细颗粒物（PM2.5）和臭氧（O3）污染对人类健康、生态环境和地球气候具有显著影响，因此得到各界的广泛关注。PM2.5和O3作为大气中最受关注的两类污染物，其浓度不仅受排放的影响，还受到气象条件的影响。其中，排放分为人为源和自然源排放，而自然源排放受到气象因子的影响，因此把自然源排放和气象条件全部归结为自然因素。本文主要关注自然因素对中国地区PM2.5和O3污染发生周期和发生区域的影响，从两者的联系中探究其影响机理。

本文首先利用小波和相干波方法分析了污染在时间上的多尺度周期，结果表明空气污染除了具有季节周期外，还有1-3周的中短期周期。污染在中短期周期上与局地气象参数具有显著的相关性。湿度条件是影响PM2.5最直接的因子，在北方，湿度增大有利于气溶胶吸湿性增长和二次气溶胶的形成，因此在北方地区，PM2.5与相对湿度表现为显著的正相关关系。在南方，背景场湿度大，吸湿性湿增长所需要的水汽充足，若水汽进一步增大，反而会促进气溶胶的湿沉降，因此PM2.5与相对湿度呈现负相关。在暖平流期间，往往伴随低压和低风速条件，气团较稳定，污染扩散条件较差，因此PM2.5与温度具有正相关关系，而与气压和风速是负相关关系。在诸多气象因子中，边界层高度表征了大气的热力学和动力学条件，较低的边界层高度往往伴有逆温和静稳天气，因此其与PM2.5浓度具有稳定负相关关系。通过正交函数分解方法（EOF），提取了中国地区污染的8个主要污染型，通过时间权重系数合成了8个污染分布对应的天气型，各个PM2.5污染区对应的天气型特征是高湿度、高温、低压、低风速、少降水和低边界层。与PM2.5存在显著相关的高空环流区域是西伯利亚和日本东部，这揭示了污染与中尺度天气型和高空罗斯贝波相关。

O3与温度的普遍正相关归因于在高温条件下有利于光化学反应生成O3，此外高温一般伴随着晴朗天空，晴空下到达地面的太阳辐射较多，而到达地面的太阳辐射是影响O3污染最敏感的气象因子。水汽是O3的重要去除因素，且水汽较大，出现云的概率也较大，此外低压环境有利于前体物的聚集，因此O3与相对湿度，云覆盖和气压都是负相关。通过O3污染天气型分析表明：O3污染区对应的天气系统特征是低湿度、高温、低压、低风速、少降水、高边界层、低云覆盖和较强太阳辐射。与O3存在显著相关的高空环流区域位于贝加尔湖东部和中国南部。

     针对近年来PM2.5与O3相反的变化趋势，本研究从气象角度揭示了部分影响因素。减排措施降低了气溶胶浓度，从而降低了其消光作用，使得到达地面的太阳辐射增多，这有利于O3的生成，另外一个原因是PM2.5的降低主要归功于硫氧化物的减排，而硫氧化物的减排对O3的降低并无显著作用。

最后分析了气候因子对冬季PM2.5的影响，该部分利用了天气诊断方法、统计方法和模式模拟相结合的方法进行论证。由于北极海冰与大气环流的相互作用，初冬海冰增加，极涡增强，这使西风带呈现纬向环流，相应地，经向环流越弱，东亚槽位置更偏东，冷空气次数越少，这样的环流形势容易形成北方型污染；反之则容易形成南方型污染。此外，ENSO正相位厄尔尼诺事件越强，副高强度越强，副高西侧暖湿气流输送也容易导致北方污染天气型。同时也研究了海上环流对夏季O3的影响，在固定排放的条件下，利用GEOS-Chem模拟了ENSO相反相位年份的O3浓度。经对比发现，ENSO正相位年份，北方地区的O3浓度降低。经过天气学诊断方法验证，ENSO的影响机制是通过影响局地的太阳辐射以及与辐射有关的气象因子从而影响O3的夏季近地面浓度。在北方，由于在ENSO正相位年份云量多和水汽更充沛，导致到达近地面太阳辐射更少，因此在北方，地面O3浓度更低。同样的方法用于东亚夏季风对O3浓度影响的研究，发现东亚夏季风越强，在黄淮之间的区域O3浓度会降低，其影响机制与动力学差异有关。夏季风越强，华北地区风速大，扩散条件好，不易形成 O3和前体物的累积。

综上所述，本研究从局地气象条件、天气型和气候因子三个层次研究了气象条件与中国中东部地区PM2.5和O3污染的关系。本文利用最新的全国污染观测数据，通过多种方法交叉验证，揭示了气候变化通过影响亚洲大气环流、中国天气型和局地气象要素，从而影响中国PM2.5和O3污染的机理和过程。通过该研究，有利于更好地认识气候异常对我国空气污染的影响，为我国空气污染防治及认识气候变化与空气污染相互作用提供科学依据。

Fine particulate matter (PM_2.5) and ozone (O₃) pollution have a significant impact on human health, the ecological environment and climate. PM_2.5 and O₃, as the two most concerned pollutants in the atmosphere, are not only affected by emissions, but also by meteorological conditions. Emissions include anthropogenic sources and natural source emissions, and natural source emissions are controled by meteorological factors. Therefore, natural emissions and meteorological conditions are all attributed to natural factors. This study mainly focuses on the impact of natural factors on the occurrence cycle and area of PM_2.5 and O₃ pollution in China, and explores their influence mechanism from the relationship between them.

Firstly, this study analyzed the multi-scale cycles of pollution by using the wavelet and coherent wave analysis methods. The results showed that air pollution has a cycle of 1-3 weeks in addition to seasonal cycles. Pollution has a significant correlation with local meteorological parameters in the 1-3 weeks cycles. Humidity condition is the most direct factor affecting PM_2.5. In the north, the increase of humidity is conducive to the growth of aerosol hygroscopicity and the formation of secondary aerosols. Therefore, in the north, PM_2.5 has a significant positive correlation with relative humidity. In the south, the background field is highly humid, and the water vapor required for hygroscopic moisture growth is sufficient. If the water vapor increases further, it will promote the wet deposition of aerosols. Therefore, PM_2.5 is negatively correlated with relative humidity. During the warm advection period, low pressure and low wind speed are often accompanied by stable air masses and poor pollution diffusion conditions. Therefore, PM_2.5 has a positive correlation with temperature and a negative correlation with air pressure and wind speed. Among many meteorological factors, the height of the boundary layer characterizes the thermodynamic and dynamic conditions of the atmosphere. The lower boundary layer height is often accompanied by temperature inversion and static weather system, so it has a stable negative correlation with the PM_2.5 concentration. Through orthogonal function (EOF) decomposition method, 8 main pollution patterns of pollution in China are extracted, and 8 weather types corresponding to pollution distribution are synthesized through time weighting coefficients. The weather type characteristics corresponding to each PM_2.5 pollution area are high humidity, high temperature, and low pressure，low wind speed, little precipitation, low boundary layer. The high-altitude circulation regions that are significantly related to PM_2.5 are Siberia and eastern Japan, which reveals that pollution is related to mesoscale weather patterns and Rossby waves.

The general positive correlation between O₃ and temperature is attributed to the fact that under the high temperature conditions, it is beneficial to the photochemical reactions to produce O₃. In addition, high temperatures are generally accompanied by clear skies. There is more solar radiation reaching the ground under clear skies, and the solar radiation reaching the ground is the most sensitive factor for O₃ pollution. Water vapor is an important removal factor for O₃, and the greater the water vapor, the greater the probability of cloud appearance. In addition, the low-pressure environment is conducive to the accumulation of precursors. Therefore, O₃ is negatively correlated with relative humidity, cloud cover and air pressure. The weather pattern characteristics of O₃ contaminated area are low humidity, high temperature, low pressure, low wind speed, less precipitation, high boundary layer, low cloud cover and high solar radiation. The high-altitude circulation areas that are significantly related to O₃ are located in the eastern part of Lake Baikal and the southern China.

Aiming at the opposite trend of PM_2.5 and O₃ in recent years, this study also revealed some of the controling factors from a meteorological view. Emission reduction measures reduce the concentration of aerosols, thereby reducing their extinction effect, and increasing solar radiation reaching the ground, which is conductive to the generation of O₃. Another reason is that the reduction of PM_2.5 is mainly due to the reduction of sulfur oxides. The reduction of sulfur oxides has no significant effect on the reduction of O₃.

Finally, the impact of climate factors on PM_2.5 in winter were analyzed. The weather diagnosis methods, statistical methods and model simulation methods were used to demonstrate the issues in this part. Due to the interactions between the Arctic sea ice and the atmospheric circulation, the sea ice in early winter increases and the polar vortex is strengthened, which makes the westerly zone present a zonal circulation. Correspondingly, the weaker the meridional circulation, the more easterly the East Asian trough, and the less cold air, such a circulation situation is prone to form northern pollution; otherwise, it is prone to form southern pollution. In addition, the stronger the El Ni?o event, the stronger the intensity of the subtropical high, and the transportation of warm and humid air to north likely to lead to the northern polluted weather pattern. The influence of ocean circulation on summer O₃ was also studied. Under the condition of fixed emission, GEOS-Chem was used to simulate the O₃ concentration in two years with opposite ENSO phases. The mechanism of ENSO is to influence the summer near-surface concentration of O₃ by affectingthe local solar radiation and the meteorological factors related to radiation by the synoptic diagnostic method. In the north, there are more clouds and more water vapor in the positive phase of ENSO, resulting in less solar radiation reaching near the surface. Therefore, in the north, the O₃ concentration on the ground is lower. The same method was used to study the influence of the East Asian summer monsoon on the O₃ concentration. It was found that the stronger the East Asian summer monsoon, the lower the O₃ concentration in the region between Huang and Huai River. The mechanism is related to the difference in dynamics. The stronger the summer monsoon, the greater the wind speed in North China, the better the diffusion conditions, and it is difficult to form the accumulation of O₃ and precursors.

In summary, this project studied the relationship between meteorological conditions and PM_2.5 (O₃) pollution in central-eastern China from three aspects of local meteorological conditions, weather patterns and climate factors. This study used the latest pollution observation data and various methods cross-validate to reveal the mechanism and process of PM_2.5 and O₃ pollution in China by affecting the atmospheric circulation in Asia, weather patterns, and local meteorological elements in China. Through this study, it is helpful to better understand the impact of climate anomalies on air pollution in China, and provide a scientific basis for the prevention and control of air pollution and the understanding of the interaction between climate change and air pollution.