Climate change projections of the North American Regional Climate Change Assessment Program (NARCCAP)   总被引：2，自引：1，他引：1  

L. O. Mearns  S. Sain  L. R. Leung  M. S. Bukovsky  S. McGinnis  S. Biner  D. Caya  R. W. Arritt  W. Gutowski  E. Takle  M. Snyder  R. G. Jones  A. M. B. Nunes  S. Tucker  D. Herzmann  L. McDaniel  L. Sloan 《Climatic change》2013,120(4):965-975

We investigate major results of the NARCCAP multiple regional climate model (RCM) experiments driven by multiple global climate models (GCMs) regarding climate change for seasonal temperature and precipitation over North America. We focus on two major questions: How do the RCM simulated climate changes differ from those of the parent GCMs and thus affect our perception of climate change over North America, and how important are the relative contributions of RCMs and GCMs to the uncertainty (variance explained) for different seasons and variables? The RCMs tend to produce stronger climate changes for precipitation: larger increases in the northern part of the domain in winter and greater decreases across a swath of the central part in summer, compared to the four GCMs driving the regional models as well as to the full set of CMIP3 GCM results. We pose some possible process-level mechanisms for the difference in intensity of change, particularly for summer. Detailed process-level studies will be necessary to establish mechanisms and credibility of these results. The GCMs explain more variance for winter temperature and the RCMs for summer temperature. The same is true for precipitation patterns. Thus, we recommend that future RCM-GCM experiments over this region include a balanced number of GCMs and RCMs.  相似文献   

The 69-μm forsterite band as a dust temperature indicator     

J. E.Bowey  M. J.Barlow  F. J.Molster  A. M.Hofmeister  C.Lee  C.Tucker  T.Lim  P. A. R.Ade  L. B. F. M.Waters 《Monthly notices of the Royal Astronomical Society》2002,331(1):L1-L6

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Source mechanism and m_b—M_s analysis of aftershocks of the San Fernando earthquake     

Brian E. Tucker  James N. Brune 《Geophysical Journal International》1977,49(2):371-426

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The acquisition of thermoremanent magnetization by multidomain single-crystal titanomagnetite     

P. Tucker  W. O'Reilly 《Geophysical Journal International》1980,60(1):21-36

Summary. Large, well-characterized single-crystals of titanomagnetite of approximate composition Fe_2.4Ti_0.6O₄ were ground into spheres and orientated along specific crystallographic axes. The field dependences of the thermoremanent magnetization (TRM) and the temperature dependences of the magnetic hysteresis properties were measured and evaluated against the available theoretical models. The models, of necessity simplifications of real materials, were unable to account for many features of the experimental curves. The discrepancies were partly resolved by consideration of the mode of blocking of each individual coercivity fraction. It was deduced that the domain-walls were pinned by both dislocation lines and by inclusions or voids. A fraction of the walls were not thermally blocked. They could however be thought of as being blocked isothermally as the applied field was relaxed. The proportion of remanence blocked in by each process was found to be dependent on the strength of the inducing field through the field dependence of the blocking temperatures. A simplified model, taking these effects into account, was developed. This predicts the main features of the TRM acquisition curve and of the alternating field and thermal demagnetization spectra.  相似文献   

Selective post-depositional realignment in a synthetic sediment     

P. Tucker 《Physics of the Earth and Planetary Interiors》1979,20(1):p11-p14

Synthetic sediments were deposited as slurries in controlled magnetic fields. After settling, the slurries were turned with respect to the field and dried. A small percentage of the remanet magnetization was associated with grains able to realign in the later field. These grains were the magnetically-hardest fraction. Routine alternating field demagnetization of sediments, usually assumed to remove the magnetic overprints, can thus in fact preferentially remove the earliest signal.  相似文献   

Trace constituents of Europa's atmosphere     

T.A. Cassidy  R.E. Johnson  O.J. Tucker 《Icarus》2009,201(1):182-190

Europa is bombarded by intense radiation that erodes the surface, launching molecules into a thin “atmosphere” representative of surface composition. In addition to atoms and molecules created in the mostly water ice surface such as H₂O, O₂, H₂, the atmosphere is known to have species representative of trace surface materials. These trace species are carried off with the 10-10⁴ H₂O molecules ejected by each energetic heavy ion, a process we have simulated using molecular dynamics. Using the results of those simulations, we found that a neutral mass spectrometer orbiting ∼100 km above the surface could detect species with surface concentrations above ∼0.03%. We have also modeled the atmospheric spatial structure of the volatile species CO₂ and SO₂ under a variety of assumptions. Detections of these species with moderate time and space resolution would allow us to constrain surface composition, chemistry and to study space weathering processes.  相似文献   

Thermal maturity and organic composition of Pennsylvanian coals and carbonaceous shales, north-central Texas: Implications for coalbed gas potential     

Paul C. Hackley  Edgar H. Guevara  Tucker F. Hentz  Robert W. Hook 《International Journal of Coal Geology》2009,77(3-4):294-309

Thermal maturity was determined for about 120 core, cuttings, and outcrop samples to investigate the potential for coalbed gas resources in Pennsylvanian strata of north-central Texas. Shallow (< 600 m; 2000 ft) coal and carbonaceous shale cuttings samples from the Middle-Upper Pennsylvanian Strawn, Canyon, and Cisco Groups in Archer and Young Counties on the Eastern Shelf of the Midland basin (northwest and downdip from the outcrop) yielded mean random vitrinite reflectance (R_o) values between about 0.4 and 0.8%. This range of R_o values indicates rank from subbituminous C to high volatile A bituminous in the shallow subsurface, which may be sufficient for early thermogenic gas generation. Near-surface (< 100 m; 300 ft) core and outcrop samples of coal from areas of historical underground coal mining in the region yielded similar R_o values of 0.5 to 0.8%. Carbonaceous shale core samples of Lower Pennsylvanian strata (lower Atoka Group) from two deeper wells (samples from ~ 1650 m; 5400 ft) in Jack and western Wise Counties in the western part of the Fort Worth basin yielded higher R_o values of about 1.0%. Pyrolysis and petrographic data for the lower Atoka samples indicate mixed Type II/Type III organic matter, suggesting generated hydrocarbons may be both gas- and oil-prone. In all other samples, organic material is dominated by Type III organic matter (vitrinite), indicating that generated hydrocarbons should be gas-prone. Individual coal beds are thin at outcrop (< 1 m; 3.3 ft), laterally discontinuous, and moderately high in ash yield and sulfur content. A possible analog for coalbed gas potential in the Pennsylvanian section of north-central Texas occurs on the northeast Oklahoma shelf and in the Cherokee basin of southeastern Kansas, where contemporaneous gas-producing coal beds are similar in thickness, quality, and rank.  相似文献   

Photometric,spectral phase and temperature effects on 4 Vesta and HED meteorites: Implications for the Dawn mission     

Vishnu Reddy  Juan A. Sanchez  Andreas Nathues  Nicholas A. Moskovitz  Jian-Yang Li  Edward A. Cloutis  Ken Archer  Roy A. Tucker  Michael J. Gaffey  J. Paul Mann  Holger Sierks  Ulrich Schade 《Icarus》2012,217(1):153-168

Phase angle and temperature are two important parameters that affect the photometric and spectral behavior of planetary surfaces in telescopic and spacecraft data. We have derived photometric and spectral phase functions for the Asteroid 4 Vesta, the first target of the Dawn mission, using ground-based telescopes operating at visible and near-infrared wavelengths (0.4–2.5 μm). Photometric lightcurve observations of Vesta were conducted on 15 nights at a phase angle range of 3.8–25.7° using duplicates of the seven narrowband Dawn Framing Camera filters (0.4–1.0 μm). Rotationally resolved visible (0.4–0.7 μm) and near-IR spectral observations (0.7–2.5 μm) were obtained on four nights over a similar phase angle range. Our Vesta photometric observations suggest the phase slope is between 0.019 and 0.029 mag/deg. The G parameter ranges from 0.22 to 0.37 consistent with previous results (e.g., Lagerkvist, C.-I., Magnusson, P., Williams, I.P., Buontempo, M.E., Argyle, R.W., Morrison, L.V. [1992]. Astron. Astrophys. Suppl. Ser. 94, 43–71; Piironen, J., Magnusson, P., Lagerkvist, C.-I., Williams, I.P., Buontempo, M.E., Morrison, L.V. [1997]. Astron. Astrophys. Suppl. Ser. 121, 489–497; Hasegawa, S. et al. [2009]. Lunar Planet. Sci. 40. ID 1503) within the uncertainty. We found that in the phase angle range of 0° < α ? 25° for every 10° increase in phase angle Vesta’s visible slope (0.5–0.7 μm) increases 20%, Band I and Band II depths increase 2.35% and 1.5% respectively, and the BAR value increase 0.30. Phase angle spectral measurements of the eucrite Moama in the lab show a decrease in Band I and Band II depths and BAR from the lowest phase angle 13° to 30°, followed by possible small increases up to 90°, and then a dramatic drop between 90° and 120° phase angle. Temperature-induced spectral effects shift the Band I and II centers of the pyroxene bands to longer wavelengths with increasing temperature. We have derived new correction equations using a temperature series (80–400 K) of HED meteorite spectra that will enable interpretation of telescopic and spacecraft spectral data using laboratory calibrations at room temperature (300 K).  相似文献   

The Dominican Republic–Central American Free Trade Agreement’s Symbolic Nod to Environmental Protection: Legal Perspectives on the Citizen Submission Process     

J. Christopher Upton  Catherine M. Tucker  Seleste Sanchez 《社会与自然资源》2017,30(10):1277-1287

The Dominican Republic–Central America Free Trade Agreement (CAFTA) contains a chapter on the environment, ostensibly included to mitigate the North American Free Trade Agreement (NAFTA) environmental oversights. The environment chapter created a citizen submission process designed to foster public participation in supporting each participating nation’s environmental laws. This article examines the outcomes to date of the citizen submission process, based on an analysis of the articles of the agreement and an examination of the rulings made on each case submitted under the citizen submission process. The analysis shows that CAFTA poses significant obstacles to citizen participation and has made minimal, if any, contributions to environmental law enforcement among the Parties to the agreement.  相似文献   

荒漠化,干旱与植被—以西非萨赫勒为例     

TucK.  CJ 张文哲 《气象科技》2000,28(2):41-46

关于西非荒漠化的本质和特征存在着许多看法。该文将追溯其历史，回顾荒漠化对气候影响的研究现状，并介绍一些有关研究结果。对荒漠化的认识通常为“沙漠”的扩张，是一个总体上不可逆转的人为过程。其过程与地表反照率增强，风沙加大以及土地生产力下降相联系。研究表明，在最近１６年里撒哈拉沙漠的边界和萨赫勒植被均变化不大，从植被水分有效利用率来看，“生产力”没有系统性降低，地表反照率也没有多少改变。自２０世纪５０年  相似文献