Air quality condition in Wuhan and its relationship to meteorological factors

Based on environmental monitoring and meteorological data in Wuhan in 2013, we have analyzed the air quality conditions in Wuhan and their influencing meteorological factors.The results indicate that annual mean Air Quality Index (AQI) is 135 in Wuhan, and days of the good quality and mild contamination account for 35% and 30% of the total days, respectively.Under four different weather conditions, the concentration value of the six pollutants (SO₂, NO₂, CO, O₃, PM_2.5 and PM₁₀) is basically the highest in fog weather, followed by haze and sunshine weather, and last in rain weather.The pollutants concentration is much higher at 00 a.m.and 08 a.m.in fog weather than that in other weather.The concentration of PM_2.5 has a weak linear correlation with precipitation, and shows a significant decrease at moderate rain weather due to the cleansing effect of precipitation on pollutants.The concentration of PM_2.5 shows a weak increase (1.3 μg·m^-3 or so on average) when daily precipitation is less than 1 mm, which is related to the humidity-increasing effect of trace precipitation on air.The PM_2.5 concentration has a strong linear correlation with the relative humidity (R_H) and the wind speed, with a correlation coefficient of 0.87 and-0.72, respectively.For every 10% increase of R_H from 70%, the PM_2.5 concentration increases by about 10 μg·m^-3.When it is calm or very high wind, the pollutants concentration is relatively high.Under southeast wind, the concentration of PM_2.5 is high in all four seasons of the year, although the highest value occurs in autumn and winter under northwest wind.The positive 24-hourly temperature difference and the negative 24-hourly pressure difference predominate during the main increasing stage of PM_2.5 concentration.