We have extended our automatic and continuously measuring ground-based Raman lidar ARTHUS (Atmospheric Raman Temperature and Humidity Sounder) with a CO2 channel. A narrow-band interference filter extracts the 2ν2 CO2 Raman line with 68 % peak transmission and 0.15 nm FWHM. We use a frequency-tripled Nd:YAG laser (200 Hz, 40 mJ in 2023, 100 mJ in 2024) and a 40-cm receiving telescope. With the current setup, we profile CO2, H2O and temperature as well as particle extinction coefficient and particle backscatter coefficient. We have operated this eye-safe system successfully in 2023 for several weeks at our university and continue to do so with a further improved system performance this spring. The first test measurements in 2023 achieved already uncertainties of <1.3 ppm at 1 km altitude with averaging of 4.4 h and 500 m at night.
Schumacher et al. (2026) studied this question.