A numerical study on indicators of long-range transport potential for anthropogenic particulate matters over northeast Asia

Several indicators of the long-range transport potential of particulate matters have been proposed. These indicators can be used in the interpretation of the long-range transport process over northeast Asia. In order to characterize the indicators of long-range transport potential for days during which the concentration of particulate matter is high, we first classified these days during which PM10 concentration was high into two extreme synoptic cases: long-range transport (LRT) case, and local emission with stagnation (LES) case. The classification employed here was on the basis of semi-empirical approach by employing the synoptic meteorological variables including relative vorticity, vorticity advection, and geostrophic wind speed/direction at a geopotential level of over 850 hPa. Simulation results of the two cases using the MM5-CMAQ modeling system were contrasted to determine suitable indicators of LRT potential.The results showed that the most effective indicator is the ratio of aromatic organic compounds to NOx, with correlation coefficients of 0.70 for toluene/NOx, and 0.72 for xylene/NOx. The ratios of N-containing species such as NOx (or NOy) to CO were the next best alternative indicators, with correlation coefficients of 0.53–0.62. The sulfur conversion ratios such as SO42−/(SO2 + SO42−) and SO42−/SO2 suggested good indicators for high sulfate condition (i.e., SO42− > 10 μg m−3). However, carbon aerosol ratio OC/EC did not show clearly separated regression lines distinguishing the LRT and LES cases, implying that ratios of both sulfur conversion in less polluted atmosphere and carbon aerosol should be considered carefully using them with confidence about their indication of the LRT potential over northeast Asia.

► Little studies on LRT indicator have been carried out over northeast Asia.
► This study proposes indicators of LRT potential for the particulate pollutant.
► The ratio of organic compounds to NOx is found to be the best indicator.
► N-containing ratios such as NOx (or NOy) to CO are the next alternative indicators.
► Sulfur conversion ratios and carbon aerosol ratio are sometimes inadequate.