求解动力方程的三种显式积分格式的比较

比较了工程上常用于求解动力方程的三种显式积分格式的能耗特性,结果表明,李小军等人的显式差分格式在物理阻尼比为0到1的范围内均具有较强的能耗特性,而且随着物理阻尼比的增大,能耗特性也增强,这种特性优于另外两种显式积分格式,能有效地克服透射边界的高频失稳,因此在处理复杂场地地震反应方面是一种比较理想的显式积分格式。     

华北地区降水的准周期信号及其阶段性变化特征

应用奇异谱（SSA）方法分析了华北地区降水的准周期信号及其阶段性变化特征，结果表明，华北地区月降水序列的年际振荡信号较强，占总方差的44．7％，显著振荡周期分别有17个月（准1～2a）、30个月（准2～3a）、60个月（准5a）和11个月（准1a），不同分区降水的准周期振荡信号各有差异。各种准周期振荡随时间的长期演变亦很明显且各不相同。奇异交叉谱（SCSA）诊断表明，华北地区降水的年际振荡与Nino区海温的准周期信号存在着显著的耦合关系，且这种耦合关系随时间是变化的，表现出耦合振荡强度的阶段性变化和耦合位相随时间的改变。各分区降水与不同Nino区海温的显著耦合周期信号及其随时间的长期演变各具特色，体现了华北地区降水对Nino区海温异常响应的复杂性。     

城市复杂地形环境下倾斜模型结合LiDAR点云的大比例尺地形图更新方法北大核心CSCD

针对无人机倾斜摄影技术受遮挡影响较大和难以穿透植被茂密地区的问题,本文提出了城市复杂地形环境下倾斜模型结合LiDAR点云进行小区域大比例尺数字地形图的更新方法。首先采用五镜头六旋翼无人机分别以垂直和平行主要建筑物楼群方向进行2次全区域拍摄,以及无人机机载激光雷达全区域采集点云,并对高度不足10 m的别墅区进行单镜头低空补飞。然后融合倾斜影像点云与机载激光点云建模,经过3种建模方案对比,融合建模的倾斜三维模型的位置精度和模型质量均最优。最后基于此模型进行测图。精度评定结果表明,城市复杂地形环境下在飞行方案和像控点布设合理的情况下,通过倾斜三维模型采集的数字地形图的平面和高程精度完全满足并优于深圳市1∶1000数字地形图动态更新的精度指标。     

概率匹配平均法在山东强降水预报中的应用

基于WRF集合预报系统开发了概率匹配平均降水产品,选取了山东省2014—2016年共13次强降水过程,检验评估了概率匹配平均法在山东省强降水预报中的综合表现。结果表明：对于不同的强降水过程,各预报产品的预报能力差异较大,尤其是对暴雨以上量级降水的预报存在较大偏差;概率匹配平均相对集合平均,对大雨以上量级降水预报有明显改善,较WRF确定性预报产品也有一定提高,对强降水预报具有一定指示意义;该方法的改进主要体现在对不同量级降水的调整上,尤其是强降水的落区,相对集合平均增大了强降水的范围和强度,但对整个区域的总降水量预报没有很好的改进作用。     

基于目标对象检验法的多种模式强降水能力的比较

针对传统TS检验方法的不足,引入了目标对象检验方法,通过对降水落区的面积、位置、形状和强度进行匹配,可获取空间场潜在的预报信息。以欧洲中心细网格、T639、山东WRF集合模式和华东区域中尺度模式(BCSH)为例,采用强降水过程模式预报最优次数及要素箱线图统计方法,得到模式及集合预报产品的性能特征,根据环流形势及影响系统对强降水分型,结果表明:热带气旋与中低纬度系统相互作用的强降水过程模式预报效果最好,最具参考性;低涡和切变线相伴随的强降水过程效果次之,且以BCSH和山东WRF集合最大值预报效果更好,各模式对低槽系统强降水预报能力一般,对温带气旋类型强降水过程模式预报效果差的概率最大。     

A New Index About the Walker Circulation

The Walker circulation (WC) has always been an important issue in atmospheric science research due to the association between the WC and tropical Pacific sea surface temperature (SST), and between the WC and ENSO events. In this paper, a new index-Omega index (OMGI) - is constructed for WC characterization based on the NCEP / NCAR reanalysis data of monthly mean vertical velocity in recent 70 years (1948-2017). Results show that the OMGI can accurately depict the variation characteristics of WC on seasonal, annual and decadal time-scales. There is a significant inverse correlation between the OMGI and equatorial eastern and central Pacific SST. Meanwhile, the peak of the OMGI appears ahead of the ENSO peak, and therefore is able to reflect the SST in the equatorial Pacific. Especially, in 35 ENSO events, the peak of the OMGI appears earlier than Ni?o 3.4 index for 19 times with 2.6 months ahead on average. In 16 El Ni?o events, the peak of the OMGI occurs ahead of the El Ni?o for 9 times with 4 months ahead on average. In 19 La Ni?a events, the OMGI peak arises 10 times earlier than the La Ni?a peak, with an average of 1.4 months ahead. OMGI shows obvious leading effect and stability over ENSO events with different strengths and types of single peak and multi peaks: the peak of the OMGI keeps about 2-3 months ahead of the ENSO. Compared with other WC indexes such as UWI and SPLI, OMGI has some advantages in the ability to describe WC changes and present the probability and thetime of prediction of ENSO event peaks.     

Climate Sensitivity and Feedbacks of a New Coupled Model CAMS-CSM to Idealized CO_2 Forcing: A Comparison with CMIP5 Models

Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO_2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences(CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5(CMIP5). Based on two idealized CO_2 forcing scenarios, i.e.,abruptly quadrupled CO_2 and CO_2 increasing 1% per year, the equilibrium climate sensitivity(ECS) and transient climate response(TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean(MME) of CMIP5 due to compensation of a relatively low ocean heat uptake(OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback(λSWCL) over the tropical Indo-Pacific Ocean.The CMIP5 ensemble shows that more negative λSWCL is related to larger increase in low-level(925–700 hPa)cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λSWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λSWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λSWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses.     

新矿物:罗布莎矿

最近在西藏罗布莎村豆荚状铬铁矿石中发现一个由70~80种矿物组成的地幔矿物群,其中包括新矿物罗布莎矿,还有金刚石、柯石英、碳硅石、方铁矿、以及Fe-Si相矿物。所有这些矿物都是从豆荚铬铁矿石的人工大样中经选矿后得到的。罗布莎矿作为主矿物而含有自然硅和fersilicite[FeSi]的包裹体或呈交生体与自然硅共生。罗布莎矿呈不规则粒状,粒径0.1~0.2mm,由细粒聚合体组成,呈钢灰色,金属光泽,不透明。以Si为基础实验分子式为Fe0.83Si2。X-射线分析资料斜方晶系,空间群Cmca,a=9.874(14)A。,b=7.784(5)A。,c=7.829(7)A。,V=601.7(9)A。3,Z=16。罗布莎矿已为国际新矿物和矿物命名委员会批准,样品保存在中国地质博物馆。     

秦岭发现金刚石:横贯中国中部巨型超高压变质带新证据及古生代和中生代两期深俯冲作用的识别

在秦岭北带榴辉岩及其围岩片麻岩的锆石中发现金刚石和大量石墨包裹体。金刚石具典型的1331～1334cm~(-1)拉曼谱峰。变质金刚石的发现证明秦岭北带榴辉岩及其围岩片麻岩经历了超高压变质作用,其俯冲深度>120 km。片麻岩锆石的SHRIMP定年表明,锆石核部代表岩浆事件的年龄或之前的残核年龄为1200～1800 Ma,超高压变质新增生边部的年龄为507±38 Ma,属早古生代。认为北秦岭超高压变质带与印支期大别超高压变质带(240～200 Ma)是时空上两个带。北秦岭超高压变质带向西可以与南阿尔金—柴北缘早古生代(490～440Ma)超高压变质带相连,向东与大别西北部的熊店和浒湾早古生代榴辉岩(420～400 Ma)相连,组成一条沿中央造山带北部分布的加里东期超高压变质带。认为主要分布在大别山南部的印支期超高压变质带应与南秦岭的高压蓝片岩带相连,组成一条分布在中央造山带南部的印支期高压超高压变质带。北秦岭超高压变质带的发现,为中央造山带存在一条西起阿尔金,东至苏鲁的近4000 km的世界上最大的一条超高压变质带的确定提供了新的关键性证据。而沿中央造山带分布的两条超高压变质带说明:①中国南北大陆在早古生代就已拼接在一起,其后,又有印支期的俯冲和碰撞叠加,加里东期超高压变质带主要分布在北部,后者在南部,两者时     

Yarlongite:A New Metallic Carbide Mineral

Yarlongite occurs in ophiolitic chromitite at the Luobusha mine (29°5′N 92°5′E,about 200 km ESE of Lhasa),Qusum County,Shannan Prefecture,Tibet Autonomous Region,People's Republic of China.Associated minerals are:diamond,moissanite,wiistite,iridium ("osmiridium"), osmium ("iridosmine"),periclase,chromite,native iron,native nickel,native chromium,forsterite, Cr-rich diopside,intermetallic compounds Ni-Fe-Cr,Ni-Cr,Cr-C,etc.Yarlongite and its associated minerals were handpicked from a large heavy mineral sa...