贵州省2020年5月极端性高温事件研究

2020年5月贵州省出现极端高温天气事件,本文利用贵州省84个气象观测站日平均气温和最高气温资料、美国气象环境预报中心的逐日再分析高度场资料以及美国海洋大气管理局的日平均海表面温度（SST）资料,利用超前滞后相关等方法对贵州省2020年5月“极端性高温事件”进行研究。得出如下结论：（1）2020年5月贵州省约有29%的站点极端日最高气温超过了1981年以来的历史极值,约58%的站点突破1981年以来5月同期历史极值,西太平洋副热带高压显示为异常西扩加强的态势,同时伴随南亚高压东伸增强,两个高压在不同高度上的配合导致深厚高压的异常出现,是此次贵州极端性高温事件发生的重要因素。（2） 2020年5月在欧亚大陆中高纬对流层上层有明显的Rossby波列结构,有利于贵州极端性高温事件出现。（3）热带西大西洋SST在月尺度内异常阶段性增暖,可作为贵州省极端性高温天气发生的重要前期信号,并且增暖过程比高温事件提前约14天,具有一定的前期指示意义。     

1971—2020年江西暴雨预警信号等级时空分布特征

利用1971—2020年江西省83站国家气象观测站逐时降水资料,采用EOF分析、Mann-Kendall突变检验、滑动t检验、Morlet小波变换等方法,对江西暴雨预警信号等级的时空分布特征进行了分析。结果表明：1)江西暴雨蓝色、黄色和橙色预警信号年平均发布频次均呈“东北多、西南少”的地域分布,暴雨红色预警主要在鄱阳湖南侧存在多发区;上饶市和景德镇市是暴雨蓝色和黄色预警信号发布频次异常的敏感区,且在江西北部与中部表现出较明显的反位相变化特征。2)暴雨蓝色预警信号发布时间表现为单峰型,主要出现在13—16时,其他三种级别暴雨预警信号发布时间均表现为双峰型,主要有上午和傍晚两个易发时段。3)暴雨红色预警信号发布主要在6—8月,其他等级暴雨预警主要在5—8月,各等级暴雨预警信号均在6月发布最多。4)各等级暴雨预警信号发布频次均存在6—8 a的年际周期振荡,目前江西暴雨蓝色和黄色预警信号发布频次进入偏少期,而暴雨橙色和红色预警信号发布进入偏多期。5)暴雨红色预警信号发布频次呈0.70次/(10 a)的线性增加趋势,且在1992年发生明显由偏少转为偏多的突变,大部地区暴雨红色预警信号发布时降水极...     

Monazite and xenotime U–Th–Pb geochronology by ion microprobe: dating highly fractionated granites at Xihuashan tungsten mine, SE China

Zircon, monazite, and xenotime have proven to be valuable chronometers for various geological processes due to their commonly high-U–Th and low common Pb contents. However, zircons that have crystallized in highly fractionated granites often have such high-U contents that radiation damage can lead to scattered U–Pb ages when measured with secondary ion mass spectrometry (SIMS). In this study, monazite and xenotime were separated from a number of highly fractionated granites at the Xihuashan tungsten mine, Southeast China, for alternative dating methods by SIMS. For monazite analysis, obvious excess ²⁰⁴Pb signal (mainly from interference of ²³²Th¹⁴⁴Nd¹⁶O₂ ⁺⁺) was observed in high-Th (>2 wt%) monazite, which hinders ²⁰⁴Pb-based common Pb corrections. A ²⁰⁷Pb-based common Pb correction method was used instead. By employing power law relationships between Pb⁺/U⁺ versus UO₂ ⁺/U⁺, Pb⁺/Th⁺ versus ThO₂ ⁺/Th⁺ and suitable exponentials, monazites with ThO₂ contents in the range of ~3–19 % do not exhibit this matrix effect. Independent SIMS U–Pb ages and Th–Pb ages of three phases of Xihuashan granite samples were consistent with each other and yielded dates of 158.7 ± 0.7, 158.0 ± 0.7, and 156.9 ± 0.7 Ma, respectively. Xenotime does show marked matrix effects due to variations of U, Th, and Y [or total rare earth element (REE), referred as ΣREE hereafter] contents. Suitable correction factors require end-member standards with extremely high or low U, Th, and Y (or ΣREE) contents. No excess ²⁰⁴Pb was observed, indicating that the ²⁰⁴Pb-based common Pb correction method is feasible. Independent ²⁰⁷Pb/²⁰⁶Pb ages can be obtained, although multi-collector mode is necessary to improve precision. The main difficulties with dating xenotime are when high-Th (U) mineral inclusions are ablated. We can identify when this occurs, however, by comparing the measured UO₂ ⁺/U⁺ and ThO₂ ⁺/Th⁺ with those in xenotime standards. Three xenotime samples from the first phase of Xihuashan granite yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb date of 159.5 ± 4.4 Ma (MSWD = 1.0) and a ²⁰⁶Pb/²³⁸U date of 159.4 ± 0.9 Ma (MSWD = 1.6), which are consistent with monazite U–Pb and Th–Pb ages from the same granites. This study demonstrates that monazite and xenotime are better SIMS chronometers for highly fractionated granites than zircon, which can yield doubtful ages due to high-U contents.     

Vulnerability of population and transportation infrastructure at the east bank of Delaware Bay due to coastal flooding in sea-level rise conditions

Catastrophic flooding associated with sea-level rise and change of hurricane patterns has put the northeastern coastal regions of the United States at a greater risk. In this paper, we predict coastal flooding at the east bank of Delaware Bay and analyze the resulting impact on residents and transportation infrastructure. The three-dimensional coastal ocean model FVCOM coupled with a two-dimensional shallow water model is used to simulate hydrodynamic flooding from coastal ocean water with fine-resolution meshes, and a topography-based hydrologic method is applied to estimate inland flooding due to precipitation. The entire flooded areas with a range of storm intensity (i.e., no storm, 10-, and 50-year storm) and sea-level rise (i.e., current, 10-, and 50-year sea level) are thus determined. The populations in the study region in 10 and 50 years are predicted using an economic-demographic model. With the aid of ArcGIS, detailed analysis of affected population and transportation systems including highway networks, railroads, and bridges is presented for all of the flood scenarios. It is concluded that sea-level rise will lead to a substantial increase in vulnerability of residents and transportation infrastructure to storm floods, and such a flood tends to affect more population in Cape May County but more transportation facilities in Cumberland County, New Jersey.     

川中东北部中-下侏罗统湖相碳酸盐岩碳氧同位素特征及其古环境意义

在钻井岩心观察和岩石学分析的基础上,对川中东北部龙岗地区中-下侏罗统自流井组和凉高山组典型钻井取心段碳酸盐岩样品进行了碳氧同位素分析。40余件样品的测试结果表明,δ¹³C_PDB值在-1.24‰～4.59‰之间,除了1个负值外,都为正值。δ¹⁸O_PDB值在-15.7‰～-9.83‰之间,都为负值。与海相和陆相碳酸盐岩同位素值对比显示,自流井期和凉高山期古湖泊均表现出内陆开放性淡水湖泊的特点,没有经过明显的海水入侵。在中-下侏罗统广泛存在的碳同位素正偏移是由湖泊初级生产力提高所导致的。岩相和同位素变化显示了古湖平面经历了2次主旋回和6次次级旋回变化,湖平面变化总体表现为东岳庙段沉积期＞大一三亚段沉积期＞大一亚段沉积期＞凉高山期＞马鞍山段沉积期。古湖泊初级生产力的变化表现为大一三亚段沉积期＞东岳庙段沉积期＞大一亚段沉积期＞凉高山期＞马鞍山段沉积期。     

http://www.sciencedirect.com/science/article/pii/S1674987113000297

This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes causing the Huronian Glaciation Event.The majority of evidence for appearances of this glaciation event can be related to the Kenorland supercontinent breakup,allied to significant atmospheric change,as well as blooms of biogeochemical oxygenic photosynthesis.In this paper,the Huronian Glaciation Event is constrained to have occurred synchronously during 2.29-2.25 Ga,accompanied by dramatic environmental changes characteristic of the Great Oxidation Event which includes the pre- 2.3 Ga hydrosphere oxidation and the post-2.3 Ga atmosphere oxygenation.     

Levels, seasonal variations, and health risks assessment of ambient air pollutants in the residential areas

People living in the urban area and the surrounding suburban area have disparities in exposure and health risks due to different levels of ambient air pollutants. The main objective of this study is to investigate the concentrations, seasonal variations, and related health risks of ambient air pollutants (PM₁₀, NO₂, and SO₂) in urban and suburban areas of Ningbo, China. The results showed that the average PM₁₀, NO₂, and SO₂ concentrations in the urban area were 85.2, 49.3, and 37.4 μg/m³, which were 1.13, 1.25, and 1.41 times the values of the suburban area during the period of March 2009 to February 2010. For the potential health risk analysis, the residents have been divided into four age categories namely, infants, children (1 year), children (8–10 years), and adults. The analysis took into account age-specific breathing rates, body weights for different age categories. The results showed that the potential health risks to respiratory disease for all age categories living in urban area were higher than those in suburban area.     

The evolution of rock failure with discontinuities due to shear creep

A two-dimensional brittle creep model for rock provides insight into the initiation of shear fracture along weak discontinuities in rock. The model accounts for material heterogeneity and introduces the concept of a mesoscopic renormalization to capture the cooperative interaction between cracks in the transition from distributed to localized damage. A series of shear creep tests on rock with discontinuities were performed to simulate the initiation and propagation of crack along a pre-existing weakness under sustained shear stress and normal stress. The investigation showed that shear stress level and the normal stress level might have significant effect on the long-term behavior of rock with weak discontinuities. Moreover, a case study of rock slope instability was also investigated, where the numerically simulated instability failure of rock slope with discontinuities showed that both tensile and shear damage at the weakest elements are the trigger for the failure surface initiation in the rock slope. Once damage occurs, redistributed stress concentrations would then intensify fracture propagation and coalescence within these damage zones, leading to the progressive development of a failure surface. Moreover, failure surface extending is not only dominated by the properties and the position of discontinuities but also influenced remarkably by the complex interaction between existing discontinuities and fracture propagation. The results are of general interest because they can be applied to the investigation of time-dependent instability in rock masses, to the mitigation of associated rock hazards in rock engineering, and even to a better understanding of the physical phenomena governing the stability of rock slope.     

我国南方初夏汛期和东亚夏季风环流

主要根据低层夏季风热力学性质与流场演变特点深入讨论我国南方初夏汛期包括华南前汛期和长江中下游梅雨期同夏季风活动的联系，分析了东亚夏季风环流建立过程的阶段性和类型，指出汛期的开始与结束同夏季风前沿位置变动一致。我国夏季风从开始到发展鼎盛时期低纬大气环流的演变过程各年不完全相同，主要可归纳为４类，每类包括４个或３个不同阶段，从而可认识到东亚夏季风体系结构的非单一性，它可有４种结构模型，即仅是东南季风Ｐ的单气流型、强东南季风Ｐ与弱西南季风Ａ的双气流型、强东南季风Ｐ和弱西南季风Ｍ的双气流型、强东南季风Ｐ和强（或弱）西南季风Ｍ以及弱西南季风Ａ的３气流型。     

内蒙古中西部宝音图群云母片岩的变质P- T轨迹与锆石年代学研究

位于内蒙古中西部地区的宝音图群,主要由云母片岩、斜长角闪岩、石英岩和大理岩等组成。其中云母片岩中发育典型的巴罗式递增变质带,目前对于该递增变质带的研究非常薄弱。本文对宝音图群的云母片岩开展了系统的岩相学、矿物化学、相平衡模拟以及锆石U-Pb年代学的研究。岩相学研究结果显示,三个云母片岩样品具有不同的峰期矿物组合,分别为石榴子石+白云母+黑云母+斜长石+石英,十字石+白云母+黑云母+斜长石+钛铁矿+石英,石榴子石+蓝晶石+白云母+黑云母+斜长石+钛铁矿+石英。此外,样品LS93和LS07存在晚期红柱石的叠加。相平衡模拟研究限定三个云母片岩的峰期温度压力分别为：577℃、0.73 GPa, 620℃、0.78 GPa和670℃、0.8 GPa,具有递增型特征,其峰期温度压力指示的地热梯度为18～20℃/km,为典型的中压相系;此外,三个样品的P-T轨迹均显示早期升温升压直至峰期阶段,随后降温降压的顺时针型,反映地壳加厚和后期抬升的演化过程。云母片岩中的锆石发育典型的变质边结构,变质边的Th/U=0.004～0.02,锆石U-Pb年代学结果显示该变质年龄为398±6 Ma,代表峰期或近峰期阶...