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141.
Anne Marie Treguier Claire Gourcuff Pascale Lherminier Herle Mercier Bernard Barnier Gurvan Madec Jean-Marc Molines Thierry Penduff Lars Czeschel Claus Böning 《Ocean Dynamics》2006,56(5-6):568-580
Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises,
carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two
cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models
show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces
well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due
to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders.
Examination of the -coordinate overturning reveals model–data discrepancies: the vertical structure in the models does not change as much as
the observed one. The East Greenland current variability is mainly wind-forced in the ATL6 model, while fluctuations due to
eddies and instabilities explain a large part of the North Atlantic Current variability. The time-residual transport of dense
water and heat due to eddy correlations between currents and properties is small across this section, which is normal to the
direction of the main current. 相似文献
142.
W.C. Jones P.A.R. Ade J.J. Bock J.R. Bond J. Borrill A. Boscaleri P. Cabella C.R. Contaldi B.P. Crill P. de Bernardis G. De Gasperis A. de Oliveira-Costa G. De Troia G. Di Stefano E. Hivon A.H. Jaffe T.S. Kisner A.E. Lange C.J. MacTavish S. Masi P.D. Mauskopf A. Melchiorri T.E. Montroy P. Natoli C.B. Netterfield E. Pascale F. Piacentini D. Pogosyan G. Polenta S. Prunet S. Ricciardi G. Romeo J.E. Ruhl P. Santini M. Tegmark M. Veneziani N. Vittorio 《New Astronomy Reviews》2006,50(11-12):945
The Boomerang experiment completed its final long duration balloon (LDB) flight over Antarctica in January 2003. The focal plane was upgraded to accommodate four sets of 145 GHz polarization sensitive bolometers (PSBs), identical to those to be flown on the Planck HFI instrument. Approximately, 195 hours of science observations were obtained during this flight, including 75 hours distributed over 1.84% of the sky and an additional 120 hours concentrated on a region covering 0.22% of the sky. We derive the angular power spectra of the cosmic microwave background (cmb) temperature and polarization anisotropies from these data. The temperature anisotropies are detected with high signal to noise on angular scales ranging from several degrees to 10 arcminutes. The curl-free (EE) component is detected at 4.8σ, and a two-sigma upper limit on the curl (BB) component of 8.6 μK2 is obtained on scales corresponding to 0.5°. Both the temperature and polarization anisotropies are found to be consistent with a concordance ΛCDM cosmology that is seeded by adiabatic density perturbations. In addition to the cmb observations, Boomerang03 surveyed a 300 square degree region centered on the Galactic plane. These observations represent the first light for polarization sensitive bolometers, which are currently operational in two South-Pole based polarimeters, as well as Planck HFI, at frequencies ranging from 100 to 350 GHz (3 mm to 850 μm). 相似文献
143.
Political and scientific uncertainties in volcanic risk management: The yellow alert in Quito in October 1998 总被引:1,自引:0,他引:1
Volcanic risk management involves volcanologists, civil authorities and the affected population. The paper reports on one
`yellow alert' in Quito in 1998. It describes the scientific context, the political announcement and the decision-making process
that preceded, as well as the social perception of the volcanic crisis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
144.
Pascale M. Biron Stuart N. Lane Andr G. Roy Kate F. Bradbrook Keith S. Richards 《地球表面变化过程与地形》1998,23(2):133-139
Bed shear stress in open channel flows is often estimated from the logarithmic vertical velocity profile. However, most measuring devices used in the field do not allow for flow velocity to be measured very close to the bed. The lack of near-bed measurements is a critical loss of information which may affect bed shear stress estimates. Detailed velocity profiles obtained from a field acoustic Doppler velocimeter over three different bed roughnesses clearly show that the inclusion of near-bed points is critical for the estimation of bed shear stress in a shallow river environment. Moreover, the results indicate that using the full flow depth instead of the bottom 20 per cent of the profile generates an underestimation of the shear stress when flow is uniform. © 1998 John Wiley & Sons, Ltd. 相似文献
145.
Vladoiu Anda Bouruet-Aubertot Pascale Cuypers Yannis Ferron Bruno Schroeder Katrin Borghini Mireno Leizour Stephane Ismail Sana Ben 《Ocean Dynamics》2019,69(7):787-807
Ocean Dynamics - The dissipation flux coefficient, a measure of the mixing efficiency of a turbulent flow, was computed from microstructure measurements collected with a vertical microstructure... 相似文献
146.
A modified morphodynamic model for investigating the response of rivers to short-term climate change
Patrick M. Verhaar Pascale M. Biron Robert I. Ferguson Trevor B. Hoey 《Geomorphology》2008,101(4):674-682
Near-future climate change will affect the discharge and base level of rivers and thus cause channel changes. The nature and pace of such changes can be simulated using morphodynamic models. As part of an investigation of how the changing hydrology of the St-Lawrence River, Quebec, Canada, will affect its tributaries we have made additions and modifications to a one-dimensional morphodynamic model developed for gravel-bed rivers (SEDROUT). The changes allow simulation of sand-bed rivers, variable discharge, downstream water level fluctuations, and flow and sediment routing in channels with islands. A revised formulation for calculating the grain size distributions of the surface and subsurface material is presented to allow for alternating sedimentation and erosion. We test the enhanced model using small-scale simulations and present-day conditions in four tributaries of the St-Lawrence River. The model is calibrated and validated for the tributaries and the capability to simulate river morphology over a 100-year period is tested. Good validation agreement on water level, cross-sectional mean velocity, and sediment transport rate is obtained for the four tributaries of the St-Lawrence River. With these modifications, modelling a very wide range of river morphodynamic problems is now possible. 相似文献