基于半级别的城市空气质量预报评估方法探讨

环境空气质量预报评估是提升预报能力的重要助力,为更好支撑空气质量精细化管理,将我国空气质量细化为12个半级别,参照英国预报评估方法,对2020年“2+26”城市AQI、 PM_2.5浓度和O₃-8h浓度预报开展探索性半级别预报效果评估,通过与AQI范围预报和AQI级别范围预报评估对比发现,半级别预报评估方法可将两者兼容合一,在城市业务预报评估中具有一定可行性和应用价值.具体的半级别预报评估结果表明,“2+26”城市AQI和O₃-8h浓度在低段级别和高段级别的预报效果明显差于中段级别,不同级别PM_2.5浓度预报效果相对稳定;AQI、 PM_2.5和O₃-8h浓度预报准确率月变化曲线分别呈双峰型、先升后降型和平缓型,PM_2.5浓度各月偏高预报显著;不同城市AQI和O₃-8h浓度预报准确率差距相对较小,PM_2.5浓度预报准确率波动较大;北京和天津AQI预报准确率高于周边省份,北京和河南PM_2...

Discussion of Air Quality Forecasting Evaluation for Cities Based on Half-level Method

Ambient air quality forecasting evaluation plays an important role in improving forecasting capability. In order to provide better support for refined air quality management, with reference to the UK air quality forecasting evaluation method, this study divided six air quality index (AQI) levels into 12 half-levels and explored AQI, PM_2.5, and O₃-8h concentration forecasting evaluation based on the half-level method in "2+26" cities during 2020. Comparison with the AQI range forecasting and AQI level range forecasting evaluation showed that the half-level forecasting evaluation method could combine these two indicators into one, providing feasibility and application value in operational air quality forecasting evaluation. Specific half-level forecasting evaluation showed that the forecasting effect of AQI and O₃-8h concentration at the low and high levels was significantly worse than that of the middle levels in "2+26" cities. The forecasting effect of the PM_2.5 concentration was relatively stable in different half-levels. The monthly variation curves of AQI, PM_2.5, and O₃-8h concentration forecasting accuracy exhibited a bimodal pattern, first rising and then falling and a flat pattern, respectively. The overestimate of PM_2.5 concentration forecasting was significant in each month. The accuracy gaps of AQI and O₃-8h concentration forecasting in different cities was relatively small; however, the PM_2.5 concentration forecasting accuracy fluctuated greatly. The AQI forecasting accuracies of Beijing and Tianjin were higher than that of neighboring provinces. Additionally, the PM_2.5 and O₃-8h concentration forecasting effects in Beijing and Henan province were relatively the best.