Seasonal variability of trans-Pacific transport of air pollution in the lower and upper troposphere

Multi-year carbon monoxide (CO) measurements made by Aura/MLS (Microwave Limber Sounder) and Terra/MOPITT (Measurements of Pollution in the Troposphere) are used to investigate the trans-Pacific transport of air pollution. These observations show different seasonal variability of the transport in the lower troposphere and in the upper troposphere. In the lower troposphere the trans-Pacific transport mainly occur in winter and spring. In the upper troposphere, however, the transport occurs in spring and summer. In addition, the transport occurs from sub-tropics to the middle latitudes in the lower troposphere. In the upper troposphere, the transport belt locates at around 30°N in spring and shifts northern-ward in summer along with the movement of the location of the tropopause. The relation between the variability of long-range transport and the variability of biomass burning, anthropogenic pollution, and deep convection over the South and East Asian is also investigated. These observations are also compared with simulations from a global air quality model GEM-AQ (Global Environmental Multi-scale - Air Quality model). In short this study gives an overall look of the trans-Pacific transport of air pollution in the troposphere.