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11.
Carey Ingram 《Geo-Marine Letters》1982,2(3-4):237-238
A design is presented for a pressure equalization conduit to eliminate suction at the lower end of seafloor coring devices
during extraction from the bottom. Tests performed in 1967 indicated that the conduit can minimize core disturbance that is
otherwise induced by the suction created during removal of the corer from the seabed. 相似文献
12.
Carey Ingram 《Geo-Marine Letters》1982,2(3-4):239-241
A design is presented for an expendable seafloor penetrometer system for real time classification of marine sediments and
estimate for shear strength. An accelerometer in the nose section of an expendable probe senses deceleration after impact
with the ocean bottom and provides this data to the underway launch platform via a two-conductor trailing wire umbilical.
Signals are amplified, digitized and processed by microcomputer to provide seafloor classification in virtual real time. 相似文献
13.
Abstract Observations in both the ice and slush layers suggest that sea water intrudes into the snow layer following a snow storm. Ice temperature values recorded at 1 cm below the snow‐ice interface show that the upward flux of sea water is of short duration. This is followed by a period of intense brine drainage characterized by the migration of a salty brine layer, with salinities up to 42 psu. These results suggest that a snow storm induces a complete (upward) flushing of the brine channel network and major modifications of snow and ice characteristics. Melt rates and downward brine fluxes were calculated using salinity measured in a 40 cm deep box placed on the ice‐water interface, which isolated a 50 × 50 cm area of sea ice from ocean mixing processes. In this semi‐isolated environment, observed salinity changes allowed us to determine melt water fluxes and brine drainage or flushing even though ice thickness measurements did not show any significant change. Melt rates up to 21 cm/month and equivalent growth rates up to 32 cm/month were measured. 相似文献
14.
Towards constraining climate sensitivity by linear analysis of feedback patterns in thousands of perturbed-physics GCM simulations 总被引：2，自引：1，他引：1
Benjamin M. Sanderson C. Piani W. J. Ingram D. A. Stone M. R. Allen 《Climate Dynamics》2008,30(2-3):175-190
A linear analysis is applied to a multi-thousand member “perturbed physics" GCM ensemble to identify the dominant physical
processes responsible for variation in climate sensitivity across the ensemble. Model simulations are provided by the distributed
computing project, climate prediction.net . A principal component analysis of model radiative response reveals two dominant independent feedback processes, each
largely controlled by a single parameter change. The leading EOF was well correlated with the value of the entrainment coefficient—a
parameter in the model’s atmospheric convection scheme. Reducing this parameter increases high vertical level moisture causing
an enhanced clear sky greenhouse effect both in the control simulation and in the response to greenhouse gas forcing. This
effect is compensated by an increase in reflected solar radiation from low level cloud upon warming. A set of ‘secondary’
cloud formation parameters partly modulate the degree of shortwave compensation from low cloud formation. The second EOF was
correlated with the scaling of ice fall speed in clouds which affects the extent of cloud cover in the control simulation.
The most prominent feature in the EOF was an increase in longwave cloud forcing. The two leading EOFs account for 70% of the
ensemble variance in λ—the global feedback parameter. Linear predictors of feedback strength from model climatology are applied
to observational datasets to estimate real world values of the overall climate feedback parameter. The predictors are found
using correlations across the ensemble. Differences between predictions are largely due to the differences in observational
estimates for top of atmosphere shortwave fluxes. Our validation does not rule out all the strong tropical convective feedbacks
leading to a large climate sensitivity. 相似文献
15.
Attribution of twentieth century temperature change to natural and anthropogenic causes 总被引：6，自引：0，他引：6
P. A. Stott S. F. B. Tett G. S. Jones M. R. Allen W. J. Ingram J. F. B. Mitchell 《Climate Dynamics》2001,17(1):1-21
We analyse possible causes of twentieth century near-surface temperature change. We use an “optimal detection” methodology
to compare seasonal and annual data from the coupled atmosphere-ocean general circulation model HadCM2 with observations averaged
over a range of spatial and temporal scales. The results indicate that the increases in temperature observed in the latter
half of the century have been caused by warming from anthropogenic increases in greenhouse gases offset by cooling from tropospheric
sulfate aerosols rather than natural variability, either internal or externally forced. We also find that greenhouse gases
are likely to have contributed significantly to the warming in the first half of the century. In addition, natural effects
may have contributed to this warming. Assuming one particular reconstruction of total solar irradiance to be correct implies,
when we take the seasonal cycle into account, that solar effects have contributed significantly to the warming observed in
the early part of the century, regardless of any relative error in the amplitudes of the anthropogenic forcings prescribed
in the model. However, this is not the case with an alternative reconstruction of total solar irradiance, based more on the
amplitude than the length of the solar cycle. We also find evidence for volcanic influences on twentieth century near-surface
temperatures. The signature of the eruption of Mount Pinatubo is detected using annual-mean data. We also find evidence for
a volcanic influence on warming in the first half of the century associated with a reduction in mid-century volcanism.
Received: 24 January 2000 / Accepted: 20 April 2000 相似文献
16.
A technique for estimating the state of an artificial satellite in the presence of unmodeled accelerations is presented. The unmodeled acceleration is approximated by a first-order Gauss-Markov sequence which can be separated into a timewise correlated component and a purely random component. Using this approximation, a sequential procedure for estimating the position, velocity, and the unmodeled acceleration is developed. The method is evaluated by reducing range-rate observations obtained by tracking the Apollo 10 and 11 spacecraft during the lunar orbit phase of the mission. Numerical results are presented which show that the observation residual pattern lies within the observation noise standard deviation. The values of the estimated components of the unmodeled acceleration are repeatable from orbit to orbit within a given mission and from mission to mission when the same ground track is covered. Finally, the variation in the radial component of the unmodeled acceleration shows a high correlation with the reported location of the lunar surface mascons. 相似文献
17.
This paper investigates the effects that geometry and control have on the absorption characteristics of wavemakers. It presents the hydrodynamic coefficients for piston and bottom hinged flap wavemakers and also for two novel wavemaker profiles. Absorption efficiencies are presented for wavemakers using one, two and three control coefficients for reactive control. This is then used to analyse the absorption efficiency of each of the different wavemakers based upon the geometry and the control strategy used. It is shown that the amount of absorption for a given paddle differs greatly depending on the choice of control coefficients used to implement complex conjugate control. Increased absorption can be achieved over a broader bandwith of frequencies when the geometry of the wavemaker is optimised for one specific frequency. 相似文献
18.
Muhling BA Roffer MA Lamkin JT Ingram GW Upton MA Gawlikowski G Muller-Karger F Habtes S Richards WJ 《Marine pollution bulletin》2012,64(4):679-687
The 2010 Deepwater Horizon oil spill impacted the northern Gulf of Mexico (GOM) during the spring spawning season of Atlantic bluefin tuna (BFT). Overlap between BFT spawning habitat and surface oil in the northern GOM was examined using satellite-derived estimates of oil coverage, and spawning habitat models. Results suggested that although eggs and larvae were likely impacted by oil-contaminated waters in the eastern GOM, high abundances of larvae were located elsewhere, especially in the western GOM. Overall, less than 10% of BFT spawning habitat was predicted to have been covered by surface oil, and less than 12% of larval BFT were predicted to have been located within contaminated waters in the northern GOM, on a weekly basis. Our results provide preliminary but important initial estimates of the effects of the spill on larval BFT mortality, as concern continues over the appropriate management responses to impacts of the spill. 相似文献
19.
Ben Ingram Dan Cornford David Evans 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(5):661-670
In this paper we discuss a fast Bayesian extension to kriging algorithms which has been used successfully for fast, automatic
mapping in emergency conditions in the Spatial Interpolation Comparison 2004 (SIC2004) exercise. The application of kriging
to automatic mapping raises several issues such as robustness, scalability, speed and parameter estimation. Various ad-hoc
solutions have been proposed and used extensively but they lack a sound theoretical basis. In this paper we show how observations
can be projected onto a representative subset of the data, without losing significant information. This allows the complexity
of the algorithm to grow as O(n
m
2), where n is the total number of observations and m is the size of the subset of the observations retained for prediction. The main contribution of this paper is to further
extend this projective method through the application of space-limited covariance functions, which can be used as an alternative
to the commonly used covariance models. In many real world applications the correlation between observations essentially vanishes
beyond a certain separation distance. Thus it makes sense to use a covariance model that encompasses this belief since this
leads to sparse covariance matrices for which optimised sparse matrix techniques can be used. In the presence of extreme values
we show that space-limited covariance functions offer an additional benefit, they maintain the smoothness locally but at the
same time lead to a more robust, and compact, global model. We show the performance of this technique coupled with the sparse
extension to the kriging algorithm on synthetic data and outline a number of computational benefits such an approach brings.
To test the relevance to automatic mapping we apply the method to the data used in a recent comparison of interpolation techniques
(SIC2004) to map the levels of background ambient gamma radiation.
相似文献
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20.