Mid-troposphere CO2 data retrieved by the AIRS(atmospheric infrared sounder) were validated with five ground-based stations and aircraft measurements in the Northern Hemisphere.AIRS CO2 products show good agreement with ground and aircraft observations.The data had a monthly average accuracy better than 3 ppmv.In this study,the spatial and temporal distribution of mid-troposphere CO2 from January 2003 to December 2008 was analyzed based on this satellite product.The average concentration of atmospheric CO2 was higher in the Northern Hemisphere than in the Southern Hemisphere.The yearly average results show a gradual increase from 2003 to 2008.In China,the annual growth rate was about 2 ppmv/a,similar to the United States,Europe,Australia and India,but was slightly lower than Canada and Russia.Mid-troposphere CO2 concentrations were higher over northern China than over southern areas,due to differences in natural conditions and industrial layout.There were four centers of high CO2 concentration between 35° and 45°N over China,with low concentrations over Yunnan Province.There was a significant seasonal CO2 variation with peak concentration in spring and the lowest concentration in autumn.
