江西省冬季大气典型污染过程的气象成因研究

选取2019年1月江西省两次大气污染过程为研究对象，利用常规气象观测资料、美国国家环境预报中心（NCEP）再分析资料、全球资料同化系统（GDAS）气象数据和空气质量数据，分别从局地气象要素变化、地面天气形势、大气动力和热力条件及污染潜在源区等进行分析，对比两次污染过程形成机制.两次污染过程地面天气形势分别为冷锋前部型和低压倒槽型.冷锋前部型污染形成主要原因为冷空气南下在江西省减弱辐合导致上游细颗粒物输送并堆积，西北风增大细颗粒物浓度降低.低压倒槽型污染形成原因为较长时间处于高湿、小风或静风、逆温下的污染累积.对两次过程中污染较为严重的九江市进行分析，冷锋前部型九江市近地面主要受西风影响，低压倒槽型主要受东北风影响，低压倒槽型九江市风速多在2 m·s^-1以下.两次污染期间大于3 m·s^-1的风速有利于污染物清除.长时间高湿、小风（< 2 m·s^-1）及风场辐合，是低压倒槽型九江市重污染维持较长时间的重要原因.低压倒槽型大气垂直结构较冷锋前部型稳定.低压倒槽型垂直湍流弱、低层风速小于2 m·s^-1，且存在多层逆温和深厚的湿区，冷锋前部型存在明显下沉运动，逆温强度明显弱于低压倒槽.九江市PM_2.5污染潜在贡献源主要来自河南东部、山东西部和安徽西北部；低压倒槽型九江市潜在源区主要位于江西省内及与江西省接壤的湖北东南部、安徽西南部.

Meteorological causes of typical air pollution process during winter in Jiangxi

By analyzing the near-surface meteorological data, National Centers for Environmental Prediction (NCEP) reanalysis, Global Data Assimilation System (GDAS) meteorological data, and air quality data, two pollution episodes in January 2019 in Jiangxi Province were investigated. The changes of local meteorological parameters, regional weather condition, atmospheric dynamic and thermal processes, and potential sources of pollutant were analyzed to understand the pollution formation mechanism.The weather patterns were characterized by cold front and low-pressure with inverted trough, respectively. The southwardly movement of cold air in Jiangxi Province can leads to the transportation and accumulation of PM_2.5 during the first episode, while the increase of the northwesterly wind can lead to the decrease of PM_2.5. The reasons for the accumulation of pollution were the combinations of high relative humidity, light or still wind and inversion temperature. According to the analysis of Jiujiang, which was seriously polluted during those two episodes, the cold front type was mainly affected by the westerly wind, while the low-pressure with inverted trough was affected by the northeasterly wind. The wind speed of the low-pressure with inverted trough type was mostly lower than 2 m·s^-1. The wind speed greater than 3 m·s^-1 was favorable to the removal of pollutants.The persistent high relative humidity, light wind and convergence of wind field were critical to the heavy pollution in Jiujiang with the low-pressure with inverted trough. The atmospheric vertical structure of the low-pressure with inverted trough type was more stable than that of the front cold type which had weak vertical turbulence, light wind(< 2 m·s^-1) in the lower atmosphere, deep moisture layer and multi-layer temperature inversion. While the front cold type had obvious subsidence movement and showed week inversion. The potential sources of PM_2.5 pollution in Jiujiang included the eastern Henan, western Shandong and northwestern Anhui; and the potential sources of low-pressure with inverted trough type were mainly located in Jiangxi Province, the southeastern of Hubei and the southwestern of Anhui adjacent to bordering Jiangxi Province.