Remote sensing of temporal and spatial variations in pool size, suspended sediment, turbidity, and Secchi depth in Tuttle Creek Reservoir, Kansas: 1993     

M. Duane Nellis  John A. Harrington  Jr.  Jaiping Wu 《Geomorphology》1998,21(3-4)

Four dates of Landsat Thematic Mapper data from 1993, April 9, July 30, August 15, and September 16, were used to assess temporal and spatial patterns of lake area and dimensions of suspended sediment concentration in Tuttle Creek Reservoir, Kansas. In 1993, excessive precipitation in the Big Blue River Basin, and throughout much of the Upper Middle West, led to widespread flooding. Rains produced substantial erosion, sediment movement down the stream network, and a runoff volume that filled Tuttle Creek Reservoir, a U.S. Army Corps of Engineers flood control structure. The April 9 data are from before the flood, the July 30 data are from the time of maximum pool size and use of the emergency spillway, and the August and September data document the declining pool sizes. Three separate analyses were performed on each of the four dates of Thematic Mapper data. One set of analyses involved applying an existing physical model that uses at-satellite reflectance for TM Band 3 to estimate variations in suspended sediment, turbidity, and Secchi depth throughout the reservoir. Maps of estimated parameters of water quality for the four individual dates were compared and analyzed to document spatial and temporal changes. The second research method involved unsupervised classification (ERDAS ISODATA algorithm) of the data from the Tuttle Creek Reservoir. Water areas were grouped into coherent classes for further spatial analysis using a two-step or layered classification procedure for each date. The third analysis used a GIS overlay technique to compare the area of the water surface for each of the four dates with the flood pool as marked on U.S.G.S. 7-1/2 minute quadrangles. Comparisons document the major change in lake area between April and July, the high levels of suspended sediment in mid-summer, and the decline in pool size and concentrations of suspended sediment by mid-September. The study illustrates the advantages of using remote sensing to assist in documenting a relatively short-term environmental hazard. This study also demonstrates the value of Landsat Thematic Mapper data for use in mapping geographic variations in water area and quality in conjunction with a major flood event.  相似文献   

Intermediate-scale sea ice — Atmosphere interactions over high southern latitudes in winter     

Dr. Andrew M. Carleton  Mr. Duane A. Carpenter 《GeoJournal》1989,18(1):87-101

Associations between polar air cloud vortices (polar lows), as an indicator of intermediate-scale atmospheric activity, and the Antarctic sea ice, are examined for the Southern Hemisphere winter (June–September). Seven consecutive winters, spanning a period of marked interannual variability of the atmospheric circulation and sea ice (1977–83), are analyzed using sets of DMSP (Defense Meteorological Satellite Program) imagery. Relatively high frequencies of polar lows are found in ice-edge and adjacent ocean latitudes. There is some evidence for an equatorward shift in the latitude of maximum monthly polar low occurrence during the June to September period. Polar low incidence over the Southern Hemisphere on interannual time scales shows a close association with positive sea ice anomalies in the longitudes of more frequent cold air outbreaks from higher latitudes. This is particularly apparent for winters of strongly anomalous circulation, such as FGGE (1979) and the major ENSO of 1982–83. However, for individual cases on daily to weekly time scales, the feedback of cold air — sea ice advance — polar low development is not always evident, and implies that additional processes may contribute to polar air cyclogenesis in the marginal ice zone.  相似文献   

An aperture synthesis study of Saturn and its rings at 3.71-cm wavelength     

F.Peter Schloerb  Duane O. Muhleman  Glenn L. Berge 《Icarus》1979,39(2):232-250

We present aperture synthesis maps of the Saturn system at a wavelength of 3.71 cm. The data used to make the maps were obtained in May–June 1976 at the Owens Valley Radio Observatory on 13 interferometer baselines. The aperture synthesis maps contain few assumptions about the brightness structure of Saturn and the rings and, therefore, may be used to check previous model-fitting results as well as search for new unmodeled features. Generally, the maps confirm the previous model-fitting results. An exception to this is that the brightness temperature of the planet that is implied by the maps is about 4% less than that deduced from model fitting. The likely explanation of this discrepancy is that random errors on the phase of the visibility function have led to an underestimate of the planet brightness temperature in the map. Maps of the residuals to the model fits have shown that the position of Saturn given in the American Ephemeris and Nautical Almanac may be in error by about 0.25 arcsec. Maps of the residuals to model fits including a position offset show that no new features of the Saturn brightness structure are required to match the present data. In particular, no azimuthal variations in the brightness temperature of the rings were detected.  相似文献   

Weathering and biokarst development on marine terraces,northwest Morocco     

Michael J. Duane  Ali T. AL‐Mishwat  Mohammed Rafique 《地球表面变化过程与地形》2003,28(13):1439-1449

Weathering features are described from an arid coastal area in northern Morocco which are indicative of invasive chasmolithic and endolithic microbial communities. Active weathering of marine terraces and karst development is associated with endolithic and epilithic algae responsible for boring, disintegration of matrix and mineral fabrics, solution and biomineralization that undermines the marine carbonate platform. Evidence of a range of biological weathering agents remains preserved, speci?cally calci?ed ?laments and sporangial material. An abundance of ?laments and spores representative of a consortium of algae, fungi, cyanobacteria and lichens is associated with the most denuded outcrops. The array of microbes contributes to the formation of the stromatolites to depths of 0·5 m within the limestone substrate. The preservation of stromatolites is supported by calci?cation of spores and ?laments, with trapping and binding of carbonate held in suspension by vadose waters. The pervasive weathering on this sector of coastline has important practical implications for coastal planning and development authorities in Morocco. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Age and significance of the Late Pleistocene Dawson tephra in eastern Beringia     

Duane Froese  John Westgate  Shari Preece  John Storer 《Quaternary Science Reviews》2002,21(20-22)

Dawson tephra, recently recognized in the Klondike area of Yukon Territory, records one of the largest Quaternary volcanic eruptions in Beringia. Its composition is similar to that of Old Crow tephra, indicating a source in the Aleutian arc-Alaska Peninsula region of southwestern Alaska. Its primary thickness in central Yukon is nearly twice that of Old Crow tephra, which has an estimated eruption volume of >50 km³. The distribution of Dawson tephra is still poorly known, but based on its source area and occurrence in central Yukon, it should be widespread across southern Alaska, Yukon and the Gulf of Alaska. New radiocarbon ages indicate the eruption occurred at about 24,000 ¹⁴C yr BP (ca 27,000 cal yr BP). The Dawson tephra is a valuable marker bed for correlating late Pleistocene records across large areas of eastern Beringia and adjacent marine records.  相似文献   

Erratum to: The Exxon and BP oil spills: a comparison of psychosocial impacts     

Duane A. Gill  Liesel A. Ritchie  J. Steven Picou  Jennifer Langhinrichsen-Rohling  Michael A. Long  Jessica W. Shenesey 《Natural Hazards》2015,79(1):673-673

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Assessment of Dynamic Downscaling of the Extreme Rainfall over East Asia Using a Regional Climate Model   总被引：1，自引：0，他引：1  

GAO Yanhong  Yongkang XUE  PENG Wen  Hyun-Suk KANG  Duane WALISER 《大气科学进展》2011,28(5):1077-1098

This study investigates the capability of the dynamic downscaling method (DDM) in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model (MM5).Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau (TP),where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries (LLB) westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.  相似文献   

Tectonic brines and sedimentary basins: further applications of fission track analysis in understanding Karoo Basin evolution (South Africa)   总被引：1，自引：0，他引：1  

Michael J. Duane  Roderick W. Brown 《Basin Research》1991,3(4):187-195

Fission track analyses of detrital components in the Permo-Triassic Karoo Basin (South Africa), highlight the potency of tectono-magmatically driven fluids to penetrate wide and far in foreland basins. The data, together with the data published on Karoo tectonics and magmatism, support a model which requires that fluids were driven north out of the Cape-Karoo orogen during the Cape Orogeny (270–200 Ma). Later fluids were redistributed and aquifers rejuvenated during (and after) the final break-up of Gondwana (<200 Ma). The fission track data indicate that thermal annealing of fission tracks in zircon occurs non-uniformly between individual zircon grains. This model is in agreement with recent models applied to deformed foreland basins and implicates tectonic fluids in U metallogenesis.  相似文献   

Multi-frequency synthetic-aperture imaging with a lightweight ground penetrating radar system     

Steven K. Koppenjan  Curt M. Allen  Duane Gardner  Howard R. Wong  Hua Lee  Stephanie J. Lockwood 《Journal of Applied Geophysics》2000,43(2-4)

The detection of buried objects, particularly hazardous waste containers and unexploded ordnance (UXO), has gained significant interest in the Unites States in the late 1990s. The desire to remediate the thousands of sites worldwide has become an increasing concern and the application of radar to this problem has received renewed attention. The US Department of Energy's Special Technologies Laboratory (STL), operated by Bechtel Nevada, has developed several frequency-modulated, continuous-wave (FM-CW) ground penetrating radar (GPR) units. To meet technical requirements for higher-resolution data, STL and the University of California, Santa Barbara (UCSB) is investigating advanced GPR hardware, signal processing, and synthetic-aperture imaging with the development of an innovative system. The goal is to design and fabricate a lightweight, battery-operated unit that does not require surface contact, can be operated by a novice user, and can achieve improved resolution. The latter is accomplished by using synthetic-aperture imaging, which forms the subsurface images by fully utilizing the data sequences collectively along a scan path. We also present the backward propagation algorithm as the basic structure of the multiple-frequency tomographic imaging technique, and the conventional fast Fourier transform (FFT) method which can be described as a degenerated case of the model where the computation procedure is approximated under the narrow-beam assumption.  相似文献   

X-ray photoionized plasmas in space and in the laboratory     

Duane A. Liedahl 《Astrophysics and Space Science》2011,336(1):251-256

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