1.重庆邮电大学 计算机科学与技术学院, 重庆 400065;2.重庆市气象科学研究所, 重庆 401147;3.四川省环境政策研究与规划院, 成都 610041;4.重庆市生态环境监测中心, 重庆 401147;5.中国科学院空天信息创新研究院, 北京 100094
与PM2.5的相关性显著提高，相关系数（r）由0.12—0.45提高至0.32—0.69；验证09：00至16：00时卫星估算结果，相关系数（r）均大于0.7，均方根误差（RMSE）为18.59±2.26 μg/m3；提取所有观测站点进行验证，r=0.82，RMSE=18.64 μg/m3。
Estimation of hourly PM2.5 concentration by using vertical and humidity correction methods in Sichuan-Chongqing
Together with the sustained and rapid development of China’s economy in the past few years, the continuous improvement of the national economy, and the trend of urbanization, is the unceasing decline of China’s air quality. As a result, frequent occurrence of haze pollution weather has seriously affected people’s health. As the main pollutant of haze, PM2.5 has become a major concern of all people. Studies have shown that people exposed to PM2.5 for a long time are likely to suffer from respiratory and cardiovascular diseases, and even die prematurely. Therefore, it is of particular importance to monitor and evaluate PM2.5 effectively and accurately. According to the requirements of national development, Sichuan Province and Chongqing City (hereinafter referred to as Sichuan and Chongqing Area) will work together to build a two-city economic circle in Chengdu-Chongqing Area. Therefore, it is urgent to study and evaluate the regional atmospheric environmental air quality. However, due to the unique topography and meteorological conditions in Sichuan and Chongqing, estimating the near-surface PM2.5 concentration by using satellite remote sensing method is difficult. Considering the complicated topography in Sichuan and Chongqing Area, “Elevation (
)” was introduced for vertical correction of regional Aerosol Optical Depth. Moreover, considering the large difference of humidity and pollutant emission in different months, the hygroscopic correction factor grid was constructed for humidity correction by fitting the hygroscopic growth factor month by month and site by site. Therefore, first, the retrieval accuracy of AOD of Japanese geostationary Himawari satellite (Himawari-8) was verified in this study. Second, the vertical correction and humidity correction methods were used to estimate the hourly near-surface PM2.5 concentration from 09:00 to 16:00 in 2017—2018 in the Sichuan-Chongqing Area, and the accuracy was verified. The area PM2.5 concentration is helpful for the detailed analysis of pollutant generation, migration and dissipation hour by hour, which provides effective data support for regional pollution prevention and control. We arrive at the following conclusions: (1) Owing to the large differences in the hygroscopic growth characteristics of aerosol particles in different regions and time ranges, the four stations, namely, Ziyuan Station in Chengdu City, Rongxian Administrative Center Station in Zigong City, Shangqing Temple Station in Chongqing City, and Jingtan 2nd Road Station in Chongqing City, are selected to analyze the temporal and spatial differences in aerosol hygroscopic growth characteristics. Results show that the aerosol hygroscopic growth capacity of different sites in the same month is different. The aerosol hygroscopic growth capacity of the same site in different months is also different, and the relative humidity of different sites at different times changes greatly. Therefore, the hygroscopic correction factor grid constructed must be used by fitting the hygroscopic growth factor month by month and site by site during the humidity correction to estimate PM2.5. (2) Compared with PM2.5 and AOD, the correlation coefficient between PM2.5 and
has significantly improved after vertical correction and humidity correction; it increased from 0.12—0.45 to 0.32—0.69. The correlation coefficient between the satellite estimated value and ground-based observation value is relatively high (r=0.82), and the RMSE is 18.64 μg/m3, which is a good estimation result. A comparison of the hourly and monthly scales shows that the estimation results from the afternoon are better than that from the morning, and that from autumn and winter are better than that from spring and summer. (3) According to the annual average spatial distribution of PM2.5 in 2017 and 2018, the concentration of PM2.5 in Sichuan and Chongqing Area is the highest in winter, lowest in summer, followed by that in spring and autumn. The vertical correction and humidity correction methods are used to estimate PM2.5 mass concentration in Sichuan and Chongqing Area in 2017 and 2018, with high accuracy and good estimation results. However, the topography and aerosol components are not considered in the estimation process. Therefore, the experimental results still needs to be improved.