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41.
C. W. Fairall Ralph Markson G. E. Schacher K. L. Davidson 《Boundary-Layer Meteorology》1980,19(4):453-469
The dissipation rate of turbulent kinetic energy, , and the temperature structure function parameter, C
T
2, have been measured over water from the near surface (Z = 3 m) to the top of the boundary layer. The near surface values of and C
T
2 were used to calculate the velocity and temperature Monin-Obukhov scaling parameters u
* and T
*. The data collected during unstable lapse rates were used to evaluate the feasibility of extrapolating the values of and C
T
2 as a function of height with empirical scaling formulae. The dissipation rate scaling formula of Wyngaard et al. (l971 a) gave a good fit to an average of the data for Z < 0.8 Z
i. In the surface layer the scaling formula of Wyngaard et al. (1971b) disagreed with the C
T
2 values by as much as 50%. This disagreement is due to an unexpected reduction in the measured values of C
T
2 forZ < 30 m. At this point it is not clear if the discrepancy is a unique property of the marine boundary layer or if it is simply some unknown instrumental or analytical problem. The mixed layer scaling results were similar to the overland results of Kaimal et al. (1976). 相似文献
42.
Ralph E. Hunter 《Sedimentary Geology》1980,27(4):241-262
Pleistocene coastal terrace deposits exposed in sea cliffs near Gold Beach, Oregon can be divided into four stratigraphic units: a basal gravelly unit and three overlying sandy units, each with mud beds, a paleosol, or the modern soil in its uppermost part. The gravelly unit consists of gravel and sand in its lower part, sand, in part pebbly or cobbly, in its middle part, and mud and sand in its upper part. Black sand and transported pieces of wood are common in the middle part of the unit, and wood is common in the mud. This unit is interpreted as a progradational deposit including environments ranging from lower forebeach at the base to backbeach flats and streams at the top.The main sandy parts of the sandy units are made up of a crossbedded sand facies, the dominant structure in which is medium-scale crossbedding, and an irregularly bedded sand facies, which is locally pebbly and is dominated by scour-and-fill structures. Deciding between shallow marine and eolian interpretations of the sandy units proved exceptionally difficult until modern analogues were found in the fine details of the internal structures. Largely on the basis of such structural details, the crossbedded sand facies is interpreted as the product of small eolian dunes, and the irregularly bedded sand facies is interpreted as deposits of interdune ephemeral streams, ephemeral ponds, and wet to dry subaerial flats. The mud beds and paleosols at the tops of the sandy units represent times of temporary stabilization of the dune field. 相似文献
43.
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45.
The Huygens Probe detected dendritic drainage-like features, methane clouds and a high surface relative humidity (∼50%) on Titan in the vicinity of its landing site [Tomasko, M.G., and 39 colleagues, 2005. Nature 438, 765-778; Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784], suggesting sources of methane that replenish this gas against photo- and charged-particle chemical loss on short (10-100) million year timescales [Atreya, S.K., Adams, E.Y., Niemann, H.B., Demick-Montelara, J.E., Owen, T.C., Fulchignoni, M., Ferri, F., Wilson, E.H., 2006. Planet. Space Sci. In press]. On the other hand, Cassini Orbiter remote sensing shows dry and even desert-like landscapes with dunes [Lorenz, R.D., and 39 colleagues, 2006a. Science 312, 724-727], some areas worked by fluvial erosion, but no large-scale bodies of liquid [Elachi, C., and 34 colleagues, 2005. Science 308, 970-974]. Either the atmospheric methane relative humidity is declining in a steady fashion over time, or the sources that maintain the relative humidity are geographically restricted, small, or hidden within the crust itself. In this paper we explore the hypothesis that the present-day methane relative humidity is maintained entirely by lakes that cover a small part of the surface area of Titan. We calculate the required minimum surface area coverage of such lakes, assess the stabilizing influence of ethane, and the implications for moist convection in the atmosphere. We show that, under Titan's surface conditions, methane evaporates rapidly enough that shorelines of any existing lakes could potentially migrate by several hundred m to tens of km per year, rates that could be detected by the Cassini orbiter. We furthermore show that the high relative humidity of methane in Titan's lower atmosphere could be maintained by evaporation from lakes covering only 0.002-0.02 of the whole surface. 相似文献
46.
Ralph Fyfe 《第四纪科学杂志》2007,22(6):571-578
New and existing pollen data from Wales, UK, are used to assess the level of landscape openness at the regional and local scale. At the regional scale, the existing pollen data support the high‐forest model of vegetation structure by 6000 cal. yr. BC prior to any palynological signal for anthropogenic impact in the region. New data from two sites in southwest Wales follow the general regional pattern of early to middle Holocene vegetation succession, but are striking owing to maintenance of high non‐arboreal pollen percentages (NAPs) throughout the mid‐Holocene. It is argued that these NAPs indicate that a significant degree of openness can be found at the local level (and beyond the confines of the peat‐forming site) within regions characterised by closed woodland. It is possible that woodland development in these areas may have been suppressed by reduced drainage, although the role of grazing animals in maintenance of clearings cannot be assessed. Implications for this local degree of openness are discussed, in particular the significance of vegetation heterogeneity at the local scale for the construction of place or locale for prehistoric communities. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
47.
48.
Jackie L. Cooper Geoffrey V. Bicknell Ralph S. Sutherland Joss Bland-Hawthorn 《Astrophysics and Space Science》2007,311(1-3):99-103
In order to better understand the formation of a starburst-driven wind, we have performed a series of three-dimensional hydrodynamical
simulations in an inhomogeneous interstellar medium. We present the results of these simulations, which provide new insights
into the formation of the optical filaments and the origin of the soft X-ray emission. 相似文献
49.
Run Liu Shaw Chen Liu Ralph J. Cicerone Chein-Jung Shiu Jun Li Jingli Wang Yuanhang Zhang 《大气科学进展》2015,32(8):1027-1037
50.
Macroinvertebrate community composition was compared across streams draining catchments dominated by either native bush, agricultural or urban land uses within the Water of Leith stream catchment near Dunedin, New Zealand. Land use was associated with differences in taxon richness and faunal composition of communities present in each stream. The mean abundance levels of Ephemeroptera, Plecoptera, and Trichoptera were highest in native bush catchments, and lowest in urban catchments. In contrast, the mean abundance of Oligochaeta exhibited the opposite pattern. Increasing dominance of the urban and agricultural streams by pollution tolerant taxa was reflected in the Macroinvertebrate Community Index and Quantitative Macroinvertebrate Community Index scores. 相似文献