Enhancement of PM2.5 Concentrations by Aerosol- Meteorology Interactions Over China

摘要

Aerosol-meteorology interactions can change surface aerosol concentrations via different mechanisms such as altering radiation budget or cloud microphysics. However, few studies investigated the impacts of different mechanisms on temporal and spatial distribution of PM_(2.5) concentrations over China. Here we used the fully coupled Weather Research and Forecasting model with online chemistry (WRF-Chem) to quantify the enhancement of PM_(2.5) concentrations by aerosol-meteorology feedback in China in 2014 for different seasons and separate the relative impacts of aerosol radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). We found that ARIs and ACIs could increase population-weighted annual mean PM_(2.5) concentration over China by 4.0 μg/m~3 and 1.6 μg/m~3, respectively. We found that ARIs play a dominant role in aerosol-meteorology interactions in winter, while the enhancement of PM_(2.5) concentration by ARIs and ACIs is comparable in other three seasons. ARIs reduced the wintertime monthly mean wind speed and planetary boundary layer (PBL) height by up to 0.1 m/s and 160 m, respectively, but increased the relative humidity by up to 4%, leading to accumulation of pollutants within PBL. Also, ARIs reduced dry deposition velocity of aerosols by up to 20%, resulting in an increase in PM_(2.5) lifetime and concentrations. ARIs can increase wintertime monthly mean surface PM_(2.5) concentration by a maximum of 30 μg/m~3 in Sichuan Basin. ACIs can also increase PM_(2.5) concentration with more significant impacts in wet seasons via reduced wet scavenging and enhanced in-cloud chemistry. Dominant processes in PM_(2.5) enhancement are also clarified in different seasons. Results show that physical process is more important than chemical processes in winter in ARIs, while chemical process of secondary inorganic aerosols production may be crucial in wet seasons via ACIs.