The phenomena of spreading ambient ozone at the west coast air basin of Taiwan

Özet

The total air pollution model (TAPM, www.cmar.csiro.au/research/tapm) was used to explore the phenomenaof spreading ambient ozone in the complex 196 km 196 km terrain of the west coast air basinof Taiwan (including ocean area). The altitude in the air basin ranges from 0 m (sea level) to 3000þ m(high mountain). The data of 2010e2014 from 21 air-quality monitoring stations were used to ensure theaccuracy of the simulation results in accordance with an average index of agreement (IOA) > 0.61. Fourozone-spreading phenomena were observed among the air basin: the northesouth spreading on theoffshore (NeS SOO), northesouth spreading around the coast (NeS SAC), eastewest spreading from theocean (EeW SFO), and eastewest spreading around the mountain front (EeW SAMF). The results indicatethat when two prevailing flows meet and interact at their boundaries, they form a convergencezone. The convergence zone presents distinctive weather conditions and accumulates air pollutants.More than wind direction, the ozone concentration is dependent on the topography and surroundingconditions. The results clearly show that the ozone-spreading phenomena follow certain rules. The NeSSOO, NeS SAC, EeW SFO, and EeW SAMF phenomena are during the northeaster, fore-southwester,southwester, and fore-northeaster monsoon months, respectively. Wind fields are a major factor inthe high concentration of ozone and ozone spreading, especially downdraft and onshore winds. Thediversion of river valleys and the mountainous barrier between the basin/hill and mountains exertobvious influences on the local wind field, strongly affecting the ozone-spreading phenomena