268 research outputs found

    The Climate of Hays, Kansas, from 1867 to 1999: Variability, Trends, and Influences

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    Data for a number of possible regional and global climate influences were compared with Hays climate data to characterize the relationships. The analysis of possible influences on Hays climate provided a rich and complex pattern of relationships.https://scholars.fhsu.edu/fort_hays_studies_series/1032/thumbnail.jp

    Transmission, reflection and localization in a random medium with absorption or gain

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    We study reflection and transmission of waves in a random tight-binding system with absorption or gain for weak disorder, using a scattering matrix formalism. Our aim is to discuss analytically the effects of absorption or gain on the statistics of wave transport. Treating the effects of absorption or gain exactly in the limit of no disorder, allows us to identify short- and long lengths regimes relative to absorption- or gain lengths, where the effects of absorption/gain on statistical properties are essentially different. In the long-lengths regime we find that a weak absorption or a weak gain induce identical statistical corrections in the inverse localization length, but lead to different corrections in the mean reflection coefficient. In contrast, a strong absorption or a strong gain strongly suppress the effect of disorder in identical ways (to leading order), both in the localization length and in the mean reflection coefficient.Comment: Important revisions and expansion caused by a crucial property of $\hat Q

    C-band SAR backscatter characteristics of Arctic sea and land ice during winter

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    Synthetic Aperture Radar (SAR) data has become an important tool for studies of polar regions, due to high spatial resolution even during the polar night and under cloudy skies. We have studied the temporal variation of sea and land ice backscatter of twenty-four SAR images from the European Remote Sensing satellite (ERS-1) covering an area in Lady Ann Strait and Jones Sound, Nunavut, from January to March 1992. The presence of fast ice in Jones Sound and glaciers and ice caps on the surrounding islands provides an ideal setting for temporal backscatter studies of ice surfaces. Sample regions for eight different ice types were selected and the temporal backscatter variation was studied. The observed backscatter values for each ice type characterize the radar signatures of the ice surfaces. This time series of twenty-four SAR images over a 3-month period provides new insights into the degree of temporal variability of each surface. Ice caps exhibit the highest backscatter value of -3.9 dB with high temporal variability. Valley glacier ice backscatter values decrease with decreasing altitude, and are temporally the most stable, with standard deviations of 0.08–0.10 dB over the 90-day period. First-year ice and lead ice show a negative trend in backscatter values in time and a positive correlation of up to 0.59 with air temperature over the 90-day period. For first-year ice and lead ice, episodes of large temperature fluctuations (±12°C) are associated with rapid changes in backscatter values (±2 dB). We attribute the backscatter increase to a temperature-induced increase in brine volume at the base of the snow pack. Multi-year ice, conglomerate ice and shore ice are relatively stable over the 3-month period, with a backscatter variation of only a few dBs. An observed lag time of up to three days between backscatter increase/decrease and air temperature can be attributed to the insulation effect of the snow cover over sea ice. The net range of the backscatter values observed on the most temporally stable surface, valley glacier ice, of about 0.30 dB indicates that the ERS-1 SAR instrument exceeds the 1 dB calibration accuracy specified for the Alaska SAR Facility processor for the three winter months

    Sea-Ice Feature Mapping using JERS-1 Imagery

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    JERS-1 SAR and OPS imagery are examined in combination with other data sets to investigate the utility of the JERS-1 sensors for mapping fine-scale sea ice conditions. Combining ERS-1 C band and JERS-1 L band SAR aids in discriminating multiyear and first-year ice. Analysis of OPS imagery for a field site in the Canadian Archipelago highlights the advantages of OPS's high spatial and spectral resolution for mapping ice structure, melt pond distribution, and surface albedo

    Libraries as Repositories of Popular Culture: Is Popular Culture Still Forgotten?

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    Purpose – To replicate a study done in 1992 on the bibliographic availability of 55 popular culture periodicals sold by a Kroger supermarket in Royal Oak, Michigan. The earlier study asked the question whether time might be a relevant variable for the number of holding libraries. Design/methodology/approach – The authors searched WorldCat for the number of reported library holdings for the same 55 popular culture periodicals and analyzed the results. Findings – 34 periodicals with holdings during both periods had a median increase of 58.4%; but, when the 83.5% increase in OCLC full membership during the same period was taken into account, holdings had a median decrease of 13.7%. For the nineteen cases with no library holdings in 1992, eight (42.1%) now had library holdings including several high circulation periodicals such as Star and Soap Opera Weekly. Practical implications – Popular culture materials read by many American are still not widely available in libraries or are not entered into WorldCat, the prime source for bibliographic holdings. Originality/value – Provides additional statistical evidence on the availability of popular culture materials in libraries

    Geostatistical and statistical classification of sea-ice properties and provinces from SAR data

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    Recent drastic reductions in the Arctic sea-ice cover have raised an interest in understanding the role of sea ice in the global system as well as pointed out a need to understand the physical processes that lead to such changes. Satellite remote-sensing data provide important information about remote ice areas, and Synthetic Aperture Radar (SAR) data have the advantages of penetration of the omnipresent cloud cover and of high spatial resolution. A challenge addressed in this paper is how to extract information on sea-ice types and sea-ice processes from SAR data. We introduce, validate and apply geostatistical and statistical approaches to automated classification of sea ice from SAR data, to be used as individual tools for mapping sea-ice properties and provinces or in combination. A key concept of the geostatistical classification method is the analysis of spatial surface structures and their anisotropies, more generally, of spatial surface roughness, at variable, intermediate-sized scales. The geostatistical approach utilizes vario parameters extracted from directional vario functions, the parameters can be mapped or combined into feature vectors for classification. The method is flexible with respect to window sizes and parameter types and detects anisotropies. In two applications to RADARSAT and ERS-2 SAR data from the area near Point Barrow, Alaska, it is demonstrated that vario-parameter maps may be utilized to distinguish regions of different sea-ice characteristics in the Beaufort Sea, the Chukchi Sea and in Elson Lagoon. In a third and a fourth case study the analysis is taken further by utilizing multi-parameter feature vectors as inputs for unsupervised and supervised statistical classification. Field measurements and high-resolution aerial observations serve as basis for validation of the geostatistical-statistical classification methods. A combination of supervised classification and vario-parameter mapping yields best results, correctly identifying several sea-ice provinces in the shore-fast ice and the pack ice. Notably, sea ice does not have to be static to be classifiable with respect to spatial structures. In consequence, the geostatistical-statistical classification may be applied to detect changes in ice dynamics, kinematics or environmental changes, such as increased melt ponding, increased snowfall or changes in the equilibrium line

    PARASITOIDS AND PARASITES OF \u3ci\u3eSPODOPTERA FRUGIPERDA\u3c/i\u3e (LEPIDOPTERA: NOCTUIDAE) IN THE AMERICAS AND CARIBBEAN BASIN: AN INVENTORY

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    An inventory of parasitoids and parasites of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), was conducted using references describing parasitized FAW eggs, larvae, pupae and adults collected from different crops or habitats throughout the Americas and the Caribbean Basin. The crops and countries where these parasites were reported occurring in the Americas is also inventoried. Maize was the crop where the FAW was more frequently collected followed by rice. Overall, Chelonus insularis (Cresson) had the broadest natural distribution in the Americas. For the North American region C. insulares , Chelonus sp., and Euplectrus platyhypenae (Howard) were the most relevant parasitoids. In Central America, C. insularis was the most prevalent parasitoid, and in the South American region the most prevalent parasites were Archytas incertus (Macq.), A. marmoratus (Tns.), C. insularis , and Meteorus laphygmae (Viereck). Diapetimorpha introita (Cresson) is the most important pupal parasitoid of FAW occurring mainly in North America. An acugutturid, Noctuidonema guyanense (Remillet & Silvain), is the most important ectoparasitic nematode attacking adults of FAW and other noctuid moths in South and Southeastern US, and Mexico in North America, Caribbean Basin, Central America, and Northern South America

    Plagiochila rutilans(Hepaticae): A Poorly Known Species from Tropical America

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