A HYDROCLIMATIC APPLICATION STRATEGY FOR THE POISSON PARTIAL DURATION MODEL1

ABSTRACT: A strategy for formulating and testing the Poisson partial duration extreme value model is presented. The procedure is demonstrated using recorded Streamflow series from a humid subtropical region of the southern United States. The observed data series are partitioned by climatic causes and tested for both the Poisson assumption and the validity of the exponential as marginal distributions. Several statistical tests are utilized in making these determinations. Some important aspects of the model as applied to humid climates are demonstrated. It was found that a majority of Streamflow series could be represented by the model and that significant differences do exist between the arrival structures of floods resulting from different climatic mechanisms. However, these differences generally do not exist in the distribution of the flood magnitudes. In addition, it is possible that model validity is restricted by drainage basin size.     

How to get there? Assessing motorists’ flash flood risk perception on daily itineraries

Flash floods are characterized by their suddenness, fast and violent movement, rarity, small scale but high level of damage. They are particularly difficult to forecast accurately and there is little lead time for warning. This makes motorists especially vulnerable. Assuming that these flash flood hazard specificities may be the significant factors leading to difficulties for drivers to perceive danger, we used cognitive mapping combined with GIS data processing to assess motorists’ flash flood risk perception on their daily itineraries. The analysis of 200 mental maps collected allows planners to have maps highlighting dangerous areas where risk perception is weak and to identify reasons for this.     

三种与地质灾害相关的突发性气象灾害应急预报系统研究新进展

本文介绍了在火山灰、核放射性物质和强沙尘暴引发的沙尘粒子的长距离输送数值模拟领域里近年来获得的有关新进展。其基本进展是:1)引进美国NOAA空气资源研究所的HYSPLIT-4模式。并以此为核心形成火山灰、核放射性物质和强沙尘暴的浓度与轨迹数值模拟与预报系统。2)提出一个非连续性空间分布污染场的平流输送方案。3)新发现一个数值模式中的误差污染机制。     

中国严寒地区住宅建筑室内细菌气溶胶污染特征及传播规律

实测严寒地区住宅建筑细菌气溶胶组分及来源,并结合微生物生长繁殖衰亡模型和数值模拟技术开展细菌气溶胶传播特性研究.结果表明,中国严寒地区住宅建筑室内的主要优势菌群为拟杆菌门（Bacteroidetes）、厚壁菌门（Firmicutes）、变形菌门（Proteobacteria）.而细菌的来源分析显示,其主要来源为粪便、土壤、极端环境、植物、水源和腐败有机物等.由于冬季人员室内活动时间较长,其中粪便来源占比偏高.细菌在室内的传播规律研究表明,在室内环境中细菌气溶胶的浓度分布与房间的结构、湍流形式和粒子重力场有关.随着房间高度的降低,室内流场越复杂.模拟分析表明室内90％的细菌气溶胶颗粒在50s内逃逸出,且随着房间高度的降低细菌气溶胶浓度逐渐降低而范围更广.室内通风有阻碍细菌气溶胶在室内积聚,稀释污染浓度的作用.     

北京市冬季PM_(2.5)污染特征与区域传输影响研究

选取北京师范大学监测点于2015年1月进行PM_(2.5)样品采集,应用离子色谱仪(IC)分析PM_(2.5)中水溶性无机离子质量浓度,采用WRF-CAMx-PSAT模型系统对采样时段PM_(2.5)及典型离子的区域来源进行了模拟。结果表明,采样期间(2015年1月2—20日)与重污染过程(2015年1月13—15日)北京PM_(2.5)质量浓度分别为(105.9±72.6)μg/m~3和(232.2±80.2)μg/m~3,PM_(2.5)中总水溶性无机离子质量浓度分别为(47.4±39.8)μg/m~3和(120.7±23.3)μg/m~3,分别占PM_(2.5)的44.2%和53.9%。SO_4~(2-)、NO_3~-和NH_4~+是水溶性离子的主要组分,非重污染过程和重污染过程这3种水溶性离子质量浓度之和分别占总水溶性离子质量浓度的80.5%和89.3%。模拟结果显示,本地源排放是北京市PM_(2.5)、SO_4~(2-)、NO_3~-、NH_4~+的主要来源,贡献率分别为81.4%、79.5%、58.1%、95.3%,北京周边源排放对PM_(2.5)贡献率较大的有保定、天津、张家口、唐山,这4市占北京周边省市排放源贡献率的72.0%。     

重庆臭氧时空分布特征及其污染成因的初步分析

近年,臭氧(O₃)正逐渐取代PM_2.5成为中国首要大气污染物.因此,研究O₃的时空分布特征及污染成因对于空气污染治理与管控具有重要价值.重庆复杂的地形造成该地区O₃的污染成因具有很大的不确定性.采用2013—2020年重庆市主城区环境监测站O₃、PM_2.5、NO₂逐小时监测数据和国家气象站观测资料,分析了O₃的时空分布特征,并探究其与复杂地形、前体物、气象要素及PM_2.5的关系.结果表明:①2013—2020年臭氧日最大8 h平均浓度的第90百分位值年际变化总体呈现先减后增的趋势.发生臭氧污染月份数量增加,臭氧污染开始月份从6月提前到4月.②2019年重庆臭氧中度和重度(中重度)污染天数最多,为6 d.2013—2015年中重度污染频率由1.09%减少至0.27%,到2019年增加至1.64%,2020年降至0.81%.③重庆中重度污染期间,O₃的空间分布受山谷风环流与城市热岛效应的共同影响.白天城区站点O₃浓度高于山区站点O₃浓度,夜间山区站点O₃浓度高于城区站点O₃浓度.④城区站点的O₃与NO₂浓度呈现显著负相关,山区站点O₃与NO₂浓度的相关系数为负值,但相关性不显著.⑤重庆大部分O₃中重度污染由局地污染主导,在非高温或者高湿的情况下同样可能发生臭氧中重度污染.臭氧中重度污染发生时,风向多为西-北风.O₃浓度与气温和风速呈显著正相关,与相对湿度呈负相关.⑥重庆O₃-PM_2.5相关性城区与山区表现不一致,城区南坪站O₃-PM_2.5在暖季呈正相关关系,冷季相关性有正有负,山区缙云山站O₃-PM_2.5在暖季和冷季都呈正相关关系.     

The impacts of climate change on the risk of natural disasters

Human emissions of greenhouse gases are already changing our climate. This paper provides an overview of the relation between climate change and weather extremes, and examines three specific cases where recent acute events have stimulated debate on the potential role of climate change: the European heatwave of 2003; the risk of inland flooding, such as recently in Central Europe and Great Britain; and the harsh Atlantic hurricane seasons of 2004 and 2005. Furthermore, it briefly assesses the relation between climate change and El Ni?o, and the potential of abrupt climate change. Several trends in weather extremes are sufficiently clear to inform risk reduction efforts. In many instances, however, the potential increases in extreme events due to climate change come on top of alarming rises in vulnerability. Hence, the additional risks due to climate change should not be analysed or treated in isolation, but instead integrated into broader efforts to reduce the risk of natural disasters.     

大塑性变形法制备块体纳米材料

综述了大塑性变形法制备块体纳米材料的发展、常用方法及其工作原理,介绍了大塑性变形法制备块体纳米材料应满足的基本条件,并在此基础上论述了大塑性变形法的实际应用,指出了目前大塑性变形法在制备块体纳米材料时存在的问题.