Evaluation of the tungsten oxide denuder tube technique as a method for the measurement of low concentrations of nitric acid in the troposphere

The applicability of the tungsten oxide denuder tube technique for the measurement of nitric acid in the rural troposphere was investigated. The technique is based on selective chemisorption of HNO₃ from the gas stream, thermal desorption, conversion to NO, and analysis by NO–O₃ chemiluminescence. Ammonia, which is also collected and desorbed as NH₃ and NO, was separated from the HNO₃-derived NO by linear temperature-programed thermal desorption. Possible interferences by NO₂, HCN, PAN, and n-propyl nitrate (NPN) were tested and found to be significant under conditions found in the lower troposphere. Simultaneous ambient measurements of HNO₃ were made with the tungsten oxide denuder tube and nylon filter methods at a rural site in the Colorado mountains (Niwot Ridge, CO). Nitric acid levels measured by the tungsten oxide denuder tube averaged a factor of 3 higher than levels measured by the nylon filter technique. Tests involving the placement of nylon materials in front of the tungsten oxide denuder tube show that there are species, as yet unidentified, present in the atmosphere that interfere with the measurement of HNO₃ by the tungsten oxide technique.     

Tropospheric ozone profiles near equator and meteorological parameters

This is a study of ozone profile shapes in the 800 to 100 millibar range obtained with balloonsonde data over Trivandrum (8.5° N) during 1975–76 and possible associations of these shapes to some meteorological parameters.Whereas monotonic ozone profiles were noted with clear weather conditions, those associated with cloud cover show three basic anomalous features. Some bulges of increased values are observed in the range of 800 to 500 mb. In the 500–100 mb range, short range or localized cloud cover or passing weather disturbances are associated with fluctuation patterns in the ozone profile and an average depleted value of ozone. The fluctuations are also associated with changing wind speed and direction at these heights.Possible causative mechanisms are discussed. Lightning associated with thundestorm, producing additional CO and NO are sought to interpret the bulges at lower heights. The decrease in values as well as the fluctuation patterns are suggested as due to possible incursion of water vapour from troposphere to stratosphere in the tropical region and dynamical effects associated with it.     

Simultaneous measurements of peroxy and nitrate radicals at Schauinsland

We present simultaneous field measurements of NO₃ and peroxy radicals made at night in a forested area (Schauinsland, Black Forest, 48° N, 8° N, 1150 ASL), together with measurements of CO, O₃, NO _x , NO _y , and hydrocarbons, as well as meteorological parameters. NO₂, NO₃, HO₂, and (RO₂) radicals are detected with matrix isolation/electron spin resonance (MIESR). NO₃ and HO₂ were found to be present in the range of 0–10 ppt, whilst organic peroxy radicals reached concentrations of 40 ppt. NO₃, RO₂, and HO₂ exhibited strong variations, in contrast to the almost constant values of the longer lived trace gases. The data suggest anticorrelation between NO₃ and RO₂ radical concentrations at night.The measured trace gas set allows the calculation of NO₃ and peroxy radical concentrations, using a chemical box model. From these simulations, it is concluded that the observed anthropogenic hydrocarbons are not sufficient to explain the observed RO₂ concentrations. The chemical budget of both NO₃ and RO₂ radicals can be understood if emissions of monoterpenes are included. The measured HO₂ can only be explained by the model, when NO concentrations at night of around 5 ppt are assumed to be present. The presence of HO₂ radicals implies the presence of hydroxyl radicals at night in concentrations of up to 10⁵ cm^–3.     

Comparison of the EMEP, RADM2 and RACM Mechanisms

A comparison of the atmospheric chemistry mechanisms EMEP (Co-operative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air Pollutants in Europe), RADM2 (Regional Acid Deposition Model, version 2) and RACM (Regional Atmospheric Chemistry Mechanism) has been conducted. Each mechanism was used to simulate the PLUME case of Kuhn et al. (1998) and to simulate an additional 150 and 81 scenarios with and without emissions, respectively. These simulations covered scenarios that ranged from relatively clean, through rural and polluted urban conditions. Ozone isopleths and scatter plots were generated from the simulations. The mechanisms were compared primarily on the basis of calculated ozone and ozone precursor concentrations. For the gas-phase ozone precursors the differences between the mechanisms were rather small under clean conditions and more significant under polluted conditions. The differences were especially significant for the concentrations of NO₂ and organic peroxy radicals. In general the EMEP mechanism yielded the most ozone and the RADM2 mechanism yielded the least. Furthermore the results suggest that a broad range simulation conditions should be used to compare mechanisms and not just a few selected scenarios.     

应用GPS资料反演南极大气可降水量的试验分析

本文研究的主要内容是从对流层天顶延迟来反演大气中的可降水量。利用我国长城和中山两站 1 998、1 999、2 0 0 0年参加全南极GPS国际联测所取得的南极地区的GPS数据 ,组成各期GPS网 ;采用高精度的GAMIT/GLOBK软件进行基线解算和网平差处理 ,使用多种数据处理方案 ,得到各时段两站对流层的天顶总延迟值 ,采用了Saastamonien和Hopfield两种模型分别进行天顶静力学延迟的解算来分离天顶静力学延迟。从两站的历史气象资料出发 ,通过回归计算得到适合两站 1、2月份的转换系数K ;然后进行天顶湿延迟至可降水量的转换 ,结合现场的气象资料进行对比分析。各期数据均取得了较为满意的结果。     

基于GPS观测量的InSAR干涉图中对流层改正方法及其论证

利用一种站间和历元间的双差算法来计算InSAR结果的大气改正量.为了逐像素改正InSAR结果,引入自适应参数的支持向量机(SVM),利用稀疏的GPS站网上所获得的大气改正值回归估计未知像元上的对流层改正值.采用南加州GPS集成网络(SCIGN)数据验证了该方法的可行性.     

融合GNSS气象参数的BP神经网络雾霾预测研究

结合IGS中心获取的BJFS站气象参数（气温（T）、气压（P）、大气可降水量（PWV））及同期PM_2.5数据,建立一种融合时序网络和回归网络的雾霾预测模型,对PM_2.5浓度进行预测。研究表明,引入GNSS气象参数的融合网络模型较单一网络模型适应性强、准确度高,在一定精度范围内可准确预测PM_2.5的变化,时效性达3 h。本文结论验证了卫星导航技术应用于雾霾天气监测及预报的可行性。     

基于神经网络模型误差补偿技术的对流层延迟模型研究

针对传统对流层延迟模型精度较低的缺点,基于神经网络模型误差补偿技术,在Hopfield模型基础上建立一个适用于北半球的高精度融合模型。以Wyoming大学提供的2010年全球120多个观测台站的气象探空数据精密解算的天顶对流层延迟(ZTD)作为近似“真值”,分析比较Hopfield模型、传统BP模型和融合模型的计算精度。结果表明,Hopfield模型的均方根误差（RMSE）为35.31 mm,传统BP模型为30.34 mm,融合模型为23.31 mm。     

对流层NO2柱浓度卫星遥感反演综述

NO2是主要的大气痕量气体, 对流层NO2垂直柱密度分布图已经用于诸如污染排放和污染物分布的科学应用研究。就NO2柱浓度的卫星差分光谱吸收反演算法(DOAS)进行了评述, 包括误差分析、验证和发展趋势。对DOAS算法中的主要技术环节进行了详细的阐述, 如ring效应算法、平流层NO2浓度算法和大气质量因子(AMF)问题。论文描述了影响卫星反演NO2浓度, 如云、NO2廓线的先验数据和气溶胶等不确定性因素。针对NO2反演应用需求提出了今后应该加强的内容, 如进一步加强NO2算法研究、发展空气质量探测的静止卫星、重视基于地基多轴被动DOAS和机载平台成像DAOS观测对卫星反演结果的验证。     

基于相空间重构和高斯过程回归的对流层延迟预测

天顶对流层延迟(zenith tropospheric delay,ZTD)是影响GPS定位精度的关键因素,为了提高ZTD的预测精度,提出一种基于相空间重构的高斯过程回归预测模型.针对ZTD时间序列的混沌特性,利用国际GNSS服务(International GNSS Service,IGS)站提供的ZTD数据,采用C...