[Characteristics of atmospheric CO2 variations and some affecting factors in urban area of Beijing]

The diurnal variation of the atmospheric CO2 at the urban area in Beijing displayed a very clear cycle, generally with the lowest value being recorded at about 15:00 local time and the highest in the nighttime. The differences between the maximums and the minimums ranged from 23.2 to 39.0 mumol.mol-1 in the four seasons and the ones of summer and fall were bigger than that of winter and spring. It showed a large seasonal cycle with a maximum in winter, from 421.5 to 441.0 mumol.mol-1, and a minimum in summer, between 367.4 and 371.6 mumol.mol-1. The peak-to-peak amplitude of atmospheric CO2 in Beijing, controlled mostly by the anthropogenic activities and seasonal variation of vegetation, was higher than that in Xinglong Station, Hebei Province and China Global Atmosphere Watch Baseline Observatory (Waliguan). The concentration of atmospheric CO2 in Beijing increased rapidly at a mean growth rate of 3.7%.a-1 from 1993 to 1995. After displaying a peak of 409.7 +/- 25.9 mumol.mol-1 in 1995, it decreased slowly.