河北涞源大湾锌钼矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

大湾斑岩-矽卡岩型锌钼矿床地处太行山北段成矿带中,是该段重要的金属矿床之一.五台群板峪口组和长城系高于庄组为主要赋矿围岩,锌钼矿体主要赋存在流纹斑岩体内及斑岩与围岩接触部位.文章对大湾矿床内2件赋矿流纹斑岩进行LA-ICP-MS锆石U-Pb年代测定,获得206Pb/238U年龄加权平均值分别为(137.1±0.9)Ma(MSWD=0.56,n=24)和(136.8±1.2)Ma(MSWD=0.40,n=22);对矿区4件辉钼矿样品进行Re-Os定年,得到加权平均年龄为(136.5±1.0)Ma,等时线年龄为(136.1±2.3)Ma,在误差范围内成岩成矿时代一致,显示大湾锌钼矿床形成于早白垩世.大湾矿床中辉钼矿的w(Re)为5.816～16.484μg/g,反映了矿床成矿物质来源具有壳幔混合特征.区内流纹斑岩和蚀变体系为进一步找矿勘查的有利标志.     

East Asian monsoon instability at the stage 5a/4 transition

The physics involved in the abrupt climate changes of the late Quaternary have eluded paleoclimatologists for many years. More paleoclimatic records characteristic of different elements of the global climate system are needed for better understanding of the cause-feedback relationships in the system. The East Asian monsoon is an important part of the global climate system and the mechanical links between the East Asian monsoon and other climatic elements around the world may hold a key to our knowledge of abrupt climate changes in East Asia and probably over a larger part of the globe. Previous studies have detected millennial-scale winter monsoon oscillations during the last glaciation and probably also during the last interglaciation in loess sequences across China. However, less attention has been paid to the abrupt summer monsoon changes and the stage 5a/ 4 transition, an important period for the evolution of the East Asian monsoon when the global climate shifted towards the last glaciation. Here we report on two loess sections from eastern China which were dated using a thermoluminescence (TL) technique. The pedogenic and other sediment parameters suggest that the summer monsoon experienced a two-step abrupt retreat at the stage 5a/4 transition. The variations in the proxies for the winter monsoon are synchronized with the summer monsoon proxies during this brief interval, implying a direct and immediate link between high latitude and low latitude mechanisms. These changes may be correlated with similar climatic oscillations observed in the North Atlantic, Europe and Antarctica, raising the possibility that the forcing factors that induced these changes are global in extent.     

垂线偏差时间变化的精度估计

对于利用Vening-Meinesz微分公式计算垂线偏差随时间变化的测定精度进行了初步估计。通过对地形改正项的影响、代表误差的影响、远区域重力异常的影响等3种主要误差的分析和实际估计，论证了它们对计算结果的综合影响不超过0.01″，比铅垂线的时间变化0.1″要高一个量级。因此认为重力方法在实践中是可行的。     

无棱镜技术在电厂施工土方量测量中的应用

随着全站仪在测量中的广泛应用,测量的精度有了很大的提高.特别是无棱镜技术的发展,改变了以往的测量手段和方法,提高了工作的效率.土方量测量是施工过程中不可避免的,为此本文介绍无棱镜测量技术在洛河电厂施工过程中测量土方量的应用情况,通过对比实验,我们对无棱镜测量技术工作效率和成果精度以及适用条件进行分析.     

高分影像场景分类的半监督深度卷积神经网络学习方法

传统基于深度卷积神经网络的场景分类方法往往需要大量标记样本用于模型的参数训练,在标记训练集数量有限的情况下,学习得到的特征泛化能力降低.针对这一问题,本文提出了高分影像分类的半监督深度卷积神经网络学习方法(3sCNN),采用自学习半监督策略,训练阶段不断增加训练样本:首先,通过有限的标记数据对深度网络进行初步训练;然后...     

2019年中国气候主要特征及主要天气气候事件

2019年我国气候总体呈现暖湿特征。全国年平均气温较常年同期偏高0.79℃,为1951年以来连续第五暖年,四季气温均偏高,春、秋季明显偏暖;年降水量为645.5 mm,较常年同期偏多2.5%,冬、春、夏季降水偏多,秋季偏少。华南前汛期开始早、结束晚,为1961年以来最长前汛期,雨量为1961年以来次多;西南雨季开始和结束均偏晚,雨量偏少;入梅晚、出梅早,梅雨量偏少;华北雨季开始晚,结束与常年一致,雨量偏少;东北雨季开始早、结束晚,雨量偏多;华西秋雨开始早、结束晚,雨量偏多。2019年,台风生成多,登陆强度总体偏弱,仅台风利奇马灾损重;暴雨洪涝、干旱、强对流、低温冷冻害和雪灾、沙尘暴等气象灾害均偏轻。     

北京及周边地区雷暴阵风锋特征统计分析

为全面和系统研究北京及周边地区阵风锋各方面特征,使用2006—2015年暖季(5—9月)北京多普勒雷达探测资料及北京、河北、天津自动气象站观测资料对北京及周边地区的阵风锋过程进行综合统计分析。结果表明,346次阵风锋过程有232次触发了对流,占总数的67%,表明阵风锋对雷暴具有较强的抬升触发能力。阵风锋在6—8月出现的日数占5—9月阵风锋总日数的85%;出现的时段主要是午后至傍晚(12—21时,北京时),维持时间0.5—3 h;阵风锋在北京东南方向生成的数量最多,且触发对流的次数也最多;其次为偏东和东北方向;偏南和西南方向生成阵风锋数量居中,而偏北、偏西和西北地区阵风锋个例相对较少,触发对流的比例也相对较低。产生阵风锋的母风暴中48%为孤立雷暴(包括孤立多单体和超级单体风暴),31%为雷暴群,21%为飑线;97%的母风暴最强回波在50 dBz以上,阵风锋的回波强度为10—25 dBz。91%的阵风锋移动速度集中在10—60 km/h,84%的阵风锋与母风暴的最大距离为1—60 km;在母风暴回波强度减弱到30 dBz以下时,80%的阵风锋能够继续维持的时间不超过2 h。阵风锋母风暴向东...     

A Method of Initial Vortex Relocation and Numerical Simulation Experiments on Tropical Cyclone Track

Using the technique of smooth filtering and cylindrical filtering, the initial vortex circulation and large-scale environmental field were separated from the background field. Then the separated initial vortex circulation was translated and reinserted in the location where it was observed. This led to the determination of a method of initial vortex relocation. For seven tropical cyclones at 23 points of measurement time in the years of 2006 and 2007, two schemes, either directly adding a tropical cyclone bogus model in the background or adding it after the relocation of the initial vortex in the background field, were employed. Simulation experiments were compared. The results showed that the mean errors of the simulated tropical cyclone tracks at 24 and 48 hours were both smaller with the scheme of adding tropical cyclone bogus model after the relocation of the initial vortex in the background field. The relocation method of the initial vortex decreases the error caused by the deviation of the initial tropical cyclone location in tropical cyclone models. The relocation method is conducive to improving the track forecast of tropical cyclone models and has a good perspective for operational application.     

MODIFIED MASS FLUX CUMULUS CONVECTIVE PARAMETERIZATION SCHEME AND ITS SIMULATION EXPERIMENT—PART Ⅰ:MASS FLUX SCHEME AND ITS SIMULATION OF THE 1991 FLOOD EVENT*

Based on the existing cumulus convective parameterization schemes,a mass flux scheme (MFS) for cumulus convective parameterization has been successfully developed by reference to the work of Chen et al. (1996).The MFS is a comprehensive scheme.In MFS,not only the importance of the large-scale moisture convergence is taken into account,but also it includes the cumulus updrafts and downdrafts,cumulus-induced subsidence in the environmental air.entrainment,detrainment and evaporation.The interaction between the cumulus and the environment is described by using a one-dimensional bulk model.At the same time the scheme includes the penetrative and shallow convections.The MFS has been successfully incorporated into the regional climate model RegCM2 developed by NCAR.The new model has been applied to simulate summer monsoon characteristics and their variations of heavy rainfall process in the Changjiang-Huaihe River Basins for three months from May to July 1991.The results show that the new model can successfully simulate this rainfall prolonged process.By comparising the model outputs of RegCM2.using the Kuo scheme and the MFS.it is found that the MFS is better in simulating the surface temperature,rainfall position and amount,and rainfall duration.     

中国冰冻圈水文过程变化研究新进展

冰冻圈显著的变化已经对冰冻圈水文过程产生了一系列影响。本文重点梳理和分析了近20年，尤其是近10年以冰川融水、融雪径流、冻土水文等为主体的中国冰冻圈水文过程变化研究方面取得的新进展：①在冰川融水变化研究方面，对不同尺度的冰川融水开展了全面研究，发现冰川融水呈现全面增加之势；对冰川融水"拐点"是否出现进行了科学辨识，有了基本认识；对冰川融水过程进行了模型模拟，取得显著进展。②在融雪径流变化研究方面，通过对不同流域融雪径流估算，可基本掌握各河流的融雪贡献率；中国融雪径流变化差异较大，增减不一；融雪期变化具有普遍性，突出特点是峰值提前。③在冻土水文研究方面，通过对地表水-活动层壤中流-多年冻土层上水之间关系的研究，揭示了冻土区径流形成的重力和热力耦合机制；多年冻土变化对地表径流的影响已经显现，主要表现在冬季（枯水季）径流增加；已经发现多年冻土退化对径流有直接补给作用，在一些流域补给量可能达到一定量级。