Abstract
Characteristics of the trans-boundary pollutant transport (outflow) during the springtime W-PASS 2008 field campaign at Cape Hedo, Okinawa, were analyzed based on the regional meteorological model WRF and chemical transport model CMAQ. We found 8 large-scale intermittent transboundary outflows occurred during the observation period, and the numerical model results successfully reproduced the time and vertical variations in the major pollutants. We also showed that the typical height of the outflow of pollutants occurred below 2 km, and these features are well simulated and showed a good agreement with the NIES lidar observations at Cape Hedo. Meteorological patterns during the pollutant outflow were classified into two patterns, i.e., the 6 cases of typical behind cold front outflow (BCF) and 2 cases of transport in the northern side of the travelling high pressure system (HPN). The model simulation showed that the outflow of BCF includes the fresh air mass, while the outflow of HPN are well aged compared to the BCF cases. Sensitivity analysis with the zero-out Chinese pollutant emission was used to evaluate the correlation of SO4 2-- O3 - CO that originated from China, and confirmed that the contribution of Chinese emissions plays a dominate role when the high concentration of pollutants are observed at Cape Hedo. A comparison of NMVOC suggests the need to update the NMVOC emission inventory in order to have a good agreement with the observed level.
