Water flow and the vertical distribution of meiofauna: A flume experiment     

Margaret A. Palmer  R. Michael Molloy 《Estuaries and Coasts》1986,9(3):225-228

Laboratory experiments were conducted in a recirculating saltwater flume to determine if flow influences the vertical distribution of meiofauna within fine cohesive sediments. Replicate flume boxcores collected from a nonvegetated mudflat were exposed to either a no flow or a flow experimental treatment. After 3 h in the flume, the boxcores were sampled by taking smaller sediment cores and sectioning these cores vertically in 2-mm intervals. There was no statistical difference in the number of copepods (adults, copepodites, and nauplii) in the top 2mm of sediment in flow vs. no flow treatments. The number of nematodes and foraminiferans within the top 2 mm of sediment was significantly lower in the flow treatments than in the no flow treatments. Downward migrations may decrease the susceptibility of these fauna to passive erosion by tidal currents.  相似文献   

Paleomagnetic and sedimentological studies at Lake Tahoe,California-Nevada     

Donald F. Palmer  Thomas L. Henyey  Richard E. Dodson 《Earth and Planetary Science Letters》1979,46(1):125-137

Three closely spaced 6-m piston cores were taken in the central part of Lake Tahoe. Cores were split into two complete replicates for paleomagnetic study and the remaining sections were used for stratigraphic and mineralogical analysis.Stratigraphic correlation of the cores is based on two distinctive horizons (volcanic ash and diatomite) and upon three different sedimentological regimes dominated by (1) poorly bedded silts and muds, (2) well bedded graded units, and (3) finely laminated silts. These correlations served as the standards for the evaluation of the paleomagnetic data. Extrapolation of¹⁴C dates obtained in the upper sections of the Lake Tahoe sediments suggests that the lower sections of the cores may reach ages of 25,000–30,000 years B.P.X-ray, optical, Curie point, and hysteresis measurements show that magnetite is the only important magnetic mineral in the sediments and occurs in the size range of 10 μm. Hematite is essentially absent. Based on large changes in the declination and inclination of the natural remanent magnetism (NRM) within single graded layers the paleomagnetic signature is a post-depositional remanent magnetism (PDRM). This PDRM is believed to be caused by magnetic orientation during compaction.Paleomagnetic measurements show three regimes that are correlated with the stratigraphic regimes. NRM declination and inclination data show good correlation between the three cores and agree well with the correlations based on sediment character. NRM intensity variations are due largely to the variations in magnetite content and its occurrence as either single detrital grains or as inclusions within the larger silicates. Thus the variation in paleo intensity was not determined.Comparisons of Lake Tahoe data with that from Mono Lake show fair correlations of declination and inclination. The occurrence of a short-wavelength, high-amplitude event in the lower section of the Lake Tahoe cores may provide confirmation of the Mono Lake geomagnetic excursion.  相似文献   

An observational study of entraining convection using balloon-borne turbulence probes and high-power Doppler radar     

S. G. Palmer  S. J. Caughey  K. W. Whyte 《Boundary-Layer Meteorology》1979,16(4):261-278

Features associated with the upper limit of convection, observed by turbulence probes supported by a tethered kite balloon and by high-power Doppler radar, are described. The observations illustrate the interaction of thermal plumes with the capping inversion (and stable air aloft) and confirm the existence of non-turbulent, intermittently turbulent and fully turbulent layers. Evidence is presented for entrainment processes occurring on scales ranging from a few metres to several hundred metres. Individual distortions of the inversion interface, tracked by the radar, have a lifetime of about 5 minutes. Other, larger scale (i.e., > 1 km) perturbations of the top of the boundary layer were observed over longer periods, and are thought to be due to topographical effects.Now at the Meteorological Office, Bracknell, U.K.  相似文献   

南海表面温度距平对我国夏季风和降水影响的数值试验   总被引：7，自引：1，他引：7  

孙照渤  章基嘉  T.N.Palmer 《气象学报》1990,48(1):113-116

我国东部夏季降水不仅与副高脊线的向北推进有关,而且与对流层低层夏季季风向北推进有关。Shukla,在研究印度季风降水量对阿拉伯海域海表温度响应时也指出,对季风环流模拟的真实性直接影响印度季风降水模拟的真实性。本文以观测分析结果为依据,用英国  相似文献   

Boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites   总被引：8，自引：0，他引：8  

Martin R. Palmer  John F. Slack 《Contributions to Mineralogy and Petrology》1989,103(4):434-451

Boron isotope ratios (¹¹B/¹⁰B) have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings. The coverage of these localities is global (5 continents) and includes the giant ore bodies at Kidd Creek and Sullivan (Canada), Broken Hill (Australia), and Ducktown (USA). Overall, the tourmalines display a wide range in ¹¹B values from –22.8 to +18.3 Possible controls over the boron isotopic composition of the tourmalines include: 1) composition of the boron source, 2) regional metamorphism, 3) water/rock ratios, 4) seawater entrainment, 5) temperature of formation, and 6) secular variations in seawater ¹¹B. The most significant control appears to be the composition of the boron source, particularly the nature of footwall lithologies; variations in water/ rock ratios and seawater entrainment are of secondary importance. The boron isotope values seem especially sensitive to the presence of evaporites (marine and non-marine) and carbonates in source rocks to the massive sulfide deposits and tourmalinites.  相似文献   

Parametrization and influence of subgridscale orography in general circulation and numerical weather prediction models     

M. J. Miller  T. N. Palmer  R. Swinbank 《Meteorology and Atmospheric Physics》1989,40(1-3):84-109

Summary The problem of representing the drag due to subgridscale orography is examined. Results from model simulations are used to illustrate clear deficiencies in the global angular momentum budgets and possible ways of correcting for these deficiencies are considered. It is argued that a formulation for the stress due to subgridscale gravity waves is required, as was first recognized by Boer et al. (1984a, b), and the impact of a scheme based on Palmer et al. (1986) is presented. The scheme is improved by using directionally-dependent subgridscale orographic variances. Results from 90-day integrations using the ECMWF and UKMO models with similar resolutions are very much in accord both with and without a wave drag parametrization scheme; showing much improved wintertime circulations.The relationship between the wave drag and the model orography is examined with the use of idealized stress profiles whereby the wave drag is limited to either near the surface or in the stratosphere. A combination of parametrized wave drag with an envelope orography performs best at this stage of development.Results are presented from a substantial series of ten-day forecast experiments with the ECMWF operational model using mean and (1 ) envelope orographies, these show significant improvements in forecast skill.With 26 Figures  相似文献   

The geology of continental margins | C.A. Burk and C.L. Drake, (Editors), 1975. Springer,Berlin, 1009 pp., U.S. $34.80     

Harold D. Palmer 《Earth》1976,12(4):423-424

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The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin   总被引：5，自引：1，他引：5  

Niklas S. Christensen  Andrew W. Wood  Nathalie Voisin  Dennis P. Lettenmaier  Richard N. Palmer 《Climatic change》2004,62(1-3):337-363

The potential effects of climate change on the hydrology and water resources of the Colorado River basin are assessed by comparing simulated hydrologic and water resources scenarios derived from downscaled climate simulations of the U.S. Department of Energy/National Center for Atmospheric Research Parallel Climate Model (PCM) to scenarios driven by observed historical (1950–1999) climate. PCM climate scenarios include an ensemble of three 105-year future climate simulations based on projected `business-as-usual'(BAU) greenhouse gas emissions and a control climate simulation based on static 1995 greenhouse gas concentrations. Downscaled transient temperature and precipitation sequences were extracted from PCM simulations, and were used to drive the Variable Infiltration Capacity (VIC) macroscale hydrology model to produce corresponding streamflow sequences. Results for the BAU scenarios were summarized into Periods 1, 2, and 3 (2010–2039,2040–2069, 2070–2098). Average annual temperature changes for the Colorado Riverbasin were 0.5 °C warmer for control climate, and 1.0, 1.7, and 2.4 °C warmer for Periods 1–3, respectively, relative to the historicalclimate. Basin-average annual precipitation for the control climate was slightly(1%) less than for observed historical climate, and 3, 6, and 3%less for future Periods 1–3, respectively. Annual runoff in the controlrun was about 10% lower than for simulated historical conditions, and 14, 18, and 17% less for Periods 1–3, respectively. Analysis of watermanagement operations using a water management model driven by simulated streamflows showed that streamflows associated with control and future BAU climates would significantly degrade the performance of the water resourcessystem relative to historical conditions, with average total basin storage reduced by 7% for the control climate and 36, 32 and 40% for Periods 1–3, respectively. Releases from Glen Canyon Dam to the LowerBasin (mandated by the Colorado River Compact) were met in 80% of years for the control climate simulation (versus 92% in the historical climate simulation), and only in 59–75% of years for the future climate runs. Annual hydropower output was also significantly reduced for the control and future climate simulations. The high sensitivity of reservoir system performance for future climate is a reflection of the fragile equilibrium that now exists in operation of the system, with system demands only slightly less than long-term mean annual inflow.  相似文献   

Characterization of Turkish coals: a nationwide perspective     

Curtis A. Palmer  Ertem Tuncal&#x;  Kristen O. Dennen  Timothy C. Coburn  Robert B. Finkelman 《International Journal of Coal Geology》2004,60(2-4):85-115

The U.S. Geological Survey (USGS) and the Turkish General Directorate of Mineral Research and Exploration (Maden Tetkik ve Arama Genel Müdürlügü, MTA) are working together to provide a better understanding of the chemical properties of Turkish coals from major Turkish lignite producing areas.The coals in Turkey are generally low rank (lignite or subbituminous) formed in several different depositional environments at different geologic times and have differing chemical properties. Eocene coals are limited to northern Turkey; Oligocene coals, found in the Thrace Basins of northwestern Turkey, are intercalated with marine sediments; Miocene coals are generally located in Western Turkey. The coal deposits, which have limnic characteristics, have relatively abundant reserves. Pliocene–Pleistocene coals are found in the eastern part of Turkey. Most of these coals have low calorific values, high moisture, and high ash contents.Analysis of 143 coal channel samples (most are lignite and subbituminous in rank, but a few are bituminous and one is anthracitic in rank) has been completed for up to 54 elements and other coal properties using a variety of analytical techniques, including inductively coupled plasma emission and mass spectrometry, instrumental neutron activation analysis, and various single element techniques and ASTM standard procedures. Many of these coals have elemental concentrations similar to U.S. lignites found in the Gulf Coast and Fort Union regions. However, maximum or mean concentrations of B, Cr, Cs, Ni, As, Br, Sb, Cs, and U in Turkey are higher than the corresponding maximum or mean values found in either the Fort Union or Gulf Coast regions.  相似文献   

Modeling the surface complexation of calcium at the rutile-water interface to 250°C     

Moira K. Ridley  Michael L. Machesky  Donald A. Palmer 《Geochimica et cosmochimica acta》2004,68(2):239-251

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