Differential absorption lidar for volcanic CO2 sensing tested in an unstable atmosphere

Motivated by the need for an extremely durable and portable instrument to quantify volcanic CO2 we have produced a corresponding differential absorption lidar (DIAL). It was tested on a volcano (Vulcano, Italy), sensing a non-uniform volcanic CO2 signal under turbulent atmospheric conditions. The measured CO2 mixing ratio trend agrees qualitatively well but quantitatively poorly with a reference CO2 measurement. The disagreement is not in line with the precision of the DIAL determined under conditions that largely exclude atmospheric effects. We show evidence that the disagreement is mainly due to atmospheric turbulence. We conclude that excluding noise associated with atmospheric turbulence, as commonly done in precision analysis of DIAL instruments, may largely underestimate the error of measured CO2 concentrations in turbulent atmospheric conditions. Implications for volcanic CO2 sensing with DIAL are outlined. © 2015 Optical Society of America.