Vortex streets in the earth's atmosphere     

J. N. Hunt  Patricia E. Wickins 《Pure and Applied Geophysics》1967,67(1):179-185

Summary Calculations of the Heisenberg parameter and Strouhal number, for mesoscale vortex streets in the atmosphere, support the analogy with the classical Kármán vortex wake. Revised estimates of the horizontal coefficient of eddy diffusion are obtained.  相似文献   

Palynological evidence for early Holocene aridity in the southern Sierra Nevada, California     

Owen K. Davis  R. Scott Anderson  Patricia L. Fall  Mary K. O'Rourke  Robert S. Thompson 《Quaternary Research》1985,24(3):322-332

Sediments of Balsam Meadow have produced a 11,000-yr pollen record from the southern Sierra Nevada of California. The Balsam Meadow diagram is divided into three zones. (1) The Artemisia zone (11,000–7000 yr B.P.) is characterized by percentages of sagebrush (Artemisia) and other nonarboreal pollen higher than can be found in the modern local vegetation. Vegetation during this interval was probably similar to the modern vegetation on the east slope of the Sierra Nevada and the climate was drier than that of today. (2) Pinus pollen exceeded 80% from 7000 to 3000 yr B.P. in the Pinus zone. The climate was moister than during the Artemisia zone. (3) Fir (Abies, Cupressaceae, and oak (Quercus) percentages increased after 3000 yr B.P. in the Abies zone as the modern vegetation at the site developed and the present cool-moist climatic regime was established. Decreased fire frequency after 1200 yr B.P. is reflected in decreased abundance of macroscopic charcoal and increased concentration of Abies magnifica and Pinus murrayana needles.  相似文献   

Reaction rate-surface area relationships during the early stages of weathering—I. Initial observations     

George R. Holdren  Patricia M. Speyer 《Geochimica et cosmochimica acta》1985,49(3):675-681

It has commonly been assumed that the weathering rates of feldspars are proportional to their exposed surface areas. However, weathering does not affect the whole surface of a grain uniformily; preferential dissolution occurs at highly localized sites, which are determined by the location of crystalline defects. To examine the importance of reactions at these sites relative to those occurring on bulk surfaces, we compared the rates of dissolution of 5 different size fractions of an alkali feldspar, whose specific surface areas (m²/g) spanned a range of a factor of twenty.At any given pH value, the bulk dissolution rates (moles/g/h) for the five fractions varied by less than a factor of two. The results suggest that reactions at crystalline defects dominate weathering processes during the early stages of dissolution. Furthermore, the exposure of these defects is not simply or easily related to total surface area. These findings strongly suggest that care must be taken to distinguish between the surface reaction controlled mechanism and a surface area controlled model which is frequently—and incorrectly—assumed to be equivalent. The data presented here are consistent with the former mechanism but strongly dispute the latter.  相似文献   

Surface Charge Concentrations on Silica in Different 1.0 M Metal-Chloride Background Electrolytes and Implications for Dissolution Rates     

Magnus Karlsson  Colin Craven  Patricia M. Dove  William H. Casey 《Aquatic Geochemistry》2001,7(1):13-32

The empirical rate laws formulated to describe the dissolution rates of oxide minerals include the surface charge concentration that results from the protonation and deprotonation of surface functional groups. Previous experiments on quartz and silica have shown that dissolution rates vary as a function of different background electrolyte solutions, however, such experiments are often conducted at elevated temperatures where it is difficult to estimate surface charge along with the dissolution rates. In the present study we measuresurface charge concentrations for silica in different electrolyte solutions at 298 K in order to quantify the extent to which the different counterions could affect the dissolution rates through their influence on the surface charge concentrations. The experimental solutions in the electrolyte series: LiCl, NaCl, KCl, RbCl, CaCl₂, SrCl₂ and BaCl₂ were prepared to maintain a constant metal concentration of 1.0 M. For the alkali-metal chlorides, the surface charge concentrations correlate with the size of the hydrated alkali metal, consistent with the idea that these counterions affect charge via outer-sphere coordination that shield proton surface complexes from one another. The reactivity trend for alkaline-earth cations is less clear, but the data demonstrate distinct differences in the acid-base propertiesof the silica surface in these different electrolytes. We then discuss how these trends are manifested in the rate equations used to interpret dissolution experiments.  相似文献   

Book reviews     

David K. Rea  Dirk Verschuren  Joseph R. Desloges  Patricia M. Anderson 《Journal of Paleolimnology》1996,16(3):357-295

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Patterns of abundance for Mnemiopsis in US coastal waters: a comparative overview     

Kremer  Patricia 《ICES Journal of Marine Science》1994,51(4):347-354

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Benthic Fluxes of Dissolved Inorganic Nitrogen in a Coastal Lagoon of the Northern Adriatic Sea: an Interpretation of Spatial Variability Based on Sediment Features and Infauna Activity   总被引：1，自引：0，他引：1  

Daniele Nizzoli  Giuseppe Castaldelli  Marco Bartoli  David Thomas Welsh  Patricia Arriaga Gomez  Anna Elisa Fano  Pierluigi Viaroli 《Marine Ecology》2002,23(S1):297-306

Abstract. Dark respiration rates, dissolved inorganic nitrogen (DIN) fluxes and nitrification rates were measured at two sites in the microtidal Sacca di Goro lagoon in September 2000. DIN fluxes correlated with the biomass of the dominant macrofauna species (the amphipod Corophium spp. at station Giralda and the polychaete Neanthes spp. at station Faro). Respiration (> 6 mmol O₂ m⁻²h⁻¹) and ammonium fluxes (> 80μmol N m⁻²h⁻¹) were higher at station Giralda despite the lower organic matter content (4.5 %) and lower macrofauna biomass (4 g AFDW m⁻²). At both sites ammonium fluxes were significantly correlated with the biomass of the benthic infauna, but Corophium stimulated ammonium NH₄⁺ fluxes 3-fold compared to Neanthes. The amphipod also enhanced nitrification rates (> 300 μmol N m⁻²h⁻¹) due to the high density of its burrows, the higher NH₄⁺ regeneration rates and the enhanced oxygen supply to the bacteria.  相似文献   

Holocene climate and glacial history of the northeastern Antarctic Peninsula: the marine sedimentary record from a long SHALDRIL core     

Bradley R. Michalchuk  John B. Anderson  Julia S. Wellner  Patricia L. Manley  Wojciech Majewski  Steve Bohaty 《Quaternary Science Reviews》2009,28(27-28):3049-3065

A high-resolution record of Holocene deglacial and climate history was obtained from a 77 m sediment core from the Firth of Tay, Antarctic Peninsula, as part of the SHALDRIL initiative. This study provides a detailed sedimentological record of Holocene paleoclimate and glacial advance and retreat from the eastern side of the peninsula. A robust chronostratigraphy was derived from thirty-three radiocarbon dates on carbonate material. This chronostratigraphic framework was used to establish the timing of glacial and climate events derived from multiple proxies including: magnetic susceptibility, electric resistivity, porosity, ice-rafted debris content, organic carbon content, nitrogen content, biogenic silica content, and diatom and foraminiferal assemblages. The core bottomed-out in a stiff diamicton interpreted as till. Gravelly and sandy mud above the till is interpreted as proximal glaciomarine sediment that represents decoupling of the glacier from the seafloor circa 9400 cal. yr BP and its subsequent landward retreat. This was approximately 5000 yr later than in the Bransfield Basin and South Shetland Islands, on the western side of the peninsula. The Firth of Tay core site remained in a proximal glaciomarine setting until 8300 cal. yr BP, at which time significant glacial retreat took place. Deposition of diatomaceous glaciomarine sediments after 8300 cal. yr BP indicates that an ice shelf has not existed in the area since this time.The onset of seasonally open marine conditions between 7800 and 6000 cal. yr BP followed the deglacial period and is interpreted as the mid-Holocene Climatic Optimum. Open marine conditions lasted until present, with a minor cooling having occurred between 6000 and 4500 cal. yr BP and a period of minor glacial retreat and/or decreased sea ice coverage between 4500 and 3500 cal. yr BP. Finally, climatic cooling and variable sea ice cover occurred from 3500 cal. yr BP to near present and it is interpreted as being part of the Neoglacial. The onset of the Neoglacial appears to have occurred earlier in the Firth of Tay than on the western side of the Antarctic Peninsula. The Medieval Warm Period and Little Ice Age were not pronounced in the Firth of Tay. The breadth and synchroneity of the rapid regional warming and glacial retreat observed in the Antarctic Peninsula during the last century appear to be unprecedented during the Holocene epoch.  相似文献   

An overview of the Lagrangian experiments undertaken during the North Atlantic regional Aerosol Characterisation Experiment (ACE‐2)     

Doug W. Johnson  Simon Osborne  Robert Wood  Karsten Suhre  Randy Johnson  Steven Businger  Patricia K. Quinn  Alfred Wiedensohler  Philip A. Durkee  Lynn M. Russell  Meinrat O. Andreae  Colin O'Dowd  Kevin J. Noone  Brian Bandy  J. Rudolph  Spyros Rapsomanikis 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):290-320

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Evolution of the aerosol, cloud and boundary‐layer dynamic and thermodynamic characteristics during the 2nd Lagrangian experiment of ACE‐2     

Simon R. Osborne  Douglas W. Johnson  Robert Wood  Brian J. Bandy  Meinrat O. Andreae  Colin D. O'Dowd  Paul Glantz  Kevin J. Noone  Christoph Gerbig  Jochen Rudolph  Timothy S. Bates  Patricia Quinn 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):375-400

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