低空冷式切变线引发区域性大暴雨成因分析

应用常规资料、自动站雨量资料、卫星云图及雷达资料,对2009年5月9-10日发生在鲁西北和鲁中北部的一次区域性大暴雨进行分析。分析发现,低层冷式切变线是引发大暴雨的主要系统,暴雨主要产生在低空冷式切变线右侧、西南低涡的东北象限以及低空急流的左前方,也是高低空急流耦合区。副高西侧的西南急流建立起从南海到华北中部的水汽通道,为大暴雨的发生发展提供暖湿空气和能量,使得低涡辐合加强,是低层切变线长时间停滞的必要条件。地面锋面气旋则是暴雨开始的启动机制,锋后东北冷空气与西南暖湿空气在山东上空交汇,促使对流发展和不稳定能量释放产生暴雨。在低层辐合、高层弱辐散的情况下,暴雨区低涡的涡动作用使得水汽块运动加强。多个对流单体合并形成的中尺度对流系统(MCS)经过大暴雨区,雷达回波表现为层状云为主的混合回波带,说明对流并不旺盛。     

内蒙古中部区地台区和地槽区元素地球化学分布特征

本文利用历史地球化学的观点，研究了内蒙中部区地台和地槽区各时代常量元素（Ｓｉ、Ｋ、Ｎａ、Ａｌ、Ｆｅ、Ｃａ、Ｍｇ）、微量元素（Ｃｕ、Ｐｂ、Ｚｎ、Ａｕ、Ａｇ、Ａｓ、Ｓｂ、Ｈｇ等）的分布特征，以及稀土元素（Ｌａ、Ｃｅ、Ｎｄ、Ｓｍ、Ｇｄ、Ｅｕ、Ｔｂ、Ｙｂ、Ｌｕ）总量变化、元素的配分和稀土元素的组成模式，总结了元素随地质年代由老到新的演化规律，指出了主要成矿元素相对富集的层位，得出内蒙中部区相对富集轻稀土、贫中稀土和重稀土的结论。     

Cleaning of lake sediment samples for diatom oxygen isotope analysis

Detrital grain contamination in a diatom sample can considerably influence the δ¹⁸O_diatom signal. In order to obtain a meaningful signal, pure samples must be used. This can be achieved via a series of cleaning stages including organic and carbonate material removal, sieving, differential settling and heavy liquid separation. The method described here works best for sediments with >20% diatom content. Based on testing various clean-up methods, we propose a sequence of four clean-up stages to produce pure diatom samples from a range of lake sediments types starting with a few grams of sediment. The diatom content and the oxygen isotope composition of the samples at each stage were measured in order to assess the effect of differential amounts of contamination. Results show that a four stage clean-up is necessary to produce clean diatom samples and that contamination by silt and clay causes lower δ¹⁸O values.     

Limnology of Two Antarctic Epishelf Lakes and their Potential to Record Periods of Ice Shelf Loss

George VI Ice Shelf is the largest ice shelf on the western side of the Antarctic Peninsula and its northern margin marks the southern most latitudinal limit of recent ice shelf retreat. As part of a project to reconstruct the long-term (Holocene) history of George VI Ice Shelf we studied two epishelf lakes impounded by the ice shelf at Ablation Point, on the east coast of Alexander Island. These lakes, Moutonnée and Ablation, are stratified water bodies with a lower marine layer and an upper freshwater layer. To determine if their sediment records could be used to detect past changes in the presence or absence of the ice shelf it was necessary to describe their present-day limnology and sedimentology. We measured water column chemistry and sampled the water column and sediments of the lakes along vertical and horizontal transects. We analysed these samples for diatoms, stable isotopes (δ¹⁸O, δ²H, δ¹³C_DIC, δ¹³C_org), geochemistry (TOC, TN, C/N ratios) and physical sedimentology (grain-size). This was supplemented by chemical and biological reference data from the catchments. Results showed that the water columns of both lakes are nutrient limited and deficient in phytoplankton. Benthic productivity is low and decreases with depth. Comparison of water column chemistry with an earlier survey shows a net increase in the thickness of the freshwater layer in Moutonnée Lake between 1973 and 2001, which could indicate that George VI Ice Shelf has thinned during this period. However, a similar trend was not observed in Ablation Lake (5 km to the north) and an alternative explanation is that the changes are a seasonal phenomena. Data from the surface sediment transects identified a number of proxies that respond to the present day stratification of the water column including diatom species composition, stable isotopes and geochemistry, particularly in Moutonnée Lake. Collectively these data have been used to develop a conceptual model for determining past ice shelf configuration in epishelf lakes. Specifically, periods of past ice shelf loss, and the removal of the ice dam, would see the present stratified epishelf lake replaced by a marine embayment. It is suggested that this change would leave a clear signature in the lake sediment record, notably the deposition of an exclusively marine biological assemblage, increased ice rafted debris and δ¹³C_org values that are indicative of marine derived organic matter. These authors contributed equally to this work     

中尺度自动气象站资料的图形化分析应用

利用GRADS软件对中尺度自动气象站资料进行分析和处理，采取格点场和站点场两种图形处理显示方法，介绍了从数据格式转换到批处理绘图等一系列方法，实现了中尺度自动气象站资料的图形化分析应用，并对其中出现的几个技术问题进行了讨论。     

集合预报中检验资料提取的并行化实现

神威集合数值天气预报系统是以国产巨型机“神威”为平台的实时业务系统, 检验子系统是其重要的组成部分。文章介绍了神威集合数值天气预报系统中检验资料提取的并行化实现方法及并行效率。     

CCD传感器在位移测量中的应用

介绍了采用ＣＣＤ作为传感器,研制用于大坝监测的引张线观测仪和倒垂线观测仪的设计方法。仪器测量范围为几厘米,精度优于０．１ｍｍ,具有结构简单,数字化,自动测量及远距离数据传输等优点。     

Geochemistry of the acid Kawah Putih lake, Patuha Volcano, West Java, Indonesia

Kawah Putih is a summit crater of Patuha volcano, West Java, Indonesia, which contains a shallow, 300 m-wide lake with strongly mineralized acid–sulfate–chloride water. The lake water has a temperature of 26–34°C, pH=<0.5–1.3, S^tot=2500–4600 ppm and Cl=5300–12 600 ppm, and floating sulfur globules with sulfide inclusions are common. Sulfur oxyanion concentrations are unusually high, with S₄O₆²⁻+S₅O₆²⁻+S₆O₆²⁻=2400 – 4200 ppm. Subaerial fumaroles (<93°C) on the lake shore have low molar SO₂/H₂S ratios (<2), which is a favorable condition to produce the observed distribution of sulfur oxyanion species. Sulfur isotope data of dissolved sulfate and native sulfur show a significant ³⁴S fractionation (ΔSO₄–S_e of 20‰), probably the result of SO₂ disproportionation in or below the lake. The lake waters show strong enrichments in ¹⁸O and D relative to local meteoric waters, a result of the combined effects of mixing between isotopically heavy fluids of deep origin and meteoric water, and evaporation-induced fractionation at the lake surface. The stable-isotope systematics combined with energy-balance considerations support very rapid fluid cycling through the lake system. Lake levels and element concentrations show strong seasonal fluctuations, indicative of a short water residence time in the lake as well.Thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases, barite, pyrite and various Pb, Sb, Cu, As, Bi-bearing sulfides when sulfur saturation is assumed. Precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur-rich bottom sediments and their identified mineral phases. Much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases, as indicated by a comparison of the fluids, volcanic rocks and lake bed sediment.Flank springs on the mountain at different elevations vary in composition, and are consistent with local rock dissolution as a dominant factor and pH-dependent element mobility. Discharges of warm sulfate- and chloride-rich water at the highest elevation and a near-neutral spring at lower level may contain a small contribution of crater-lake water. The acid fluid-induced processes at Patuha have led to the accumulation of elements that are commonly associated with volcano-hosted epithermal ore deposits. The dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern.     

三峡库区秋雨的气候演变规律

利用三峡库区28个站1960～1996年10月～11月的逐日降水资料,分析秋雨发生的气候概况、降雨日数分布,降雨量分布、秋雨过程及其频率分布,研究秋雨的年际变化规律,其结果可为长江三峡工程提供参考,有助于做好三峡工程的气象保障工作.