Radiation stress due to ocean waves and the resulting currents and set-up/set-down     

Carl Newell  Thomas Mullarkey  Mark Clyne 《Ocean Dynamics》2006,56(3-4):376-376

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Sexual productivity and spring intramarsh distribution of a key salt-marsh microbial secondary producer     

Steven Y. Newell  Jennifer Wasowski 《Estuaries and Coasts》1995,18(1):241-249

Phaeosphaeria spartinicola is known to be an important fungal (ascomycetous) secondary producer in the smooth-cordgrass (Spartina alterniflora) decomposition system of western Atlantic salt marshes, yet its degree of predominance among the ascomycete assemblages of salt marshes and the concentration of its sexual reproductive structures (ascomata) have been largely unknown. During May–June, we measured by direct microscopy the percent occupancy of leaf abaxial area and concentrations of ascomata in leaf blades of smooth cordgrass at three elevations in three drainage systems within the marshes of Sapelo Island, Georgia, United States. We also measured in water-saturation chambers the rates at which the ascomata expelled ascopoores (sexual propagules) out of decaying leaves from marsh sites containing or not containing shredder gastropods.P. spartinicola ascomata were found at averages of 36% to 93% of grid-circles (3-mm radius) on decaying leaf blades, with lower values at points directly adjacent to the leaf sheath, on leaves at earlier stages of decay, and at elevational subsites where shredder snails were more active. Marsh elevation had no effect of its own on percent occupation. No other species of ascomycetes were found at overall avarage frequencies greater than 3%. Average concentration of ascomata along the intervascular rows where they were located was 1 ascoma per 0.5 mm row (～1000 cm^?2 abaxial leaf surface, translating to production of 1.6×10⁷ ascomata m^?2 intermediate-height marsh per standing crop of living stems). The fraction of total fungal production allocated to ascomata is speculatively and crudely estimated at about 9%, without taking into account potential loss to invertebrate shredders. At sites with abundances of snails >-50 m^?2 peaks of ascospore expulsion (about 50–75 spores cm^?2 leaf h^?1, 3–5× the overall average rate) observed at snail-free sites were absent. Our measured rate of ascospore expulsion (averaged over snail-free and high-snail sites, and possibly an underestimate) translated to 6.5×10⁴ spores m^?2 marsh h^?1 for times of freshwater saturation of leaves, and one-third that value for times of saltwater wetting.  相似文献   

The dynamic cusp at low altitudes: a case study utilizing Viking,DMSP-F7, and Sondrestrom incoherent scatter radar observations     

J. Watermann  O. de la Beaujardière  D. Lummerzheim  J. Woch  P. T. Newell  T. A. Potemra  F. J. Rich  M. Shapshak 《Annales Geophysicae》1994,12(12):1144-1157

Coincident multi-instrument magnetospheric and ionospheric observations have made it possible to determine the position of the ionospheric footprint of the magnetospheric cusp and to monitor its evolution over time. The data used include charged particle and magnetic field measurements from the Earth-orbiting Viking and DMSP-F7 satellites, electric field measurements from Viking, interplanetary magnetic field and plasma data from IMP-8, and Sondrestrom incoherent scatter radar observations of the ionospheric plasma density, temperature, and convection. Viking detected cusp precipitation poleward of 75.5○ invariant latitude. The ionospheric response to the observed electron precipitation was simulated using an auroral model. It predicts enhanced plasma density and elevated electron temperature in the upper E- and F-regions. Sondrestrom radar observations are in agreement with the predictions. The radar detected a cusp signature on each of five consecutive antenna elevation scans covering 1.2 h local time. The cusp appeared to be about 2○ invariant latitude wide, and its ionospheric footprint shifted equatorward by nearly 2○ during this time, possibly influenced by an overall decrease in the IMF B_z component. The radar plasma drift data and the Viking magnetic and electric field data suggest that the cusp was associated with a continuous, rather than a patchy, merging between the IMF and the geomagnetic field.  相似文献   

Modes of variability of global sea surface temperature,free atmosphere temperature and oceanic surface energy flux     

Wenjie Hu  Reginald E. Newell  Zhong-Xiang Wu 《Climate Dynamics》1994,10(8):377-393

Monthly mean sea surface temperature (SST), free air temperature from satellite microwave sounding units (MSU) and oceanic surface energy fluxes are subjected to empirical orthogonal function (EOF) analysis for a common decade to investigate the physical relationships involved. The first seasonal modes of surface solar energy flux and SST show similar inter-hemispheric patterns with an annual cycle. Solar flux appears to control this pattern of SST. The first seasonal mode of MSU is similar with, additionally, land-sea differences; MSU is apparently partly controlled by absorption of solar near-infrared radiation and partly by sensible heat from the land surface. The second and third seasonal eigenvector of SST and solar flux exhibit semi-annual oscillations associated with a pattern of cloudiness in the subtropics accompanying the translation of the Hadley cell rising motion between the hemispheres. The second seasonal mode of MSU is dominated by an El Niño signal. The first nonseasonal EOFs of SST and solar flux exhibit El Niño characteristics with the solar pattern being governed by west-to-east translation of a Walker cell type pattern. The first non-seasonal EOF of MSU shows a tropical strip pattern for the El Niño mode, which is well correlated with the latent heat fluxes in the tropical east Pacific but not in the tropical west Pacific. Two possible explanations are: an increase in subsidence throughout the tropical strip driven by extra evaporation in the tropical east Pacific and consequent additional latent heat liberation; a decrease of meridional heat flux out of the tropics.  相似文献   

OASIS: A Graphical Decision Support System for Ground-Water Contaminant Modeling     

Charles J. Newell  John F. Haasbeek  Philip B. Bedient 《Ground water》1990,28(2):224-234

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Bio-optical signatures and biogeochemistry from intense upwelling and relaxation in coastal California     

Raphael M. Kudela  Newell Garfield  Kenneth W. Bruland 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):2999

The NSF-sponsored Coastal Ocean Processes Wind Events and Shelf Transport (WEST) experiment investigates the interplay between wind-driven transport and shelf productivity; while eastern boundary shelves are characterized by high productivity due to upward fluxes of nutrients into the euphotic zone, wind forcing also represents negative physical and biological controls via offshore transport and deep (light-limiting) mixing of primary producers. Although this interaction has been well documented for eastern boundary systems generally and for California specifically, one of the primary goals of WEST was to characterize more fully the interplay between positive and negative effects of wind stress, which result in the consistently elevated biological productivity in these shelf regions. During 3 month-long summer cruises (2000–2002) we observed extremes in upwelling/relaxation, using both in situ instrumentation and remotely sensed data. Relationships between optical and physical properties were examined, with emphasis on biogeochemical implications. During 2000, the WEST region was optically dominated by phytoplankton and covarying constituents. During 2001 and 2002, periods of more intense upwelling favorable winds, we observed a transition to optical properties dominated by detrital and inorganic materials. In all years, the continental shelf break provided a natural boundary between optically distinct shelf and open ocean waters. During 2002, we obtained discrete trace-metal measurements of particulate iron and aluminum; we develop a bio-optical proxy for acetic-acid leachable iron from backscatter and fluorescence, and demonstrate that particulate iron is not well correlated to traditional upwelling proxies such as macronutrients, temperature, and salinity. We conclude that the shelf break between ca. 100 and 200 m water depth serves as a natural break point between coastal and oceanic water masses in this region, and that the elevated biomass and productivity associated with this eastern boundary current regime is dominated by these iron rich, shallow shelf waters.  相似文献   

Influence of upwelling saline groundwater on iron and manganese cycling in the Rio Grande floodplain aquifer     

Matthew F. Kirk  Laura J. Crossey  Cristina Takacs-Vesbach  Dennis L. Newell  Robert S. Bowman 《Applied Geochemistry》2009

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Does the polar cap disappear under an extended strong northward IMF?     

Yongliang Zhang  Larry J. Paxton  Patrick T. Newell  Ching-I. Meng 《Journal of Atmospheric and Solar》2009,71(17-18):2006-2012

The suggestion that the polar cap can completely disappear under certain northward IMF conditions is still controversial. We know that the size of the polar cap is strongly controlled by the interplanetary magnetic field (IMF). Under a southward IMF, the polar cap is usually large and filled with weak diffuse polar rain electrons. The polar cap shrinks under a northward IMF. Here we use the global auroral images and coincident particle measurements on May 15, 2005 to show that the discrete arcs (due to precipitation of both electrons and ions) expanded from the dayside oval to the nightside oval and filled the whole polar ionosphere after a long (8 h) and strong (～5–30 nT) northward IMF B_z, The observations suggested that the polar cap disappeared under a closed magnetosphere.  相似文献   

Radiation stress due to ocean waves and the resulting currents and set-up/set-down   总被引：1，自引：0，他引：1  

Carl Newell  Thomas Mullarkey  Mark Clyne 《Ocean Dynamics》2005,55(5-6):499-514

The authors have developed a model to predict the radiation stresses in the coastal zone and to estimate currents and set-up/set-down of mean sea level. The values of radiation stress are calculated from velocity potential, which can be obtained by analytical means or from a finite element model of the elliptic extended mild slope equation depending on the complexity of the situation in question. The values of radiation stress are then input into a hydrodynamic model which gives the resulting set-up/set-down and currents caused by these stresses. The developed model includes convective acceleration and bottom friction. The radiation stress results of the model have been compared with analytical results and published values. Results for set-up/set-down and currents have been compared with published results for seven other similar models. The model has been compared with published results for set-up/set-down and currents created in the vicinity of a detached breakwater and also around a conical island. The results of the authors’ model compare well with the analytical results, and published results for similar models. An erratum to this article can be found at  相似文献   

Application of A Correspondence Principle to the Free Vibrations of Some Viscoelastic Solids     

R. C. Y. Chin  G. W. Hedstrom  G. Majda 《Geophysical Journal International》1986,86(1):137-166

In this study we apply the correspondence principle for free vibrations of a homogeneous viscoelastic solid derived by Fisher & Leitman to obtain the torsional modes of a homogeneous viscoelastic rod. We also extend the correspondence principle, showing that it may be used to find the frequencies of Love waves in a stratified viscoelastic medium. Finally, we apply the correspondence principle to four viscoelastic materials, the Kelvin-Voigt solid, the Maxwell solid, the standard linear solid, and the Achenbach-Chao solid. We show that in each of these cases some care must be used in applying the correspondence principle because of the presence of multiple solutions. We also examine measures of dissipation of the free vibrations, and we determine the conditions under which the logarithmic decrement may be approximated by the process-independent l/ Q of O'Connell & Budiansky.  相似文献