【作者】 冯业荣；

【导师】 王安宇；

【作者基本信息】 中山大学 ， 气象学， 2006， 博士

【摘要】 本论文主要从事了五个方面的研究工作。一、将CMAQ/MM5/SMOKE空气质量模式成功地移植到华南地区，并进行了本地化，使其成为研究空气污染物形成、迁移、扩散、转化和清除的一个科学工具；二、对华南地区各类排放源进行了较全面的估算，形成了可运用于空气质量数值模式的网格排放数据；三、对珠江三角洲热带气旋产生的灰霾天气进行了分析,揭示了热带气旋与灰霾之间的统计关系；四、对强热带风暴“茉莉”引起的珠江三角洲极端灰霾事件进行了数值模拟，揭示了热带气旋对灰霾天气的作用及其影响机理；五、对污染物扩散方程各项的作用进行了过程分析计算，揭示不同的过程对气溶胶组分浓度变化的作用。主要取得了以下几项研究成果：一、SMOKE/CMAQ/MM5空气质量数值模式系统是一个十分复杂的数值模式系统，它集中了排放源处理、中尺度气象模式和化学传输模式，各个系统间相互依赖，相互反馈，移植和运行相当复杂。首次成功地将该模式系统在华南本地化，并成功地用于研究和预报珠江三角洲灰霾。二、首次通过SMOKE模式估算了华南地区点源、面源、生物源和机动车排放源，得到了用于珠江三角洲空气质量数值模拟和预报的源排放数据，排放源的分辨率较高，考虑的排放源比较全面，为开展珠江三角洲空气质量预报提供了重要的基础条件。三、统计分析发现，热带气旋能够造成珠江三角洲一定数量的灰霾天气，但占灰霾总日数的比例不大。造成珠江三角洲灰霾天气的热带气旋主要以夏秋季的热带气旋为主，这些热带气旋的路径多数在菲律宾东部洋面转向。巴士海峡和南海东北部附近区域活动的热带气旋容易导致珠江三角洲的高PM10浓度。四、通过强热带风暴“茉莉”数值模拟发现，热带气旋通过热力和动力过程造成珠江三角洲严重灰霾天气。茉莉活动期间，珠江三角洲低层为高压脊控制，低空气流辐散明显，而在高空则存在明显的气流辐合，导致系统性下沉运动控制珠江三角洲。随着茉莉逐渐靠近，热带气旋中心上升运动所强迫的外围下沉作用进一步加强了珠江三角洲的下沉运动。下沉运动的动力作用直接降低了珠江三角洲行星边界层的高度，使地面气流停滞，抑制了气溶胶颗粒的扩散和输送；下沉气流在对流层低层产生明显的绝热增温和干燥效应，日增温幅度达2－4℃，大气对流层低层变得非常干燥，导致大气静力稳定度明显增大，如同一个干暖的盖子，把珠江三角洲边界层空气罩着，使得珠江三角洲局地源排放的颗粒物不断积聚，形成地面高PM10浓度。热带气旋导致天晴无雨，一方面气溶胶不能靠降水清除；另一方面，白天光化反应加强有利于光化学烟雾产生和二次气溶胶形成。热带气旋影响期间，夜间地表辐射加强，加上高空的下沉增温，使得边界层逆温强度明显增大，导致夜间气溶胶浓度显著增加。五、气溶胶浓度变化过程分析发现二次气溶胶浓度的变化趋势与PM10浓度一致，说明强热带风暴“茉莉”对二次气溶胶的形成也有重要作用。次生有机碳气溶胶、硝酸盐和铵盐均在夜间出现浓度峰值，与地面湿度峰值比较一致，说明水汽条件在气粒转化中有重要作用。研究发现，不同的气溶胶组分，影响其浓度变化的过程是不同的。但大体上，垂直扩散、水平输送和气粒转化是主要过程，说明大气层结、大尺度运动和气溶胶形成过程是影响气溶胶浓度变化的重要因素。更多还原

【Abstract】 This study were carried out in five aspects.1) The coupled CMAQ / MM5/SMOKE air quality modeling system was successfully transplanted and localized over southern China and thus provides an advanced tool to make studies on the formation, transport, dispersion, transformation and removal of the atmospheric pollutants; 2) Full estimation of various kinds of emissions was made over southern china to form the gridded emissions data for air quality modeling;3) A statistical analysis was conducted on the relation between tropical cyclone (TC) and the haze in the Pearl River Delta (PRD); 4) A numerical simulation for an extreme haze event in PRD related to severe tropical storm MELOR was conducted. Results from the simulation revealed the impact and the influencing mechanism of the tropical cyclone on the haze; 5)Process analyses were performed for all terms in the dispersion equation of air pollutants to indicate the contribution of each process to the concentrations of several aerosol components.Major results of this study are summarized below.1. The CMAQ/MM5/SMOKE air quality modeling system was a combination of three complicated numerical systems. It comprises emission processing model, mesoscale meteorological model and chemical transport model. These systems are mutually dependent and interactive. The processes for transplanting and running the systems are rather complicated. It was the first time to localize successfully in the PRD this air quality modeling system which was then applied to make successful study and prediction of the haze.2. It was the first time to utilize SMOKE model to estimate the emissions of point source, area source, biogenic source and mobile source over the southern China. The high resolution emissions data with full consideration of various emissions for use in air quality modeling in the PRD were obtained for the first time. This provides an important foundation for air quality prediction.3. Statistical analyses revealed that tropical cyclone could produce haze in the PRD. But the number of haze days related to TC was quite small. Most TCs that could bring haze in the PRD were those appeared in summer and autumn. These TCs frequently made turning over the sea east of Philippines. TCs appeared in the Bashi Strait and in the northeast of South China Sea were conducive to producing high PM10 in the PRD.4. Simulations for severe tropical storm MELOR indicated that TC causes haze in the PRD by both thermal and dynamic processes. During the activity of MELOR, lower troposphere in the PRD was controlled by high pressure ridge with obvious flow divergence. While in the upper troposphere, the convergence of air flow was also significant. Thus the strong systematic subsidence dominated the PRD. As MELOR approaching, the ascending motion at the center of the TC forced a compensating downward motion that intensified the downdraft in the PRD. The downdraft in the PRD directly lowered the height of planetary boundary layer (PBL), causing flow stagnation and further confining the diffusion and transport of aerosols. The downdraft also generated significant adiabatic heating by a warming of 2-4℃daily and drying in the lower troposphere, intensifying greatly the lower layer static stability. This stable air layer acted like a warm and dry cover that mantled the boundary layer in the PRD, causing accumulation of aerosol particles and thus the formation of high PM10 concentrations at the surface. The TC caused clear sky in the PRD, producing no rain to clear away the aerosols. On the other hand, the daytime photochemical processes were also in favor of the generation of photochemical smog and the formation of secondary aerosols. During the TC, nocturnal inversion in the surface layer was enhanced through radioactive cooling along with the subsidence warming in the upper air, causing aerosol concentrations to increase at night.5. Process analyses of concentrations of aerosols indicated that the concentrations of secondary aerosols varied similar to PM10, implying the important effect of severe tropical storm MELOR on the formation of secondary aerosols. The concentrations of secondary organic aerosols, nitrates and ammonium varied consistently with surface humidity. This may indicates that water vapor may play an important role in the gas-particle conversion. Research also revealed that different components of aerosols might experience different processes for their concentrations formation, but in general, the vertical diffusion, the horizontal transport and gas-particle conversion are the major processes. This implies that atmospheric stratification, largescale motion and aerosol formation are the important factors for the variation of aerosols concentrations.更多还原