Enhanced estimation of sonobuoy trajectories by velocity reconstruction with near-surface drifters     

Y. Chang  D. Hammond  A.C. Haza  P. Hogan  H.S. Huntley  A.D. Kirwan  B.L. Lipphardt  V. Taillandier  A. Griffa  T.M. Özgökmen 《Ocean Modelling》2011,36(3-4):179-197

An investigation to improve trajectory prediction using Lagrangian data is presented. The velocity field of a data assimilating model, EAS-16, is corrected using drifter observations taken during an experiment off Taiwan. The results are tested using another independent Lagrangian data set provided by sonobuoys launched in the same area. The latter have instrument chains that extend well into the water column. Consequently the corrected model velocities were projected into the water column in order to calculate sonobuoy trajectories. The drifter and sonobuoy trajectories both show two distinct regimes in the considered area of approximately 1/2° square. One regime is dominated by shelf dynamics, the other by meandering of the Kuroshio, with a sharp boundary dividing the two. These two regimes are not reproduced by the trajectories of the EAS-16 model. When the drifter data are blended with the model velocities, synthetic sonobuoy trajectories track the observed ones much better, and the two regimes are clearly depicted. Two different methods for the velocity reconstruction are tested. One is based on a variational approach and the other on a normal mode decomposition. Both methods show qualitatively similar improvements in the prediction of sonobuoys trajectories, with a quantitative improvement in the total rms error of approximately 50% and 25%, respectively.  相似文献   

Evaluation of the budget for silicic acid in Cascadia Basin deep water     

Tabitha A. Esther  Douglas E. Hammond  Susan L. Hautala  H. Paul Johnson  Richard J. Schwartz  Amelia N. Paukert 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(5):677-686

Between 2 and 3 km depth, North Pacific deep waters contain a plume of water with high silicic acid concentrations. The plume extends outward from Cascadia Basin (the Washington Margin), where waters can contain in excess of 200 μM off the coast of Oregon and Washington. To identify the source of the high Si concentrations in Cascadia Basin, we measured silicic acid and germanium concentrations in deep waters, and their fluxes from sediments using incubated cores. The mean flux of silicic acid into bottom waters is 0.81±0.05 mmol/m²-day, and the Ge/Si ratio of this flux is 0.7±0.1 μmol/mol. A box model, incorporating these results with hydrographic data, indicates that (1) no more than 5% of the silicic acid added to Basin deep waters can have a hydrothermal source (either hot or warm seeps), and (2) the total input of silicic acid to Basin deep waters is 0.06±0.02 Tmol/y. This input is nearly all from remineralized biogenic debris and should contribute about 0.5% of the 14 Tmol/y that are estimated to be necessary to maintain the North Pacific plume.  相似文献   

The trade-off between gender,energy and climate change in Africa: the case of Niger Republic     

Antwi  Sarpong Hammond 《GeoJournal》2022,87(1):183-195

GeoJournal - This article examines the role of gender in climate change adaptation and energy access in Africa. Drawing on the energy situation in Niger Republic, it argues that redressing...  相似文献   

Theoretical plasma distributions consistent with Ulysses magnetic field observations in a solar wind tangential discontinuity     

J. De Keyser  M. Roth  J. Lemaire  B. T. Tsurutani  C. M. Ho  C. M. Hammond 《Solar physics》1996,166(2):415-422

The overall multi-layer structure of the magnetic field profile observed by Ulysses across a broad solar wind tangential discontinuity can be reproduced fairly well by means of a kinetic model. Such a simulation provides complementary information about the velocity distribution functions, which are not always available from the plasma experiment due to the low time resolution inherent in plasma measurements. The success of such a simulation proves that the kinetic model can be used as a realistic basis for further studies of the structure and stability of solar wind tangential discontinuities.  相似文献   

Seabed drifter movement in San Diego Bay and adjacent waters     

Robert R. Hammond  William J. Wallace 《Estuarine, Coastal and Shelf Science》1982,14(6):623-634

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Bayesian estimation of fish school cluster composition applied to a Bering Sea acoustic survey   总被引：1，自引：0，他引：1  

Hammond  T. R.; Swartzman  G. L.; Richardson  T. S. 《ICES Journal of Marine Science》2001,58(6):1133-1149

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An application of the Bayesian approach to stock assessment model uncertainty     

Hammond  T. R.; O'Brien  C. M. 《ICES Journal of Marine Science》2001,58(3):648-656

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Harbour porpoise (Phocoena phocoena L.) by-catch in set gillnets in the Celtic Sea     

Tregenza  N. J. C.; Berrow  S. D.; Hammond  P. S.; Leaper  R. 《ICES Journal of Marine Science》1997,54(5):896-904

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Gulf stream ground truth project: Results of the NRL airborned sensors     

Charles R. McClain  Davidson T. Chen  Donald L. Hammond 《Ocean Engineering》1980,7(1):55-97

Results of an airborne study of the waves in the Gulf Stream are presented. These results show that the active microwave sensors (high-flight radar and wind-wave radar) provide consistent and accurate estimates of significant wave height and surface wind speed, respectively. The correlation between the wave height measurements of the high-flight radar and a laser profilometer is excellent.  相似文献   

Archaean lode gold mineralisation in banded iron formation at the Kalahari Goldridge deposit, Kraaipan Greenstone Belt, South Africa     

Napoleon Q. Hammond  John M. Moore 《Mineralium Deposita》2006,41(5):483-503

The Kalahari Goldridge Mine is located within the Archaean Kraaipan Greenstone Belt, about 60 km southwest of Mafikeng in the North West Province, South Africa. The ore body thickness varies from 15 to 45 m along a strike length of about 1.5 km within approximately N–S striking banded iron formation (BIF). The stratabound ore body is hosted primarily by BIF, which consists of alternating chert and magnetite–chlorite–stilpnomelane–sulphide–carbonate bands of millimetre- to centimetre scale. A footwall of sericite–carbonate–chlorite schist underlain by mafic amphibolite occurs to the west and carbonaceous metapelites in the hanging wall to the east. Overlying the hanging wall, carbonaceous metapelites, units of coarse-grained metagreywackes fining upwards, become increasingly conglomeratic up the stratigraphy. Small-scale isoclinal folds, brecciation, extension fractures and boudinage of cherty BIF units reflect brittle-ductile deformation. Fold axial planes have foliation, with subvertical plunges parallel to prominent rodding and mineral lineation in the footwall rocks. Gold mineralisation is associated with two generations of quartz–carbonate veins, dipping approximately 20° to 40° W. The first generation consists of ladder-vein sets (group IIA) preferentially developed in centimetre-scale Fe-rich mesobands, whereas the second generation consists of large quartz–carbonate veins (group IIB), which locally crosscut the entire ore body and extend into the footwall and hanging wall. The ore body is controlled by mesoscale isoclinal folds approximately 67° E, orthogonal to the plane of mineralised, gently dipping veins, defining the principal stretching direction and development of fluid-focussing conduits. The intersections of the mineralised veins and foliation planes of the host rock plunges approximately 08° to the north. Pervasive hydrothermal alteration is characterised by chloritisation, carbonatisation, sulphidation and K-metasomatism. Gold is closely associated with sulphides, mainly pyrite and pyrrhotite, and to a lesser extent, with bismuth tellurides and carbonate minerals. Mass balance transfer calculations indicate that hydrothermal alteration of BIF involved enrichment of Au, Ag, Bi, Te, S and CO₂ (LOI), MgO, Ba, K and Rb, but significant depletion of SiO₂ and, to a lesser extent, Fe₂O₃. Extensive replacement of magnetite and chlorite in BIF and other pelitic sedimentary rocks by sulphide and carbonate minerals, both on mesoscopic and microscopic scales, is evidence of interaction of CO₂- and H₂S-bearing fluids with the Fe-rich host rocks. The fineness of gold grains ranges from 823 to 921, similar to that of other epigenetic Archaean BIF-hosted gold deposits, worldwide.  相似文献