Paper based, among others, on the SCOUT-O3 data from EVDC:

Schumann, U., Kiemle, C., Schlager, H., Weigel, R., Borrmann, S., D'Amato, F., Krämer, M., Matthey, R., Protat, A., Voigt, C., and Volk, C. M.: Long-lived contrails and convective cirrus above the tropical tropopause, Atmos. Chem. Phys., under review, doi:10.5194/acp-2016-940, 2016.