Spatial and Temporal Distribution Characteristics of Tropospheric CO over Asia Using MOPITT Data

Significant differences exist between simulated and observed carbon monoxide(CO). It is therefore necessary to combine more observations to validate and improve the ability of model simulations. The complexity of the source-sink characteristics and the paucity of observation data from sites in South Asia mean there is a lack of understanding regarding the distribution and variation of CO in this region. In an attempt to address this knowledge gap, the present study uses 12 years (2000-2011) of MOPITT-retrieved CO data to study the spatial and temporal distribution characteristics of CO in South Asia (MOPITT: Measurements of Pollution in the Troposphere). The influence of atmospheric movements on the CO distribution is analyzed through combination with ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis wind data and NOAA outgoing longwave radiation (OLR) data. The main conclusions are: 1) There is a high CO concentration belt in the upper troposphere throughout the year, but its location changes latitudinally in four seasons; in particular, the belt area is the smallest but the concentration is the highest in summer. 2) The tropospheric CO profile shows a consecutive (isolated) high concentration distribution pattern in the east (west) of the South Asian monsoon area, which validates the effect on CO of horizontal transport by the easterly jet. 3) The CO concentration variation trends in the south and north latitudes generally are opposite, showing a decreasing (increasing) trend at 500 (300) hPa. 4) The concentration distribution of CO in the upper troposphere over South Asia is highly correlated with the vertical velocity near the equator, which provides a new view for studying CO source issues.