Articles | Volume 9, issue 12
Research article
05 Dec 2016
Research article |  | 05 Dec 2016

Adapted ECC ozonesonde for long-duration flights aboard boundary-layer pressurised balloons

François Gheusi, Pierre Durand, Nicolas Verdier, François Dulac, Jean-Luc Attié, Philippe Commun, Brice Barret, Claude Basdevant, Antoine Clenet, Solène Derrien, Alexis Doerenbecher, Laaziz El Amraoui, Alain Fontaine, Emeric Hache, Corinne Jambert, Elodie Jaumouillé, Yves Meyerfeld, Laurent Roblou, and Flore Tocquer

Abstract. Since the 1970s, the French space agency CNES has developed boundary-layer pressurised balloons (BLPBs) with the capability to transport lightweight scientific payloads at isopycnic level and offer a quasi-Lagrangian sampling of the lower atmosphere over very long distances and durations (up to several weeks).

Electrochemical concentration cell (ECC) ozonesondes are widely used under small sounding balloons. However, their autonomy is limited to a few hours owing to power consumption and electrolyte evaporation. An adaptation of the ECC sonde has been developed specifically for long-duration BLPB flights.

Compared to conventional ECC sondes, the main feature is the possibility of programming periodic measurement sequences (with possible remote control during the flight). To increase the ozonesonde autonomy, the strategy has been adopted of short measurement sequences (2–3 min) regularly spaced in time (e.g. every 15 min). The rest of the time, the sonde pump is turned off.

Results of preliminary ground-based tests are first presented. In particular, the sonde was able to provide correct ozone concentrations against a reference UV-absorption ozone analyser every 15 min for 4 days.

Then we illustrate results from 16 BLBP flights launched over the western Mediterranean during three summer field campaigns of the ChArMEx project ( TRAQA in 2012, and ADRIMED and SAFMED in 2013. BLPB drifting altitudes were in the range 0.25–3.2 km. The longest flight lasted more than 32 h and covered more than 1000 km. Satisfactory data were obtained when compared to independent ozone measurements close in space and time. The quasi-Lagrangian measurements allowed a first look at ozone diurnal evolution in the marine boundary layer as well as in the lower free troposphere. During some flight segments, there was indication of photochemical ozone production in the marine boundary layer or even in the free troposphere, at rates ranging from 1 to 2 ppbv h −1, which is slower than previously found in the boundary layer over land in the same region.

Short summary
Boundary-layer pressurised balloons allow for horizontal multi-day flights in the lower atmosphere, carrying light scientific payloads. Ozonesondes, usually used for balloon soundings have too short a lifetime for such flights. An adaptation is proposed, whereby conventional sondes are operated with short measurement phases alternating with longer periods of dormancy. The sondes were operated over the western Mediterranean, offering an original perspective on tropospheric ozone.