We present a statistical technique for ranging the edges of active storms cell using a very simple narrowband receiver tuned to 1 MHz (the MW band in radio, just below HF frequencies). We show that a principle based on the “30–30 rule” can be used to define practical warning levels. From the measurements carried out in Finland, we show that the narrowband source intensities of cloud-to-ground lightning vary log-normally; this results in a ranging uncertainty of about 20%, which can be reduced if a suitable floating average is used. Based on one storm, we suggest that the differences between intra-cloud and ground-to-cloud signals at 1 MHz are small enough to make an IC–CG discrimination. Eliminating such a discrimination allows all lightning impulses to be used in the range and improves the accuracy, since more flashes are then available as inputs into the distance-estimation algorithm. Although the system is only validated against a single storm, we provide definitions by which this and other narrowband detectors could be independently verified; existing narrowband devices have not been verified in this manner, due in part to a lack of such standardized definitions. 相似文献
A detailed characterisation was carried out for soil sampled from sites with different levels of contamination before and after the cultivation of oats and barley. Mineralogical composition, concentration of exchangeable cations, dynamics of soil pH and acid neutralisation buffer capacity of the soil were studied. A total of 21 elements in the soil and 28 elements in the plants were determined by instrumental neutron activation analysis. Distribution of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn and Pb in soil leachates was studied by sequential leaching procedure and ICP-AES. It was found that plants significantly affect most of the soil characteristics including the leaching of heavy metals. 相似文献
A novel high-resolution (2–4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70–100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.
The aim of this work was to study the forest fire potential and frequency of forest fires under the projected climate change in Finland (N 60°–N 70°). Forest fire index, generally utilized in Finland, was used as an indicator for forest fire potential due to climatological parameters. Climatic scenarios were based on the A2 emission scenario. According to the results, the forest fire potential will have increased by the end of this century; as a result of increased evaporative demand, which will increase more than the rise in precipitation and especially in southern Finland. The annual number of forest fire alarm days is expected to increase in southern Finland to 96–160 days by the end of this century, compared to the current 60–100 days. In the north, the corresponding increase was from 30 to 36 days. The expected increase in the annual frequency of forest fires over the whole country was about 20% by the end of this century compared to the present day. The greatest increase in the frequency of fires, per 1,000 km2, was in the southernmost part of the country, with six to nine fires expected annually per 1,000 km2 at the end of this century, meaning a 24–29% increase compared to the present day frequencies. 相似文献
We develop a three-parameter H, G1, G2 magnitude phase function for asteroids starting from the current two-parameter H, G phase function. We describe stochastic optimization of the basis functions of the magnitude phase function based on a carefully chosen set of asteroid photometric observations covering the principal types of phase dependencies. We then illustrate the magnitude phase function with a chosen set of observations. It is shown that the H, G1, G2 phase function systematically improves fits to the existing data and considerably so, warranting the utilization of three parameters instead of two. With the help of the linear three-parameter phase function, we derive a nonlinear two-parameter H, G12 phase function, and demonstrate its applicability in predicting phase dependencies based on small numbers of observations. 相似文献
Regions are contested processes in which various layers of borders become articulated, deconstructed and reconstructed by both activists and advocates. While many scholars currently tend to highlight the relational character of spaces, this study – acknowledging that seeing regions as relational or territorial is a highly contextual matter – emphasizes the territorial approach by stressing the multiple layers of borders and how they help to constitute and nurture regional identity. Focusing on deinstitutionalization of a region, it is argued here that regional restructuring can trigger activism, as proved by the activist movement at issue in the case study. This case study of a merger between two municipalities in Finland illustrates that when threatened with integration, (old) regions seem to be of especial importance as bordered territories of identification. 相似文献
In this study, we aim to reconstruct long-term limnoecological development of the clay-turbid Lake Tiiläänjärvi in Askola, southern Finland, using fossil Chironomidae assemblages. The study lake suffers from hypereutrophic conditions and late-winter and end-of-summer anoxia. The retrieved sediment record revealed a succession from oligo-mesotrophic (~AD 1940–2000) to eutrophic community (~AD 2000–2010) that finally reached hypereutrophic climax community in the most recent sediments. The initial state of the record was characterized by stable ecological conditions, but the biological integrity (community and functional diversity) was completely lost in the upper part of the sediment profile. The number of taxa markedly decreased following the nutrient enrichment and only one taxon (Chironomus plumosus-type), tolerant of temporary anoxia, remained in the surface sample. During the period of available observational data (since AD 1978), variance in midge community composition was mostly explained by limnological factors, namely total phosphorus (TP), whereas the influence of climate was statistically insignificant, thus enabling quantitative midge-based reconstruction of autumnal epilimnetic TP. The midge-based reconstruction showed an identical trend compared to sediment characteristics, which correspond to increased lake productivity and anthropogenic activities in the catchment. The inferred values for the initial state indicated mesotrophic conditions, which are typical for non-disturbed clay-turbid lakes in southern Finland, and a subsequent increase to eutrophic conditions, with hypereutrophic state reached at the top of the core. This development corresponds with the instrumentally monitored development. In addition, when the reconstruction was compared with the instrumental values, the inferences were mostly (75 % of the samples) within the error estimates of the model. The present results provide invaluable information on the limnoecological development of Lake Tiiläänjärvi, and more generally, support the theory that fossil remains of chironomids provide a useful tool for assessments of eutrophication history and biological integrity. 相似文献
A project implemented to study the effects of space weather on the Finnish natural gas pipeline was started in August 1998. The aims of the project were (1) to derive a model for calculating geomagnetically induced currents (GIC) and pipe-to-soil (P/S) voltages in the Finnish natural gas pipeline, (2) to perform measurements of GIC and P/S voltages in the pipeline and (3) to derive statistical predictions for the occurrences of GIC and P/S voltages at different locations in the pipeline network.GIC and P/S voltage were recorded at a compressor station. The GIC measurement was made with two magnetometers, one right above the pipe, and another at the Nurmijärvi Geophysical Observatory about 30 km southwest. The largest GIC since November 1998 has been 30 A. The P/S voltage recording was stopped in May 1999, but GIC is still measured.GIC statistics were derived based on the recordings of the geomagnetic field at Nurmijärvi. The geoelectric field was calculated by using the plane wave model. This field was input to the general pipeline model resulting in the distribution of currents and P/S voltages at selected points in the pipeline. As could be expected, the largest P/S voltage variations occur at the ends of the pipeline network, while the largest GIC flow in the middle parts. 相似文献
Two varve counts made nearly 20 yrs apart and by different authors in the small and well sheltered meromictic lake of Valkiajärvi were compared with a view to establishing how similar, or otherwise, these two independent varve chronologies might be. The results were significant, the difference between the two varve counts being less than 2% for most of the sediment length, even though the average varve thickness was only 0.3 mm. The continuous and essentially uniform varve record - so far the longest in Finland - covers 8400 yrs and could be applied for accurate dating of palaeoenvironmental indicators in the sediment. As an example, we present a varve-dated pollen diagram for Lake Valkiajärvi.In addition, some magnetic parameters (susceptibility, ARM, SIRM) were measured on the sediment sequence to support the stratigraphic division and correlation of the cores, and to outline the development of the basin since the last deglaciation. Magnetic variables reflected mainly the variation in minerogenic material in the sediment, and were therefore related to changes in the catchment. The magnetic parameters also showed a drastic change some 6000 yrs ago, the reason for which, unfortunately, is still not fully understood. 相似文献