[Temporal variation of background atmospheric CO2 and CH4 at Mount Waliguan, China]

In this paper, the continuous (2009-2010) measurement of atmospheric CO2 and CH4 from the Mount Waliguan Baseline Observatory of Western China are presented. The results show that about 17% of CO2 observations are classified as polluted due to more frequently influence of regional emission on local measurement in summer time. The mean concentration of CO2 measured at the period of 2009 to 2010 was 390.72 x 10(-6) which was 17.4 x 10(-6) higher than that measured from 1995 to 2008, and the median concentration of CH4 was 1851.11 x 10(-9) which was 16 x 10(-9) higher than that from 2002 to 2006, which implied that the regional emission of CO2 and CH4 was continuously increased. The unavailable data were filled by back propagation neural network (BPNN) and optimized by genetic algorithm (GA) , which were analyzed by the Fourier analysis of time series of air temperature, wind speed, concentration of CO2 and CH4. At the daily time scale, strong spectrum peak occurred and concentration recorded at periods of 12 and 24 hours,due to the daily sun activity changes. At the monthly time scale, the spectrum gap occurred in CO2 concentration at periods of 30 day suggesting that the effect of meteorological and phenological factors on the variation of CO2 concentration was insignificant.