成都地区秋冬季污染天气形势下PM2.5的扩散与输送

基于ERA-Interim再分析资料、大气污染资料以及气象资料，利用T-mode主成分分析法（PCT）将成都地区2016~2018年PM_2.5污染严重的1、2、11、12月份的海平面气压场和10m风场分成8种天气类型，分析不同天气类型下的空气污染状况及污染气象参数特征，进而从污染气象学的角度揭示重污染天气类型下的气象特征和潜在污染来源，结果表明：①成都地区在高压后部型、低前高后型、鞍型场、北方高压底部型中PM_2.5污染会加重，属于污染型天气类型，而在西路冷锋前部型、高压边缘型、西北高压底部型、东路冷锋前部型中，PM_2.5污染显著减弱，属于清洁型天气类型.②在污染型天气类型下，成都地区出现的逆温层较强，混合层高度较低均不利于PM_2.5的扩散稀释，且边界层内南风分量明显增大，东北风减弱，边界层通风量（VI）较小，风场对污染物的扩散能力也较弱.③对污染天气类型下成都的PM_2.5污染输送与潜在来源进行研究，认为成都南部及西南部地区在各个污染天气类型下都对其PM_2.5的质量浓度有明显的影响，另外在鞍型场天气类型下，成都东部及东北部地区也是成都PM_2.5污染的源区之一，而在北方高压底部型中，成都地区的PM_2.5主要受到其周围地区的影响，外地的污染物输入较少.

The diffusion and transport of PM2.5 under the polluted weather conditions during autumn and winter seasons in Chengdu

Based on ERA-Interim reanalysis data, air pollution data and meteorological data, the T-mode principal component analysis (PCT) was used to classify the sea level pressure field and the 10m wind field in Chengdu into eight weather types. The air pollution status and the characteristics of pollution meteorological parameters under different weather types were analyzed, and the meteorological characteristics and potential pollution sources under heavy pollution weather types were described from the perspective of pollution meteorology. First, PM_2.5 Pollution in Chengdu area would be aggravated and developed the polluted weather event when the weather type was in high-pressure rear part type, low-front high-back type, saddle-type field and northern high-pressure bottom type. The PM_2.5 pollution was significantly weaker and belonged to the clean type under other four weather types:the west road cold-front front type, the high-pressure edge type, the northwest high pressure bottom type, and the east road cold-front front type. Second, the inversion layer in Chengdu area was stronger and the lower height of the mixed layer was not conducive to the diffusion dilution of PM_2.5 under the polluted weather type. In addition, the southern wind component in the boundary layer was obviously increased, and the northeast wind was weakened. The amount of ventilation was small, thus the wind field had a weak ability to diffuse pollutants. Third, we studied the PM_2.5 pollution transport and potential sources of Chengdu under the polluted weather type. We believed that the southern and southwestern regions of Chengdu had significant effects on the mass concentration of PM_2.5 under various types of polluted weather, and under the saddle weather type, the eastern and northeastern parts of Chengdu were contributing to Chengdu PM_2.5 pollution. Under the northern high-pressure bottom type, the PM_2.5 in the Chengdu area was mainly affected by pollutants in the surrounding areas, and the pollutants imported from other areas were relatively small.