亚太清洁发展和气候新伙伴计划

编者按：2005年7月28日在老挝万象,中国、美国、印度、澳大利亚、韩国和日本六国共同发表了《"亚太清洁发展与气候新伙伴计划"意向声明》,旨在发展高效成本清洁技术以及二氧化碳捕获和储存技术,从而达到减排的目的。这项计划是亚太地区的一个区域性合作新机制。参加该计划的成员国拥有世界上近一半的人口,并创造了全球GDP总和的一半,其能源消耗和温室气体排放总量也几乎占全球的一半。该计划虽不具有法律约束力,但其宗旨与《联合国气候变化框架公约》的目标是一致的。 本文内容主要来自澳洲亚太经济合作组织研究中心主席艾伦·奥克斯利（Alan Oxley）先生有关该计划的一份研究报告,并于2005年11月3日在北京举行的新闻发布会上得到艾伦先生的允许,经过本刊编辑部和有关专家编译,在本刊发表其报告的主要内容,以飨读者。     

Tracer Flux Balance at an Urban Canyon Intersection

Despite their importance for pollutant dispersion in urban areas, the special features of dispersion at street intersections are rarely taken into account by operational air quality models. Several previous studies have demonstrated the complex flow patterns that occur at street intersections, even with simple geometry. This study presents results from wind-tunnel experiments on a reduced scale model of a complex but realistic urban intersection, located in central London. Tracer concentration measurements were used to derive three-dimensional maps of the concentration field within the intersection. In combination with a previous study (Carpentieri et al., Boundary-Layer Meteorol 133:277–296, 2009) where the velocity field was measured in the same model, a methodology for the calculation of the mean tracer flux balance at the intersection was developed and applied. The calculation highlighted several limitations of current state-of-the-art canyon dispersion models, arising mainly from the complex geometry of the intersection. Despite its limitations, the proposed methodology could be further developed in order to derive, assess and implement street intersection dispersion models for complex urban areas.     

Airborne total eclipse observation of the extreme solar limb at 400 μm

The total solar eclipse of February 26, 1979 was monitored at far infrared wavelengths from the NASA Lear Jet Observatory flying at 12.9 km in the eclipse shadow. The resultant eclipse curve for radiation within a bandwidth of 20 cm^–1 centered upon 25 cm^–1 (400 m) was measured and analysed at an equivalent angular resolution of 1 arc sec over a 100 arc sec region adjacent to the limb to provide information on the intensity distribution of continuum radiation close to this limb. The curve has been compared to predictions derived from models of the solar atmosphere for the specific geometry of this eclipse, and is shown to match most closely that derived from a uniform distribution of radiation across the disk. This is in distinct contrast to the result obtained in the only other comparable experiment, carried out over Africa in 1973 from a supersonic Concorde aircraft, in which an intense but narrow spike of far infrared radiation at the extreme solar limb was inferred from the data. The absence also in the present observations of the significant limb brightening predicted by the HSRA model (in which homogeneity within the source region is assumed) is in substantial agreement with lower resolution results from mountain altitudes. This result is interpreted as further evidence for the presence in the Sun's lower chromosphere of significant inhomogeneity with a scale size of at least 1000 km at this depth.     

BEACH RIDGES AND PALEOGEOGRAPHY,CENTRAL BAJA CALIFORNIA,MEXICO

Two spatially separated sets of beach ridges were studied in Baja California. Each set contains several well-preserved beach ridges and each is adjacent to an arroyo mouth. Modern beach ridges mark coastal location whereas abandoned paleobeach ridges record coastal change. Paleobeach ridges were dated by absolute and relative techniques for rate-change, chronology, and longshore correlation purposes. With time, shape becomes more planar, foreslope angle is reduced, and there is a progressive tendency for constituent shingle to disintegrate and develop both rinds and surficial roughness. One paleobeach ridge on the lowest emergent terrace was assigned a 1,150 ± 230 yr. B.P. radiocarbon date whereas another beach ridge 18 km farther north has a partially overlapping date. Older but undated beach ridges also exist on the lowest emergent terrace as well as on the highest persistent terrace. Those beach ridges on the highest persistent terrace are highly weathered and Pleistocene in age. All beach ridges have paleogeographic implications and suggest that shoreline orientation has been generally stable although its position has shifted laterally by up to 720m westward in the last 1,150 ± 230 years.     

Geochemistry and geochronology of chemical weathering,Butler Hill Granite,Missouri

Major element, Rb, Sr and Sr isotope abundances were examined in an ancient (Cambrian) weathering zone in the Butler Hill Granite, Missouri. Most of the major elements behaved predictably and systematically as a result of weathering intensity. MgO and the alkalis (Na₂O and K₂O) show highly erratic variations in both fresh and weathered rocks, suggesting considerable initial heterogeneity in the composition of biotite and feldspar. Rb predictably follows the behaviour of K during weathering (showing erratic variations similar to K), whereas Sr follows Ca (decreasing steadily as a result of weathering intensity). A method is postulated to date ancient weathering episodes using Rb-Sr data from a sequence of fresh to highly weathered samples. Data from the Butler Hill Granite (1185 m.y.) lend support to the proposed dating technique but show that more detailed sampling of the most intensely weathered regions is needed to produce more accurate results in future studies.     

Lunar atmospheric H2 detections by the LAMP UV spectrograph on the Lunar Reconnaissance Orbiter

We report on the detection of H₂ as seen in our analysis of twilight observations of the lunar atmosphere observed by the LAMP instrument aboard NASA’s Lunar Reconnaissance Orbiter. Using a large amount of data collected on the lunar atmosphere between September 2009 and March 2013, we have detected and identified, the presence of H₂ in the native lunar atmosphere, for the first time. We derive a surface density for H₂ of 1.2 ± 0.4 × 10³ cm⁻³ at 120 K. This is about 10 times smaller than originally predicted, and several times smaller than previous upper limits from the Apollo era data.     

Metallic copper in ordinary chondrites

Abstract— Metallic Cu of moderately high purity (～985 mg/g Cu, ～15 mg/g Ni) occurs in at least 66% of ordinary chondrites (OC) as heterogeneously distributed, small (typically ≤20 μm) rounded to irregular grains. The mean modal abundance of metallic Cu in H, L and LL chondrites is low: 1.0 to 1.4 × 10^?4 vol%, corresponding to only 4–5% of the total Cu in OC whole rocks. In more than 75% of the metallic-Cu-bearing OC, at least some metallic Cu occurs at metallic-Fe-Ni-troilite grain boundaries. In some cases it also occurs within troilite, within metallic Fe-Ni, or at the boundaries these phases form with silicates or chromite. Ordinary chondrites that contain a relatively large number of occurrences of metallic Cu/mm² have a tendency to have experienced moderately high degrees of shock. Shock processes can cause local melting and transportation of metallic Fe-Ni and troilite; because metallic Cu is mainly associated with these phases, it also gets redistributed during shock events. In the most common petrographic assemblage containing metallic Cu, the Cu is adjacent to small irregular troilite grains surrounded by taenite plus tetrataenite; this assemblage resembles fizzed troilite and may have formed by localized shock melting or remelting of a metal-troilite assemblage.     

Finding KBO Flyby Targets for New Horizons

Development of the New Horizons mission to Pluto and the Kuiper Belt is now fully funded by NASA (Stern and Spencer, this volume). If all goes well, New Horizons will be launched in January 2006, followed by a Jupiter gravity assist in 2007, with Pluto arrival expected in either 2015 or 2016, depending on the launch vehicle chosen. A backup launch date of early 2007, without a Jupiter flyby, would give a Pluto arrival in 2019 or 2020. In either case, a flyby of at least one Kuiper Belt object (KBO) is planned following the Pluto encounter, sometime before the spacecraft reaches a heliocentric distance of 50 AU, in 2021 or 2023 for the 2006 launch, and 2027 or 2029 for the 2007 launch. However, none of the almost 1000 currently-known KBOs will pass close enough to the spacecraft trajectory to be targeted by New Horizons, so the KBO flyby depends on finding a suitable target among the estimated 500,000 KBOs larger than 40 km in diameter. This paper discusses the issues involved in finding one or more KBO targets for New Horizons. The New Horizons team plans its own searches for mission KBOs but will welcome other U.S, or international team who wish to become involved in exchange for mission participation at the KBO.     

藏北高原地壳及上地幔导电性结构——超宽频带大地电磁测深研究结果

为了研究西藏中、北部壳、幔导电性结构,讨论高原中、北部岩石圈热状态,1998年和1999年（INDEPTH（Ⅲ） MT）在西藏中、北部完成了德庆—龙尾错（500线）和那曲—格尔木（600线）超宽频带大地电磁深探测剖面的研究.研究结果表明,西藏中、北部以昆仑山断裂为界,其南北壳、幔电性结构有很大差异.昆仑山断裂以北地壳和上地幔为高阻区.而昆仑山以南,地壳和上地幔的导电性有明显的分层结构：地壳上部以不连续的高阻体为主,夹有局部低阻异常体,沿南北方向上地壳的电性结构复杂,具有不连续、分块的特点;但中、下地壳为大范围的高导异常区,区内发育有大规模、不相连续、产状各异的高导体,其电阻率均小于4Ωm;在班公—怒江和金沙江缝合带之下,壳内高导体都具有向上地幔延伸的趋势,存在连通壳、幔的低阻通道.根据西藏高原中、北部壳、幔电性结构的研究推断：如同藏南一样,这里也普遍存在部分熔融体和热流体,它们的成因主要与班公—怒江和金沙江缝合带的壳-幔热交换、热活动有关,这是两期形成的壳-幔热交换通道.其中,班公—怒江缝合带的壳-幔热交换通道形成时间比金沙江缝合带早.因此,研究区壳、幔的热活动是从南边和西边开始,向北、向东扩展,导致现今西藏中、北部地壳和上地幔的热流分布由西向东、由南向北增大.