Atmospheric Co2 Data Filtering Method And Characteristics Of The Mole Fractions At Wutaishan Station In Shanxi Of China

Wutaishan (WTS) Station on Wutai Mountain (2208 m a.s.l.), which is also known as the "North China Roof," in Shanxi Province, is surrounded by lush forest vegetation and situated far (30 km) from industrial emission sources. This study filtered online observation data of the atmospheric CO2 (G2301; Picarro) at WTS Station from March 2017 till February 2018 using both robust extraction of the baseline signal (REBS), and meteorological data (MET) in order to obtain the average background concentration, which is representative of the region (Shanxi Province and the surrounding areas). The background concentration of CO2 averaged (410.9 +/- 6.4) x 10(-6) (mole ratio, the same below), and the daily variation ranged from 2.4 x 10(-6) to 4.8 x 10(-6), which is relatively low, across the four seasons. The concentration and the surface wind speed displayed negative correlations during spring and winter, with R being -0.44 and -0.46, respectively. Analyzing the backward trajectories, we concluded that wind from the SE-S-SW sector noticeably increased the local CO2 concentration by transporting from high altitudes (i.e., high air masses) or along the surface.