- 1CEA DAM DIF, Arpajon Cedex, France (thomas.farges@cea.fr)
- 2Pacific Northwest National Laboratory, Richland, WA, USA
- 3Sandia National Laboratories, Albuquerque, NM, USA
On 3 August 2021, Sandia launched a flotilla of four Heliotrope solar hot air balloons (Bowman et al., 2020) from Belen regional airport in New Mexico (USA) to coincide with the launch of the Boeing Starliner rocket. These Heliotrope balloons allow level flights between 15 and 25 km altitude for several hours from sunrise to sunset. Despite the cancellation of the rocket launch, the microbarometers on board these balloons were able to record in the stratosphere the acoustic signals emitted by eight chemical explosions and the lightning that occurred in a thunderstorm cell. This storm cell was located between 10 and 40 km from three of the four balloons.
In this presentation, we first identify the individual signals that may be due to lightning. For this we use the method proposed by Farges and Blanc (2010) for ground-based thunder measurements and by Lamb et al. (2018) for the first stratospheric balloon lightning measurements. Signal analysis has enabled us to (i) confirm that the acoustic energy of thunder decreases as the inverse square of the distance, and (ii) identify that the electrostatic mechanism of thunder production in the infrasonic range (Wilson, 1921; Dessler, 1973; Pasko, 2009) is indeed present when the observer is located just above or just below the thundercloud. One of the balloons was equipped with two microbarometers separated vertically by around 30 m. The time difference between the two microbarometers for the arrival of signals from a flash of lightning is characteristic of the angle of incidence of the wave. It can be seen that this time difference evolves as expected as the balloon moves away from the storm cell.
Finally, we show for the first time that with a network of three sensors located in the stratosphere, it is possible to give a 3D localization of the first arrival of lightning signals. An equivalent acoustic source inside the cloud is clearly identified when the discharge is of the intranuage type, whereas the acoustic source is located between the ground and the cloud when the discharge is of the cloud-to-ground type.
SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
How to cite: Farges, T., Burgos, G., Bowman, D. C., Gainville, O., Albert, S. A., and Le Pichon, A.: Characterisation and localisation of lightning by a flotilla of stratospheric balloons., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5799, https://doi.org/10.5194/egusphere-egu25-5799, 2025.
