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171.
Minnie Y. Mao Rob Sharp D. J. Saikia Ray P. Norris Melanie Johnston-Hollitt Enno Middelberg Jim E. J. Lovell 《Journal of Astrophysics and Astronomy》2011,32(4):585-588
Using the Australia Telescope Compact Array (ATCA), ATLAS (Australia Telescope Large Area Survey) is imaging two fields totalling
7 square degrees down to 10 μJy beam − 1 at 1.4 GHz. We have found 6 wide-angle tail galaxies (WATs), 4 of which have sufficient data to identify associated galaxy
overdensities. The largest WAT, at a red-shift of 0.22, appears to be associated with an overdensity of galaxies that is spread
over an unusually large extent of 12 Mpc, with a velocity range of 4500 km s − 1. Here we present the WATs in ATLAS and discuss the implications of these observations for future large-scale radio surveys
such as ASKAP-EMU. 相似文献
172.
The availability of multiple history matched models is essential for proper handling of uncertainty in determining the optimal development of producing hydrocarbon fields. The ensemble Kalman Filter in particular is becoming recognized as an efficient method for quantitative conditioning of multiple models to history data. It is known, however, that the ensemble Kalman Filter (EnKF) may have problems with finding solutions in history matching cases that are highly nonlinear and involve very large numbers of data, such is typical when time-lapse seismic surveys are available. Recently, a parameterization of seismic anomalies due to saturation effects was proposed in terms of arrival times of fronts that reduces both nonlinearity and the effective number of data. A disadvantage of the parameterization in terms of arrival times is that it requires simulation of models beyond the update time. An alternative distance parameterization is proposed here for flood fronts, or more generally, for isolines of arbitrary seismic attributes representing a front that removes the need for additional simulation time. An accurate fast marching method for solution of the Eikonal equation in Cartesian grids is used to calculate distances between observed and simulated fronts, which are used as innovations in the EnKF. Experiments are presented that demonstrate the functioning of the method in synthetic 2D and realistic 3D cases. Results are compared with those resulting from use of saturation data, as they could potentially be inverted from seismic data, with and without localization. The proposed algorithm significantly reduces the number of data while still capturing the essential information. It furthermore removes the need for seismic inversion when the oil-water front is only identified, and it produces a more favorable distribution of simulated data, leading to a very efficient and improved functioning of the EnKF. 相似文献
173.
Cycles and shifts: 1,300 years of multi-decadal temperature variability in the Gulf of Alaska 总被引:2,自引:0,他引:2
The Gulf of Alaska (GOA) is highly sensitive to shifts in North Pacific climate variability. Here we present an extended tree-ring
record of January–September GOA coastal surface air temperatures using tree-ring width data from coniferous trees growing
in the mountain ranges along the GOA. The reconstruction (1514–1999), based on living trees, explains 44% of the temperature
variance, although, as the number of chronologies decreases back in time, this value decreases to, and remains around ∼30%
before 1840. Verification of the calibrated models is, however, robust. Utilizing sub-fossil wood, we extend the GOA reconstruction
back to the early eighth century. The GOA reconstruction correlates significantly (95% CL) with both the Pacific Decadal Oscillation
Index (0.53) and North Pacific Index (−0.42) and therefore likely yields important information on past climate variability
in the North Pacific region. Intervention analysis on the GOA reconstruction identifies the known twentieth century climate
shifts around the 1940s and 1970s, although the mid-1920s shift is only weakly expressed. In the context of the full 1,300 years
record, the well studied 1976 shift is not unique. Multi-taper method spectral analysis shows that the spectral properties
of the living and sub-fossil data are similar, with both records showing significant (95% CL) spectral peaks at ∼9–11, 13–14
and 18–19 years. Singular spectrum analysis identifies (in order of importance) significant oscillatory modes at 18.7, 50.4,
38.0, 91.8, 24.4, 15.3 and 14.1 years. The amplitude of these modes varies through time. It has been suggested (Minobe in
Geophys Res Lett 26:855–858, 1999) that the regime shifts during the twentieth century can be explained by the interaction between pentadecadal (50.4 years)
and bidecadal (18.7 years) oscillatory modes. Removal of these two modes of variance from our GOA time series does indeed
remove the twentieth century shifts, but many are still identified prior to the twentieth century. Our analysis suggests that
climate variability of the GOA is very complex, and that much more work is required to understand the underlying oscillatory
behavior that is observed in instrumental and proxy records from the North Pacific region.
相似文献
Rob WilsonEmail: |
174.
Mohammad Abou Romieh Rob Westaway Mohamad Daoud Yousef Radwan Rayan Yassminh Ahlam Khalil Abeer Al‐Ashkar Susan Loughlin Katherine Arrell David Bridgland 《地学学报》2009,21(6):427-437
The Africa–Arabia plate boundary comprises the Red Sea oceanic spreading centre and the left‐lateral Dead Sea Fault Zone (DSFZ); however, previous work has indicated kinematic inconsistency between its continental and oceanic parts. The Palmyra Fold Belt (PFB) splays ENE from the DSFZ in SW Syria and persists for ~400 km to the River Euphrates, but its significance within the regional pattern of active crustal deformation has hitherto been unclear. We report deformation of Euphrates terraces consistent with Quaternary right‐lateral transpression within the PFB, indicating anticlockwise rotation (estimated as 0.3° Ma?1 about 36.0°N 39.8°E) of the block between the PFB and the northern DSFZ relative to the Arabian Plate interior. The northern DSFZ is shown to be kinematically consistent with the combination of Euler vectors for the PFB and the Red Sea spreading, resolving the inconsistency previously evident. The SW PFB causes a significant earthquake hazard, previously unrecognized, to the city of Damascus. 相似文献
175.
Abstract Economic studies suggest that market leakage rates of greenhouse gas abatement can reach the two-digit percentage range. Although the Marrakesh Accords require Clean Development Mechanism (CDM) projects to account for leakage, most projects neglect market leakage. Insufficient leakage accounting is facilitated by a lack of applicable methods regarding the quantification and attribution of project-related leakage effects. This article proposes a method for attributing CDM-related market leakage effects to individual projects. To this purpose, alternative attribution methods are analysed. We find that project-specific approaches fail to take account of market leakage effects. Consequently, we propose to estimate aggregate market leakage effects and attribute them proportionally to individual projects. We suggest that predetermined commodity-specific leakage factors are applied by project developers to any emission reductions that are associated with a project's leakage-relevant demand or supply changes. This approach is conservative, equitable, incentive-compatible and applicable at manageable costs. 相似文献
176.
A large-eddy simulation study was performed to characterize turbulence in sparse, row-oriented canopies. This was accomplished by simulating a set of heterogeneous row-oriented canopies with varying row vegetation density and spacing. To determine the effects of heterogeneity, results were compared to horizontally homogeneous canopies with an equivalent ‘effective’ leaf area index. By using a proper effective leaf area index, plane-averaged mean velocities and bulk scaling parameters contained only small errors when heterogeneity was ignored. However, many cases had significantly larger second- and third-order velocity moments in the presence of heterogeneity. Some heterogeneous canopies also contained dispersive fluxes in the lower canopy that were over 20 % as large as the turbulent flux. Impacts of heterogeneity were most pronounced in the cases of large row leaf area density and widely spaced rows. Despite the substantial amount of open space in the sparse canopies, vertical velocity skewness and quadrant-hole analysis indicated that the flow behaved predominantly as a canopy layer even though integral length scales at the canopy top no longer followed mixing-layer scaling. This was supported by the fact that similar composite-averaged coherent structures could be readily identified in both the heterogeneous and homogeneous canopies. Heterogeneity had an effect on coherent structures, in that structure detection events were most likely to occur just upwind of the vegetation rows. In simulations with large row spacing, these structures also penetrated deeper into the canopy when compared to the equivalent homogeneous canopy. 相似文献
177.
178.
A simple approximate analysis is presented for interpretation of cone penetration results when the cone resistance is affected by layering of soils with different stiffnesses. It is argued that the cone resistance senses the presence of a nearby layer elastically, and an approximate elastic analysis is developed to quantify the effect. Good comparisons with calibration chamber experimental results are found. 相似文献
179.
Ian J. W. Giesbrecht William C. Floyd Suzanne E. Tank Ken P. Lertzman Brian P. V. Hunt Maartje C. Korver Allison A. Oliver Ray Brunsting Paul Sanborn Santiago G. Gonzalez Arriola Gordon W. Frazer Kyra A. St. Pierre Shawn Hateley James McPhail Colby Owen Stewart Butler Bryn Fedje Emma Myers Lucy Quayle Emily Haughton Isabelle Desmarais Rob White David J. Levy-Booth Colleen T. E. Kellogg Jennifer M. Jackson William W. Mohn Steven J. Hallam Justin Del Bel Belluz 《水文研究》2021,35(6):e14198
The Kwakshua Watersheds Observatory (KWO) is an integrative watersheds observatory on the coastal margin of a rain-dominated bog-forest landscape in British Columbia (BC), Canada. Established in 2013, the goal of the KWO is to understand and model the flux of terrestrial materials from land to sea – the origins, pathways, processes and ecosystem consequences – in the context of long-term environmental change. The KWO consists of seven gauged watersheds and a network of observation sites spanning from land to sea and along drainage gradients within catchments. Time-series datasets include year-round measurements of weather, soil hydrology, streamflow, aquatic biogeochemistry, microbial ecology and nearshore oceanographic conditions. Sensor measurements are recorded every 5 min and water samples are collected approximately monthly. Additional observations are made during high-flow conditions. We used remote sensing to map watershed terrain, drainage networks, soils and terrestrial ecosystems. The watersheds range in size from 3.2 to 12.8 km2, with varying catchment characteristics that influence hydrological and biogeochemical responses. Despite local variation, the overall study area is a global hotspot for yields of dissolved organic carbon, dissolved organic nitrogen and dissolved iron at the coastal margin. This observatory helps fill an important gap in the global network of observatories, in terms of spatial location (central coast of BC), climate (temperate oceanic), hydrology (very high runoff, pluvial regime), geology (igneous intrusive, glacially scoured), vegetation (bog rainforest) and soils (large stores of organic carbon). 相似文献
180.