Evaluation of environmental fate and sinks of PCDD/Fs during specific extreme weather events in Taiwan

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants (POPs) that are formed and released unintentionally from anthropogenic sources. The high persistence of PCDD/Fs results in the concentrations of these contaminants in environment decreasing only very slowly. Two transport pathways, air and water, carry PCDD/Fs into all regions of the world. Recently, more frequent extreme weather events, such as storms and floods, have been projected to occur as a result of global warming. Extreme weather events have a documented impact on the remobilization and subsequent bioavailability of POPs. In this study, three specific episodes, namely winter monsoon, southeast biomass burning and tropical cyclone (typhoon) events, which influence the environmental fate and transport of PCDD/Fs in Taiwan, were evaluated based on a climate change scenario. During the winter (northeast) monsoon period, the temperature and relative humidity observed in northern Taiwan decreases sharply. During this time, the quantity of PCDD/Fs adsorbed onto suspended particles, as observed at background sites, was found to increase from 300 ± 127 to 630 ± 115 pg I-TEQ g-TSP⁻¹, which is even higher than that measured in Taipei City (438 ± 80 pg I-TEQ g-TSP⁻¹). Hence, the winter monsoon not only brings cold air but also transports air pollutants and dust over long distances from mainland China to Taiwan. During the 2010 Southeast Asia biomass burning events (2010/3/22–3/28), the level of atmospheric PCDD/Fs were measured in central Taiwan (Mt. Lulin) and in the source region of northern Thailand (Chiang Mai); this revealed that the variations in atmospheric PCDD/F concentrations at these two sites followed a similar pattern. On 25 March 2010, the atmospheric PCDD/F concentration increased dramatically from 1.43 to 6.09 fg I-TEQ m⁻³ at Mt. Lulin and from 7.64 to 12.1 fg I-TEQ m⁻³ in northern Thailand. However, the atmospheric PCDD/F concentration decreased dramatically 1 day after the biomass burning event. Based on the measurements from a dated sediment core collected at a reservoir in northern Taiwan, the sharp increases in input fluxes of PCDD/Fs and mineral-derived elements levels in 1990 (20 ng I-TEQ m⁻² year⁻¹), 2001 (17 ng I-TEQ m⁻² year⁻¹), 2004 (16 ng I-TEQ m⁻² year⁻¹) and 2005 (15 ng I-TEQ m⁻² year⁻¹) seem to be a result of a deep turbid layer formed upstream due to landslides and/or mud flows during the typhoon season. This finding demonstrates the effect of typhoon events on the long-term remobilization of PCDD/Fs as well as supporting the hypothesis that such events would have the potential to remobilize pollutants that have been deposited previously.     

Fundamentals about the flow of geomagnetically induced currents in a power system applicable to estimating space weather risks and designing remedies

Geomagnetically induced currents (GIC) in technological systems, like electric power transmission grids, at the Earth's surface are caused by space weather processes, whose origin is in the Sun. In power systems, transformers may be saturated due to GIC leading to different problems extending from an increase of harmonics to a blackout of the system and damage of transformers. To design reasonable measures against impending problems, GIC magnitudes in the network should be estimated in different circumstances. This paper tackles basic features of GIC flow in a fictitious five-transformer/four-line power system, which is simple enough to make the equations easily manageable but complex enough to yield real and usable information. It is shown that the direction of the geoelectric field affects GIC at different sites but the dependence is not straightforward since GIC produced in one part of the system flows to others. Generally, transmission lines experience much larger GIC than transformers. Series capacitors in transmission lines prevent the flow of dc-like GIC but, without a careful analysis, their installation may result in larger GIC at some transformers of the system thus increasing the risk of problems.     

多普勒天气雷达风场反演技术研究进展

多普勒天气雷达是研究中小尺度天气系统的重要工具，但却只能提供风场的径向速度，因而必须通过风场反演技术来求解二维或三维风场。详细分析了各种单部、多部和多基地多普勒天气雷达风场反演技术及其优缺点，同时指出了应重点研究的方向。从反演结果来看，基于变分法的反演技术明显优于其它方法，这是今后的一个主要研究方向；利用四维同化理论，在数值模式初始场中使用反演数据，是反演技术应用的重点。     

广州市大气污染与气象条件关系的统计分析

利用地面天气图、高空天气图（850hPa、500hPa）以及气象要素资料，统计分析了2002-2004年广州市10个典型的空气污染过程与各种天气系统以及气象要素间的联系，得出了秋冬季、春季和夏季广州市大气污染与各种天气类型的一些关系，并对地面各种气象要素与污染过程的关系进行了半定量分析，得出了广州市大气污染过程的一些天气概念模型及气象要素指标。     

北方麦收期间连阴雨天气环流特征

利用1980-2004年5月下旬至6月中旬北方麦收区30个代表站降水实况资料，连阴雨期间亚欧范围500hPa逐日形势图和500hPa高度平均图等，分析总结了近25年来北方麦收期间连阴雨的天气气候和环流形势特征；对北方麦收期间出现的连阴雨天气过程与环流形势和影响系统的关系进行初步探讨，确定连阴雨天气的概念模型。分析表明，阻塞高压形势且贝加尔湖附近伴有冷涡是造成连阴雨天气最主要的环流特征；在500hPa地转风υ场上，麦收区多处于南北风交界处；长连阴雨期间，850hPa东亚地区中低纬度盛行南风为主要特征。     

2019年12月大气环流和天气分析

2019年12月大气环流主要特征为:北半球极涡为偶极型分布,环流呈三波型,东亚槽略偏弱,南支槽偏强,且副热带高压位置偏西。12月,全国平均降水量为11.2 mm,较常年同期(10.5 mm)偏多6.7%;全国平均气温为-2.7℃,较常年同期(-3.2℃)偏高0.5℃。月内共出现3次较强降水过程和3次中等强度冷空气过程。另外,7—10日、20—26日我国中东部地区发生了两次持续性大范围雾-霾天气过程。     

择优法降水集合预报试验的研究

基于集合平均预报方法的基础上，提出了择优法降水集合预报方法，以多物理过程集合预报系统为例，对该方法进行阐述和试验。利用集合预报系统各成员过去24 h预报的500 hPa和700 hPa温度差（T500-700）与实况温度差的相关系数作为集合预报成员的筛选因子，选择相关系数较大的成员作为集合成员进行降水集合预报试验。初步试验结果表明，择优法降水集合预报要略优于集合平均法的预报，24 h降水集合预报有所改善。择优法降水集合预报简单易行，在计算资源有限的情况下，可优先计算择优的成员，因此比集合平均法节约计算时间，提高集合预报时效，具有一定的业务应用价值。     

“7.17”庐山雷击事件分析

通过对 2 0 0 2年 7月 1 7日雷电过程的天气形势、卫星云图、多普勒雷达资料 ,以及雷电探测定位系统资料的分析 ,指出水汽云图上的强水汽累积区、雷达回波上的回波合并与高层强回波区以及雷达回波速度场上的“零值线”等特征 ,是判断雷电发生和强对流天气的重要依据     

2003年8月渭河洪灾成因分析及对策

本文介绍了手机短信目前的发展前景，阐明气象部门对气象信息的管理应高度重视，不能简单地将气象信息廉价地批发给其它信息提供商，从而造成气象信息的严重贬值。     

中尺度数值预报模式初边值作用的试验研究

通过一次影响华南地区的锋面降水过程实例，进行了静力与非静力中尺度模式、不同驱动模式、不同初边值组合、不同边值更新周期、不同起报时次等27组对比试验。较全面细致地从不同侧面分析讨论了初、边值对中尺度模式的影响规律及特点，得出了一些有学术和应用价值的结论。如中尺度模式预报的总体趋势决定于其驱动模式，初值仅显著影响中尺度模式大约前10小时的预报，以后的预报趋势则主要决定于边值的信息；边值对模式内区的影响主要通过各种时间尺度天气信息(天气波动)的传播和移动来实现；土壤含水量等模式外参量初值可影响较长时效的预报；模式通过边界只能引入大于等于边值更新周期4倍的时间尺度的信息，更快的信息则被过滤掉；等等。其中一些结论对今后发展中尺度数值预报及其资料同化具有参考价值。