【作者】 顾莹；

【导师】 束炯；

【作者基本信息】 华东师范大学 ， 自然地理学， 2010， 博士

【摘要】 城市化的迅猛发展改变了原有的土地利用方式,城市工业的高度集中和机动车保有量的快速增长使城市区域的大气污染日益严重。本文以臭氧(O3)为例,在对上海地区O3污染现状及上海城市化影响进行初步研究的基础上,针对土地利用变化引起的城市化和O3前体物氮氧化物(NOx)排放量的改变对O3污染影响的问题,利用耦合城市冠层模型(UCM)的新一代中尺度模式系统(WRF-Chem)进行了数值模拟研究。同时建立O3预报-动力统计模式来进行O3预报。主要工作及结论如下：(1)在对卢湾站和六里站O3观测资料整理的基础上,论述了上海地区O3污染现状及变化特征。结果表明,上海地区O3污染严重,4-9月是O3污染的高发期；O3浓度呈现“双峰双谷型”的月变化规律和“单峰型”的日变化规律；存在明显的“周末效应”。O3浓度随NOx变化表现出非线性的变化规律；O3峰值的出现时间滞后于NOx约5小时。气温高、湿度低、风速小以及太阳辐射强是O3生成的有利气象条件。(2)选用与O3污染过程同步的高低空天气图,依据天气学原理,通过分析各层上高低压系统的配置以及上海在气压场中所处的相对位置,得到了上海地区O3污染形成的天气形势。结果表明,高压型和均压场型是影响O3形成的主要地面天气形势。在这两种天气形势下,配合高低空有利气象条件,上海地区容易出现高浓度O3过程。(3)利用RS、GIS和统计学方法,从土地利用、人为热和建筑物高度三方面讨论了上海城市化发展的影响,得到如下结果：上海城市用地迅速扩张；人为热排放量逐年上升,与气温的关系显著；三类典型城市用地的建筑物平均高度分别为12米、27米和48米。这一工作为数值模式提供了基础数据。(4)介绍了中尺度模式系统WRF-Chem的发展、流程、动力学框架、物理过程参数化方案、化学过程及其处理方法；城市冠层模型(UCM)的物理框架。同时,建立了适合WRF-Chem的排放处理模块。(5)运用WRF-Chem模式,在考虑扩大城市用地、运用城市冠层模块、城市人为热影响以及NOx排放量改变的基础上,就2007年三次高浓度O3天气过程,设置五组灵敏性试验进行模拟。结果表明：土地利用变化引起的城市化使城市O3日均浓度升高,这与城市“热岛”效应、城市“干岛”效应以及地面风场的改变有关。而城市化对郊区O3日均浓度的影响并没有表现出一致性。城市化过程中NOx排放量的增加对上海地区O3的空间分布格局影响不大,但使O3日均浓度减少。(6)建立了基于系统辨识理论的上海O3实时迭代动力-统计预报模式,分等级试预报结果的准确率可达90%以上。尝试利用WRF模拟结果作为观测值代入动力-统计预报模式进行预报,虽然预报结果和数值模式结果一样与观测值有一定差距,但分等级预报的结果较为理想。在全球变暖的背景下,快速的城市化对大气环境的影响成为了城市气候学研究的一个重要课题。数值模拟方法是研究城市化对大气环境影响的有效手段之一。通过本文的研究,我们取得了一些有意义的结论,为城市气候学和大气污染研究提供科学依据。更多还原

【Abstract】 Rapid urbanization plays a tremendous impact on land-use and developing industry and increased vehicles aggravate regional air pollution. In this paper the current level of ozone(03) pollution and the impacts of urbanization in Shanghai were analyzed. In order to study the effects of land-use change and increased nitrogen oxides (NOX) emissions, the next generation meso-scale model(WRF-Chem) was run with urban canopy model(UCM) coupled. A model output system was also developed to predict O3 concentrations. The main researches and conclusions can be summarized as:(1) The current level of O3 pollution and its variation features were discussed based on observations at Luwan and Liuli. The results show that O3 pollution in Shanghai is serious and mainly occurs from April to September. The monthly and daily variations of O3 concentrations are characterized by a bimodal and double dip curve and a unimodal curve respectively. An obvious O3 "weekend effect" also exists in Shanghai. O3 concentrations have a non-linear relation to NOX concentrations. The lag time of O3 daily peak is about 5 hours. Meteorological conditions as high temperature, low humidity, slow wind speed and intensive solar radiation are favorable to O3 formation.(2) According to synoptic meteorological theory, favorable weather patterns of high concentrations are concluded by analyzing the pattern of high and low pressure systems and the relative location of Shanghai on the weather charts. The results show that high concentration O3 usually occurs when Shanghai is controlled by high-pressure and located in the uniform pressure fields with favorable upper air conditions.(3) In order to learn urbanization impacts, land-use change, anthropogenic heat and building heights were discussed based on RS data、GIS software and statistic theory. The results indicate that the urban and built-up land expanded rapidly. Anthropogenic heat emissions grow year after year, which has great impact on temperature. The average building heights of three typical urban and built-up lands are 12m,27m and 48m. The above researches can support numerical simulation later. (4) The paper also introduces the history, dynamic framework, main physical schemes, chemical mechanisms of WRF-Chem and UCM. Besides, an emission processing module was set up to prepare data for WRF-Chem.(5) The expansion of urban areas, the function of UCM, the emission of anthropogenic heat and the change of NOx emissions were considered as main aspects during urbanization. Accordingly, five sensitivity experiments were designed to run WRF-Chem for simulating three 5-day O3 episodes. The results show the urbanization caused by land-use change increases daily average O3 concentrations in urban areas, which is related to urban heat island effect, urban dry island effect and the change of surface wind fields. However, daily average concentrations in rural areas vary with different cases. The increase of NOx emission reduces daily average O3 concentrations but has few impacts on its spatial distribution.(6) O3 real-time iteration model was established based on system identification theory. It is known as a model output system(MOS). Using the observations as the forecasting value, the accuracy of level-predicted results is over 90%. Though the results using WRF-Chem output have some differences with observations, its accuracy of level-predicted results is satisfactory.Nowadays, the impact of urbanization on atmospheric environment is a hot spot of urban climate study. Numerical simulation is an effective method in this research. Though some results are obtained from the above study, further work is necessary not only to improve this paper but also for better understanding of urbanization impacts on O3.更多还原