Abstract:

Atmospheric stability, mixed layer thickness and the atmospheric environmental capacity coefficient are calculated by using the fixed timing observation data during 1961-2010 in Anhui province. The air quality index is also involved here to explore the relationship between atmospheric environmental capacity and air quality. Results indicated that neutral stability accounts for the highest proportion and stability one comes second. Neutral stability presented a significantly decreasing trends while the stability and instability showed increasing trends. Seasonal difference were existed for instability and stability, but not for neutral instability. The annual mean atmospheric mixed layer thickness (AMLT) exhibited a significantly declining trend. Common characteristics were also found with seasonal mean AMLT in summer, autumn, and winter, while the spring mean AMLT demonstrated an abrupt change in the 2000. AMLT in spring and summer were generally higher than that in autumn and winter. The atmospheric environmental capacity coefficient showed obvious spatial differences with high values in the middle reaches of the Huaihe River, southern Dabie Mountain and midwest area of the region along the Yangtze River, which comparatively showed low values in most areas north to Huaihe River, northern Dabie Moutain and south area to the south of the lower reaches of the Yangtze River. There was a remarkably declining trend with the atmospheric environmental capacity coefficient all over Anhui province, which demonstrated prominent interdecadal variation characteristics. Seasonal atmospheric environmental capacity coefficient presented a "double peak value" pattern and reached its minimum mostly in autumn and winter, which went against the diffusion, transmission and elimination of the air pollutants, thus the air quality might get worse with limited capacity. Generally, significantly increasing trend for stability, as well as declining trend with AMLT and rapidly decreasing trend for wind speed might be the possible reasons for the continuing decreasing trend with atmospheric environmental capacity coefficient and corresponding self-purification capability in Anhui province.

Key words: atmospheric stability, atmospheric mixed layer thickness, atmospheric environmental capacity coefficient, air quality index (AQI), Anhui province