Simulation on the Transport Processes of CO from Surface Layer to Upper Troposphere in Summer over Asian Monsoon Region

Based on the annual Emission Database for Global Atmospheric Research （EDGAR，Version 3.2） CO emissions data, the preliminary mechanism of the extreme center coming into being and related transport process transported upwards by deep convection and confined by the anticyclonic circulation in the North Hemisphere in summer 2006 is investigated by using a Lagrangian particle transport and dispersion model FLEXPART containing a simple convective parameterization. There is a good agreement in the temporal trend although a litter difference (the volume fraction can reach 2×10-8－3×10-8) between simulated CO and observations derived from satellite is obtained over Asia monsoon region possibly due to the uncertainty of CO emissions. The authors investigate the respective roles of large scale transport and convection in determining CO maximum in Upper Troposphere (UT) in the Asian monsoon region. It is found that the model can also simulate the CO distribution characteristic even only droved by the large scale wind fields. But the enhanced results can be obtained with the consideration of convection. The results show that convection does not have a significant impact on the CO budget comparing with the large scale circulation. The maximum CO value regions in UT in the Asian monsoon areas in summer mainly have an origination from the atmosphere boundary layer surface from the north of Indian Peninsula, the middle of Africa，and the northeast part of China. In Asian monsoon regions, two main transportation processes of CO account for the exceptional distribution of CO in upper troposphere. On the one hand, high density CO in the lower troposphere can be lifted upwards into UT quickly, even can be advected vertically further to the altitudes near the tropopause (about 16 km) by large scale，and mesoscale and small scale convective circulation, and then, much of the CO is then advected in the upper troposphere southwestward with the cross equatorial Hadley flow. On the other hand, the eastward and poleward transportations in the middle and lower troposphere turn the central southern India, Arabia, even the middle part of Africa into origins for long distance transport of CO in the Asian monsoon regions.