The Preboreal climate reversal and a subsequent solar‐forced climate shift

Accurate chronologies are essential for linking palaeoclimate archives. Carbon‐14 wiggle‐match dating was used to produce an accurate chronology for part of an early Holocene peat sequence from the Borchert (The Netherlands). Following the Younger Dryas–Preboreal transition, two climatic shifts could be inferred. Around 11 400 cal. yr BP the expansion of birch (Betula) forest was interrupted by a dry continental phase with dominantly open grassland vegetation, coeval with the PBO (Preboreal Oscillation), as observed in the GRIP ice core. At 11 250 cal. yr BP a sudden shift to a humid climate occurred. This second change appears to be contemporaneous with: (i) a sharp increase of atmospheric ¹⁴C; (ii) a temporary decline of atmospheric CO₂; and (iii) an increase in the GRIP ¹⁰Be flux. The close correspondence with excursions of cosmogenic nuclides points to a decline in solar activity, which may have forced the changes in climate and vegetation at around 11 250 cal. yr BP. Copyright © 2004 John Wiley & Sons, Ltd.     

Temperature dependence of large-scale water-retention curves: a case study

A local-scale model for temperature-dependence of water-retention curves may be applicable to large scales. Consideration of this temperature dependence is important for modeling unsaturated flow and transport in the subsurface in numerous cases. Although significant progress has been made in understanding and modeling this temperature effect, almost all the previous studies have been limited to small scales (on the order of several centimeters). Numerical experiments were used to investigate the possibility of extending a local-scale model for the temperature-dependence of water retention curves to large scales (on the order of meters). Temperature effects on large-scale hydraulic properties are of interest in many practical applications. Numerical experiment results indicate that the local-scale model can indeed be applicable to large-scale problems for special porous media with high air entry values. A typical porous medium of this kind is the porous tuff matrix in the unsaturated zone of Yucca Mountain, Nevada, the proposed geologic disposal site for national high-level nuclear wastes. Whether this finding can approximately hold for general cases needs to be investigated in future studies.     

库车坳陷侏罗系煤成气动力学模拟研究

应用黄金管—高压釜封闭体系热模拟实验与GC、GC-IRMS分析技术,结合KINETICS专用软件,对库车坳陷侏罗系煤成气进行了动力学模拟研究。库车坳陷侏罗系煤具有高的产气性,在高演化阶段主要产甲烷气;侏罗系煤热解气甲烷碳同位素为-36‰～-25‰,乙烷碳同位素为-28‰～-16‰;甲烷、C2-C5气态烃的生成活化能分别为(47～64k)calm/ol、(55～72k)calm/ol,频率因子各为5.265×1013s-1、5.388×1018s-1。在此基础上,进一步探讨了克拉2气田天然气的成因。研究认为,克拉2气田天然气属阶段捕获的煤成气,主要聚集了5～1Ma时期的天然气,其成熟度Ro分布范围为1.3%～2.5%。     

Mallow Springs,County Cork,Ireland

Because of its copious and reliable rainfall, Ireland has an abundance of springs. Many of the larger ones issue from the Carboniferous limestone that occurs in over 40% of the country. The spring water is mainly a calcium bicarbonate type with a temperature of about 10°C. In the 18th century, warm and cold springs were developed as spas in various parts of Ireland. The popularity of these springs was short and most were in major decline by 1850. Today only one cold spa at Lisdoonvarna, Co. Clare is still operating. Springs in Ireland were places of religious significance for the pre-Christian Druidic religion. In the Christian period they became holy wells, under the patronage of various saints. Cures for many different ailments were attributed to water from these wells.     

The impact of hydrological changes on travertine deposits related to thermal springs in the Pamukkale area (SW Turkey)

Pamukkale thermal waters (35 °C), exhibiting calcium-bicarbonate-sulfate composition and high carbon dioxide concentration, are of a predominantly meteoric origin. The meteoric fluid, circulating through faults and fractures, is heated by magmatic intrusions at great depth, and ascends from deep reservoirs to the surface. Mixing with relatively cold groundwater in the near surface zone promotes different saturation conditions with respect to calcium carbonate that later precipitates at depth and/or the surface. Dissolution-deposition processes of calcium carbonate both at surface and depth environments may help to reconstruct past climate direction in the field. During wet climate conditions a high-rate of calcium carbonate accumulation would be expected to occur at the surface because thermal fluid would be under-saturated with respect to calcium carbonate at depth because of a relatively higher mixing ratio with cold groundwater. During dry climate conditions the thermal fluid would be super-saturated at depth because of the highly acidic environment. Hydrometeorological studies reveal that the annual precipitation at the Pamukkale hydrothermal field tends to decrease with time. This climatic change in the area was also detected from geological records. While humid climate conditions prevailed during the late Quaternary, the area has recently been affected by arid/semi-arid climate conditions, followed by some episodic transitions. This study has shown how the system has possibly reacted to different climate conditions since antiquity.     

南边界强迫的非线性临界层与副高的形成、维持和振荡

用非线性准地转正压涡度方程模式，在南边界取定常强迫波，采用４种方案模拟了非线性临界层及其上激发的Ｋｅｌｖｉｎ猫眼，以确定热带的定常强迫对副高的形成、维持和振荡的影响。结果表明，南边界定常强迫仍在非线性临界层内激发行星尺度的准定常反气旋的Ｋｅｌｖｉｎ猫眼流场，猫眼的移动、强度和形状变化与夏季副高比较相似．而北边界定常强迫所得结果与夏季副高差异较大。因此，南边界所激发的非线性临界层上的Ｋｅｌｖｉｎ猫眼可能是夏季副高形成、维持和振荡的一种更为重要的新物理机制。文中还提出准定常行星波穿越副热带的非线性临界层的物理机制。     

长江三峡陕西营旋转滑坡

研究了陕西营旋转滑坡的成生条件、形成机理,旋转滑坡的必备约束边界,滑动受力数据分析及滑坡发展趋势。对于深入研究旋转滑坡可起到借鉴作用。     

1981年7月9-14日四川持续性暴雨分析

1981年7月9—14日岷江、沱江、涪江和嘉陵江流域出现持续性暴雨,并在四川省造成了历史上最严重的洪涝灾害。该文利用逐日降水资料、NCEP/NCAR 2.5°×2.5°逐日再分析资料和日本GMS卫星资料反演的TBB资料进行诊断分析以探讨此次暴雨持续的原因。结果表明:由于对流层低层的暖平流和其他大尺度强迫,高空槽长时间维持在长江上游地区,有利于槽后冷空气下沉南伸,与来自孟加拉湾的暖湿气流在盆地交汇,致使西南涡东移甚慢,于7月11—14日活跃在四川盆地上空。当西南涡沿梅雨锋缓慢东移时,长生命史的中尺度对流系统(MCS)在岷江、沱江、涪江和嘉陵江流域连续多次生消,导致暴雨系统持续维持在这些地区。大尺度的强迫在暴雨区上空产生了大范围持续性的上升运动,而暴雨所需的强上升运动主要由大量局地对流有效位能释放提供。对流层低层持续的水汽辐合和位势不稳定能量的输送则为暴雨的持续提供了充足的水汽和能量。与2004年9月发生在四川盆地东部的严重致洪持续性暴雨比较发现,虽然两次持续性暴雨发生的环流背景不同,但暴雨发生的物理机理一致,暴雨过程中持续性的上升运动均主要由大尺度强迫等引起,而且两次持续性暴雨的发生均与来自孟加拉湾的强水汽输送有关。     

气候系统及模式中反馈机制研究 I.概念和方法

气候系统中存在着各种各样的气候反馈机制,而气候模式对这些反馈机制描述的差异,正是造成不同模式对同一直接辐射强迫（如二氧化碳加倍）的响应不同的主要原因。因此,只有正确描述气候系统中的各种反馈作用,气候模式才可能用来对未来的气候变化进行预测。为此,本文首先介绍了气候系统及模式反馈机制分析研究时所常用的一些概念,如气候敏感性参数、云辐射强迫等,随后概述了气候模式反馈机制比较分析时常用的各种方法,并指出了这些方法各自的优缺点。而详细的有关气候系统及模式中反馈作用及其机制的分析则在文章的第ＩＩ部分给出。     

基本气流在局域流型演化过程中的作用

用一个β平面准地转正压模式,实施了5组时间积分为72个模式日的试验,分析了不同基本气流对局域流型演化特征的作用。结果指出:强的基本气流相应于持续性干旱流型;弱的基本气流相应于间歇性的干旱流型。