Simulation of long-range transport aerosols from the Asian Continent to Taiwan by a Southward Asian high-pressure system

Aerosol is frequently transported by a southward high-pressure system from the Asian Continent to Taiwan and had been recorded a 100% increase in mass level compared to nonevent days from2002 to 2005.During this time period, PM2.5 sulfatewas found to increase as high as 155% on event days as compared to non-event days. In this study, Asian emission estimations, Taiwan Emission Database System (TEDS), and meteorological simulation results fromthe fifth-generationMesoscaleModel (MM5)were used as inputs for the Community Multiscale Air Quality (CMAQ) model to simulate a long-range transport of PM2.5 event in a southward high-pressure system from the Asian Continent to Taiwan. The simulation on aerosol mass level and the associated aerosol components were foundwithin a reasonable accuracy.During thetransportprocess, thepercentage of semi-volatile PM2.5 organic carbon in PM2.5 plume only slightly decreased from 22–24%in Shanghai to 21%near Taiwan. However, the percentage of PM2.5 nitrate in PM2.5 decreased from 16–25% to 1%. In contrast, the percentage of PM2.5 sulfate in PM2.5 increased from16–19%to 35%. It is interesting to note that the percentage of PM2.5 ammonium and PM2.5 elemental carbon in PM2.5 remained nearly constant. Simulation results revealed that transported pollutants dominate the air quality in Taipei when the southward high-pressure system moved to Taiwan. Such condition demonstrates the dynamic chemical transformation of pollutants during the transport process from continental origin over the sea area and to the downwind land.