青藏高原近地层低压系统移动路径及其特征

利用ECMWF 600 hPa高度场加密逐月再分析资料,分析了强、弱季风年高原近地层低压系统的移动路径及其特征。研究结果表明：低压系统于4月在青海省西南部形成,5月沿西南方向移入西藏地区,此后低压系统呈南北向波动西移,直至到达“西至点”后转向东退于10月衰减消散;强季风年低压系统中心强度总体上较弱季风年强。强季风年低压系统移动路径偏北,南北向波动振幅较小,弱季风年低压系统移动路径偏南,南北向波动振幅较大,呈“V”形分布;孕育初生阶段低压系统的形成过程在弱季风年出现“反复”现象;发展成熟阶段高原近地层低压系统南侧印度上空低压系统形成,并且强季风年较弱季风年形成时间偏迟,位置偏南;衰减消亡阶段高原近地层低压系统西北侧的高压系统减弱消散,10月东伸高压脊的脊点在弱季风年较强季风年偏东。     

地质勘探钻孔轨迹计算新模型

确定钻孔轨迹是分析处理钻孔偏斜问题的前提。将测斜参数中的孔深s作为变量,用多项式函数逼近的方式建立钻孔轨迹的参数方程,推导了确定钻孔轨迹空间位置的数学模型,通过算例表明模型有较好的精度。     

2015年11月沈阳地区一次PM2.5重污染过程综合分析

利用多源观测资料综合分析了2015年11月沈阳地区一次PM2.5 重污染天气的气象条件、垂直风场演变、大气边界层特征以及污染物的来源。结果表明:本次重污染过程中,沈阳市区PM2.5浓度长达81h超过250μg · m^-3 ,其中峰值浓度达到1287μg · m^-3 ,重污染期间PM2.5 /PM10 的比例最高为90%。受地面倒槽和黄淮气旋影响,近地面层持续存在的逆温层、高相对湿度和弱偏北风为颗粒物吸湿增长和长时间聚集提供有利的天气条件。风廓线雷达风场资料显示在重污染期间,近地面层存在弱风速区、凌乱风场和弱下沉气流。利用风廓线雷达资料计算了边界层通风量(Ventilation Index,VI)和局地环流指数(Recirculation,R),边界层通风量VI和PM2.5 存在明显的负相关,非污染日VI是重污染日的2倍,局地环流指数R在重污染天气前大于0.9,而在污染期间部分空间R小于0.8。通过后向轨迹模式和火点监测资料分析发现,沈阳上空300m高度气团来自于生物质燃烧区域,而且沈阳地区NO2和CO浓度的变化与PM2.5一致,说明本次重污染过程也可能和生物质燃烧有关。     

Assessing the Influence of the ENSO on Tropical Cyclone Prevailing Tracks in the Western North Pacific

Using a statistical model for simulating tropical cyclone (TC) formation and a trajectory model for simulating TC tracks, the influence of the El Nino-Southern Oscillation (ENSO) on the peak-season (July-September) TC prevailing tracks in the western North Pacific basin is assessed based on 14 selected El Nino and 14 selected La Nina years during the period 1950-2007. It is found that the combination of statistical formation model and a trajectory model can simulate well the primary features of TC prevai...     

热带气旋“Malakas”与中纬度系统的相互作用及其结构变化

本文利用中尺度数值模式WRF和LAGRANTO轨迹模式对2010年变性台风"Malakas"进行数值模拟和轨迹分析,分析了Malakas在变性过程中与中纬度系统的相互作用,以及在相互作用过程中Malakas的结构变化特征。结果表明:Malakas变性过程经历了三个阶段:(1)高层扰动加强期,高层的正位涡产生的气旋性环流使低层Malakas中心北部的斜压带西侧产生负的温度平流,表现为冷空气的入侵;(2)Malakas和中纬度系统相互作用时期,台风北上导致斜压带出现,深对流的爆发使低层暖湿气流沿着斜压带上升,快速上升气流中的潜热释放导致低PV空气向对流层上部净输送,在其北部高层重新构建出一个脊;(3)Malakas变性成温带气旋,残存的台风内核与斜压带逐渐合并,负的位涡平流带着非绝热外出流驱动了下游最初脊的构建,加速并且固定了中纬度急流,并整体放大了上层Rossby波模式。     

基于拉格朗日方法的江淮梅雨水汽输送特征分析

利用NCEP再分析资料,引入基于拉格朗日方法的气流轨迹模式(HYSPLITv4.9),结合用于海量轨迹分析的气块追踪分析方法,探讨了江淮梅雨气候平均的水汽输送特征以及梅雨异常年水汽输送的差异。结果表明,在气候态下,江淮梅雨的水汽主要来自印度洋、孟加拉湾—中国南海、太平洋和欧亚大陆4个区域,其对江淮梅雨的水汽输送贡献分别为35%、19%、22%和19%。其中,印度洋、孟加拉湾—中国南海和太平洋上的输送气流主要来自850 hPa以下的对流层低层,而欧亚大陆的输送气流主要来自600 hPa左右的对流层中层。进一步对比梅雨异常年水汽输送的差异,发现孟加拉湾—中国南海、太平洋和印度洋的水汽输送对江淮梅雨的异常有重要影响,梅雨偏多年来自孟加拉湾—中国南海的水汽输送较多,其对江淮梅雨的水汽输送贡献为24%,比梅雨偏少年约增加了13%,梅雨偏少年则是来自太平洋和印度洋的水汽输送较多,对江淮梅雨的水汽输送贡献分别达到了40%和30%,比梅雨偏多年约增加了5%和10%。     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

Pseudo-fractal interpolation for risk analysis

This paper describes a new method of analyzing the risk incurred when the outcome of a decision depends on interpolated values, for example, on the flow through an aquifer sparsely sampled for permeability or on the ratio of waste to ore in a mineral deposit sparsely sampled for grade. The method uses large families of interpolations constructed between sample values using adaptations of the well-known midpoint displacement method for generating pseudo-fractional Brownian motion trajectories. The parameters defining each family are chosen interactively by specialists to incorporate their expert knowledge. Each family, or ensemble, then defines a population of values for any global characteristic (functional) such as flow rate or waste ratio. The probabilities of various outcomes are estimated by counting them and calculating their ratios. For example, if 900 out of 1000 are acceptable the chance of success is estimated to be 90%.     

武汉市冬季灰霾期PM2.5中水溶性无机离子的特征

2018年1月,利用颗粒物采样器采集武汉市大气PM_2.5样品并进行水溶性无机离子（F^-、Cl^-、NO₃^-、SO₄^2-、Na⁺、NH₄⁺、K⁺、Mg²⁺、Ca²⁺）的分析.结果表明,NO₃^-、SO₄^2-、NH₄⁺是PM_2.5中最主要的3种水溶性无机离子,除Mg²⁺与Ca²⁺外,PM_2.5与WSⅡs （水溶性无机离子）之间的相关性显著,且移动源贡献占主导地位.阴阳离子平衡表明武汉市冬季灰霾期PM_2.5呈中性或弱酸性.通过混合单粒子拉格朗日综合轨迹模式模拟并采用分层聚类得出了4种主要的后向气流轨迹及相应的PM_2.5和水溶性离子浓度,结果表明区域传输对此次灰霾期影响较大.     

Automatic change detection in lane-level road networks using GPS trajectories

Lane-level road network updating is crucial for urban traffic applications that use geographic information systems contributing to, for example, intelligent driving, route planning and traffic control. Researchers have developed various algorithms to update road networks using sensor data, such as high-definition images or GPS data; however, approaches that involve change detection for road networks at lane level using GPS data are less common. This paper presents a novel method for automatic change detection of lane-level road networks based on GPS trajectories of vehicles. The proposed method includes two steps: map matching at lane level and lane-level change recognition. To integrate the most up-to-date GPS data with a lane-level road network, this research uses a fuzzy logic road network matching method. The proposed map-matching method starts with a confirmation of candidate lane-level road segments that use error ellipses derived from the GPS data, and then computes the membership degree between GPS data and candidate lane-level segments. The GPS trajectory data is classified into successful or unsuccessful matches using a set of defuzzification rules. Any topological and geometrical changes to road networks are detected by analysing the two kinds of matching results and comparing their relationships with the original road network. Change detection results for road networks in Wuhan, China using collected GPS trajectories show that these methods can be successfully applied to detect lane-level road changes including added lanes, closed lanes and lane-changing and turning rules, while achieving a robust detection precision of above 80%.