Understanding the dynamical-microphysical-electrical processes associated with severe thunderstorms over the Beijing metropolitan region

The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.     

中国省域广播电视业发展水平的空间计量研究

以2008~2014年中国31个省域的统计数据为基础,采用空间计量经济学方法对中国广播电视业发展水平的空间格局及其影响因素进行测算与分析。研究发现,中国省域广播电视业发展水平最高的集聚分布于东部沿海地区,部分东部地区和中部地区发展一般,西北、西南地区发展水平较低,总体呈现从东向西递减的梯度变化,但全国整体发展水平呈现显著上升趋势。经济发展水平、消费需求、财政投入和信息技术水平与中国广播电视产业呈现正相关,而产业结构与广播电视产业呈现负相关,且各省地理空间的邻接上未表现出溢出效应。     

Numerical modeling of hyperpycnal flows in an idealized river mouth

Numerical experiments in an idealized river mouth are conducted using a three-dimensional hydrodynamics model (EFDC model) to examine the impacts of suspended sediment concentration (SSC), settling velocity of sediment and tidal mixing on the formation and maintenance of estuarine hyperpycnal flows. The standard experiment presents an illustrative view of hyperpycnal flows that carry high-concentrated sediment and low-salinity water in the bottom layer (>1.0 m in thickness) along the subaqueous slope. The structure and intra-tidal variation of the simulated hyperpycnal flows are quite similar to those previously observed off the Huanghe (Yellow River) mouth. Results from the three control experiments show that SSC of river effluents is the most important parameter to the formation of hyperpycnal flows. High SSC will increase the bulk density of river effluents and thus offset the density difference between freshwater and seawater. Low SSC of river effluents will produce a surface river plume, as commonly observed in most large estuaries. Both the settling velocity of sediment particles and the tidal mixing play an important role in maintaining the hyperpycnal flows. Increasing settling velocity enhances the deposition of sediment from the hyperpycnal layer and thus accelerates the attenuation of hyperpycnal flows, whereas increasing tidal mixing destroys the stratification of water column and therefore makes the hyperpycnal flows less evident. Our results from numerical experiments are of importance to understand the initiation and maintenance of hyperpycnal flows in estuaries and provide a reference to the rapidly decaying hyperpycnal flows off the Huanghe river mouth due to climatic and anthropogenic forcing over the past several decades.     

Binary Star Fractions from the LAMOST DR4

Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multiepoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions,are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with Teff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy.     

HOUGH变换在海浪遥感图像处理中的应用

本文提出了一种以FIOUGH变换为基础的海浪波长波向分析法,并对SEASAT合成孔径雷达获取的海洋遥感图像进行了方向和波长分析。该方法模拟人类纹理视觉机理,首先应用CFCM动态聚类方法对波峰、波谷和过渡带进行分类,然后采用随机行走模型对分类图像进行滤波,以获得整图的全局走向信息,再以此先验信息为先导对分类后的纹理图像进行定向跟踪拟合,得到代表海浪波峰的直线族图,最后在再对此图进行HOUGH变换和分析的基础上得到精确的波长与波向。     

1987年8月10日灵武5.5级地震前后小震活动图象及震区应力场特征

本文对1987年8月10日灵武5.5级地震进行了综合研究。其地震序列属前震—主震—余震型,前震和余震沿该区两条主要断裂分布,主震位于两条断裂交汇部位。震前形成了明显的小震活动空区。这次地震的发震构造走向为322°,长16km。震区应力场主压应力方向为268°。本文还指出,强烈的水平和垂直差异运动是灵武地区频繁多震的主要原因。     

用车贝雪夫多项式预报气象产量地理分布的试验

本文以辽宁省中北部地区玉米气象产量区域分布的预报为例,论述了车贝雪夫多项式在农业气象预报中的若干应用。作者用不规则格点上的车贝雪夫多项式,以大气环流为候选预报因子,求得展开式系数依赖于4—6个因子的方程,并由此报出区域各县产量,绘出预报图,作试报检验。结果表明:车贝雪夫多项式可用于区域产量预报。最后讨论了此方法在农业气象预报其他领域(如发育期、病虫害预报)中的应用前景,指出车贝雪夫多项式用于生物学、地学预报中的意义。     

吉南古元古代集安群泥质变质岩P—T—t轨迹及其地质意义

吉南古元古代分布区大地构造划分为辽吉裂谷系和浑江裂陷槽，集安群是辽吉裂谷系早期产物。泥质变质岩呈北东向分布于裂谷带内，经历了形成期后的中高级变质作用。本文在岩石建造、地质构造等研究基础上，通过变质作用研究，利用变质石榴石环带分析方法，建立了集安泥质变质岩Ｐ－Ｔ－ｔ轨迹。该轨迹表明集安群形成以来经历了两次拉张变质作用。在变质作用动态过程中，泥质原岩发生变质变形，Ｐ－Ｔ－ｔ轨迹反映了该区古元古代地质演     

Stable isotope characteristics and origin of ore-forming fluids in copper-gold-polymetallic deposits within strike-slip pull-apart basin of Weishan-Yongping continental collision orogenic belt, Yunnan Province, China

More than 140 middle-small sized deposits or minerals are present in the Weishan-Yongping ore concentration area which is located in the southern part of a typical Lanping strike-slip and pull-apart basin. It has plenty of mineral resources derived from the collision between the Indian and Asian plates. The ore-forming fluid system in the Weishan-Yongping ore concentration area can be divided into two subsystems, namely, the Zijinshan subsystem and Gonglang arc subsystem. The ore-forming fluids of Cu, Co deposits in the Gonglang arc fluid subsystem have δD values between −83.8‰ and −69‰, δ¹⁸O values between 4.17‰ and 10.45‰, and δ¹³C values between −13.6‰ and 3.7‰, suggesting that the ore-forming fluids of Cu, Co deposits were derived mainly from magmatic water and partly from formation water. The ore-forming fluids of Au, Pb, Zn, Fe deposits in the Zijinshan subsystem have δD values between −117.4‰ and −76‰, δ¹⁸O values between 5.32‰ and 9.56‰, and Δ¹³C values between −10.07‰ and −1.5‰. The ore-forming fluids of Sb deposits have δD values between −95‰ and −78‰, δ¹⁸O values between 4.5‰ and 32.3‰, and Δ¹³C values between −26.4‰ and −1.9‰. Hence, the ore-forming fluids of the Zijinshan subsystem must have been derived mainly from formation water and partly from magmatic water. Affected by the collision between the Indian and Asian plates, ore-forming fluids in Weishan-Yongping basin migrated considerably from southwest to northeast. At first, the Gonglang arc subsystem with high temperature and high salinity was formed. With the development of the ore-forming fluids, the Zijinshan subsystem with lower temperature and lower salinity was subsequently formed. Translated from Mineral Deposits, 2006, 25(1): 60–70 [译自: 矿床地质]     

陈传康的学术生命路径和学术树

通过扩展传统的生命路径 ( life path)概念、并建立学术树 ( discipline tree)概念 ,研究已故当代中国著名地理学家、旅游学家陈传康教授的学术史。在统计了陈传康教授全部 1 2 1 2种次的学术著述的基础上 ,首先在时间纬度上建立了学术生命路径曲线、系统式和时序式生命路径表 ,用以统计分析陈传康教授的学术论著种次的分布情况和变迁过程 ,一方面反映出著作量随中国当代历史的脉动而出现的起伏变化 ,另一方面通过观察时间轴上这些著述的学科点的分布变化 ,不仅体现 2 0世纪 5 0年代～ 90年代陈传康学术偏好的转徙 ,也反映出 5 0年间中国地理学整体的变化轨迹。利用学术树的概念 ,统计分析陈传康一生构筑的个人学术体系 ,最终勾勒出其一生经营的学术群落的整体景观。