Fuzzy set approach to assessing similarity of categorical maps

For the evaluation of results from remote sensing and high-resolution spatial models it is often necessary to assess the similarity of sets of maps. This paper describes a method to compare raster maps of categorical data. The method applies fuzzy set theory and involves both fuzziness of location and fuzziness of category. The fuzzy comparison yields a map, which specifies for each cell the degree of similarity on a scale of 0 to 1. Besides this spatial assessment of similarity also an overall value for similarity is derived. This statistic corrects the cell-average similarity value for the expected similarity. It can be considered the fuzzy equivalent of the Kappa statistic and is therefore called K_Fuzzy. A hypothetical case demonstrates how the comparison method distinguishes minor changes and fluctuations within patterns from major changes. Finally, a practical case illustrates how the method can be useful in a validation process.     

Identification of two distinctive types of centimeter radio bursts with flare location

Two distinct types of centimeter solar bursts, classified simple, have been identified and related to the position (with respect to a sunspot) of the related flare. Type S in which the flare occurs directly over the spot has a radio spectrum with a maximum beyond 10 GHz, type P which occurs away from the spot has its maximum occurring near 3 GHz. Considering the structure of the spot magnetic field and invoking the synchrotron effect, it is shown that the origin of the radio burst may be attributed to a burst of energetic electrons with an energy peak near 3 MeV.     

Propagation of native Arctic and alpine species with a restoration potential

Arctic and alpine plant communities today are subject to an increasing frequency and intensity of anthropogenic disturbances. Good understanding of reproductive behaviour and regenerative capacity of native species is important in a restoration situation following human disturbance in Arctic and alpine vegetation. Seeds, bulbils or cuttings from 12 native Arctic and alpine species were collected from Longyearbyen in Svalbard and Dovre Mountain on the Norwegian mainland. Propagation ability was tested in greenhouse conditions. Seeds of Papaver dahlianum, Oxyria digyna, Luzula arcuata ssp. confusa , and bulbils of Bistorta vivipara all had more than 50% germination. Dryas octopetala had less than 10% germination. Both quick and slow germinators were identified among the tested species. Seed storage temperature (+4 °C, −1 °C and −20 °C) showed no overall effect on germination. The rooting capacity of cuttings from evergreen and deciduous species was tested. Arctostaphylos uvaursi, Empetrum nigrum ssp. hermaphroditum, Vaccinium vitis-idaea, Salix herbacea and S. polaris had more than 70% rooting ability, while Dryas octopetala and Cassiope tetragona had less than 10%. Saxifraga oppositifolia showed large variation in rooting ability, ranging from 20-90%. The species with high germination and rooting ability are used in an extended restoration experiment in the study areas.     

Crop residue effects on aerodynamic processes and wind erosion

Summary This study focuses on both the mechanisms and degree of wind erosion control that various residue levels provide. First, scale parameters of Weibull wind-speed distributions at meteorological stations were modified to predict friction velocity distributions at eroding field sites. Simplified erosion prediction equations then were used to evaluate wind erosion on highly erodible, loose, sandy soils. Parameters for the erosion prediction equations were developed from wind tunnel data on soil loss and threshold friction velocities at various residue levels. Erosion-control mechanisms of flat residue include restricting soil emission from the surface and increasing threshold wind speeds. A minimum of 30 to 60 percent flat cover is needed to provide adequate control on highly erodible sands. The control level by flat residue can be increased by using short fields. Erosion-control mechanisms of standing residue include reducing the soil-surface friction velocity and intercepting saltating soil. Standing residue is more effective than flat residue, and 5 percent vertical silhouette area of standing residue per unit horizontal area provides adequate erosion-control in low and moderate wind regimes.Contribution from USDA, ARS in cooperation with Kansas Agricultural Experiment Station, Contribution Number 95-41-J.With 6 Figures     

The search for landfill sites – requirements and implementation in Lower Saxony, Germany

 In Germany, landfilling and incineration are the main techniques for the disposal of waste. However, due to humid climatic conditions, leakage of contaminated water from landfills into the subsurface poses a considerable threat to the environment. Therefore, the German states require high safety standards for the construction of a landfill. Emphasis is put on the presence of natural geological barrier rocks. Clay and silts, claystones and siltstones are best suited to meet the requirements defined in legal waste regulations. With regard to retardation capacity, thickness is considered of higher importance than hydraulic permeability. Suitable areas have to be reduced by legally excluded areas. A site search program in Lower Saxony revealed that only 1% of the total state area falls into the best suitability category. Geoscientific investigations on the remaining suitable areas have to become more detailed in the search progress. Geographical information systems (GIS) are the most adequate tools to work on all involved data and to present and outline the results. GIS make the results transparent and understandable to the public. These investigations are a necessary part of the environmental impact assessment which is obligatory for a landfill site's construction. Criteria catalogues take all important aspects of the search process into consideration and help to find the most suitable site. Received: 17 March 1997 · Accepted: 6 June 1997     

The Archipelago

Editorial

The Archipelago     

Interstellar molecule formation in grain mantles: The laboratory analog experiments,results and implications

Laboratory and theoretical studies have been made of the effects of ultraviolet photolysis of interstellar grain mantles which consist of combinations of hydrogen, oxygen, carbon and nitrogen — dirty ice. It is shown that processes involving photolysis (photoprocessing) of interstellar grains are important during most of their lifetime even including the time they spend in dense clouds. A laboratory designed to simulate the interstellar conditions is described. This is the first time such a laboratory has been able to provide results which may be directly scaled to the astrophysical situations involving interstellar grains and their environment. The evolution of grain analogs is followed by observing the infrared absorption spectra of photolyzed samples of ices deposited at 10 K. The creation and storage of radicals and the production of molecules occur as a result of reactions within the solid. A large number of molecules and radicals observed in the interstellar gas appear in the irradiated ices. Energy released during warm-up is seen from visible luminescence and inferred from vapor pressure enhancement which occurs during warming of photolyzed samples relative to unphotolyzed samples. The evolution of a grain and its role as a source as well as a sink of molecules is pictured as a statistical process within dense clouds. The gradual accretion on and photolysis of an individual grain provides the stored chemical energy the release of which is sporadically triggered by relatively mild events (such as low velocity grain-grain collisions) to produce the impulsive heating needed to eject or evaporate a portion of the grain mantle. An extremely complex and rather refractory substance possessing the infrared signatures of amino groups and carboxylic acid groups and having a maximum mass of 514 amu has been produced at a rate corresponding to a mass conversion rate of interstellar grains of between 2% and 20% in 10⁷ yr. The shape and position of the astronomically observed 3.1 m band is duplicated in the laboratory and is shown to be a natural consequence of the processing of grain mantles.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978.     

Analysis of multibeam-Hydrosweep echo peaks for seabed characterisation

Echo-peak data of outer and normal incidence beams from five different Southern Ocean bottom topographic regions have been analysed. The Rice and Extremal probability density function (PDF) statistical approaches reveal that the seabed roughness is, in general, Gaussian in nature except in the case of the Kainan Maru seamount summit (area D). The outer beams of the Enderby abyssal plain (area C) echo-peak PDF statistics reveal the highest possible large-scale feature dominance. Interestingly, Extremal PDF fit parameters (!) from the Agulhas Basin (area A) show a less dominant large-scale roughness than in the case of area C. Large-scale feature dominance up to 15° beam angle is observed in the case of mixed roughness seabeds such as area B (southwest Indian ridge) and area E (Meteor Rise). No increase in the 30°-beam Extremal PDF parameters is observed in these areas. Maximum microtopographic roughness is documented in area D on the summit of Kainan Maru seamount. The estimated fit parameters using Extremal statistics of outer-beam peak data provide a better understanding of the scattering process. Previously determined power law and volume roughness parameters using composite roughness theory are given for the five different areas. These support the results obtained using Rice and Extremal PDFs. The existence of higher volume roughness parameters and power law parameters for medium-scale roughness, along with dominant microtopographic features, are evident from the results of this study.     

Suspended sediment yield and transfer processes in a small High-Arctic glacier basin,Svalbard

Observations of suspended sediment concentration and discharge at two sites on the proglacial river network draining from a predominantly cold-based, High-Arctic glacier (Austre Brøggerbreen) are described. Analysis of these observations illustrates: (i) the relatively low suspended sediment yield from this basin in comparison with many other glacier basins reported in the open literature; (ii) sustained and possibly increasing availability of suspended sediment to the fluvial system as the ablation season progresses; and (iii) the role of the proglacial sandur as both a sediment source and sink. Field observations coupled with the results of the data analysis are used to make inferences concerning the changing nature and relative importance of sediment sources within the basin. © 1998 John Wiley & Sons, Ltd.