【作者】 左浩毅；

【导师】 高洁；

【作者基本信息】 四川大学 ， 凝聚态物理， 2007， 博士

【摘要】 人类在发展自身的同时也污染了我们赖以生存的自然环境。随着工业的发展，大气的污染情况越来越严重，各种污染现象接连不断，典型污染包括气体污染(如二氧化氮，二氧化硫等)和气溶胶污染等。二氧化氮，二氧化硫之类的气体会直接危害人们的呼吸系统，是造成酸雨的主要原因；而大气气溶胶对于人类来讲有害有利，一方面它是形成降雨的必要条件，但另一方面又会给人体的健康带来危害。所以必须对这些污染物进行有效的监控，光学方法是进行监测的理想方法，有灵敏度高，速度快，可实现实时监测的特点，且不会产生任何新的污染。本文在对大气环境的光学研究现状调研基础上，主要在以下方面进行了大量的理论与实验研究工作首先研究了利用差分吸收光谱法监测大气二氧化氮浓度。该方法的研究在国内得到了普遍重视。该方法建立在吸收定律之上，通过比较样品光谱和参考光谱获得二氧化氮吸收信息。关于二氧化氮的探测，一个重要的问题是如何从比值光谱中区分二氧化氮吸收信息(快变信息)和其它所有消光信息的总和(缓变信息)，在过去的二氧化氮浓度反演中缓变吸收信息的低阶拟合多项式阶次的选择是任意的(通常二至五阶任意选择)，本文发现这会给反演带来误差，且多项式阶次不同，误差也不同，故本文利用二氧化氮吸收截面的相对形状不应发生变化的事实，提出利用非线性回归法确定缓变吸收信息，使确定的缓变结构更加准确，从而提高了反演的精度，并获得了成都和西岭雪山地区的实测数据。还研究了用散射光反演二氧化氮总浓度的方法，利用散射光进行监测优点是信噪比高，不需精确跟踪太阳，易于操作，但文章发现只有在特定的散射角度下才能利用散射光进行测量，采用该方法测得了成都地区的二氧化氮总浓度；还建立了一个利用瑞利散射光反演二氧化氮垂直分布的初级模型，该模型利用了散射光谱中二氧化氮吸收的强弱共同决定于二氧化氮总浓度和二氧化氮垂直分布的特点，并结合了一些简单合理的假设。利用该模型反演获得了成都地区二氧化氮垂直分布，从反演结果来看，该结果能在一定程度上反映二氧化氮真实的垂直分布，但模型本身较为简单和粗糙，要精确确定二氧化氮垂直分布还需要结合大气传输，光化学反应等信息。然后研究了利用Mie散射理论结合气溶胶光学厚度的测量反演气溶胶尺度分布和总浓度的方法。在过去的气溶胶尺度反演中多是采用的非独立模式，即根据统计结果事先假定气溶胶尺度分布符合某一函数形式(如负指数，对数正态等)，然后通过对比实测气溶胶光学厚度和理论计算的气溶胶光学厚度确定函数当中的参数，以确定具体分布函数。另外由于Mie散射理论计算的复杂性，在计算中常不得不采用近似算法，这都会给反演结果带来误差。本文以严格的Mie散射理论为基础，研究了独立模式下(即事先不假定气溶胶尺度分布的形式)反演气溶胶尺度分布和总浓度的方法。该方法将气溶胶尺度分布函数离散，假设在每一个区间内分布函数为一个常数，将这些常数的值确定后便可获得气溶胶尺度分布，问题转化成了解一个矩阵，但该矩阵高度病态，会导致的反演结果不可靠，所以文章分别采用了普通线性回归法，模拟退火算法和遗传算法进行了反演模拟，通过模拟结果的比较发现遗传算法最为适用。在此基础上以飞机上采集的太阳光谱为参考反演获得了成都地区气溶胶尺度分布和总浓度。文章还作了详细的误差分析，讨论了散射光对反演结果的影响，计算发现，在一般的大气状况下，散射光的影响可以忽略。本章最后一节还就反演中存在的一些问题作了详细讨论。最后文章还利用Mie散射理论和色度学理论计算了不同角度下单分散系球形微粒散射色度，给出了一幅0.1-10um半径下所有散射角度上(0—180°)的球形微粒的高分辨率散射色度谱。在此基础上模拟了“宝光”现象，以一次散射为前提，详细讨论了“宝光”外形和雾滴尺度分布的关系，发现决定“宝光”外形的是云雾层表面雾滴的尺度分布，表面大尺度雾滴含量越大，“宝光”越明显，且色彩越丰富，反之亦然；在一般情况下，云雾是以小尺度雾滴为主，所以难以看到“宝光”现象，故在一定程度上可以根据“宝光”的外形定性判断云雾层表面雾滴的尺度分布。还在一次散射的前提下模拟了天空光色度和大气气溶胶尺度分布的关系，发现小尺度气溶胶含量越大，天空将越接近蔚蓝色；如果大尺度气溶胶含量越大，天空色彩越是黯淡；关于天空光的偏振度与气溶胶尺度分布的关系也进行了详细计算。上述研究工作结果对利用光学方法检测与控制大气污染，对利用光学方法理解与研究大气光学现象具有重要的理论与实际意义。更多还原

【Abstract】 With the development of our society, the environment is being polluted. Theindustry has got rapid progress, leading to the more and more serious atmospherepollution, including the gas pollution （e.g. sulfur dioxide, nitrogen dioxide etc） andaerosol pollution etc. The gas such as sulfur dioxide and nitrogen dioxide is the mainreason of acid rain, and also is the threat against peoples. And the aerosol, to someextent, is indispensable to human, for it is the requirement for raining, but theaerosol will also do harm to human’s health if it is too much. Therefore, suchpollutant is necessarily to be monitored effectively. In the diversified monitoringmethod, the optical technique is of excellence because of its high sensitivity, andhigh speed, what is more, it will not produce new pollutant. This technique is thesubject of this thesis.Firstly showed in this thesis is the research of monitoring nitrogen dioxide usingdifferential optical absorption spectroscopy（DOAS） method. DOAS is based on theBeer-Lambert law, the absorption information could be got by comparing the samplespectroscopy and the reference spectroscopy. Of which the key problem isseparating the absorption structure of nitrogen dioxide （rapid-variation absorptionstructure） and the summation of other extinction structures （slow-variationabsorption structure）. In the traditional retrieve of NO₂ density, the choice ofslow-variation fitted curves is of random, which, it is discovered by this thesis, maylead to great error of the result. To solve the problem, this thesis advanced a methodsearching for the slow-variation absorption structure through nonlinear regression,by which the precision of retrieved NO₂ density is improved obviously. The methodof monitoring the NO₂ density by scattering light is also displayed, the advantage ofwhich is the high signal-to-noise, needlessness of accurate tacking of the sun. Andby this method the NO₂ density of ChengDu was got. And by the Rayleigh scattering,a primary model to retrieve the vertical distribution profile （VDP） of NO₂ isestablished, by this model the VDP of NO₂ of ChengDu is retrieved, to some extent,the retrieved result can reflect the real VDP Of NO₂, but after all, the modal is quite simple and rough, to get the VDP of NO₂ accurately, the information of atmospheretransmission and the photochemistry is indispensable.The following research is about the measurement of the aerosol size-distributionand density, which is based on the Mie Scattering theory combine to themeasurement of the aerosol’s optical depth. In past, the retrieval is founded on thedependence-pattem, that is to suppose the size-distribution to be some type offunction （Junge or Gamme etc） prior, and then calculate the parameters of thefunction through the measured optical depth to obtain the concrete size-distribution.In addition, because of the complexity of the Mie theory, in past the rigorouscalculation is always replaced by approximate arithmetic. All of above will lead toerror of the results, this paper researched the independence-pattern retrieving method,which used the rigorous Mie Scattering theory. The kemel problem of theindependence-pattem is to calculate a matrix, but the matrix is of high morbidity,which will lead to the instability of the result. In order to get the stable retrievalresult, the common linear-regress, Simulated Annealing Arithmetic （SAA） and theGenetic Arithmetic （GA） is used in the retrieving simulation respectively, throughthe simulating it is found that the GA is the best arithmetic. Based on which theaerosol size-distribution and density of ChengDu was got. In addition, the paperdisplayed the detailed analysis of error, that is the influence of scattering light on theresults, which showed little influence in usual atmosphere condition.Finally is the calculation of the scattering chroma of spheric particle at differentscattering angle based on the Mie theory and chroma theory, a high resolutionchroma chart is displayed. Based on which the Glory phenomenon is simulated, therelation of Glory and the fogdrops size is discussed in detail, it is found that thecolor of Glory is determined by size distribution of surface fogdrops, none but thecontent of large surface fogdrops achieve some level, it is possible to observingGlory. And the sky chroma is also simulated. The multi-scattering is replaced by asimple model in the simulation.The above research result is significative to monitoring the atmosphere pollutionusing optical method and the research of the atmosphere optical phenomenon.更多还原