Comparative influences of airborne pollutants and meteorological parameters on atmospheric visibility and turbidity

The purpose of this paper was to investigate how atmospheric air pollutants and meteorological conditions affect atmospheric visibility and turbidity. Meteorological parameter and anthropogenic air pollutant values were recorded during 2004 and 2005 at the Wuchi weather station and the Sha-lu environmental quality database station at the Taichung Harbor near the Taiwan Strait. Local weather conditions (temperature, relative humidity and solar radiation) and airborne pollutant (PM10, SO2, NO2, CO and O3) concentrations were used to analyze the relative effects of atmospheric air pollutants and meteorological conditions on atmospheric visibility and turbidity. Based on the analytic results, air pollutant concentrations significantly influence visibility and atmospheric turbidity. Wind speed is an important meteorological parameter that affects atmospheric turbidity parameters at the same atmospheric air pollutant concentrations throughout the periods of observation. At wind speeds of greater than 7 m/s, the turbidity factor βVis is below 0.3 and visibility is greater than 6.5 km. Under very turbid conditions, βVis > 0.4, the wind velocity is below 5 m/s, regardless of the atmospheric pollutant concentration. When visibility is ≥ 11 km, the PM10 concentration is predicted to be below 150 μg/m3 and the atmosphere is regarded as clear. Under very turbid conditions, the PM10 concentration exceeds 250 μg/m3.