COLD2: balloon-borne experiments, atmospheric compounds measurements, flight of 5 September 2019

The stratosphere is a key component in the climate system, for its effect on UV filtering and its contribution to the greenhouse effect. For this reason, the possibility to conduct a series of balloon flights, with several light instruments able to monitor the activity and the evolution of the stratosphere, would be of great importance for the study of climate changes, both to make a comparison with satellite measurements and to validate atmospheric models.

In this experiment, the instrument COLD2 [(Viciani et al., Sensors 2018, 18, 2380; doi:10.3390/s18072380], a mid-infrared quantum cascade laser spectrometer, was tested on board a stratospheric balloon for the in-situ concentration measurements of CO and N2O. The measurement of CO, which is a short-lived tracer, can give indication on the recent troposphere-stratosphere exchanges. The measurement of N2O, which is a long-lived tracer, can supply insight into the deep multi-year stratospheric circulation. These data, if joined to the measurement of other tracers and aerosols, can be very useful for a comparison with atmospheric models.

We demonstrated the possibility to use a portable laser spectrometer, with small size (80 x 25 x 41 cm3) and light weight (23 kg), powered by its own battery (in a separate package) and operating completely unattended, to acquire profiles of trace gases on board a stratospheric balloon. During the HEMERA flight on 5/9/2019 from Esrange Space Center, the instrument COLD2 provided the mixing ratio vertical profiles of CO (in-flight sensitivity of 1 ppb and accuracy of 3%) and N2O (in-flight sensitivity of 10 ppb and accuracy of 6%) during ascent, from about 8 to 30 km.