利用声发射研究郯庐断裂北段古应力事件

采用声发射实验方法,测试分析了郯庐断裂带北段古构造应力场,结果显示郯庐断裂北段西侧自晚奥陶世以来,经历了8次古构造事件,最大主应力有效值为153.6MPa;从早二叠世至早燕山期,测区构造运动很弱;早白垩世以来有4次古构造事件。由此推断依兰-伊通断裂和哈尔滨-长春断裂形成于古生代,燕山运动使其演化成大型走滑断裂。     

太原市灰霾期间黑碳气溶胶形貌与成分分析

为掌握太原市冬季灰霾发生期间黑碳气溶胶形貌特征和化学成分变化特点,分别于2011-12-30 T 08:00至2012-01-01 T 04:00和2018-11-25 T 08:00至2018-11-27 T 04:00灰霾发生期间在山西大学环境与资源学院楼顶使用MAY七级冲击式颗粒采样器每隔4 h采集空气动力学直径...     

Freezing rain events: a major weather hazard in the conterminous US

Freezing rain (FZRA) is well documented as a major weather hazard, producing damage to structures, the environment, and humans, and delaying various operations such as transportation. Assessing the risk of freezing rain events requires information for various areas of the nation about the frequency, duration, and intensity of these events along with the associated weather conditions that affect the damage caused by freezing rain. This includes temperatures (dry and wet bulb), the amount of precipitation, and winds during freezing rain. The purpose of this work was to develop a national and regional climatology of freezing rain events in the US for the period of 1928–2001 to addresses these conditions.     

秦岭太白盆地晚更新世晚期环境变迁

本文依据太白盆地拐里村晚更新世晚期沉积物中花粉谱,重建当时主要为含桦树的森林草原或灌丛草原,未见森林。孢粉波动幅度明显,记录了气候的强烈变化。该剖面存在四次孢粉贫乏事件(深度为15.6-15.8m、10.7-10.9m、5.6-5.8m和3.4-3.6m),其特点为木本植物花粉急剧减少,乔本植物花粉几乎为零,草本植物花粉增多。上述孢粉贫乏事件与渭南黄土古风化强度、磁化率以及SPECMAP氧同位素曲线具有较好的可比性,反映气候的冷暖波动基本一致,从而表明该区气候变化与全球气候变化基本同步。      

阿拉善变质基底古元古代晚期的构造热事件

阿拉善地块可分为太古宙的叠布斯格杂岩(岩群)、古元古代的巴彦乌拉山杂岩(岩组)和古-中元古代的阿拉善杂岩(岩群)、波罗斯坦庙片麻杂岩和毕级格台片麻杂岩。太古宙的叠布斯格岩群和片麻岩中的锆石记录了1926Ma和1802Ma的变质事件年龄,角闪石记录了1918Ma的变质事件年龄,斜长石记录了1722Ma的冷却年龄。同时,在波罗斯坦庙变形的片麻状杂岩中的锆石记录了1839Ma的岩浆事件年龄。该区古元古代晚期的构造热事件,可初步将划分为2000～1900Ma的早期事件和1850～1800Ma的晚期事件,并在时间和特点上与大青山-集宁-大同一带变质地体中广泛发育古元古代晚期的岩浆-变质事件非常相似,进而表明,华北克拉通西部陆块中的古元古代晚期造山带(孔兹岩带)向西可延伸到阿拉善东部地区。     

末次冰期间冰阶晚期长江中游风尘堆积及环境意义

定山砂山剖面的下层灰黄色土-淤泥沉积，为末次冰期间冰阶（40～22kaBP）区域降尘堆积。灰黄色土层与淤泥为同源异相沉积，粒度组合基本相同，无特征性差异。频数曲线都以双峰为特征，第一峰为主峰，众值8～32 μm；第二为次峰，众值250～500μm。9.75±0.25Φ~4.25±0.25Φ(1 ~62.5μm)在垂向上具有相似的线形变化，组成第一峰态，各粒级垂向上的含量变化是区域冬季风强弱变化的敏感指标；2.25±0.25Φ ~-0.75±0.25Φ (180~2000 μm)具有相似的线形，组成第二峰态，各粒级剖面含量变化则揭示了冬半年环境干湿状况与局地尘暴事件。在对应区域降尘堆积较弱的两个时段，存在局地尘暴的增强事件，指示局地冬半年环境干燥。     

南秦岭晚古生代海底喷气-沉积成矿系统

南秦岭显生宙喷气沉积成矿起始于晚志留世,泥盆纪是热水沉积成矿的主富集期,形成了以Ｐｂ,Ｚｎ为主的,伴生有Ｃｕ,Ａｇ,Ａｕ,Ｆｅ的矿床（体）和Ａｕ,Ｈｇ,Ｓｂ,Ａｓ等富集体,一般可划分出沉积和成岩两个阶段。之后发生了至少三个阶段的后生成矿作用,包括变质、改造、叠加成矿,以及局部的再造成矿。这一成矿系统有统一的物源和相似的金属组合,下伏沉积柱和基底提供了充足的Ｐｂ,Ｚｎ,Ａｕ,Ａｇ,Ｃｕ,Ｈｇ,Ｓｂ,Ａｓ以及Ｆｅ,Ｂａ等。成矿与该区地壳的构造盆地建造岩浆变质变形等演化相伴随,不同阶段与不同性质成矿流体的形成与贯穿造山前后的一系列热事件有密切成因联系,形成了这一金属硫化物成矿系统,并以主富集期和主要成矿形式给予命名     

我国南方地区夏季低温变化特征及其成因

采用中国气象局整编的日平均气温资料、NCEP/NCAR再分析日平均资料,分析了1960-2004年我国南方地区尤其是长江中下游地区夏季低温的变化特征及成因.结果表明:我国南方地区夏季气温在20世纪70年代末出现一个转折,在此之前气温普遍偏低,在此之后气温普遍升高;江南地区是夏季低温频发且强度较大的区域;各个层次高度场环流形势的变化以及降水和总云量的变化都对夏季低温的形成有一定作用.     

Dust Storms in North China in 2002： A Case Study of the Low Frequency Oscillation

The low frequency oscillation in both hemispheres and its possible role in the dust weather storm events over North China in 2002 are analyzed as a case study. Results show that the Aleutian Low is linked with the Circumpolar Vortex in the Southern Hemisphere on a 30-60-day oscillation, with a weak Circumpolar Vortex tending to deepen the Aleutian Low which may be helpful for the generation of dust storm events. The possible mechanism behind this is the inter-hemispheric interaction of the mean meridional circulation, with the major variability over East Asia. The zonal mean westerly wind at high latitudes of the Southern Hemisphere in the upper level troposphere may lead that of the Northern Hemisphere, which then impacts the local circulation in the Northern Hemisphere. Thus, the low frequency oscillation teleconnection is one possible linkage in the coupling between the Southern Hemisphere circulation and dust events over North China. However, the interannual variation of the low frequency oscillation is unclear.     

Influence of the Arctic on the Predictability of Eurasian Winter Extreme Weather Events

The linkage between the Arctic and midlatitudes has received much attention recently due to the rapidly changing climate.Many investigations have been conducted to reveal the relationship between the Arctic and Eurasian extreme events from the perspective of climatological statistics.As a prediction source for extreme events in Eurasia,Arctic conditions are crucial for extreme event predictions.Therefore,it is urgent to explore the Arctic influence on the predictability of Eurasian extreme events due to the large uncertainties in Arctic conditions.Considering the sensitivity and nonlinearity of the atmospheric circulations in midlatitude to Arctic conditions,it is necessary to investigate the Arctic influences on Eurasian extreme weather events in case studies at weather time scales.Previous studies indicate that only perturbations in specific patterns have fast growth.Thus,the conditional nonlinear optimal perturbation approach is recommended for exploring the uncertainties in Arctic initial and boundary conditions and their synergistic effect on Eurasian extreme events.Moreover,the mechanism for extreme event formation may differ in different cases.Therefore,more extreme cases should be investigated to reach robust conclusions.