Automated ground-based remote sensing measurements of greenhouse gases at the Białystok site in comparison with collocated in situ measurements and model data

Abstract. The in situ boundary layer measurement site in Białystok (Poland) has been upgraded with a fully automated observatory for total greenhouse gas column measurements. The automated Fourier Transform Spectrometer (FTS) complements the on-site in situ facilities and FTS solar absorption measurements have been recorded nearly continuously in clear and partially cloudy conditions since March 2009. Here, the FTS measurements are compared with the collocated tall tower data. Additionally, simulations of the Jena CO₂ inversion model are evaluated with the Białystok measurement facilities. The simulated seasonal CO₂ cycle is slightly overestimated by a mean difference of 1.2 ppm ± 0.9 ppm (1σ) in comparison with the FTS measurements. CO₂ concentrations at the surface, measured at the tall tower (5 m, 90 m, 300 m), are slightly underestimated by −1.5 ppm, −1.6 ppm, and −0.7 ppm respectively during the day and by −9.1 ppm, −5.9 ppm, and −1.3 ppm during the night. The comparison of the simulated CO₂ profiles with low aircraft profiles shows a slight overestimation of the lower troposphere (by up to 1 ppm) and an underestimation in near-surface heights until 800 m (by up to 2.5 ppm). In an appendix the automated FTS observatory, including the hardware components and the automation software, is described in its basics.