a realistic ‘driving’ profile m(z) for a maritime low, warm stratocumulus cloud, and comparing with various recent observations. The results show that the parameterization is acceptable, especially after tuning its rain collection constant C1. It is somewhat sensitive to the vertical resolution of the host model, though. Extending the calculations by considering typical cloud and raindrop size spectra, extra variables such as drizzle amounts and droplet effective radii (forced by the bulk Sundqvist rain rates) could be estimated by numerical integration. Also, these seem to agree fairly well with the available observations. 相似文献