[Discussion of Air Quality Forecasting Evaluation for Cities Based on Half-level Method]
Xiao-Yan Wang1, Li-Li Zhu1, Rong Xu1
1China National Environmental Monitoring Centre, Beijing 100012, China.
Huan Jing Ke Xue= Huanjing Kexue
|July 6, 2022
Summary
A new half-level forecasting evaluation method improves air quality index (AQI) and pollutant forecasting. This method enhances air quality management by revealing forecasting accuracy variations across different pollution levels and regions.
Area of Science:
- Environmental Science
- Atmospheric Science
- Data Science
Background:
- Effective ambient air quality forecasting is crucial for refined air quality management.
- Existing evaluation methods may not fully capture forecasting nuances.
- The UK's evaluation method provides a reference for improved techniques.
Purpose of the Study:
- To explore a novel half-level forecasting evaluation method for air quality.
- To assess the performance of this method for Air Quality Index (AQI), PM2.5, and O3-8h concentrations.
- To provide insights for operational air quality forecasting and management.
Main Methods:
- Divided six AQI levels into 12 half-levels, referencing the UK's evaluation approach.
- Evaluated AQI, PM2.5, and O3-8h concentration forecasts using the half-level method in "2+26" Chinese cities during 2020.
- Compared the half-level method with traditional AQI range and level range forecasting evaluations.
Main Results:
- The half-level method effectively integrates range and level forecasting, showing practical value.
- Forecasting accuracy for AQI and O3-8h was significantly lower at low and high pollution levels.
- PM2.5 forecasting accuracy remained relatively stable across levels, though monthly variations showed distinct patterns (bimodal for AQI/O3-8h, flat for PM2.5).
- PM2.5 forecasts were consistently overestimated; AQI and O3-8h accuracy varied less between cities, unlike PM2.5 which showed greater fluctuation.
- Beijing and Tianjin demonstrated higher AQI forecast accuracy; Beijing and Henan province showed better PM2.5 and O3-8h forecast performance.
Conclusions:
- The half-level forecasting evaluation method is feasible and valuable for operational air quality assessment.
- Forecasting performance varies significantly by pollutant and pollution level, highlighting areas for improvement.
- Regional differences in forecasting accuracy exist, with specific cities and provinces showing better performance for certain pollutants.
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