1979年夏末欧亚上空的温度变化

在1979年夏末,15°N以北的欧亚地区温度分布发生了显著的变化。在300mb上,大约8月23日欧亚地区沿 20°—25°N平均的纬向平均温度急剧地减小。南亚(50°—100°E)夏季风的撤退是造成这种纬向平均温度减小的重要原因。300mb纬向平均温度的突然减小在8月18日也发生在中纬度大范围地区(40°—55°N),这比南亚夏季风的撤退约早5天左右。 在夏到秋的过渡时期,南北方向垂直环流的强度和位置在欧亚地区也经历了明显变化。在20—25°N,过渡时期(8月18—27日)纬向平均的上升气流明显减弱。减弱的综向平均加热率可能是造成这种减小的主要因子。在45°N,过渡期纬向平均的下沉气流和冷却(辐射)率显著增加有关。 在15°N附近,300mb近于以40天周期准周期地脉动。这种脉动似与40天过滤的绝热冷却(加热)和欧亚平均经圈环流有关的非绝热加热(冷却)之间小的不平衡有联系。     

多元分析和天气预报

1.引言很多统计方法都可用于作几天以上的天气预报,而对于短期预报来说,往往用非统计方法来作更为合适。对于单个变量来说,已经有一些人们所熟悉的统计预报方法。但是在气象学中,通常要求同时作出多个变量的预报。虽然在多元时间序列预报方面已经开展了一些工作,但其效果如何,尚不十分清楚。本文对多元分析的标准方法(不是多元时间序列方法)进行了探讨,用以说明这些方法是如何用于预报的。这些方法大多数是气象工作者所熟悉的,但人们对它们在气象预报中的作用则了解甚少。本     

Is environmental antimony a potential health problem？

Antimony has long been recognized as a non-essential, potentially toxic element. It has recently been suggested, on the basis of measured elemental profiles in peat bogs, that natural levels of Sb in the environment have been overestimated by a factor of 10 and that anthropogenic Sb deposition from the atmosphere has closely followed that of Pb. The implication is that the health effects of environmental Sb may have been seriously underestimated. To examine these propositions, we have compared new data for Sb and Pb in dated cores from four Scottish ombrotrophic peat bogs, Carsegowan Moss, Flanders Moss, Red Moss of Balerno and Turclossie Moss, in southwest, west-central, east-central and northeast Scotland, respectively. Dried peat sections, 1 to 2 cm thick, were subjected to microwave-assisted digestion in nitric/hydrofluoric acid and subsequently analyzed for a range of elements （including Sb, Pb, and the conservative elements Sc, Ti） and Pb isotopic composition by ICP-OES and ICP-MS as appropriate. Three certified reference materials, including NIMT/UOE/FM/001 Peat, were used for quality control purposes. Radiometric dating of upper and lower sections of the cores was carried out using gamma spectrometry for ^21-Pb and accelerator mass spectrometry for ^14C, respectively Some 2000 years ago, in Roman times, both Sb and Pb were clearly elevated in Scottish peat but typically at concentrations below 0.1 mg/kg and 5 mg/kg, respectively, with an average anthropogenic Sb/Pb ratio of-0.01.     

中国北方晚第四纪气候变化的沙漠与黄土记录* ——以光释光年代为基础的直接对比

中国北方有约200×10⁴km²的面积被黄土、沙漠和荒漠戈壁沉积物覆盖,这些地区堆积物的形成变化与第四纪气候变化密切相关。关于中国北方沙漠与黄土记录晚第四纪古气候变化的研究不少,但是,由于受到方法和条件等限制,系统的(高密度的)和独立的年代学工作比较薄弱,从而使诸多已经发表的关于沙漠-黄土记录的亚轨道时间尺度气候变化的结论受到质疑。文章通过对黄土高原代表性的4个末次冰期以来的黄土剖面以及毛乌素、浑善达克和科尔沁沙地的20多个末次冰期-全新世的沙-砂质古土壤剖面的研究,获得了150多个独立的光释光年龄数据。在此基础上,结合200多个样品的粒度、有机质含量和磁化率数据,重建末次冰期以来中国北方气候变化过程,对比分析沙地与黄土古气候记录的联系。结果表明,中国北方古气候在57.5~52.5kaB.P.相对干旱,41.5~37.3kaB.P.相对湿润,26~22kaB.P.逐渐干旱,22~18kaB.P.极端干旱,15~10kaB.P.干旱,10~8kaB.P.为干旱减弱的时期,8.0~2.4kaB.P.相对湿润,而2.4kaB.P.以来气候为相对干旱。其间,在8.0~2.4kaB.P.的湿润时期有几次干旱事件,而2.4kaB.P.以来气候变化频繁。具有独立年代控制的黄土和沙漠记录表明,中国北方的气候变化对轨道时间尺度的太阳辐射变化有大约3~4ka的滞后。     

南极洲沙克尔顿山榴辉岩相变质作用的首次证据:东、西冈瓦纳之间缝合带的遗迹?

南极洲东部的沙克尔顿山(Shackleton Range)位于S80°—81°,东西向狭长分布,长约240km,宽50~70km,为活动的Ross造山带与稳定的南极洲东克拉通之间的过渡带。许多人把它视为一条具薄皮的冲断推覆构造的碰撞造山带。沙克尔山岩石包括含石榴子石和/或尖晶石橄榄岩和辉岩。石榴子石在正常地壳厚度之下的含橄榄石岩石中是不稳定的,但要求与榴辉岩相一样的压力条件。石榴子石-橄榄石组合的存在表明为高压条件,这一点在沙克尔顿山还存在异议。对高级片麻岩地带含石榴子石超镁铁质岩的产出有不同的解释。一种可能性是作为稳定相的含有石榴子石的…     

北京PM10的生物活性与微量元素的相关性研究

在使用质粒DNA评价法对北京PM₁₀的生物活性进行研究的基础上, 结合PM₁₀中微量元素分析结果, 探讨了PM₁₀对质粒DNA产生损伤的原因. 研究表明北京不同季节、不同地区PM₁₀对DNA的氧化性损伤有明显的差别. 冬季市区和对照点PM₁₀(全样)的TM50分别是900和74 μg·mL^-1, 水溶组分的TM50分别是540和86 μg·mL^-1; 夏季市区和对照点PM₁₀(全样)的TM50分别是116和210 μg·mL^-1, 水溶组分的TM50分别是180和306 μg·mL^-1; 北京PM₁₀的生物活性的差别主要来自PM₁₀中微量元素含量的不同. PM₁₀(全样)中Pb, Zn和As三种元素对质粒DNA氧化性损伤能力较强; 而PM₁₀水溶组分中Mn, V, Zn同TM50的相关性较高; Zn元素可能是导致PM10具有氧化性损伤能力的主要微量重金属元素.     

Trace element characteristics of partial melts produced by melting of metabasalts at high pressures: Constraints on the formation condition of adakitic melts

Modern adakite, Archean tonalite-trondhjemite- granodiorite (TTG) and adakitic rocks derived from lower continental crust are high Na and Al felsic rocks and are characterized by strong heavy REE and Y de- pletion and high Sr/Y and La/Yb ratios, which sug…     

The Detection of Multimodal Oscillations on alpha Ursae Majoris

We have used the star camera on the Wide-Field Infrared Explorer satellite to observe the K0 III star alpha UMa, and we report the apparent detection of 10 oscillation modes. The lowest frequency mode is at 1.82 μHz, and it appears to be the fundamental mode. The mean spacing between the mode frequencies is 2.94 μHz, which implies that all detected modes are radial. The mode frequencies are consistent with the physical parameters of a K0 III star, if we assume that only radial modes are excited. Mode amplitudes are 100-400 μmag, which is consistent with the scaling relation of Kjeldsen & Bedding.     

A Spectroscopic Redshift for the Cl 0024+16 Multiple Arc System: Implications for the Central Mass Distribution

We show that the energy-level splitting that arises from grain rotation ensures that paramagnetic dissipation acts at its maximum rate, i.e., the conditions for paramagnetic resonance are automatically fulfilled. We refer to this process as "resonance relaxation." The differences between the predictions of classical Davis-Greenstein relaxation and resonance relaxation are most pronounced for grains rotating faster than 1 GHz, i.e., in the domain in which classical paramagnetic relaxation is suppressed. This mechanism can partially align even very small grains, resulting in linearly polarized microwave emission that could interfere with efforts to measure the polarization of the cosmic microwave background.     

The Lowest Submillimeter-Wave Transitions of CH: The Laboratory Measurement of the Rest Frequencies

The lowest rotational transitions of CH in the ground electronic state (X2Pi), J=3&solm0;2, N=1<--J=1&solm0;2, N=1, have been observed in the laboratory in the 532.8 and 536.8 GHz regions. All six possible hyperfine components are identified, and the precise transition frequencies are determined.