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71.
Markus Kissler-Patig 《Astrophysics and Space Science》2002,281(1-2):487-491
Old, metal-poor globular clusters trace the formation and evolution of early-type galaxies. Their are the best probes, at
low redshift, of the building-up of galaxy halos at high redshift. Their properties constrain the characteristics of their
progenitors. Recent results suggest that DLAs atz > 3 are the likely hosts for their formation. Finally, they shed light on the old, metal-poor halos probably present around
all early-type galaxies.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
72.
73.
Atmospheric boundary-layer structure observed during a haze event due to forest-fire smoke 总被引:1,自引:0,他引:1
Markus?PahlowEmail author Jan?Kleissl Marc?B.?Parlange 《Boundary-Layer Meteorology》2005,114(1):53-70
During a haze event in Baltimore, U.S.A. from July 6 to 8, 2002, smoke from forest fires in the Québec region (Canada), degraded air quality and impacted upon local climate, decreasing solar radiation and air temperature. The smoke particles in and above the atmospheric boundary layer (ABL) served as a tracer and provided a unique opportunity to investigate the ABL structure, especially entrainment. Elastic backscatter lidar measurements taken during the haze event distinctly reveal the downward sweeps (or wisps) of smoke-laden air from the free atmosphere into the ABL. Visualisations of mechanisms such as dry convection, the entrainment process, detrainment, coherent entrainment structures, and mixing inside the ABL, are presented. Thermals overshooting at the ABL top are shown to create disturbances in the form of gravity waves in the free atmosphere aloft, as evidenced by a corresponding ripple structure at the bottom of the smoke layer. Lidar data, aerosol ground-based measurements and supporting meteorological data are used to link free atmosphere, mixed-layer and ground-level aerosols. During the peak period of the haze event (July 7, 2002), the correlation between time series of elastic backscatter lidar data within the mixed layer and the scattering coefficient from a nephelometer at ground level was found to be high (R=0.96 for z =324 m, and R=0.89 for z=504 m). Ground-level aerosol concentration was at a maximum about 2 h after the smoke layer intersected with the growing ABL, confirming that the wisps do not initially reach the ground. 相似文献
74.
Wolfgang?StinnesbeckEmail author Gerta?Keller Thierry?Adatte Markus?Harting Doris?Stüben Georg?Istrate Utz?Kramar 《International Journal of Earth Sciences》2004,93(6):1042-1065
CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894–794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction. 相似文献
75.
Momcilo Markus Donald J. Wuebbles Xin-Zhong Liang Katharine Hayhoe David A. R. Kristovich 《Climatic change》2012,111(3-4):879-902
Past heavy precipitation events in the Chicago metropolitan area have caused significant flood-related economic and environmental damages. A key component in flood management policies and actions is determining flood magnitudes for specified return periods. This is a particularly difficult task in areas with a complex and changing climate and land-use, such as the Chicago metropolitan area. The standard design storm methodology based on the NOAA Atlas 14 and ISWS Bulletin 70 has been used in the past to estimate flood hydrographs with variable return periods in this region. In a changing climate, however, these publications may not be accurate. This study presents and illustrates a methodology for diagnostic analysis of future climate scenarios in the framework of urban flooding, and assesses the corresponding uncertainties. First, the design storms are calculated using data downscaled by a regional climate model (RCM) at 30-km spacing for the present and 2050s under the IPCC A1Fi (high) and B1 (low) emissions scenarios. Next, the corresponding flood discharges at six watersheds in suburban Chicago are estimated using a hydrologic event model. The resulting scenarios in flood frequency were first assessed through a set of diagnostic tests for precipitation timing and frequency. The study did not reveal any significant changes in the 2050s in the average timing of heavy storms, but their regularity decreased. The average timing did not exhibit any significant spatial variability throughout the region. The precipitation frequency analysis revealed distinct differences between the northern and southeastern subregions of the Chicago metropolitan area. The quantiles in the northern subregion averaged for 2-year, 5-year, and 10-year return periods exhibited a 20% and 16% increase in daily precipitation for scenarios B1 and A1Fi, respectively. The southeastern subregion, however, exhibited a decrease of 12% for scenario B1 and a minor increase of 3% for scenario A1Fi. The hydrologic effects of changing precipitation on the flood quantiles were illustrated using six small watersheds in the region. The relative increases or decreases in precipitation translated into even larger relative increases or decreases in flood peaks, due to the nonlinear nature of the rainfall-runoff process. Simulations using multiple climate models, for longer periods, finer spatio-temporal resolution, and larger areal coverage could be used to more accurately account for numerous uncertainties in the precipitation and flood projections. 相似文献
76.
Ralf Döscher Klaus Wyser H. E. Markus Meier Minwei Qian René Redler 《Climate Dynamics》2010,34(7-8):1157-1176
The relative importance of regional processes inside the Arctic climate system and the large scale atmospheric circulation for Arctic interannual climate variability has been estimated with the help of a regional Arctic coupled ocean-ice-atmosphere model. The study focuses on sea ice and surface climate during the 1980s and 1990s. Simulations agree reasonably well with observations. Correlations between the winter North Atlantic Oscillation index and the summer Arctic sea ice thickness and summer sea ice extent are found. Spread of sea ice extent within an ensemble of model runs can be associated with a surface pressure gradient between the Nordic Seas and the Kara Sea. Trends in the sea ice thickness field are widely significant and can formally be attributed to large scale forcing outside the Arctic model domain. Concerning predictability, results indicate that the variability generated by the external forcing is more important in most regions than the internally generated variability. However, both are in the same order of magnitude. Local areas such as the Northern Greenland coast together with Fram Straits and parts of the Greenland Sea show a strong importance of internally generated variability, which is associated with wind direction variability due to interaction with atmospheric dynamics on the Greenland ice sheet. High predictability of sea ice extent is supported by north-easterly winds from the Arctic Ocean to Scandinavia. 相似文献
77.
Rainer Kaltenbaek Gerald Hechenblaikner Nikolai Kiesel Oriol Romero-Isart Keith C. Schwab Ulrich Johann Markus Aspelmeyer 《Experimental Astronomy》2012,34(2):123-164
Quantum physics challenges our understanding of the nature of physical reality and of space-time and suggests the necessity of radical revisions of their underlying concepts. Experimental tests of quantum phenomena involving massive macroscopic objects would provide novel insights into these fundamental questions. Making use of the unique environment provided by space, MAQRO aims at investigating this largely unexplored realm of macroscopic quantum physics. MAQRO has originally been proposed as a medium-sized fundamental-science space mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments: DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative Acceleration Sensing Experiment). The main scientific objective of MAQRO, which is addressed by the experiment DECIDE, is to test the predictions of quantum theory for quantum superpositions of macroscopic objects containing more than 108 atoms. Under these conditions, deviations due to various suggested alternative models to quantum theory would become visible. These models have been suggested to harmonize the paradoxical quantum phenomena both with the classical macroscopic world and with our notion of Minkowski space-time. The second scientific objective of MAQRO, which is addressed by the experiment CASE, is to demonstrate the performance of a novel type of inertial sensor based on optically trapped microspheres. CASE is a technology demonstrator that shows how the modular design of DECIDE allows to easily incorporate it with other missions that have compatible requirements in terms of spacecraft and orbit. CASE can, at the same time, serve as a test bench for the weak equivalence principle, i.e., the universality of free fall with test-masses differing in their mass by 7 orders of magnitude. 相似文献
78.
Flexible management of fishing rights and a sustainable fisheries industry in Europe 总被引:3,自引:0,他引:3
Although overexploitation of commercial fish stocks in European waters has been in the public debate now for more than 20 years, the European Union has so far failed to implement sustainable fisheries management. Millions in subsidies paid to the fishing industry have led to significant excess capacity in the fishing fleet. Various feeble attempts to stop overexploitation of marine resources have failed. The cause is that fishing policy is highly dominated by short-term socioeconomic interests. There is an urgent need for a new fisheries management system in Europe that supports reductions in the fishing fleet, increases responsibility among fishers and guarantees long-term conservation of natural marine resources.Transferable rights to fish have proved a reliable and effective means of creating incentives to conserve marine resources. By strengthening individual fishing rights under flexible quota management systems, the EU Member States could, within the Common Fisheries Policy, make a significant contribution to conserving fish stocks, to reducing excess capacity and to raising the profitability of the fisheries industry. A closer look at existing reservations against a flexible management system shows most of the objections to be overstated or capable of resolution. 相似文献
79.
L’Her Alexandre Reinert Markus Prants Sergey Carton Xavier Morvan Mathieu 《Ocean Dynamics》2021,71(5):601-612
Ocean Dynamics - The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the... 相似文献
80.
Markus J. Aschwanden Jong Kwan Lee G. Allen Gary Michael Smith Bernd Inhester 《Solar physics》2008,248(2):359-377
The three-dimensional (3D) modeling of coronal loops and filaments requires algorithms that automatically trace curvilinear
features in solar EUV or soft X-ray images. We compare five existing algorithms that have been developed and customized to
trace curvilinear features in solar images: i) the oriented-connectivity method (OCM), which is an extension of the Strous pixel-labeling algorithm (developed by Lee,
Newman, and Gary); ii) the dynamic aperture-based loop-segmentation method (developed by Lee, Newman, and Gary); iii) unbiased detection of curvilinear structures (developed by Steger, Raghupathy, and Smith); iv) the oriented-direction method (developed by Aschwanden); and v) ridge detection by automated scaling (developed by Inhester). We test the five existing numerical codes with a TRACE image
that shows a bipolar active region and contains over 100 discernable loops. We evaluate the performance of the five codes
by comparing the cumulative distribution of loop lengths, the median and maximum loop length, the completeness or detection
efficiency, the accuracy, and flux sensitivity. These algorithms are useful for the reconstruction of the 3D geometry of coronal
loops from stereoscopic observations with the STEREO spacecraft, or for quantitative comparisons of observed EUV loop geometries
with (nonlinear force-free) magnetic field extrapolation models. 相似文献